Interference by the new antibiotic cefpirome and other cephalosporins in clinical laboratory tests, with special regard to the "Jaffé" reaction.

The new cephalosporin, cefpirome, was investigated for its possible interference in clinical laboratory tests, especially the determination of creatinine. Tests for bilirubin, cholesterol, protein, urea, and uric acid were also studied. A selection of commercially available compounds such as cefoperazone, cefazolin, cefamandole, cefoxitin, latamoxef, ceftriaxon, cefotiam, cephaloridine, cephalotin, cefotaxime, cefazedone and cefuroxime, and cefodizime (a compound under development) were also included in these investigations. Interference was found only with the "Jaffé method" for the determination of creatinine. Pronounced interactions with alkaline picrate were observed with cefpirome, cefoxitin, cephalotin and cephaloridine, whereas the other compounds showed only weak reaction or no reaction at all. The cephalosporins did not interfere in any of the other tests mentioned above. Care must therefore be taken in the determination of creatinine in samples from patients under treatment with these drugs. The assay methods of choice at present are enzymatic or specific HPLC assays.