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Abstract

French

Purpose of Review:

People living with chronic kidney disease (CKD), individuals receiving dialysis therapies, and those with both native and transplant kidneys undergo routine blood testing for regular follow-up and monitoring of CKD and its complications. There is a lack of evidence supporting the established frequency and utility of testing, which is largely based on historical practice and expert consensus. While early identification and correction of critical laboratory values can lead to improved clinical outcomes, surveillance bloodwork does not always lead to changes or improvements in patient care. As with all investigations, bloodwork has implications for patients, health care providers and our health care system, impacting costs and the environment. Frequent monitoring of highly variable laboratory values may also lead to overtreatment or undertreatment. The purpose of this review is to synthesize the existing evidence pertaining to current blood testing frequencies across the spectrum of patients with CKD to fully inform the appropriateness of care.

Sources of information:

The sources included published studies and available guidelines regarding the frequency of routine surveillance bloodwork in patients with CKD G3-5, including those receiving all types of dialysis therapies, and recipients of a kidney transplant.

Methods:

Information was gathered from database searches using a search strategy that included keywords related to bloodwork, lab work, frequency, chronic kidney disease, kidney transplant, and dialysis modalities. Reference lists of relevant studies were also screened.

Key findings:

There is a paucity of evidence underpinning monthly routine lab testing across the spectrum of patients with CKD. Five observational studies compared outcomes between in-center hemodialysis patients undergoing monthly bloodwork and those receiving less frequent bloodwork (every six weeks). Of those five studies, four demonstrated that it is safe to undergo less frequent testing. The totality of current data, while limited, suggests that for in-center hemodialysis patients, less frequent testing is a safe strategy. No such data exist for other dialysis or non-dialysis CKD populations. Evidence is needed to inform an appropriate testing frequency across the spectrum of patients with CKD to optimize care at the patient, provider, system, and planetary levels.

Limitations:

A formal systematic review was not undertaken, and therefore, there is a possibility of bias in the included studies.

Keywords

chronic kidney disease dialysis laboratory testing quality of life sustainability

Introduction

The burden of chronic kidney disease (CKD) is large and growing. Worldwide, an estimated 11% to 13% of the global population has CKD;¹ and in 2020, in Canada, 71.9 of 1000 individuals had CKD G3 or higher, and over 48,000 Canadians were living with kidney failure.^2,3 Furthermore, over 2.5 million people receive kidney replacement therapy worldwide, and this number is expected to double to 5.4 million by 2030.⁴

As in many other regions, patients with CKD in British Columbia (BC), including those on dialysis, undergo routine blood testing to assess for disease progression as well as to identify and correct biochemical abnormalities such as hyperkalemia.⁵ The frequency and utility of testing, however, are not supported by evidence.⁶ In 2012, the Kidney Disease: Improving Global Outcomes (KDIGO) working group published recommendations regarding the frequency of blood testing for patients with CKD according to CKD stage^7,8 (Table 1). For example, in patients with CKD without anemia, they recommend a range of frequencies between annual testing of hemoglobin in CKD G3 patients to testing every three months for CKD G5D patients-dialysis-dependent (G5D).⁷ These recommendations have also been supported by the Canadian Society of Nephrology.^9,10 All of these recommendations are, however, not graded and are largely based on historical practice and expert consensus. The new 2024 KDIGO Guidelines for the management of CKD recommend various frequencies of eGFR screening depending on eGFR and albuminuria category. For instance, in patients with CKD G4, eGFR testing three times per year is recommended, but for patients in a similar eGFR category but with A3 albuminuria, eGFR testing is recommended 4 times per year.¹¹ Similarly, patients with CKD G5 are recommended to undergo eGFR screening four or more times per year, regardless of albuminuria category. While these guidelines to do not make any statement regarding the testing frequency of hemoglobin or other biochemical parameters, it is reasonable that practitioners could evaluate these parameters at the same time, ie, with a similar frequency as eGFR testing. Similarly, current KDIGO recommendations for surveillance laboratory testing among kidney transplant patients are based on expert consensus without clear supporting evidence.¹² In the first half-year post-transplant, KDIGO recommends more intensive graft monitoring frequency, including measuring creatinine as frequently as weekly, whereas after approximately six months post-transplant, creatinine and hematologic profiles are recommended to be measured monthly. Once patients reach one-year post-transplant, creatinine monitoring every two to three months and annual complete blood count (CBC) evaluation are recommended. Transplant British Columbia recommendations differ only slightly, stating that after six months post-transplant, kidney transplant recipients should have routine bloodwork every month, which consists of a CBC, creatinine, urea, and electrolyte levels.¹³ After one-year post-transplant, routine bloodwork every four to six weeks is recommended.¹³

Table 1.

