Dose of paricalcitol inversely associates with risk of hospitalization

Abstract

Background: Among patients receiving chronic HD, therapy with paricalcitol (Z) was associated with reduced mortality and morbidity compared to treatment with calcitriol (C). Furthermore, patients who did not receive any vitamin D therapy experienced highest mortality and morbidity. This study examined the hypothesis of a relationship between the dose of Z and subsequent hospitalization, more specifically, that patients receiving lower doses of Z would have a higher risk of being hospitalized. Methods: We performed a retrospective cohort study of patients new to HD who received treatment with Z or C between Jan 1999 and Dec 2001 using Poisson regression models. The primary exposure variable was the average dose/day, examined as categorical data by quintiles, during a 3‐month and then 12‐month follow‐up period excluding the days in hospitals. This latter exclusion was made due to uncertainty of the treatment during the period of hospitalization. Additional covariates included vitamin‐D group (Z vs. C), age, gender, race, and diabetes status, serum albumin, alkaline phosphatase, calcium, phosphorus, and iPTH. Results: We first examined dose of Z and C over a 3‐month period and then hospitalizations over the ensuing year. We did not find a dose‐response relationship in these analyses – i.e., dose over the first three months of dialysis is not associated with increased or reduced risk of hospitalizations during the ensuing 12 months. We then examined average dose of Z or C over the entire year and risk for hospitalization during the same year. Compared to total doses, average doses (total dose over the entire year divided by number of dialysis sessions during the same year) are less prone to bias. Risk of hospitalizations according to dose (lowest dose, Quintile 1) of injectable vitamin D is shown in the table below: Quintile HR 95% CI 1 1.093 1.025–1.165 2 1.073 1.007–1.143 3 1.055 0.990–1.124 4 1.050 0.978–1.116 5 1.0 REF Compared to those who received the highest doses of injectable vitamin D, those receiving the lowest had a 9% increased risk for a hospitalization. At each level, the risk for hospitalizations was 4% lower with Z compared to C. Conclusion: This pilot study indicates that higher average doses of Z are associated with a lower risk of hospitalization and suggests additional beneficial effects of vitamin D beyond mineral metabolism and PTH control.