Evaluation of commercially available diagnostic test kits for rubella

Three standard hemagglutination-inhibition (HAI) methods were compared with 11 commercially available diagnostic test kits for determination of immunity and serologic diagnosis of rubella using a panel of 100 sera. The three standard HAI methods involved removal of serum inhibitors with kaolin, heparin-MnCl2, or dextran sulfate-CaCl2. The HAI kaolin (Flow Laboratories, McLean, Virginia) and Rubelisa (Microbiological Associates Bioproducts, Walkersville, Maryland) kits gave the best specificity as judged by the absence of false-positive results. Rubacell (Abbott Laboratories, Chicago, Illinois), Rubindex (Ortho Diagnostics, Raritan, New Jersey), Fiax (International Diagnostic Technology, Santa Clara, California), and Rubesure (Calbiochem-Behring, La Jolla, California) gave the best sensitivity as judged by the absence of false-negative results. The kits with the highest degree of both specificity and sensitivity were HAI kaolin (Flow), HAI heparin-MnCl2 (Flow), Rubacell (Abbott), and Rubindex (Ortho). In paired sera from five patients with clinical rubella, seroconversions were shown by seven of the kits. One of the kits, Cordia R (Cordis Laboratories, Miami, Florida), showed no significant rise in antibody titer with one pair of sera. Antibody titers in the same serum varied widely between the different kits.