Background Human cathelicidin antimicrobial protein (hCAP18) is an antimicrobial and immunomodulatory peptide that has pleiotropic effects and is transcriptionally regulated by vitamin D. Because the administration of vitamin D analogues has been linked to decreased mortality among patients with end-stage renal disease, we hypothesized that low hCAP18 levels would identify those who are at increased risk of death attributable to infection while undergoing hemodialysis.

Methods We performed a case-control study nested in a prospective cohort of patients ([Formula: see text]) initiating incident hemodialysis. Case patients ([Formula: see text]) were those who died of an infectious disease within 1 year; control patients ([Formula: see text]) were those who survived at least 1 year while undergoing dialysis.

Results Mean (+/-SD) baseline levels of hCAP18 in case patients and control patients were [Formula: see text] ng/mL and [Formula: see text] ng/mL, respectively ([Formula: see text]). hCAP18 levels had a modest correlation with 1,25-dihydroxyvitamin D levels ([Formula: see text]; [Formula: see text]) but not with 25-hydroxyvitamin D levels ([Formula: see text]; [Formula: see text]). Patients with hCAP18 levels in the lowest tertile had a 2-fold increased risk (odds ratio, 2.1; 95% confidence interval, 1.2-3.5) of death attributable to infection; after multivariable adjustment, this relationship remained statistically significant (odds ratio, 3.7; 95% confidence interval, 1.2-11.2).

Conclusions In individuals initiating chronic hemodialysis, low baseline levels of hCAP18, a vitamin D-regulated antimicrobial protein, are independently associated with an increased risk of death attributable to infection.