Abstract
Background
This study evaluated a point-of-care capillary hemoglobin assay compared to physiologic indicators, such as systolic blood pressure (SBP), heart rate (HR), and Focused Assessment with Sonography in Trauma (FAST) imaging, in predicting transfusion outcomes for trauma patients.
Methods
This retrospective cohort study evaluated adult trauma patients presenting to a single Level I trauma center with an initial point-of-care capillary hemoglobin (POC-Hb; HemoCue®) obtained in the trauma bay. Patients were stratified by receipt of blood transfusion within 24 hours of arrival. Prehospital and emergency department vital signs, FAST results, transfusion timing, and volume were analyzed. Multivariable logistic regression identified variables independently associated with transfusion. Nonparametric tests (Mann-Whitney U, Kruskal-Wallis with post-hoc testing) and Spearman’s rank correlation assessed associations between POC-Hb values and transfusion timing and volume.
Results
Of 1552 included patients, 552 received blood transfusions and had significantly lower POC-Hb values compared to non-transfused patients (11.5 vs 13.5 g/dL; P < 0.001). POC-Hb was not associated with transfusion on multivariable analysis, and showed no correlation with time to transfusion. Positive FAST results (OR 19.4, 95% CI 8.1-46.2, P < 0.001) and SBP on arrival (OR 48.5, 95% CI 15.0-156.7, P < 0.001) were associated with transfusion.
Conclusion
Lower initial POC-Hb was associated with transfusion and weakly correlated with blood product volume on unadjusted analyses, but was not independently associated with transfusion or with time to transfusion after adjustment. SBP and FAST demonstrated stronger associations with transfusion outcomes and intensity. These findings support prioritizing physiologic indicators and FAST results over point-of-care hemoglobin when assessing transfusion need in trauma patients.
Keywords
Introduction
Hemorrhage remains a leading cause of preventable death in trauma, and timely recognition of patients who require blood transfusion is critical to improving outcomes. 1 Trauma surgeons must make rapid decisions based on a combination of physiologic parameters, mechanism of injury, and limited diagnostic data—often before conventional laboratory results are available. 2 Although systolic blood pressure (SBP), heart rate (HR), and point-of-care imaging such as the Focused Assessment with Sonography for Trauma (FAST) are well-established components of early trauma assessment, the role of point-of-care hemoglobin (POC-Hb) measurement remains uncertain.3,4
POC-Hb offers rapid bedside assessment and has been used in emergency and prehospital settings as a potential adjunct to guide early transfusion decisions.5,6 However, hemoglobin concentration is known to lag behind acute blood loss due to compensatory hemodynamic adjustments and hemodilution, raising concerns that POC-Hb values may not accurately reflect early hemorrhage or predict transfusion necessity.7,8 Prior studies have yielded mixed results, and few have evaluated POC-Hb in direct comparison with physiologic indicators and FAST imaging within a modern trauma workflow.5,7,9
Given the emphasis on early identification of hemorrhage in Advanced Trauma Life Support (ATLS) guidelines and contemporary trauma practice, understanding the predictive value of POC-Hb relative to real-time clinical parameters is essential. 2 A clearer characterization of its utility could inform whether POC-Hb should meaningfully influence transfusion decisions or whether trauma surgeons should rely primarily on physiologic indicators and bedside imaging.
This study aimed to evaluate the associations between POC-Hb and transfusion receipt, transfusion timing, and transfusion volume in trauma patients, and to compare the strength of these associations with those of established indicators, including systolic blood pressure, heart rate, and FAST examination results. We hypothesized that POC-Hb would not be independently associated with transfusion when controlling for physiological parameters. If demonstrated, this would suggest limited utility for this testing in the acute trauma setting.
Methods
Study Design and Data Source
This retrospective observational study was conducted at a single Level I trauma center verified by the American College of Surgeons. Institutional Review Board approval was obtained prior to data collection, with a waiver of informed consent granted due to minimal risk and the use of existing clinical data.
Study Population
All adult trauma patients receiving a transfusion in the trauma bay between January 1, 2021, and December 31, 2024, were included. Pediatric patients (<18 years old), prisoners, and pregnant patients were excluded. To evaluate factors associated with transfusion, these patients were compared with non-transfused trauma patients. Of the 22,140 adult trauma patients who did not receive transfusions, a computer-generated random sample of 1000 patients was selected to serve as a comparison group. Sampling was performed to reduce group size imbalance and maintain computational feasibility while preserving representativeness through random selection.
