Prevalence of histological β2-microglobulin amyloidosis in CAPD patients compared with hemodialysis patients

Background. The prevalence of beta 2-microglobulin amyloidosis (A beta(2)m) in patients on continuous ambulatory peritoneal dialysis (CAPD) is unknown. Methods. We prospectively obtained a median of 2 (range 1 to 4) joint samples from 26 CAPD patients aged 44 to 93 (median 73) years at post-mortem evaluation after 4.5 to 126 (median 27) months solely on CAPD (N = 19) or primarily on CAPD (that is, less than or equal to 10% and less than or equal to 1 year of renal replacement therapy time on other modalities: N = 7). The diagnosis of A beta(2)m rested on Congo red staining (typical birefringence) and positive immunostaining of amyloid deposits by a monoclonal anti-beta(2)m antibody. Results. A beta(2)m was diagnosed in 8 of 26 patients (31%). Prevalence ranged from 20% (2 of 10 patients) within less than or equal to 24 months CAPD to 30% (3 of 10 patients) after 24 to 48 months and 50% (3 of 6 patients) after 49 to 126 months (P = 0.11). The prevalence of A beta(2)m was similar in patients without or with one or more peritonitis episodes. No significant difference in prevalence (P = 0.118) was found between CAPD patients (8 +/26; 31%) and hemodialysis patients (13+/26; 50%) carefully matched for time on dialysis and age at the onset of dialysis. Conclusions. The prevalence of histological A beta(2)m reaches 31% after a median duration of 27 months of CAPD. This prevalence is not significantly different from that observed in a group of HD patients matched for age and dialysis duration.