Détection des alloanticorps antiérythrocytaires sur les équipements Groupamatic par une technique trypsine-polybrène-citrate

Abstract

Summary This new technique Trypsin-Polybren-Citrate (T.P.C.) is based on Lalezari's method. It comprises two steps : the first one being an unspecific agglutination due to the use of polybren, the second one a disagglutination phase due to the trisodium citrate, which breaks up the false agglutination but leaves the specific ones. 100 μl of plasma to be tested are mixed with 50 μl of crystallized trypsin pretreated red cell tests, and 50 μl of polybren. After 8 minutes of contact and 2 minutes of centrifugation, the previously warmed citrate is loaded in the cuvette by means of a supplementary pump located above the agitation station. This pump is the only mecanical modification needed for this technique. The sensitivity evaluation was made on selected samples collected either on EDTA, ACD or dry tubes. Homozygote red cell tests are preferably used, particularly for Kidd and Duffy antigens. The T.P.C. sensitivity is higher or equal to the one of the optimal manual reference technique for the Rh, Kell, Lewis and P systems. The T.P.C. sensitivity is equal to the one of the manual technique for the Kidd and Duffy systems ; on the other hand, some samples are not detected whathever their titer may be, without any relation with any parameter, trypsin for example. Most of the anti-M are not screened, the antigens being hardly modified by the enzyme treatment. Ss and Lutheran system sensitivity is not yet studied. The specificity was evaluated by testing 3 585 donor plasma samples at random. 7.4 % of positive reactions were obtained in T.P.C., out of these 1.4 % were confirmed and identified in manual techniques (Rhesus, Lewis, Kell and P 1 antibodies). 1.3 % corresponded to the presence of cold autoantibodies, afterwards eliminated by the use of 37°C prewarmed citrate. 4.7 % have not been identified, most of them corresponding to T.P.C. false positive reactions ; some of them, negative with manual techniques, recognize several panel samples in T.P.C., and that without any related specificity.