Outcomes of Interest and Data Collected
The primary outcome was receipt of blood transfusion. Secondary outcomes included time to first transfusion, defined as minutes from emergency department arrival to administration of the first blood product, and blood product volumes administered.
Patients who received blood transfusions were compared with those who did not. Data collected included demographic variables (age and sex), injury-related characteristics (mechanism of injury and Injury Severity Score), and initial physiologic parameters (prehospital and emergency department systolic blood pressure and heart rate), FAST examination results, transfusion timing and blood product volumes—packed red blood cells (RBC 24H), fresh frozen plasma (FFP 24H), platelets (PLT 24H), and cryoprecipitate (CRY 24H) administered within 24 hours of arrival, with whole blood (WB 4H) volume assessed within the first 4 hours.
Initial point-of-care hemoglobin (POC-Hb) was measured during trauma activation using the HemoCue® hemoglobin analyzer, a portable photometric device routinely used in the trauma bay for rapid bedside hemoglobin assessment.5,10 POC-Hb measurements were obtained at the discretion of the trauma team without a standardized protocol. They were typically performed early during the initial trauma evaluation (primary or early secondary survey), with timing varying based on clinical factors such as hemodynamic status and provider judgment.
Statistical Analysis
Continuous variables were summarized using means with standard deviations or medians with interquartile ranges, as appropriate. Categorical variables were reported as frequencies and percentages. Variables were selected a priori based on clinical relevance and established trauma literature, including Advanced Trauma Life Support (ATLS) principles, with input from the study investigators. 2 POC-Hb values were also examined using a <10 g/dL threshold selected a priori based on prior trauma literature.8
SBP categories were defined as hypotensive (<90 mmHg), low-normal (90-119 mmHg), normotensive (120-139 mmHg), and elevated (≥140 mmHg), and HR categories were defined as bradycardia (<60 beats/min), normocardia (60-100 beats/min), and tachycardia (>100 beats/min).
Multivariable logistic regression with a binomial distribution and logit link was used to evaluate variables independently associated with blood transfusion, including point-of-care hemoglobin, laboratory hemoglobin, prehospital and emergency department systolic blood pressure and heart rate categories, and FAST examination results. Categorical predictors were entered using indicator variables with clinically normal ranges as reference categories.
Associations between POC-Hb and time to transfusion and blood product volumes were assessed using Spearman’s rank correlation. Group comparisons were performed using Mann-Whitney U or Kruskal-Wallis tests with Dunn’s post-hoc comparisons when appropriate. Figures display point estimates with 95% confidence intervals unless otherwise specified. All analyses were two-sided, with P < 0.05 considered statistically significant. Statistical analyses were performed using JASP (Version 0.95; University of Amsterdam, Netherlands).
Results
Demographics and Baseline Characteristics of Entire Cohort
Demographics and Baseline Characteristics of Entire Cohort
Note: Values are reported as median (interquartile range) or mean ± standard deviation, as appropriate. Totals may not sum due to unavailable data for certain variables.
HemoCue Hemoglobin and Transfusion Outcomes
Patients who received RBC transfusions had lower initial HemoCue hemoglobin values than non-transfused patients (11.5 vs 13.5 g/dL; mean difference −2.0 g/dL, 95% CI −2.3 to −1.8; P < 0.001), with transfusion occurring more frequently among patients with HemoCue <10 g/dL than ≥10 g/dL (68.2% vs 29.8%, P < 0.001).
HemoCue hemoglobin was not associated with time to transfusion (Spearman r = −0.03, P = 0.472). Weak negative correlations were observed between HemoCue values and transfused volumes of RBC 24H, FFP 24H, PLT 24H, and WB 4H (|r| < 0.20 for all), while CRY 24H volume was not significantly correlated (P = 0.067) (Table 1, Figure 1). Associations between Point-of-Care Hemoglobin and Transfusion Timing and Blood Product Volumes. Note: Lines represent fitted trends from Spearman rank correlations, with shaded bands indicating 95% confidence intervals
FAST Positivity and Transfusion Outcomes
FAST-positive patients had a shorter time to transfusion than FAST-negative patients (median 14 [IQR 8-38] vs 41 [14-137] minutes; P < 0.001) and received greater 24-hour volumes of RBCs, FFP, and PLTs, as well as whole blood within 4 hours (all P < 0.01). CRY use within 24 hours was higher among FAST-positive patients but did not reach statistical significance (P = 0.056) (Table 1, Figure 2A). Physiologic & FAST Associations with Blood Products and Timing. Note: (A) FAST ultrasound results, (B) prehospital heart rate categories, (C) emergency department heart rate categories, (D) prehospital systolic blood pressure categories, and (E) emergency department systolic blood pressure categories shown in relation to blood product volumes and timing of transfusion. Bars represent medians; error bars indicate 95% confidence intervals.
