FALSE INCREASE IN C-REACTIVE PROTEIN ATTRIBUTABLE TO HETEROPHILIC ANTIBODIES IN 2 RENAL-TRANSPLANT PATIENTS TREATED WITH RABBIT ANTILYMPHOCYTE GLOBULIN

Increased serum C-reactive protein (sCRP) is a sensitive marker of ren al graft rejection. We describe the cases of two children with uncompl icated renal transplantation who had false-positive sCRP values on ana lyzers using rabbit anti-CRP but values within the reference range wit h anti-CRP from other animal species. Cross-reaction with heterophilic antibodies was suggested by clinical and biological signs of serum si ckness and daily treatment with rabbit antilymphocyte globulin (ALG). The interference depended on the serum concentration of the cross-reac tant and was removed by subtotal IgG adsorption to Protein A or Protei n G or by immunoadsorption using rabbit ALG or total IgG in non-immune rabbit serum. Anti-rabbit IgG and IgM antibodies were detected in bot h patients. These are the first reported cases of cross-reaction with heterophilic antibodies in a turbidimetric CRP assay.