Impact of Hospital‐Acquired Infection on Vitamin D Status in Critically Ill Patients

Abstract

Background Vitamin D appears to have important effects on human immune functions, including ex vivo upregulation of the antimicrobial peptide LL-37 in monocytes. Vitamin D depletion is common in critical illness (CI), but little is known about the inter-relationships between hospital-acquired infection and vitamin D status. Objective: Examine changes in blood levels of 25-hydroxyvitamin D [25(OH)D], vitamin D binding protein (VDBP), and LL-37 over time in critically ill patients with or without new bloodstream infections (BSI) or pneumonia (PNA). Methods Fifty-four subjects were dichotomized based on the presence or absence of new BSI (n=13) or PNA (n=12) diagnosed within 28 days of entry. Plasma 25(OH)D (chemiluminescence), VDBP and LL-37 (ELISA) were measured at baseline, 14 and 28 days. Mixed linear models were used for analyses. Results Subjects (age: 60 ± 13.6 yr) had severe CI (APACHE II: 21.3 ± 8.0) and 76% were vitamin D deficient (25(OH)D < 20 ng/mL). Baseline plasma 25(OH)D, LL-37 and VDBP were similar in those ± infection. However, 25(OH)D levels decreased significantly over time in subjects with PNA (P=0.002). LL-37 levels were unaltered over time ± infection and were unrelated to 25(OH)D levels. VDBP levels were unchanged in subjects with BSI, but increased over time in those without BSI (P<0.0001). VDBP levels remained unchanged in subjects with PNA, but rose over time in those without PNA (P=0.0003). Conclusions Changes in plasma 25(OH)D and VDBP were associated with prevalence of hospital-acquired infection in CI and may be an acute-phase response. Further study should investigate if such changes influence vitamin D bioavailability or susceptibility to infection.