Anti-Nform antibody in hemodialysis patients

The anti-Nform antibody is produced by dialysis patients following reuse of dialyzers sterilized with formaldehyde and it has been implicated as a cause of hemolytic anemia. Formaldehyde is one of the common disinfectants used for reprocessing capillary hemodialyzers. The safety of formaldehyde and the clinical significance of anti-Nform antibody need further evaluation. Amongst 45 patients practising dialyzer reuse, anti-Nform antibody was detected in 5 (11.1%), but not amongst 111 patients not reusing their dialyzer (p < 0.005). The presence of anti-Nform was not related to the sex, or duration of dialysis with positive anti-Nform antibody. Direct Coombs' test was positive amongst 80% of all tested patients with anti-Nform antibody, and in 38% of patients reusing dialyzers but without anti-Nform antibody. No tests of hemolysis (including direct Coombs' test) discriminated between anti-Nform antibody-positive and -negative patients, nor between anti-Nform antibody patients with and without overt hemolysis. The best diagnostic test for hemolysis in anti-Nform antibody-positive patients was hematocrit rise after cessation of dialyzer reuse. It appears that despite the induction of anti-Nform antibody, hemolysis is rarely a serious consequence of dialyzer reuse.