[Study of four kits used for titration of tetanus antibody for selection of plasma donors intended to fractionation].

Unlabelled: Antitetanus antibodies titration is carried out by French National Blood Services (FNBSs) with the aim of seeking donors whose title of antibodies are greater or equal to 8 IU/ml. Different kits are used: ELISA antitetanus toxoid IgG (The Binding Site), ELISAT (Diagast), tetanus toxoid IgG ELISA (Diamed), ELISA IgG tetanus (Ingen). As the results obtained using these different reagents show some discrepancies with the control results carried out by the Laboratoire Français des Biotechnologies (LFB), it appeared necessary to harmonize the selection practices. With this intention a study of the different kits was initiated.

Method: Different samples were used during this evaluation: (1) the Reference Control (RC) used by the FNBS; (2) a serum sample of high title; (3) a range of dilution of national standard. The following tests were carried out: (1) robustness with the evaluation of the contamination and the board effect; (2) linearity and repeatability (eight deposits of each standard, RC and points of national standard dilutions); (3) reproducibility; (4) homogeneity. After automatic dilution of the samples, the plates were then processed according to the protocol of the manufacturer.

Results: The study gives the CV in percentage of repeatability and reproducibility, the values of the standards provided as well as the bias compared to the RC and the uncertainty of measurements.

Conclusion: This study gave the possibility to rank each kit compared to RC and to specify the variations which surround each result. This variation can explain the discrepancy of conformity of plasma when title is close to the threshold of selection.