KDIGO Recommendations for Laboratory Monitoring Among Patients With CKD.^7,8

Parameter	Population	Recommendation
Hemoglobin (no anemia)	CKD G3	Annually
	CKD G4
	CKD5-ND
	CKD5-PD	Every three months
	CKD5-HD	Every three months
Hemoglobin (with anemia, not on ESA)	CKD G3	Every three months
	CKD G4
	CKD5-ND
	CKD5-PD
	CKD5-HD	Every month
Hemoglobin (with anemia, on ESA)	CKD G3	Every three months^a
	CKD G4
	CKD5-ND
	CKD5-PD	Every month
	CKD5-HD	Every month
Mineral bone disorder parameters	CKD G3	Calcium and phosphate: every six to 12 months PTH: according to baseline level and disease progression
	CKD G4	Calcium and phosphate: every three to six months PTH: every six to 12 months
	CKD5-ND	Calcium and phosphate: every one to three months PTH: every three to six months
	CKD5-PD
	CKD5-HD

Note. ESA = erythropoietin-stimulating agent; ND = non-dialysis dependent; HD = hemodialysis; PD = peritoneal dialysis; PTH = parathyroid hormone.

Every month during the initiation phase of therapy.

Synthesis of evidence supporting routine bloodwork frequency in patients with CKD is an important research priority for several reasons. Frequent bloodwork may affect patient status, practitioner workload, and cost. Furthermore, patient satisfaction in their care may be affected by overtreatment or undertreatment of often variable and questionably clinically relevant laboratory abnormalities (ie, mild hyperkalemia, hyperphosphatemia) and by caregiver attention diverted from actual patient priorities that may include control of blood pressure and uremic symptoms including fatigue and pruritus.

Frequent lab testing among patients with kidney disease has been recognized as being at best low value (conferring no or minimal benefit, or risk of harm exceeding likely benefit, or lacking proportional added benefit when considering global cost) and at worst harmful (potential for over investigation, lost opportunity cost for health system, generating a large volume of health care waste).^14,15 Health care contributes 5.2% of global greenhouse gas emissions annually, and health systems must transition to net zero and no unnecessary waste.¹⁶ Laboratory testing can contribute to greenhouse gas emissions through manufacturing and transport of reagents, patient travel to the site of testing, equipment operation, consumable (ie, reagent, containers, bandages) use, and end use (disposal). A cornerstone of planetary health practice is appropriateness of care, and Choosing Wisely Canada’s new Climate Action recommendations and Using Labs Wisely initiative call for consideration of what tests add value to care.^17,18

This review provides a summary of the evidence underpinning current patterns of routine laboratory testing across the full spectrum of people with CKD, including those receiving dialysis and recipients of a kidney transplant, and discusses the possible effects of less frequent testing at the patient, practitioner, system, and environmental levels.

Methods

A PubMed search was performed to identify literature on bloodwork frequency among patients with CKD. Our search strategy included combinations of the keywords: bloodwork, laboratory, frequency, interval, CKD, home dialysis, peritoneal dialysis (PD), hemodialysis (HD), and dialysis. Our parameters of interest included hemoglobin, potassium, calcium, phosphate, parathyroid hormone (PTH), and albumin. There were no limitations on the search. Separate searches using the same search terms were also performed to identify studies addressing a similar question in kidney transplant patients. Reference lists of relevant studies were also screened. Studies were included if they were relevant to our population of interest and addressed either the evidence behind or consequences of routine bloodwork. As this was not a systematic review, no risk of bias assessment was performed on the studies.

Review

Search Results

Chronic kidney disease G3 to G5D, excluding facility-based hemodialysis

There is limited evidence justifying the proposed intervals for routine laboratory testing among patients with CKD. Our search revealed no published studies on CKD G3 to CKD G5 patients including those receiving home HD or PD. There are no studies of which we are aware that examine the optimal frequency of routine blood testing among kidney transplant recipients.

Facility-based hemodialysis

Our search yielded 5 observational studies, but no randomized controlled data, that support the safety of patients undergoing less frequent than monthly testing. The included studies are summarized in Table 2.

Table 2.

Characteristics and Findings of Included Studies.