First Field Heart Rate
No significant differences were observed in 24-hour transfusion volumes of RBCs, FFP, PLTs, or CRY across categories (all P > 0.05). WB administered within 4 hours differed by heart rate category (P < 0.001), with tachycardic patients receiving greater volumes than normocardic patients. Prehospital heart rate was not associated with time to transfusion (P = 0.365) (Figure 2B).
Emergency Department Heart Rate
Emergency department heart rate category was associated with transfusion outcomes, with tachycardic patients receiving greater RBC volumes (P = 0.024) and greater whole blood within 4 hours (P < 0.001), while FFP, PLTs, and CRY volumes did not differ across categories. Time to transfusion differed by ED heart rate category (P < 0.001), with tachycardic patients receiving transfusion earlier than normocardic and bradycardic patients (Figure 2C).
First Field Systolic Blood Pressure
Prehospital SBP category was associated with 24-hour transfusion volumes of RBCs, FFP, and CRY, as well as whole blood administered within 4 hours (all P < 0.05). Hypotensive patients received greater RBC and whole blood volumes than other SBP categories. Time to transfusion differed by prehospital SBP category (P < 0.001), with hypotensive patients receiving transfusion earliest, followed by low-normal SBP, while elevated SBP was associated with the longest delay (Figure 2D).
Emergency Department Systolic Blood Pressure
ED SBP category was associated with greater transfusion volumes of RBCs, FFP, and whole blood within 4 hours (all P < 0.01), while PLTs and CRY did not differ across categories. Time to transfusion also differed by ED SBP category (P < 0.001), with hypotensive and low-normal patients receiving transfusion earlier than normotensive patients, while elevated SBP was associated with the longest delays (Figure 2E).
Factors Independently Associated With Transfusion
Multivariable Logistic Regression of Factors Independently Associated With Blood Transfusion
Note. The multivariable logistic regression model included HemoCue Hgb, laboratory Hgb, 1ST Field and ED HR categories, 1st Field and ED SBP categories, and FAST examination result. HR and SBP categories were entered as nominal categorical predictors using indicator variables, with normocardia (60-100 bpm) and normotension (120-139 mmHg) specified as the reference categories. FAST results were coded as negative (reference) or positive.
Systolic blood pressure demonstrated the strongest associations with transfusion, with emergency department hypotension (OR 48.5, 95% CI 15.0-156.7, P < 0.001) and low-normal SBP (OR 5.6, 95% CI 3.2-9.6, P < 0.001) showing markedly higher odds compared with normal SBP; prehospital hypotension also remained significant (OR 2.9, 95% CI 1.3-6.7, P = 0.011). FAST positivity was strongly associated with transfusion (OR 19.4, 95% CI 8.1-46.2, P < 0.001). The model demonstrated significant improvement over the null model (Δχ2 = 584.1, P < 0.001) (Table 2).
Discussion
Early recognition of hemorrhage and timely initiation of transfusion are central priorities in trauma resuscitation, yet clinicians must often make these decisions before conventional laboratory results are available. 11 In this retrospective cohort, we evaluated point-of-care hemoglobin alongside established physiologic parameters and FAST examination findings in relation to transfusion need, timing, and volume. Overall, point-of-care hemoglobin demonstrated limited incremental value for early transfusion decision-making, whereas FAST positivity and systolic blood pressure—particularly on emergency department arrival—were the most consistent and clinically informative indicators of significant hemorrhage.
