D'Avolio · Nutrients 2020 · Retrospective case-control study · n=?

25-Hydroxyvitamin D Concentrations Are Lower in Patients with Positive PCR for SARS-CoV-2.

Cited 446 times in the scientific literature.

Level 4 - case-series / case-control

Retrospective observational comparison of PCR-positive versus PCR-negative patients.

PubMed 32397511 · doi:10.3390/nu12051359 · record verified 2026-08-31

What was done

Researchers retrospectively measured plasma 25-hydroxyvitamin D (25(OH)D) concentrations in a cohort of patients tested for SARS-CoV-2 by PCR in Switzerland, comparing levels between PCR-positive and PCR-negative individuals, with further stratification for patients older than 70 years.

What was found

Patients who tested positive for SARS-CoV-2 by PCR had significantly lower median 25(OH)D concentrations (11.1 ng/mL) than PCR-negative patients (24.6 ng/mL; p = 0.004). This significant difference persisted when evaluating patients aged >70 years.

Why it matters

This study provides early preliminary evidence linking lower circulating vitamin D levels with SARS-CoV-2 PCR positivity, supporting the rationale for prospective trials on vitamin D supplementation.

Limits

The abstract omits total sample size, demographics, and timing of blood sampling relative to infection. As a retrospective observational study, it cannot establish causality, rule out confounding, or exclude reverse causation where acute infection lowers plasma 25(OH)D levels.

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