Authors	Location	Study design	Methods	Clinical outcomes	Biochemical and other outcomes
Chidiac et al¹⁹	Lebanon	Retrospective study	In 210 chronic in-center HD patients, the authors looked at patient medical records to determine the number of yearly interventions for iron/ESA/phosphate binder/vitamin D.	The median number of yearly interventions was five (3,7) for ESAs, four (2,6) for IV iron, one (0, 2.25) for phosphate binders, and zero (0,1) for alfacalcidol. Patients with higher ferritin, frequent changes in ESA, more changes in alfacalcidol, and higher PTH had higher number of prescription’s changes in ESA, IV iron, phosphate binders, and alfacalcidol, respectively. The median number of interventions per year based on routine laboratory testing did not exceed six times for all parameters in this study. This suggests that the routine testing in CKD G5D patients can be reduced without any impact on the quality of care. Based on these findings, the authors suggested testing for hemoglobin, serum calcium, and phosphate every two months and for URR and PTH twice a year.
Kim et al²⁰	Korea	Longitudinal observational cohort study	In Korea, the recommended testing frequency for maintenance HD patients was to check blood count, electrolytes, urea, creatinine, total protein, glucose, uric acid, calcium, magnesium, phosphorus at least monthly. Iron, ferritin, TIBC, PTH, and HbA_1c were checked every 3 months. Approximately 35 000 chronic in-center HD patients were separated according to whether they undergo regular recommended testing (~30 000) vs non-adherence to testing (~5000) which was not explicitly defined aside from being different than recommendations. The primary outcome was all-cause mortality.	Patients who underwent regular laboratory testing had a longer dialysis duration and lower diastolic blood pressure than those who did not. After adjusting for demographic and clinical parameters, regular laboratory testing independently reduced mortality risk (hazard ratio = 0.90; 95% confidence interval = 0.85-0.95; P < .001). Regular laboratory testing was associated with decreased mortality in patients, regardless of age, gender, or dialysis vintage. Subgroup analysis revealed that regular laboratory testing was associated with decreased mortality in patients without ischemic heart disease, congestive heart failure, or cerebrovascular disease; with diabetes mellitus; or in patients without anemia or hypoalbuminemia.	Patients who underwent regular laboratory testing had lower serum phosphorus, higher hemoglobin, and higher single-pool Kt/V levels than those who did not.
Shome-Vasanthan et al²¹	Calgary, Canada	Prospective cohort study	The authors studied adults who were 18 years or older who had been on HD for at least three months. In total, there were 972 chronic HD patients. The authors compared a retrospective control group that received testing every six weeks for a year and then a prospective intervention group who received testing every eight weeks. The primary outcomes included odds of patient lab values being within target and proportion of hyperkalemia.	There was a reduction in mortality during the intervention period with a hazard ratio of 0.28 (95% CI = 0.16-0.50, P < .01). There was no significant difference in the number of hospitalization days per patient in the intervention period compared with the control period (95% CI = 0.70-1.05) (P = .13). Fewer patients were hospitalized during the intervention period, and the odds of not being hospitalized during the intervention period were 2.3 times higher (95% CI = 1.81-2.81, P < .01).	There was no significant change in patients’ odds of being within the accepted targets during the intervention period compared with the control period for hemoglobin, TSAT, calcium, or PTH. A slightly lower proportion of phosphate values (9%, 95% CI = 0.84-0.99, P = .02) were within target, and the odds of having hyperkalemia were higher by 18% in the control group (95% CI = 1.04-1.33, P = .01). A 0.7% increase in potassium values greater than 6 mmol/L was demonstrated in patients who underwent less frequent bloodwork. The program saved $32 962 by reducing bloodwork from every six weeks to every eight weeks.
Silver et al²²	Ontario, Canada	Retrospective interrupted time series, quality improvement	The population comprised 250-400 chronic in-center HD patients between 2012 and 2015. The authors conducted monthly testing for two years and then transitioned the patient cohort to testing every six weeks for approximately one year. The primary outcomes were hemoglobin and phosphate targets. Secondary outcomes included calcium levels, PTH levels, use of EPO, and all-cause mortality.	The hemodialysis unit mortality rate remained stable (average of 2% per month).	The proportion of patients who achieved hemoglobin (10-12g/dL) and phosphate (2.5-4.6 mg/dL) targets remained stable (average of 60% and 46%, respectively), with no measurements beyond three standard deviations from the mean. The proportion of patients who achieved recommended calcium and PTH levels remained stable throughout the study period at 48% and 55%, respectively. Reducing bloodwork frequency to every 6 weeks was associated with a saving of $85 per patient-year, corresponding to a program-wide savings of $35,000.
Thomas et al²³	Ontario, Canada	Retrospective population cohort study	The population comprised in-center chronic HD patients between 2011 and 2016. In total, 17 centers conducted monthly testing, and eight centers conducted testing every six weeks. The primary outcome was all-cause mortality, and secondary outcomes were MACE, all-cause hospitalizations, ED visits, and hyperkalemia.	In total, 7454 prevalent patients received care at 17 HD programs with monthly blood sampling protocols (n = 5335 patients) and at eight programs with blood sampling every six weeks (n = 2119 patients). More frequent monitoring was not associated with a lower risk for all-cause mortality compared to blood sampling every six weeks (adjusted HR = 1.16; 95% CI = 0.99-1.38). Monthly monitoring was not associated with a lower risk for any of the secondary outcomes among prevalent HD patients. For incident patients undergoing monthly testing, there was increased risk of cardiovascular events (adjusted HR = 1.18; 95% CI = 1.00-1.39), all-cause hospitalization (adjusted HR = 1.11; 95% CI = 1.03-1.20), and episodes of hyperkalemia (adjusted HR = 1.20; 95% CI = 1.00-1.44).

Note. ED = emergency department; EPO = erythropoietin; ESA = erythropoietin stimulating agent; HD = hemodialysis; HbA1c = hemoglobin A1c; IV: intravenous; MACE = major adverse cardiovascular events; PTH = parathyroid hormone ; TIBC = total iron binding capacity; TSAT = transferrin saturation; URR = urea reduction ratio.

Evidence in support of guideline-based testing

Current Korean guidelines recommend monthly blood testing for maintenance HD patients.²⁴ In their longitudinal observational cohort study, Kim et al²⁰ demonstrated in a large group of HD patients that those who adhered to local guidelines and underwent routine monthly testing during a monitoring period of three months had a mortality benefit (hazard ratio [HR] = 0.90, 95% confidence interval [CI] = 0.85-0.95, P < .001) five years after the study period compared to those who were non-adherent to the guidelines. Non-adherence was defined as not undergoing blood testing at least monthly during the monitoring period. Investigators did not explicitly state that monthly testing was not performed due to missed dialysis sessions; however, those who underwent routine monthly testing were noted to have longer dialysis duration, lower rates of hypertension and lower diastolic blood pressure, higher urea clearance, higher hemoglobin, and lower serum phosphorus—all of which could reasonably explain their findings.

