Calcium Use Increases Risk of Calciphylaxis: A Case-Control Study

Abstract

Objective To investigate the risk factors for the development of calciphylaxis in renal failure, a poorly understood and often fatal condition characterized by calcium deposition in tissues. Design Retrospective case-control study. Setting University hospital peritoneal dialysis center. Patients Eight continuous ambulatory peritoneal dialysis (CAPD) patients with calciphylaxis were identified in a 3-year period. We matched up to five controls for dialysis modality and length of time on dialysis with each case. Statistics Multivariate conditional logistic regression analysis for matched case-controls. Main Outcome Measures Laboratory data and demographics were collected as well as cumulative calcium and vitamin D ingestion over the year prior to disease onset. Results All the patients were female, versus only 38% (14/37) of controls ( p < 0.0001). While not statistically significant, a majority of the patients were diabetic [62.5% (5/8) vs 32% (12/37)]. Peak and average levels of serum calcium, phosphate, calcium x phosphate product, parathyroid hormone (PTH), albumin, iron, total iron-binding capacity (TIBC), and ferritin were not significantly different in cases compared with controls. The use of calcitriol alone or with calcium carbonate was not found to be a significant risk factor for the development of calciphylaxis. In a multivariate analysis, iron intake seemed to be protective, contrary to previous reports, while the use of calcium carbonate was associated with a strong trend to increased risk of calciphylaxis development (odds ratio = 1.029/g and 1.011/g calcium ingested per month, at 1 and 2 – 3 months prior to calciphylaxis development; p = 0.0556 and 0.0565, respectively). Conclusion These data, although limited by the small numbers of index cases, suggest that calcium ingestion is a risk factor for calciphylaxis. The increased use of calcium salts as a phosphate binder in recent years might explain the apparent increased incidence of calciphylaxis in our and other centers. The preponderance of female diabetics among cases reported elsewhere was confirmed in our study.