Relationship between Serum Cobalamin Levels and Disease Severity in COVID-19 Patients

³ Cancer Research Center, Hamadan University of Medical Sciences, Hamadan, Iran

⁴ Department of Pathology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran

⁵ Department of Paramedicine, Amol School of Paramedical Sciences, Mazandaran University of Medical Sciences, Sari, Iran

⁶ Department of Biostatistics, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran

⁷ Department of Radiopharmacy, School of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran

*Corresponding author: Zahra Shaghaghi, Cancer Research Center, Hamadan University of Medical Sciences, Hamadan, Iran. Email: z.shaghaghi@umsha.ac.ir

EXTENDED ABSTRACT

Background

Coronavirus disease 2019 (COVID-19) ranges from mild respiratory illness to severe systemic disease characterized by acute respiratory distress syndrome, excessive inflammatory signaling, multiorgan dysfunction, and death [1–3]. Because severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to cause clinically important illness, nutritional and immunologic factors that may modify host susceptibility or disease progression have received considerable attention [4]. B-group vitamins, particularly vitamin B12 (cobalamin), support cellular metabolism, immune function, endothelial integrity, and regulation of inflammatory responses [5].

Cobalamin deficiency may increase reactive oxygen species and oxidative stress through elevations in methylmalonic acid and homocysteine, with potential consequences for endothelial dysfunction, platelet activation, tissue-factor expression, and coagulation [6]. The article also cites evidence supporting high-dose cobalamin as a potential adjunct in critical illness [7], while transcobalamin-mediated transport and vitamin B12 signaling have been linked to modulation of inflammatory cytokines and nuclear factor pathways [8,9]. Computational and biochemical evidence described in the article further suggests that cobalamin may interfere with SARS-CoV-2 replication, including inhibition of RNA-dependent RNA polymerase activity [10]. Given limited clinical evidence regarding cobalamin status and COVID-19 severity, this study evaluated serum cobalamin levels in hospitalized patients and examined their relationship with disease severity and prognosis.

Methods

This cross-sectional study included 117 hospitalized patients older than 18 years with COVID-19 who were admitted to Sina (Farshchian) Hospital in Hamadan, Iran, during 1401 (2022–2023). Initial diagnosis was based on clinical manifestations, including cough, dyspnea, chest pain, or fever, together with chest computed tomography findings; infection was confirmed by real-time PCR of nasopharyngeal swabs. Hospitalization criteria included a respiratory rate greater than 30 breaths/min, oxygen saturation below 93%, or pulmonary infiltration on computed tomography compatible with COVID-19.

Patients were categorized into three severity groups according to World Health Organization criteria [11]. The mild-to-moderate group had oxygen saturation of 90–93% and pulmonary infiltration below 50%. Severe disease was defined by oxygen saturation below 90%, pulmonary infiltration above 50%, and respiratory rate above 30 breaths/min. Critical disease included respiratory failure, shock, or multiorgan dysfunction with oxygen saturation below 88%. Demographic data, comorbidities and predisposing factors, and clinical symptoms were recorded. Information on prior vitamin B12 deficiency was also collected.

After at least 12 hours of fasting, approximately 8 mL of venous blood was collected in EDTA-containing tubes. Plasma was separated by centrifugation at 3000 g for 7 minutes and stored at -20 °C until analysis. Serum cobalamin was measured by ELISA using a Monobind kit and a Stat Fax 3200 analyzer. Continuous variables were analyzed with analysis of variance or Kruskal-Wallis testing, and categorical variables with chi-square testing. Significant omnibus comparisons were followed by Tukey or Dunn-Bonferroni post-hoc tests as appropriate. Binary logistic regression assessed associations of age, hospital stay, and cobalamin with mortality. Receiver operating characteristic (ROC) analysis evaluated the ability of cobalamin to discriminate death from survival and identified a cut-off value. Analyses were performed using SPSS version 26 and MedCalc. The study was approved by the Ethics Committee of Hamadan University of Medical Sciences (IR.UMSHA.REC.1401.519), and written informed consent was obtained from all participants.