In a 2024 study conducted in Calgary, Shome-Vasanthan et al²¹ examined bloodwork targets in a prospective intervention group of 787 in-center HD patients who underwent routine bloodwork every eight weeks and compared them to 787 patients in a retrospective control group who underwent testing every six weeks. There were 602 patients overlapping both cohorts. The frequency of routine bloodwork was found to be every 39.5 days in the control group and every 54.2 days in the intervention group. They found that in patients undergoing less frequent testing, there was a reduction in the odds of phosphate values within the target (P = .02). They also found that there was an increase in odds of having hyperkalemia (>6.0 mmol/L) during the intervention period (P = .01), but the absolute increase in percentage of tests with critical hyperkalemia was 0.28%.

There are also a few studies addressing bloodwork frequency for select parameters. Dialysis guidelines in Japan call for biweekly or monthly measurements of mineral and bone metabolism parameters. Yokoyama et al²⁵ demonstrated that in HD patients with secondary hyperparathyroidism with calcium and PTH levels above the target range, weekly and monthly monitoring, respectively, were associated with achievement of guideline-specified ranges. Weekly monitoring of phosphate, however, was not associated with achievement of guideline-specified phosphate ranges. Greenberg et al²⁶ studied a similar population and first measured PTH levels every three months as per KDIGO and Kidney Disease Quality Outcomes Initiative (KDOQI) guidelines and then transitioned patients over to monthly monitoring. They found that there was a significant increase in the percentage of patients with PTH in the target range of 150 to 300 pg/mL after switching to monthly monitoring. There were, however, no significant differences in calcium or phosphorus levels or their product after switching to more frequent testing.

Evidence in support of less frequent testing

Silver et al²² performed a retrospective interrupted time series analysis whereby after nearly two years of routine monthly bloodwork, they transitioned the HD patients in their dialysis center to bloodwork every six weeks for one year. They found that the proportion of their patient cohort meeting hemoglobin and phosphate targets did not significantly differ before and after the transition. The mortality rate among the dialysis cohort also remained stable (average 2% per month). Furthermore, they calculated that $35 000 CAD was saved by this less frequent testing.

In a retrospective cohort study in Ontario, Thomas et al²³ compared maintenance HD patients undergoing bloodwork every six weeks to those who continued routine monthly testing. Overall, 17 dialysis facilities continued to test their maintenance HD patients monthly, and eight facilities switched to testing every six weeks. At the end of the study, which spanned five years, there were no differences in all-cause mortality among patients undergoing testing every four weeks or six weeks. Furthermore, there was no difference in all-cause hospitalizations, major adverse cardiovascular events, and hyperkalemia. However, in incident HD patients, there was a greater risk of these secondary outcomes among patients that underwent more frequent, ie, monthly, testing.

In a Lebanese study in 2022, authors studied the number of yearly interventions for iron supplementation, erythropoietin-stimulating agents, phosphate binder, and vitamin D supplementation among chronic HD patients.¹⁹ They found that the median number of interventions was six for all parameters. For HD facilities, Lebanese national guidelines call for monthly testing of hemoglobin, electrolytes, urea reduction ratio, serum phosphate, and serum calcium, as well as testing every four months of PTH, ferritin, and transferrin saturation. Given that the number of interventions did not exceed the total frequency of bloodwork per year, they suggested that blood testing frequency can be reduced without any impact on clinical outcomes or quality of care. More specifically, they suggested testing every two months for hemoglobin, phosphate, and calcium, as well as bi-annually for urea reduction ratio and PTH.

In the 2024 study of maintenance HD patients conducted by Shome-Vasanthan et al²¹ (see section “Evidence in support of guideline-based testing”), there were no significant changes in the odds of having hemoglobin, transferrin saturation, calcium, or PTH within target. There were also fewer patients hospitalized during the intervention period, and there was a lower risk of death. Finally, the authors calculated that they saved a total of $32,962 CAD from the reduced anemia and mineral bone disorder bloodwork during the intervention period.

Variability in bloodwork parameters

It is well established that abnormalities in certain parameters such as hemoglobin and potassium are associated with worse clinical outcomes and mortality among dialysis patients.^27-29 Therefore, early identification and correction of out-of-range laboratory values may lead to improved clinical outcomes. It is underrecognized, however, that variability in parameters such as phosphate and hemoglobin is also associated with poorer outcomes.^30,31 In addition to biological and analytic variability in these parameters, variability due to dietary and pharmacologic interventions also occurs, which may or may not be known to the ordering physician. Seasonal variation has been demonstrated in sodium, bicarbonate, urea, calcium, and albumin.^32-34 Phosphate and PTH levels have known diurnal variation, as does potassium.³⁵ Consumption of phosphate-containing products 1 hour prior to laboratory testing can also alter blood test results by small amounts.³⁶ Thus, establishing “true” baseline phosphate levels may be difficult. Others have suggested that monthly phosphate measurements may not be accurate measurements of phosphate control, as they are only snapshots and may not be reflective of overall phosphate trends.³⁷ Intervening on potentially transiently elevated phosphate levels increases pill burden and polypharmacy for dialysis patients, which may impact a number of parameters, such as worse quality of life, medication side effects, increase in pill burden, and prescribing cascades due to adverse effects.³⁸ We do recognize that there are patients with greater variability in lab work parameters, however, and perhaps more frequent lab monitoring may be helpful to establish trends, but this could come at the expense of unnecessary interventions due to the frequent monitoring schedule.

