Association of seasonality and serum albumin concentration with vitamin D deficiency in subjects with chronic hepatitis C infection living in a sunny country.

Objective: This study aimed to analyse the relationship between vitamin D deficiency and the season when the blood sample was obtained from subjects with chronic hepatitis C (CHC) infection.

Design: A cross-sectional study was conducted on a representative sample. Vitamin D deficiency was defined as a serum 25-hydroxyvitamin D [25(OH)D] concentration <50 nmol/l, based on the values set forth by the Endocrine Society guideline for higher-risk populations. Seasonality was defined according to solstices and equinoxes. The association of seasonality and clinical/laboratory characteristics with vitamin D deficiency was assessed using a multivariate logistic regression analysis.

Setting: NUPAIG Viral Hepatitis Outpatient Clinic of the Universidade Federal de São Paulo - Brazil.

Participants: Adult subjects with CHC infection (n 306).

Results: The prevalence of vitamin D deficiency was 16 %, whereas the median serum 25(OH)D concentration was 87 (interquartile range, 59; third quartile = 118) nmol/l. Serum concentration was consistently lower in samples collected in spring and winter than in other seasons. In multivariate analysis, vitamin D deficiency was found to be independently associated with male gender, serum albumin concentration and with samples drawn in winter and spring.

Conclusions: The findings show not only the relevance to consider season as a factor influencing 25(OH)D concentration but also the need to actively screen for hypovitaminosis D in all patients with CHC infection, especially in females and those with low albumin concentration.