BCSH-NIBSC ANTI-D REFERENCE REAGENT FOR ANTIGLOBULIN TESTS - THE IN-HOUSE ASSESSMENT OF RED-CELL WASHING CENTRIFUGES AND OF OPERATOR VARIABILITY IN THE DETECTION OF WEAK, MACROSCOPIC AGGLUTINATION

A batch of an anti-D preparation, reference 91/608, has been prepared for the preparation of red cells weakly sensitized with IgG that can r eveal inhibition of the antiglobulin test by one volume of human serum , diluted 1: 1000. The preparation provides an objective assessment of red cell washer efficacy and the confidential, in-house assessment of operator variability in detecting weak but definite macroscopic agglu tination by blind, replicate tests. Red cell washer efficacy and poor operator reading procedures causing disruption of weak agglutination a re two major causes of false-negative antiglobulin tests; neither are adequately detected by the common quality-control procedure of adding strongly IgG-sensitized red cells (Coombs control cells') to apparentl y negative antiglobulin tests. However, weakly IgG-sensitized red cell s do offer a valuable control function that can detect some degree of cell washer inefficiency and reading errors although such cells are no t a substitute for the more sensitive replicate testing. Test protocol s are provided to assess the efficacy of cell washing machines and ope rator skills in the detection of weak but definite macroscopic aggluti nation.