Effects of comorbidities on COVID-19 biomarkers: a retrospective study

INTRODUCTION

Coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the most dreaded pandemic of recent times. A significant proportion of the COVID-19 patients have been reported to suffer from other pathophysiological conditions as well. COVID-19, caused by SARS-CoV-2, represents the most devastating pandemic in recent history. A substantial number of patients suffer from various pathophysiological conditions alongside COVID-19 infection. Comorbidities often lead to adverse outcomes.¹ Numerous researchers have documented poor prognoses resulting from COVID-19-associated comorbidities, particularly acute and chronic conditions.^2-6 Consequently, this investigation was undertaken to address these concerns.

Objectives

Diabetes, CVD, renal and pulmonary diseases, are frequently observed comorbidities that increase the case fatality rate in acute respiratory diseases caused by SARS-CoV. The present investigation was aimed at assessing the effects of comorbidities on biomarkers of COVID-19.

METHODS

This retrospective cohort study analysed data from 369 COVID-19 patients admitted to Viveka Hospitals, Nagpur, Maharashtra, India, between April 1, 2020, and July 31, 2021. Biomarkers including D-dimer, ferritin, CRP, and LDH, along with comorbidities, were documented at admission, day 15, and day 30 post-discharge from hospital records. Multimorbidity classification was performed using the Charlson multimorbidity index (CCI).⁷

Study design

It was a retrospective cohort study.

Study size

The 369 COVID-19 patients selected for the study.

Inclusion criteria

The study included all adults (> 18 years old) hospitalized in non-ICU isolated patients with COVID-19 infection confirmed by “nasopharyngeal reverse transcription polymerase chain reaction (RT-PCR) positive for SARS-CoV2” of all disease severity.

Exclusion criteria

The study excluded all adults (>18 years old) hospitalized in ICU isolated patients with COVID-19 infection confirmed by “nasopharyngeal RT-PCR positive for SARS-CoV2 of all disease severity.

Statistical analysis

Data was analysed using chi-square test and ANOVA. The study was initiated after approval from the institutional ethics committee.

RESULTS

Comorbidity, multimorbidity and CCI-wise distribution of COVID-19 patients (n=368)

The study revealed diabetes as the most prevalent comorbidity (44.87%), followed by HTN (27.07%) and CVD (25.78%). A substantial majority (79.95%) presented with combined DM+CVD+HTN. The CCI distribution showed 39.02% patients with CCI score 2, while 26.28% had a score of 3. Most patients exhibited multiple comorbidities, with isolated conditions being rare (DM: 1.90%, CVD: 0.54%) (Table 1).

Gender-wise comorbidity

Table 2 shows that males comprise 89.67% (n=330) and females 10.33% (n=38). The triple comorbidity DM+CVD+HTN was most prevalent, affecting 78.79% of males and 92.11% of females. CVD+HTN was present in 13.64% of males and 7.89% of females. Isolated DM occurred in 2.42% of males only, while isolated CVD was rare (0.61% in males). Additional comorbidities including arthritis, bronchitis, and asthma were found exclusively in males (4.55%). Statistical analysis revealed no significant gender-based association with comorbidity patterns (χ²=4.494, p=0.481).

Age-wise comorbidity

The study showed that the predominant comorbidity pattern was DM+CVD+HTN, affecting 295 patients (80.16%), with highest prevalence in the 46-59 age group (83.55%). The 26-45 age group was largest (43.48%), followed by 46-59 years (41.30%). Isolated comorbidities were rare: DM in 2.17% and CVD in 0.54% of patients. CVD+HTN affected 13.04% overall, particularly in older patients (18.37% in >60 years). Additional comorbidities including arthritis, bronchitis, and asthma were present in 4.08% of patients. Statistical analysis (χ²=21.993, p=0.108) revealed no significant association between age groups and comorbidity distribution pattern. The biomarker analysis revealed distinct patterns across different comorbidity combinations.

D-dimer and comorbidity

D-dimer levels showed considerable variation, with isolated diabetes patients displaying the highest initial mean values (1177.88±855.17 ng/ml), while isolated CVD patients had the lowest (351±258.8 ng/ml).

However, these differences were not statistically significant at admission (F=0.63, p=0.67), 15 days post-discharge (F=0.76, p=0.58), or 30 days post-discharge (F=2.1, p=0.06). Notably, CVD+HTN patients exhibited elevated D-dimer levels at 30 days (644.88±1698.23 ng/ml).