Testing bloodwork monthly may be a feasible strategy for patients who have recently started dialysis compared to those of a longer dialysis vintage, since initiation of PD or HD results in correction of the uremic milieu, electrolyte abnormalities, and acid-base imbalances. To our knowledge, there are no studies examining the variability of blood test results in relation to dialysis vintage, but there is some evidence that laboratory parameters do change over time on dialysis. Lower hemoglobin levels, iron stores, and dialysis adequacy have been shown to be associated with dialysis vintage above 12 months.³⁹ The same study on in-center HD patients demonstrated that there was no association between calcium and phosphate levels and dialysis vintage. Albumin was shown to be lower as well but was not statistically significantly different by vintage, although other investigators have demonstrated an increase in albumin during the first half year of HD.⁴⁰ Another study among chronic HD patients monitored for 15 years demonstrated that albumin variability reached its nadir 1 year after starting dialysis, then stabilized but continued to trend upward.⁴¹ Altogether, a more personalized approach that considers dialysis vintage, clinical stability, and bloodwork variability may be warranted when determining the ideal interval of testing in stable dialysis patients.

Therefore, frequent monitoring of highly variable laboratory values calls into question the significance of isolated abnormal lab results and may consequently lead to overtreatment or undertreatment. These data provide a strong rationale for re-thinking the ideal frequency of routine bloodwork among patients with CKD, as there is potential for increased morbidity with more frequent testing. An important limitation of this discussion is, however, that bloodwork variability was not explicitly included in our database search.

Implications of Less Frequent Bloodwork

Synthesis of the above-described observational literature of in-center HD patients’ bloodwork frequency thus indicates that less frequent testing may result in slightly higher incidences of abnormal lab values but that overall, there are low incidences of adverse outcomes with no convincing effects on mortality. There are no other published studies on ideal bloodwork frequency across other CKD populations. Less testing results in costs savings and is less environmentally intensive (See Environmental Considerations). While our focus remains on clinical outcomes, reflection is appropriate on whether checking laboratory values that are variable and often not clinically significant, ie, phosphate, is worth the additional costs.

Impact on Patients

While more frequent testing may theoretically lead to early identification and correction of critical laboratory values, the vast majority of lab results for patients who receive chronic dialysis care are within acceptable limits and not in a critical range. Therefore, frequent testing needs to be balanced against the possible risks of over-testing and overtreatment, which can potentially be problematic for both patients and the health care system. Furthermore, as we have summarized, there do not appear to be clinical benefits of more frequent testing. For instance, dialysis patients have already been shown to have poor quality of life due to comorbidities, loss of independence, and low levels of physical activity.^42,43 Unnecessary testing can add additional burden and lead to further morbidity due to unnecessary phlebotomies (worsening anemia which could subsequently lead to an increase in iron infusions or blood transfusions) and medication use. With respect to patients not on dialysis or those not undergoing in-center HD, there are financial implications of increased testing such as transportation costs, as well as potential loss of income for patients and/or their carers due to missed work to attend laboratory appointments. From an environmental impact standpoint, it has been shown that patient travel to health care services comprises 5% of National Health Service (NHS) England’s carbon emissions.⁴⁴

Impact on Health Care Providers

Frequent testing may also have some unintended negative implications for health care practitioners. As an example, the BC Renal Agency has established best practice algorithms for ordering, reviewing, and following up on bloodwork.⁵ The algorithms assume that the laboratory alerts the attending nephrologist or nurse practitioner about any critical laboratory values. If the results are not critical, however, the standard of care is for a health care practitioner to review the bloodwork within 3 days of the blood test result being available. These results then trigger a medication or dietary review and subsequent intervention by additional members of the health care team if deemed necessary. An example of such an algorithm can be found in Figure 1. An estimate of time spent by each member of the health care team is approximately a minimum of 15 minutes (includes review, plan development, follow-up communication). Thus, the cumulative workload for either physicians or for associated health care professional team members is substantial, without clear evidence demonstrating value or benefit of the activity. According to research from the Canadian Medical Association (CMA) where physicians across the country were surveyed, two thirds of physicians reported that administrative tasks (which include time documenting on electronic medical records and ordering tests) have increased over the past 5 years.⁴⁵ Moreover, the CMA calculated that approximately 18.5 million hours are spent on unnecessary administrative tasks per year and that, according to physicians, this significantly affects job satisfaction and directly contributes to poor mental health. In stable patients with CKD, more frequent testing has the advantage of reassuring, possibly unnecessarily, health care practitioners if the blood test results are stable but is time-consuming and increases health care practitioner’s “administrative” burden (Table 3).

