Risk/benefit in prophylaxis and treatment of secondary hyperparathyroidism. A comparison of two low calcium peritoneal dialysis fluids

OBJECTIVE: A comparison of (i) levels of plasma ionized calcium (Ca), phosphate (P) and iPTH, (ii) risk of hypercalcaemia and (iii) need for Al-containing P binders, in patients on CAPD treated with calcium carbonate as the main P binder and twice weekly oral doses of alfacalcidol for control of secondary hyperparathyroidism during a 1 year follow-up after switching from a dialysis fluid with a Ca concentration of 1.75 mmol/l to 1.25 mmol/l (n = 39) or 1.35 mmol/l (n = 37).

RESULTS: In both groups, a significant initial increase of iPTH was seen. However, iPTH was again suppressed to baseline levels after 2-6 weeks of treatment. No statistically significant difference was observed between the two groups. In both groups median PTH levels were kept below 2.5 times the upper normal limit for non-uraemic patients; median P concentrations below 1.80 mmol/l and median iCa levels within 1.25-1.30 mmol/l. The incidence of hypercalcaemia was low and did not differ between the two groups (1.04 vs 1.20 cases of plasma iCa > 1.45 mmol/l per 100 treatment weeks). The proportion of patients requiring treatment with Al-containing P binders was unchanged from the start to the end of the study period, but significantly greater in the group dialysed with a Ca concentration of 1.25 mmol/l (an average of 21% as compared to 10% in the other group).

CONCLUSION: When changing from high Ca dialysate (1.75 mmol/l) to dialysate with a Ca concentration of 1.25 or 1.35 mmol/l, close attention to PTH control has to be paid during the initial months of treatment. Adequate control of plasma levels of iCa, P and PTH could be achieved with both lower Ca dialysates without either hypercalcemia or use of Al-containing P binders in the majority of patients. The small number of patients treated with Al-containing P binders, however, would probably benefit from dialysis fluids with even lower Ca concentrations.