[Automatic detection of syphilis on Groupamatic. Preliminary results]

Detection of immune anti-A and anti-B allo-antibodies with groupamatic system

An inhibition technique using soluble AB group substances for screening of 'immune' anti-A and anti-B allo-antibodies has been set up on Groupamatic. This screening is performed on all blood units of group O, A and B to be transfused. The ratio of potentially dangerous donors in case of non-isogroup transfusion is 2.86% of the total number of screened donors. This detection is performed simultaneously with other immunohaematological and serological tests: ABO and Rh grouping, screening of irregular allo-antibodies, screening of syphilis.

Automation of a flocculation test for syphilis on Groupamatic equipment

A flocculation reaction employing a cardiolipid antigen was used for syphilis screening on Groupamatic equipment in parallel with conventional screening reactions: Kolmer CF, RPCF, Kahn, Kline, and RPR. The positive samples were confirmed by FTA-200, FTA-ABS, TPI, and in some cases by TPHA. There were 5,212 known samples which had already been tested by all methods and of which 1,648 were positive, and 58,636 screened samples including 65 positives. Half of the samples in the first series were taken without anticoagulant; the remainder were collected in potassium EDTA. The percentage of false positives with the Groupamatic was about 1-4 per cent. The percentage of false negatives among positve (greater than or equal+) samples varied from 0-18 to 1-3 per cent.; on the other hand the sensitivity was less good for samples giving doubtful and/or dissociated reactions in conventional screening reactions. The specificity and sensitivity of this technique are acceptable for a blood transfusion centre. The reproducibility is excellent and the automatic reading of results accurate. Additional advantages are rapidity (340 samples processed per hour); simultaneous performance of eleven other immunohaematological reactions; no contamination between samples; automatic reading, interpretation, and print-out of results; and saving of time because samples are not filed sequentially and are automatically identified when the results are obtained. Although the importance of syphilis in blood transfusion seems small, estimates of the risk are difficult and further investigations are planned.