Figure 1.

Flowchart of steps in routine laboratory testing.

Table 3.

Benefits and Drawbacks of More Frequent and Less Frequent Testing Strategies.

		Testing frequency
	Less	More
Benefits	Increased patient quality of life (anxiety, travel, and changes in medications)Less time-consuming and less workload for HCPsLess waste and use of health care resources (materials and health care delivery)Reduced carbon footprint and improved sustainability	Identify high-risk blood values requiring interventionCan monitor adherence to therapiesCan ensure the effectiveness of therapies, ie, dialysis adequacyReassurance of HCPsImproved understanding of trajectory and clinical care for patients (engagement tool)More frequent feedback for patients
Drawbacks	Less ability to identify critical laboratory valueswhich may delay interventionMay lead to less patient engagement in careCan lead to patient anxiety, ie, not knowing that their blood work is normalLess rapport with patient and their familiesMore difficult to monitor adherence and adequacy of therapy	Increased workload and more time-consuming for HCPsIncreased waste and use of health care resourcesLarger carbon footprint and less sustainableCan lead to greater patient anxiety, ie, over-testing and over-intervention and decreased patient quality of lifeIncreased risk of nosocomial infectionsIncome loss from patients as well as their loved ones who accompany them

Note. HCP = health care provider.

Impacts on Health Care Resources

Unnecessary testing also has substantial implications on health care resources. In 2017, the Canadian Institute for Healthcare Improvement and Choosing Wisely Canada released a report illustrating that while unnecessary health care interventions and testing were decreasing in recent years, there is still a considerable amount of unnecessary testing within the Canadian health care system.⁴⁶ In BC, a routine set of bloodwork (CBC, electrolytes, creatinine, urea, extended electrolytes including ionized calcium, albumin) costs approximately $49.23⁴⁷ (Table 4). Per year, when testing monthly, this would result in per patient cost of $590.76. If bloodwork was instead undertaken every six weeks, the average eight blood draws per year would cost $393.84, a per person savings of $196.92. Without even considering the costs associated with bloodwork for nearly 20,000 pre-dialysis patients with CKD, transitioning our 7500 dialysis and transplant patients from monthly blood testing to testing every six weeks could lead to theoretical savings of just over one million dollars per year in BC alone (Table 6). This is also just a conservative estimate, as it only includes the cost of laboratory processing and does not include the blood draws, transportation to the lab, and other testing-associated costs (Figure 2).

Table 4.

Financial and Environmental Costs of Specific Laboratory Tests (Excluding Material and Human Resource Costs) in British Columbia.

Laboratory parameter	Cost in British Columbia ($ CAD)	GHG emissions per lab test (g CO₂e)
Complete blood count + differential	10.96	4.6
Sodium	1.38	11.5
Potassium	1.39
Chloride	1.49
Bicarbonate	2.37	Unknown
Creatinine	1.52	67.8
Urea^a	1.57	32.1
Albumin	1.55	27.9
Calcium (total)	1.55	17.4
Calcium (ionized)^b	14.02	Unknown
Magnesium	1.62	25.2
Phosphate	1.62	35.3
Alanine aminotransferase	1.47	64
Alkaline phosphatase	1.57	80.5
Total protein	1.60	44.9
Total	49.23	443.3

Source. Adapted from Spoyalo et al.⁴⁸

Measured pre- and post-hemodialysis.

Excluding ionized calcium, the total cost would be $35.21 per patient.

Figure 2.

Costs associated with routine bloodwork visit.

Additional financial costs incurred by health providers’ (nurse, pharmacist, dietitian) review of lab tests are demonstrated in the following calculation. Assuming each spends 15 minutes reviewing abnormal blood test results, if each earns an average of $45 per hour, then approximately $11 of individual salary can be allocated per abnormal bloodwork result. Given that there are approximately 7500 dialysis or kidney transplant patients undergoing monthly bloodwork, one can quickly see how much potentially “unnecessary” labor costs this would incur for the health care system.

Environmental Considerations

A planetary health approach to care prioritizes reducing demand for health services via health promotion and disease prevention, followed by appropriate use of health care resources, then reducing emissions from health services provided.¹⁷ The primary focus of this review is the exploration of safe demand-side mitigation via the appropriate use of laboratory testing in kidney patients.

Choosing Wisely’s new “climate conscious” recommendations span 22 specialty areas, across which “unnecessary laboratory test ordering” is recognized as a category of waste.⁴⁹ McAlister et al¹⁵ describe routine laboratory panels in kidney care, defined as those obtained in the absence of specific clinical indication, as “low value.” These authors explore value as a subjective construct that depends on clinical (patient outcome), societal (equity, environmental impact), and financial effects. There would be little disagreement in the value of testing for hyperkalemia in a high-risk patient (for instance, a patient who missed an HD treatment, reported ingestion of foods high in potassium, and presented to dialysis care with diffuse muscle weakness), although some might argue that a low-potassium bath and prompt provision of dialysis would remedy assumed hyperkalemia without the need for testing. Societal factors to consider are justice-related—health care waste, opportunity costs for the health system, and intergenerational and interspecies equity relating to environmental degradation and resource consumption.