Ferritin and comorbidity

Ferritin levels demonstrated similar non-significant patterns across comorbidity groups. Initial ferritin was highest in isolated diabetes patients (499.44±490.71 ng/ml) and lowest in isolated CVD patients (143.5±58.68 ng/ml), with p=0.88. At 15 days, CVD+HTN patients showed elevated levels (374.61±1146.95 ng/ml), though this remained statistically insignificant (p=0.53).

By 30 days, isolated CVD patients paradoxically showed increased ferritin (355±205.06 ng/ml), but overall differences remained non-significant (p=0.77).

CRP and comorbidity

CRP levels exhibited no significant associations with comorbidity patterns at any time point (initial: p=0.96; A15D: p=0.74; A30D: p=0.48).

Isolated CVD patients consistently showed elevated CRP initially and at 15 days (86.35±11.81 mg/l), while CVD+HTN patients demonstrated the highest values at 15 days (109.21±377.32 mg/l). However, these elevations lacked statistical significance.

LDH and comorbidity

In stark contrast, LDH levels showed highly significant associations with comorbidity status. Patients with isolated diabetes demonstrated markedly elevated LDH levels both initially (1726.6±4137.34 U/l) and at 15 days (1726.63±4137.34 U/l), significantly higher than all other comorbidity groups (F=8.99, p=0.000 and F=9.07, p=0.000, respectively).

The DM+CVD+HTN combination, CVD+HTN, and DM+CVD+arthritis/bronchitis/asthma groups showed relatively similar LDH values ranging from the 227-297 U/L.

Isolated CVD patients maintained intermediate levels (462.5±183.14 U/l), while CVD+HTN/asthma/bronchitis patients had the lowest values (123-151.67 U/l).

*a-dsimilar superscripts differ significantly.

DISCUSSION

Comorbidity-wise distribution of COVID-19 patients

Multiple studies have documented that comorbidities such as CVD and HTN combined with DM represent the most common conditions in COVID-19 patients.^8-10 The current investigation revealed a higher prevalence of DM (44.87%), HTN (27.07%), and CVD (25.78%) among participants. Prior research demonstrated a comorbidity rate of 50.7%, with HTN (21.6%) and DM (15%) being the most frequent.¹¹ Another study identified HTN (16.9%) as the predominant comorbidity, followed by diabetes (8.2%).¹² Various studies have established chronic diseases and COVID-19 infection as associated with diverse risk factors, including DM, obesity, HTN, heart failure, COPD, chronic kidney disease, and CVD.^4,13-19

The present study demonstrated that approximately 65.3% of patients had a CCI score of 2-3, with only 2.7% having scores of 6-7. A systematic review and meta-analysis of hospitalized patients revealed that CCI scores ≥3 correlated with increased mortality, with each point increase raising mortality risk by 16%.²⁰

Gender-wise comorbidity

In India, males and elderly individuals demonstrated greater susceptibility to COVID 19.²¹ This study revealed higher comorbidity prevalence in males. COVID-19 mortality rates for infected individuals were 2.8% in Chinese men compared to 1.7% in Chinese women.²² Biological variations in immune systems between genders may influence COVID-19 resistance. Males exhibited increased vulnerability due to distinct lifestyle factors including smoking, drinking, working patterns, sex hormones, HTN, and additional comorbidities.²³ Women naturally generate higher levels of interferon, particularly type I interferon and T lymphocytes, which eliminate infected cells. The female hormone estradiol provides infection protection. Conversely, research suggests testosterone may suppress male immune responses, potentially explaining the observed gender disparity.^24,25

Age-wise comorbidity

Comorbidities such as CVD+HTN+DM are highly prevalent in older adults and have been associated with worse outcomes in COVID-19.²⁶ The present investigation demonstrated that the predominant comorbidity pattern was DM+CVD+HTN, affecting 295 patients (80.16%), with the highest prevalence in the 46-59 age group (83.55%). According to a study, older adults with comorbidities were the most vulnerable for adverse outcomes, the risk of adverse outcomes among older adults without comorbidities was less than that of younger adults with comorbidities.²⁷ Another study reported that HTN (8.8%), DM (7.67%), and CVD such as CHF and hypothyroidism (p=0.0481), were higher in incidence among the age group 60-69 years and were statistically significant (p<0.0001). It was also seen that DM+HTN were notably more common in ages 70-79 years, 50-59 years, and 40-49 years.²⁸

