Abstract
Introduction
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel pathogen that caused an outbreak of coronavirus disease (COVID-19) in 2019, spreading rapidly throughout the world. 1 Diabetes mellitus (DM) is one of the most common comorbidities in COVID-19 patients, and it is linked to catastrophic outcomes such as intensive care unit (ICU) admission, invasive ventilation and mortality. 2 COVID-19 individuals with diabetes have a 10% mortality rate, according to a recent study from the United Arab Emirates. 3 In newly diagnosed diabetic individuals, rates of mortality and the need for mechanical ventilation were also found to be substantially higher than for those with pre-existing diabetes. Accordingly, COVID-19-infected patients are negatively affected by uncontrolled hyperglycaemia. 4 Pre-diabetes is a long-lasting state in which glycaemic levels vary. Pre-diabetes are at a high risk for developing type 2. 5 Several studies have established the association between poor outcomes of COVID-19 and pre-diabetes.6,7 ICU admissions and longer hospital stays were also found to be more frequent in COVID-19 patients with pre-diabetes. 8
Neutrophils have prognostic value for COVID-19 severity. The activation and quantity of neutrophils were reported to correlate with the severity of COVID-19 outcomes. 9 A positive correlation was also established between neutrophil count, C-reactive protein (CRP) and D-dimer with disease progression. 10 More recently, we assessed the association of vitamin D deficiency with clinical presentation of COVID-19 and we found that inflammatory markers were negatively correlated with vitamin D level in COVID-19 patients. 11 Vitamin D deficiency was found to be prevalent in hyperglycaemic patients. 12 Accordingly, the current study aimed to evaluate the correlation between neutrophilia and inflammatory response markers and 25(OH)D level in hyperglycaemic COVID-19 patients.
Subjects and Methods
Study design and participants
This is retrospective observational study included 514 COVID-19 patients, aged 23–88 years, who were admitted to Prince Mohammed Bin Abdulaziz Hospital in Riyadh, Saudi Arabia, between January 2021 and October 2021. They were diagnosed by reverse transcription polymerase chain reaction (RT-PCR), and further assessment was done by computed tomography (CT) scans of the chest.
All patients received the same treatment protocol (i.e., oseltamivir, azithromycin, hydroxychloroquine and paracetamol), without corticosteroid therapy, and their regular treatment for diabetes and hypertension.
Inclusion criteria
For the control groups, COVID-19 patients with no clinical or laboratory evidence of DM or any other disease were included. For the hyperglycaemic patients, COVID-19 patients with type 2 diabetes were included. Hyperglycaemia was defined as haemoglobin A1C (HbA1c) levels of 5.7–6.4% for pre-diabetes and HbA1c levels of ≥6.5% for DM. 13
Exclusion criteria
The exclusion criteria for both the control and patient groups included the following: 1) patients with malabsorptive states, metabolic syndrome, gestational diabetes or type 1 diabetes, and 2) patients with other diseases such as hepatic diseases, chronic illness, malignancy, renal diseases or any blood diseases. In addition, to ensure the true measurement of serum 25(OH)D and cytokine levels, patients who received vitamin D or calcium supplementation and patients who were undergoing anti-inflammatory treatment were excluded from the study.
Data collection
The demographic and clinical data of all included patients were obtained from hospital electronic records and databases and analysed independently by two researchers. The procedures were carried out after receiving prior approval from the research ethics committee of Taif University (42-0010).
Laboratory analysis
The Bio-Rad VARIANTTM HbA1c Program (Bio-Rad Laboratories, Inc., Hercules, CA, United States) was used to evaluate HbA1c level, which was measured using high-performance liquid chromatography (HPLC). Haematological analysis—including the measurement of complete blood count (CBC), erythrocyte sedimentation rate (ESR) and D-dimer—and serum biochemistry assays—including the measurement of CRP, ferritin, folate and 25-hydroxy vitamin D (25(OH)D)—were performed. Blood samples were obtained in ethylenediaminetetraacetic acid (EDTA) tubes for CBC, following the protocol outlined by the manufacturer (i.e., Beckman Coulter). The total amount of neutrophils in the white blood cell (WBC) count is known as the absolute neutrophil count (ANC). This is usually done as part of a differential CBC. The ANC is calculated by multiplying the total number of WBCs by the neutrophil percentage and dividing by 100. 14 Neutrophilia and neutropenia were considered present if the ANC was above 7.5 × 109/L or less than 1500 cells/mm³, respectively. 14 Sodium ESR was measured by collecting blood in a blacktop ESR vacuum tube using the Westergren method.