Results

Among 117 patients, 47 were classified as mild-to-moderate, 46 as severe, and 24 as critical. Mean age increased across severity categories from 51.81±15.18 years in the mild-to-moderate group to 63.11±13.38 years in the severe group and 77.08±7.85 years in the critical group (P<0.001). Mean body mass index was 27.28±3.87, 28.41±4.37, and 31.38±5.15 kg/m², respectively (P=0.001). The most prominent difference involved serum cobalamin: mean levels were 1032.08±95.02 pg/mL in the mild-to-moderate group, 68.77±12.29 pg/mL in the severe group, and 51.35±3.58 pg/mL in the critical group (P<0.001). Women represented 66.0%, 60.9%, and 62.5% of these groups, respectively.

Table 1. Demographic and clinical characteristics of patients with COVID-19.

Clinical manifestations also varied with severity. Fever occurred in 23.40% of mild-to-moderate, 39.10% of severe, and 62.50% of critical cases (P=0.022). Chest pain was reported in 19.10%, 4.30%, and 0%, respectively (P=0.017), while fatigue was present in 36.20%, 54.30%, and 16.70% (P=0.022). Cough, dyspnea, palpitations, headache, sputum production, diarrhea, anorexia, and loss of smell or taste did not differ significantly across the three groups according to Table 1. Body temperature was similar among groups (P=0.953), whereas oxygen saturation decreased with increasing severity: 88.285±5.44% in mild-to-moderate disease, 85.05±6.47% in severe disease, and 82.71±8.11% in critical disease (P<0.001). Mean oxygen requirement increased from 7.10±1.77 L to 9.47±2.59 L and 11.46±3.60 L (P<0.001). Mean hospital stay similarly increased from 4.43±1.46 days to 6.83±4.71 days and 8.63±4.99 days (P<0.001).

Clinical outcome was strongly related to severity. All 47 mild-to-moderate patients were discharged and none died. In the severe group, 43 patients (93.5%) were discharged and 3 (6.5%) died; in the critical group, 18 (75.0%) were discharged and 6 (25.0%) died. The association between mortality and severity was significant (P=0.001). Patients who died had lower mean cobalamin levels than discharged patients in both sexes, while cobalamin concentrations were markedly higher overall in the mild-to-moderate group than in the severe and critical groups.

In binary logistic regression, length of hospital stay was significantly associated with mortality: each additional day was associated with an odds ratio of 1.23 (P=0.008), reported in the Results section as a 23% increase in mortality with age and cobalamin held constant. Age was not significant (OR=1.04, P=0.602), and the cobalamin coefficient was also not significant in this model (OR=0.981, P=0.812).

Table 3. Regression analysis with patient mortality as the dependent variable.

ROC analysis nevertheless showed good discrimination by cobalamin for mortality status. The area under the curve was 0.837 (P<0.001), with a 95% confidence interval of 0.758–0.899. At the reported cut-off of 57.5 pg/mL, sensitivity was 88.89% and specificity was 75.93%. According to the article, values below 57.5 pg/mL predicted death, whereas values above this threshold predicted hospital discharge.

Conclusion

Lower serum cobalamin concentrations were associated with greater COVID-19 severity, lower oxygen saturation, higher oxygen requirements, longer hospitalization, and worse clinical outcomes in this hospitalized cohort. Cobalamin also showed good ROC performance for discriminating mortality, although it was not independently significant in the reported multivariable logistic model. The authors concluded that vitamin B12 status may have prognostic value and that cobalamin supplementation could have beneficial effects in COVID-19; they recommended larger and longer-term studies to confirm these findings.

Keywords: Cobalamin, COVID-19, SARS-CoV-2, Vitamin B12

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