D-dimer and comorbidity

The current study demonstrated that isolated diabetes patients had the highest D-dimer levels, though insignificant. Multiple studies revealed a significant association between high D-dimer level and severity of COVID-19 among diabetic patients.^29-31 A study reported that diabetics were associated with higher levels of D-dimer compared to non-diabetics.³² The present study also showed the lowest D-dimer for isolated CVD patients. In contrast, the high D-dimer concentrations have been reported to be associated with CVD and prognosis in COVID-19 patients.^33,28

Ferritin and comorbidity

The present study demonstrated the highest mean ferritin levels in DM patients and the lowest in CVD. COVID-19 patients with one or more comorbidities, DM, thrombotic complications, and cancer had significantly higher levels of ferritin than those without (p<0.01).³⁴ Multiple studies revealed that patients with diabetes had higher ferritin levels than those without.³⁵ Multiple scientists have reported that the serum ferritin levels of patients with DM significantly increased with increasing HbA1c levels (p<0.01) in non-COVID-19 patients.³⁶ Perhaps the trend of increasing ferritin in diabetic patients has also been reflected in COVID-19 patients.³⁷

The present study demonstrated higher levels of ferritin in patients with HTN as a comorbidity. The prevalence of HTN increased as ferritin levels increased in non-COVID individuals.³⁷ However, a study reported that COVID-19 patients with HTN had slightly lower levels of ferritin than those patients who were without WMD.³⁴

CRP and comorbidity

CRP has been found as an important marker that changes significantly in severe patients with COVID‐19.³⁸ In the present study, the highest CRP levels were observed in COVID-19 patients with CVD in the initial days of the illness. Scientists also reported a higher mean difference in CRP (78.2 mg/l) (p<0.001) for ≥3 comorbidities.³⁸ DM+HTN were significantly correlated with CRP level (p=0.05), whereas dyspepsia did not demonstrate a significant relationship with CRP level (p>0.05).

Patients with HTN had a 2.709-fold risk of having increased CRP levels compared with patients without HTN.³⁹ Studies demonstrated that serum CRP were significantly higher in COVID-19 diabetic patients. This occurs because of the inflammatory reaction and tissue damage that occurs, and the increase in CRP is closely related to the severity of the DM condition that accompanies COVID-19 patients.

LDH and comorbidity

The current investigation found that individuals with diabetes alone exhibited significantly increased LDH levels, a finding consistent with previous research demonstrating higher LDH in diabetic individuals.³⁵ The levels of LDH, CRP and glucose on admission can each individually able to predict 75% or more of COVID‐19 severity.⁴⁰ LDH was a greater predictor of severity compared to glucose and CRP alone (p<0.001). LDH did not change even after the 15 days post-discharge.

Limitations

Study limited for Nagpur district (MH, India) only.

CONCLUSION

The biomarkers viz., D-dimer, ferritin and CRP and LDH recorded at admission, after 15^th day and 30^th day of discharge were retrieved from the hospital records. The presence of comorbidity was not substantially correlated with either gender (p=0.481) or age (p=0.108). CVD patients had the highest CRP levels, while diabetic patients had the highest d-dimer, ferritin, and LDH values. Initial assessments of d-Dimer, ferritin, and CRP, as well as follow-ups at 15 and 30 days, revealed no significant changes (p>0.05) between groups with diabetes and other comorbidities. In contrast, patients with diabetes had substantially different mean LDH levels (p=0.00) than those with other comorbidities. In terms of comorbidity, the COVID-19 biomarkers, such as d-dimer, ferritin, and CRP, did not differ substantially. When comorbidity is present, the mean LDH levels change dramatically. The mean levels of COVID-19 biomarkers-D-dimer, ferritin, and CRP-measured at admission and at 15- and 30-days post-discharge showed no significant differences across comorbidity groups. In contrast, LDH levels at two time points differed significantly with respect to comorbidity. This significant variation in LDH suggests that it may serve as a useful indicator for assessing disease severity in patients with comorbid conditions.

ACKNOWLEDGEMENTS

Authors would like to thank to Viveka Hospitals, Nagpur, Maharashtra, India for extending support in carrying out the research.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee of Viveka Hospitals, Nagpur, Maharashtra, India with Reg. No. ECR/1639/INST/MH/2021

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