According to the manufacturer protocol, 25(OH)D serum level was measured using an Abcam human vitamin D enzyme-linked immunosorbent assay (ELISA) kit. The assay’s sensitivity was 1.98 ng/mL, and the measurement range was 0.5–1010 ng/mL. Vitamin D deficiency was considered present when the serum level of vitamin D was < 20 ng/mL. Serum CRP was measured with an autoanalyser and immunoturbidimetric analysis (CRP II Latex X2; Denka Seiken). Serum-ferritin levels were evaluated using an ELISA kit (RCD012 R, BioVendor), as was plasma D-dimer (NB 110–8376, Novus Biologicals). Folate was measured using a human folic acid ELISA kit (Colorimetric; NBP2-59966, Novus Biologicals) with a detection range of 12.5–200 pg/mL. Vitamin B12 was determined using a human vitamin B12 ELISA kit (Cat. No. VB369B, Calbiotech, El Cajon), and the detection range was 100–2000 pg/mL.
Statistical analyses
The data were analysed using appropriate statistical tests within SPSS version 20.0 (SPSS Inc., Chicago, IL, United States). Quantitative data were expressed as mean ± standard deviation (SD) and median (interquartile range; IQR), and they were tested using an analysis of variance (ANOVA) followed by Tukey’s honestly significant difference (HSD) and a Kruskal–Wallis test. Multiple comparisons between categorical groups were performed through post-hoc tests. Qualitative data were expressed as frequency and percentage, and a chi-squared (χ2) test was applied. The association between NAC and the studied parameters was assessed using the Pearson correlation coefficient. The confidence interval was set to 95%, and the significance level was set at p < 0.05.
Results
Demographic, clinical and laboratory characteristics of the study groups.
*p < 0.05, **p < 0.01.
aStatistically significant difference with the non-diabetic group.
bStatistically significant difference with the pre-diabetic group.
Laboratory findings related to neutrophil count in the study’s patients.
*p < 0.05, **p < 0.01.
Comparison between neutrophil count and studied variables.
*p < 0.05, **p < 0.01.
aStatistically significant difference with normal count.
bStatistically significant difference of neutrophilia with neutropenia.
The correlation between neutrophil count and the other variables in the studied groups was then further analysed. Figure 1 demonstrates that the ANC were positively correlated with age (r = 0.201), CRP (r = 0.239), ESR (r = 0.194), D-dimer (r = 0.153) and ferritin (r = 0.214; p < 0.001). In contrast, 25(OH)D showed a significant negative correlation with ANC (r = −0.027; p < 0.001). Scatter plot of comparison between neutrophil count and age (a), 25(OH)D (b), CRP (c), ESR (d), D-dimer (e) and ferritin (f). The ANC showed a significant positive correlation with age, CRP, ESR, D-dimer and ferritin, and a significant negative correlation with 25(OH)D (p ≤ 0.001).
Discussion
In the current study, the majority of enrolled Coronavirus disease (COVID-19) patients (70.6%) were with hyperglycaemia. Also, we found that the pre-diabetic and diabetic groups included elderly patients and had a higher level of C - reactive protein (CRP), a higher erythrocyte sedimentation rate (ESR) and a significant elevation in D-dimer.
In accordance with our findings, Alguwaihes, Al-Sofiani 15 reported a higher incidence of Diabetes Mellitus (DM) (300 out of 439) among hospitalised COVID-19 patients. A nationwide study in China reported that patients with severe COVID-19 were associated with a higher prevalence of DM than were those with a non-severe form of the disease (16.2% vs. 5.7%). 16
Age and elevated inflammatory markers predict COVID-19 progression. 17 It has been reported that elderly diabetic individuals are at a higher risk of developing complications from COVID-19, resulting in a higher proportion of intensive care unit (ICU) admission and a greater mortality rate.18–20 Further, Hui et al. 21 found that diabetic patients had a higher median age (p = 0.001) than did non-diabetic patients.