It is intuitive that early CKD recognition, risk factor modification, and effective slowing of CKD progression would result in less laboratory testing in most instances. To our knowledge, the relative frequency of lab evaluation in patients with CKD G4 or CKD G5ND—who may be expected to have hyperkalemia or hemodynamically mediated lower eGFR from renin-angiotensin system or mineralocorticoid receptor blockade agents, hence more frequent evaluation—compared to those receiving peritoneal or HD, is unreported.

Kidney replacement therapies are environmentally intensive, with published yearly CO₂ emissions (CO₂e) ranging from 1.5 to 4.5 tons CO₂e per patient per year for PD (these studies did not include blood testing), and HD ranging from 3.7 to 10.2 tons CO₂e per patient per year (both HD studies included blood testing).^50-52 The carbon footprint of a single HD treatment, 58.9 kg CO₂e in one US study, is equivalent to 238 km vehicle travel.^53,54 Connor et al determined that 0.16% of a kidney service’s emissions are from lab testing. As no emissions factor was available for blood tests at the time of their 2010 analysis, a carbon cost of 50 g CO₂e per blood test processed was assigned.⁵¹ The same emission factor was assigned in a 2013 study evaluating the carbon footprint of an Australian satellite HD facility, and in this study, less than 0.1% of emissions were attributed to “Diagnostics.”⁵² In both studies, neither the frequency, nor the type of blood tests ordered, was described.

McAlister et al⁵⁵ sought to determine the greenhouse gas (GHG) emissions from laboratory tests including a CBC and an electrolyte panel (the authors did not specify which electrolytes were included; however, both creatinine and urea were included). They found that one hematology test emits 89 g CO2e (95% CI = 73–91 g/test) and that each electrolyte, creatinine, and urea panel emits 99 g (95% CI = 84-113 g). Importantly, they determined that the majority of emissions (60%-95%) came from collecting the sample itself (ie, phlebotomy and vial costs), whereas emissions from laboratory reagents and power use were much smaller. This is important because it highlights the environmental benefit of “add-on” testing (when additional results may be belatedly requested from compatible vials of already drawn blood sample(s) still located within the lab) over re-drawing blood from patients and use of further vials.

Spoyalo et al⁴⁸ calculated the financial and environmental costs of bloodwork in hospitalized general surgery patients. Financial costs were defined as the “cost of labour, transport and the consumables, reagents and energy required to process each test.” The environmental costs, ie, the carbon footprint, were the greenhouse gas emissions associated with the production, transport, processing, and disposal of each consumable involved in laboratory testing and its associated packaging. Using data from Spoyalo et al, monthly per-person bloodwork for HD and PD patients in BC would result in 873.3 g and 659.2 g CO₂e, respectively (Table 5). A sample calculation showing derivation of emissions from monthly HD and PD laboratory testing is included in Appendix. As noted in Table 5, the emissions are higher for HD due to consumables, as two lab draws (pre- and post-HD bloodwork) are involved compared to PD, which only requires one “set” of testing. There is also a slight overestimation in HD phlebotomy emissions since bloodwork is drawn from the HD circuit. Therefore, supplies used in conventional lab draws such as tourniquets, which incur a carbon cost of approximately 10 g, would not be required and could be subtracted from the HD phlebotomy emissions. Overall, however, these calculations likely underestimate the total environmental impact of testing, since emissions beyond testing itself, such as transportation to and from the testing facility, are not included. Applied to the entire CKD population in BC, transitioning from monthly to every 6 weeks testing would emit approximately 11 tons less CO₂e emissions (Table 6).

Table 5.

Environmental Costs (Excluding Patient Transportation) for a Single Laboratory Visit by Dialysis Modality and CKD Category in British Columbia.

(a) Hemodialysis.
Factors		Emissions (kg CO₂e)
Laboratory tests		0.443
Phlebotomy (pre- and post-HD)		0.300
Materials		0.130
Total		0.873
(b) Peritoneal dialysis
Factors		Emissions (kg CO₂e)
Laboratory tests		0.411
Phlebotomy		0.150
Materials		0.098
Total		0.659
(c) One-year total CO₂e emissions
	CKD3-5ND	PD	HD^a
Laboratory tests	0.411 kg × 4 × 19 433 = 31 963.40 kg	0.411 kg × 12 × 890 = 4391.62 kg	0.443 kg × 12 × 2692 = 14 320.36 kg
Phlebotomy	0.150 kg × 4 × 19 433 = 11 659.80 kg	0.150 kg × 12 × 890 = 1602 kg	0.300 kg × 12 × 2692 = 9691.2 kg
Vials	0.098 kg × 4 ×19 433 = 7617.74 kg	0.098 kg × 12 × 890 = 1046.64 kg	0.130 kg × 12 × 2692 = 4199.52 kg
Total	51 240.94 kg	7040.26 kg	28 211.09 kg

Source. Adapted from Spoyalo et al.⁴⁸

Note. Emissions from laboratory tests in patients undergoing HD or PD include those generated from routine monthly bloodwork: CBC and differential, Na, K, Cl, HCO₃, creatinine, urea (×2 for HD only), albumin, total calcium, Mg, Ph, ALT, AST, and total protein. Phlebotomy emissions include those from needles, gloves, plastics, and tourniquets, as well as the pneumatic tube system. Material emissions in PD include one green vial, purple vial, and gold-top vial. An extra green vial is used for HD patients, as both pre-HD and post-HD bloodwork is required.

