The Relationship of Serum 25-Hydroxyvitamin D at Admission and Severity of Illness in COVID-19 Patients.

Background: COVID-19 is a rapidly propagating respiratory virus causing a global pandemic. At the time of development of this study, not much was known about susceptibility to severe illness, especially without other known risk factors. Retrospective research suggested vitamin D level may correlate with severity of illness. This prospective, observational study seeks to determine if vitamin D level at admission is correlated with severity of illness as determined by needing intensive care unit (ICU)-level care within this first 28 days after admission. This study also looked at the relationship of vitamin D level at admission and mortality, need for ventilator, and number of hospital-free, ICU-free, and ventilator-free days in the 28 days after initial admission.

Methods: This study is a prospective, observational study of patients admitted to Brooke Army Medical Center (BAMC), San Antonio, TX, for a diagnosis or complication of COVID-19 illness. A vitamin D level was drawn at admission and chart review was used at the end of 28 days after admission to identify outcome measures. Fisher's Exact test was used for categorical variables, and Kruskal-Wallis test was used for all continuous variables.

Results: Deficient vitamin D level at admission (less than 20ng/mL) was associated with an increased risk of requiring ICU-level care during the 28-day period after initial admission (p=0.028). Secondary outcomes measurements also favored the hypothesis, but none were statistically significant.

Conclusions: This prospective, observational study further strengthens the hypothesis vitamin D level at admission is correlated with severity of illness in COVID-19 illness; however, this small study was limited in its ability to control for confounders. It does not prove causation, nor does it imply vitamin D supplementation will prevent COVID-19 or improve outcomes in COVID-19. Further research should aim to include a larger cohort to better understand the relationship of vitamin D level and severity of illness in COVID-19 disease.