Inflammatory markers such as ESR, CRP, and ferritin are significantly correlated with COVID-19 severity and outcomes.22–24 CRP is a partial mediator of the correlation between the severity of COVID-19 and DM, confirming the importance of inflammation in the pathogenesis of COVID-19 severity in diabetic patients. 25 Similar to our findings, Guo et al. 26 found that diabetic patients had a higher level of CRP (44.8 mg/L vs. 25.8 mg/L; p = 0.003) compared with non-diabetic patients with COVID-19. Moreover, it has been established that COVID-19 patients with DM have higher levels of inflammatory biomarkers such as CRP and ESR than do non-diabetic patients, reflecting the severity of infection in this group.3,27 D‐dimer is a thrombotic biomarker and one of the main psychopathological aspects of COVID-19. 28 Consistent with our results, Miri et al. 29 reported a higher level of D-dimer in diabetic patients compared to non-diabetic patients. Moreover, it has been reported that the high D-dimer level in diabetic patients is significantly associated with COVID-19 severity.30,31
Regarding neutrophil level, our results found a significant difference among the categorical groups (i.e., patients with a normal neutrophil count, neutropenia and neutrophilia) in terms of age (p < 0.001), 25(OH)D (p = 0.012), CRP (p < 0.001), ESR (p < 0.001), D-dimer (p < 0.001) and ferritin (p < 0.001). Thus, we then investigated whether there is a relationship between change in neutrophil count and age, inflammatory markers (i.e., CRP, ESR and ferritin), thrombotic marker (i.e., D-dimer) and 25(OH)D. Expectedly, it was found that age, inflammatory markers (i.e., CRP, ESR and ferritin) and thrombotic marker (i.e., D-dimer) were all significantly and positively correlated with the change in ANC (p < 0.001).
Neutrophils have prognostic value for COVID-19 severity. It has been reported that neutrophilia predicts poor outcomes in patients with COVID-19 and severe respiratory failure. 32 An elevated neutrophil count is an immunological phenotype of severe COVID-19. 33 The activation of neutrophils in the lungs causes cytotoxicity, inflammation and overall lung damage. Based on the fact that collateral lung damage leads to hypoxemic respiratory failure, neutrophils have recently been suggested to have a role in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), both of which are associated with COVID-19. 33 In a retrospective study of COVID-19 patients’ initial laboratory indices, 34.5% were found to have neutrophilia, and patients with ARDS had more neutrophils than did those without ARDS (p < 0.001). 30
The function of circulating neutrophils in COVID-19 patients is significantly impacted in a variety of ways, including increased neutrophil extracellular trap (NET) formation, increased reactive oxygen species generation (i.e., oxidative burst) and enhanced phagocytosis. Numerous studies have identified the changes in NETosis and oxidative burst in COVID-19. 33 Some researchers believe that NETs may play a role in the abnormal immunological response seen in patients with high neutrophil counts and SARS-CoV-2 infections.33,34
A higher neutrophil count is an infection-related biomarker that predicts a poor prognosis for COVID-19. It has been reported that NETs can contribute to inflammation-associated lung damage, fibrosis and thrombosis. 35 Previously, a positive correlation has been established between neutrophil count, CRP and D-dimer. 36
Much evidence has demonstrated the association between DM and vitamin D deficiency.37–39 Vitamin D deficiency was also found to be linked with the positivity and severity of COVID-19. 40 Further, similar to our study, the level of serum 25(OH)D was found to be adversely linked with neutrophil count and CRP level. 41
There are several limitations to our study. First, power analysis for sample size calculation was not done. Second, the design of the study was retrospective in nature, as participants were enrolled through hospital-based cohort groups; thus, the findings and data are limited to the accuracy of the hospital’s record keeping. In addition, the neutrophil level before the start of SARS-CoV-2 infection was not known for the included hyperglycaemic patients, and thus, we cannot define the causal relationship between neutrophil count and hyperglycaemia and its clinical implications as a marker of poor outcomes in hyperglycaemic COVID-19 patients. Information about other outcome variables related to disease severity, including in-hospital mortality and medication data, could not be obtained and analysed in this study. Last, the small sample size may not be a representative distribution of hyperglycaemic patients. Despite the study’s limitations, we believe that the findings of the current study are a valuable contribution to the limited literature on hyperglycaemic COVID-19 patients. The study may also provide endocrinologists and other clinicians with evidence-based recommendations to use in COVID-19 management and treatment.
Conclusions
We assessed neutrophil level and its association with the inflammatory response in hyperglycaemic patients with COVID-19. Our results suggest that neutrophilia is proportionally associated with the inflammatory markers of COVID-19 infection and adversely associated with 25(OH)D level in in pre-diabetic and diabetic patients.
Footnotes
Acknowledgments
The authors would like to thank Taif University, Taif, Saudi Arabia, for their support (Taif University Researchers Supporting Project number: TURSP-2020/80), Taif University, Taif, Saudi Arabia, the authors gratefully acknowledge the support of the Deanship of Scientific Research, Taif University.
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The work was funded by Taif University, Taif, Saudi Arabia. (Taif University Researchers Supporting Project number: TURSP- 2020/80).