Including home HD.

Table 6.

Financial and Environmental Impact of Reducing Frequency of Monthly Testing to Every Six Weeks Among CKD5D and Kidney Transplant Patients in British Columbia.

(a) Costs
	N	Monthly (12 tests)	Every 6 weeks (8 tests)	Savings
PD	890	$525 776.40	$350 517.60	$175 258.80
IC-HD	2544	$1 502 893.44	$1 001 928.96	$500 964.48
Home HD	148	$87 432.48	$58 288.32	$29 144.16
Kidney transplant recipients	3978^a	$987 180.48^b	$658 120.32^b	$329 060.16
Total	7560	$3 103 282.80	$2 068 855.20	$1 034 427.60
(b) CO₂ emissions
	N	Monthly (12 tests)	Every 6 weeks (8 tests)	Savings
PD	890	4391.62 kg	2927.74 kg	1463.88 kg
IC-HD	2544	13 533.06 kg	9022.04 kg	4511.02 kg
Home HD	148	787.30 kg	524.87 kg	262.43 kg
Kidney transplant recipients	3978^a	15 848.35 kg	10 565.57 kg	5282.78 kg
Total	7560	34 560.33 kg	23 040.22 kg	11 520.11 kg

Note. Current population sizes taken from BC Renal Agency.⁵⁶ PD = peritoneal dialysis; IC-HD = in-center hemodialysis; home HD = home hemodialysis.

As of 2023.

$20.68 not including albumin or extended electrolytes.

Reducing the frequency of bloodwork for kidney patients would be one part of a strategy to reduce system carbon emissions. Consideration could also be given to foregoing the standard, routine bloodwork panel, choosing instead to test specific parameters of interest more frequently, most likely potassium, and creatinine/eGFR.

Potential Benefits of Monthly Bloodwork

While we have highlighted many benefits of undergoing less frequent testing, it should be acknowledged that there are reasons why an existing routine bloodwork frequency could be beneficial for people with kidney disease. For example, routine bloodwork could be a method of monitoring adherence to treatment for patients in whom adherence is questionable. Furthermore, patients or their family members are often keen to know whether their laboratory parameters are stable or if a particular intervention such as a phosphate binder is having the desired effect. This may be especially true of patients who receive assistance from a family member to perform their home dialysis. Feedback regarding laboratory parameters can empower patients and their families to continue with lifestyle modifications and other therapies including dialysis. Another possibility is that patients from more rural areas may have to travel a long distance for monthly appointments or other commitments, and thus, it would make more sense to coordinate their appointments with laboratory visits to reduce travel time and costs. Therefore, a one-size-fits-all approach of less frequent testing may not be a viable strategy in a large and variable CKD population. However, a prudent next step could be to understand what factors are associated with blood test result variability among patients with CKD to determine which subset of patients may benefit from less frequent testing.

Limitations

Limitations of the current study include that, as this was not a systematic review, there is the potential for author bias in the included studies. Furthermore, while every effort was made to include all relevant studies, this may not represent a comprehensive overview of all available evidence.

Conclusion

In patients with CKD, including dialysis and kidney transplant patients, current recommendations for routine blood testing are neither evidence-based nor value-aligned. In dialysis patients who are receiving treatment for kidney failure, the rationale for monthly bloodwork is questioned given the regularity of the treatment and clinical assessment. In outpatient CKD G3 to CKD G5ND and kidney transplant patients, although it is reasonable to regularly monitor, we suggest that the frequency of laboratory surveillance be individualized based on clinical trajectory, psychosocial factors such as quality of life, and weighing the broader patient and societal impacts of more frequent testing. More evidence is needed to inform an appropriate interval of routine laboratory testing in patients across the CKD spectrum, as over-testing and overtreatment have implications on patient quality of life, practitioner workload, health care resources, and the environment.

Footnotes

Appendix

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Alessandro Cau

Caroline Stigant

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Frequency of Routine Bloodwork Among Patients With Chronic Kidney Disease: A Narrative Review to Inform Appropriateness of Care

Abstract

Purpose of Review:

Sources of information:

Methods:

Key findings:

Limitations:

Keywords

Introduction

Methods

Review

Search Results

Chronic kidney disease G3 to G5D, excluding facility-based hemodialysis

Facility-based hemodialysis

Evidence in support of guideline-based testing

Evidence in support of less frequent testing

Variability in bloodwork parameters

Implications of Less Frequent Bloodwork

Impact on Patients

Impact on Health Care Providers

Impacts on Health Care Resources

Environmental Considerations

Potential Benefits of Monthly Bloodwork

Limitations

Conclusion

Footnotes

Appendix

Declaration of Conflicting Interests

Funding

ORCID iDs

References