Although patients who ultimately required transfusion presented with lower initial HemoCue hemoglobin values and a threshold of <10 g/dL identified a subgroup with higher transfusion rates, POC-Hb was not independently associated with transfusion once physiologic variables were considered. This threshold was selected a priori based on prior trauma literature. 12 Furthermore, HemoCue values were not associated with time to transfusion and demonstrated only weak correlations with blood product volumes. These findings align with prior literature demonstrating that early hemoglobin measurements may underestimate acute blood loss due to delayed equilibration, hemodilution, and ongoing hemorrhage during early resuscitation. 9 The observed association between laboratory hemoglobin and transfusion may reflect differences in timing, as laboratory values obtained later may better capture evolving blood loss. However, laboratory hemoglobin is also limited by processing delays in the acute setting. Collectively, these results suggest that hemoglobin measurements—whether point-of-care or laboratory—should not be used in isolation, but rather interpreted alongside physiologic parameters and clinical assessment in the early trauma setting.
In contrast, FAST positivity emerged as one of the strongest factors associated with transfusion across all outcomes examined. FAST-positive patients were transfused earlier and received greater volumes of blood products, reinforcing FAST’s established role in identifying hemoperitoneum or pericardial effusion—direct anatomic evidence of hemorrhage—and support its continued prioritization during early trauma assessment and resuscitation. 13
Systolic blood pressure demonstrated a similarly robust and graded association with transfusion outcomes. Emergency department hypotension and low-normal SBP were associated with markedly increased odds of transfusion, while elevated SBP was associated with lower transfusion rates and longer delays. Prehospital SBP showed a similar but attenuated pattern. These findings highlight emergency department systolic blood pressure as a dynamic and clinically meaningful marker of hemorrhage severity, consistent with its central role in ATLS-based shock assessment.2,8
Heart rate demonstrated a more modest and context-dependent relationship with transfusion outcomes. Prehospital heart rate was not independently associated with transfusion, whereas emergency department tachycardia was associated with increased odds of transfusion and greater blood product utilization. This divergence likely reflects physiologic evolution during transport and early resuscitation, suggesting that emergency department heart rate provides more actionable information than initial prehospital measurements.
Taken together, these findings support a clear hierarchy of early transfusion indicators. FAST examination and systolic blood pressure were the strongest and most consistent markers of transfusion need and timing, with emergency department heart rate providing additional but less robust discriminatory value. In contrast, POC-Hb did not meaningfully contribute once physiologic parameters were incorporated. For trauma surgeons, these results emphasize prioritizing dynamic physiologic assessment and FAST imaging over point-of-care hemoglobin when making early transfusion decisions in the trauma bay.
While POC-Hb provides rapid bedside assessment, our findings suggest that its utility as a routine standalone predictor of transfusion need is limited. POC-Hb may be better suited as an adjunct to clinical assessment, particularly when interpreted alongside physiologic parameters and FAST examination findings. Accordingly, we do not recommend reliance on POC-Hb alone for transfusion decision-making in the trauma bay. At our institution, these findings have prompted adjustment toward more selective use rather than routine measurement in all trauma patients. Given the additional cost and resource utilization associated with routine POC-Hb testing, such selective use may also improve efficiency without compromising clinical decision-making. Future studies reviewing effectiveness of change in practice will be performed.
This study has limitations inherent to its retrospective design, including potential unmeasured confounding and variability in provider transfusion practices. HemoCue hemoglobin values were manually abstracted and may be subject to transcription error, reflecting real-world documentation. FAST examinations and prehospital and emergency department vital signs were not available for all patients, consistent with variability in trauma bay workflows. Analyses were performed using the available data. Prehospital vital signs represent initial monitor recordings and may differ from emergency department measurements due to transport conditions or early interventions. Finally, this was a single-center study, which may limit generalizability, although the large sample size supports internal validity.
Conclusion
In this retrospective trauma cohort, point-of-care hemoglobin demonstrated limited incremental value for identifying patients requiring early or higher-intensity transfusion. In contrast, FAST examination and systolic blood pressure—particularly hypotension and low-normal values on emergency department arrival—were consistently associated with transfusion need, earlier transfusion, and greater transfusion volumes. These findings support prioritizing physiologic assessment and FAST imaging over point-of-care hemoglobin when guiding early transfusion decisions in the trauma bay. Prospective studies are needed to evaluate whether point-of-care hemoglobin, when integrated with physiologic parameters and FAST imaging, can meaningfully contribute to early hemorrhage recognition. Such studies may help define the optimal role of point-of-care diagnostics within trauma resuscitation workflows.
Footnotes
Ethics Considerations
This study was approved by the site’s Institutional Review Board (IRB #4820) with a waiver of informed consent due to the retrospective use of deidentified data.
Author Contributions
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
The data supporting the findings of this study are available from the corresponding author upon reasonable request.