TARTRATE-RESISTANT ACID-PHOSPHATASE (TRAP ) IN SECONDARY HYPERPARATHYROIDISM - IS IT A MARKER OF BONE-RESORPTION IN PATIENTS ON HEMODIALYSIS AND PERITONEAL-DIALYSIS

We have studied the relationship between tartrate-resistant acid phosp hatase (TRAP) and other parameters of bone metabolism, such as intact PTH, osteocalcin (OC) and alkaline phosphatase (AP) in 68 patients tre ated on hemodialysis and 54 on CAPD. The average age was 54 +/- 14 yea rs for HD and 53 +/- 14 for CAPD patients. The mean time on dialysis w as 70 +/- 67 months on HD and 34 +/- 25 on CAPD (p < 0.01). Fifty per cent of patients on HD and 52 % on CAPD were males. The prevalence of Diabetes Mellitus was 11.7 % on HD and 29.6 % en CAPD (p < 0.05). Echo graphic signs of chronic hepatopathy were present among 19.1 % on HD a nd 5.6 % on CAPD (p < 0.05). Serum levels of TRAP were elevated in eve ry patient on HD and all except one, on CAPD. Serum TRAP levels among HD patients were higher than those on CAPD (8.2 +/- 2 vs 6.9 +/- 15 UI /l, p < 0.001). Plasma PTH and OC levels were also higher in HD patien ts (343 +/- 431 vs 129 +/- 109, p < 0.05 and 37.3 +/- 24,9 vs 14.6 +/- 7,9 ng/ml, p < 0.001 respectively). TRAP serum levels showed the foll owing significant correlations among HD patients: PTH (r = 0.37), AP ( r = 0.26) and OC (r = 0.44). On the contrary, on CAPD patients TRAP on ly correlated significantly with serum creatinine (r= 0.61). Gender, d ialysis membrane or dialysate did not influence these relationships. W hen different degress of hyperparathyroidism were considered, for pati ents with PTH lower than 350 pg/ml the correlation between TRAP and OC was the only one maintened, correlations between TRAP and PTH and AP wese lost. Patients on HD taking calcium channel blockers showed lower values of serum TRAP (7.3 +/- 1.5 vs 8.7 +/- 2 UI/l, p < 0. 05). No d ifferences related to age, sex, time on dialysis, plasma PTH or doses of calcium carbonate, aluminum hydroxide or calcitriol were found. Dib etes Mellitus or chronic hepatopathy did not influence TRAP levels. Am ong 4 patients, after parathyroidectomy we observed a decrease of 16-7 5 % in the previous TRAP levels in the first 10 days. However, AP also diminished after the procedure, but in a slower manner. In me patient who showed the lowest decrease of TRAP levels, this was a consequence of incomplete parathyroidectomy. We conclude that TRAP serum levels a re elevated among almost all dialysis patients. Secondary hyperparathy roidism is the main reason for this increase in HD patients. On CAPD p atients serum creatinine also shoved a direct influence on TRAP levels , the origin of which remains to be determined. From our point of view , TRAP serum levels constitute a new tool for the interpretation of th e phenomena related to renal osteodystrophy.