VALIDATION PROTOCOL OF ANALYTICAL HEMOSTASIS SYSTEMS - MEASUREMENT OFANTI-XA ACTIVITY OF LOW-MOLECULAR-WEIGHT HEPARINS

A standard validation protocol adapted to the chromogenic assay of ant i-Xa activity of low-molecular-weight heparins Tvas used in a multicen ter study to assess its suitability for comparing and evaluating analy tical hemostasis systems, The protocol included: familiarization with the system (repeatability); assessment of limits of linearity, detecti on limits, and cross-contamination; and validation (reproducibility an d accuracy of measurements of treated patients' plasmas), We calibrate d the systems with the same range of lyophilized plasmas daily and eva luated repeatability and reproducibility by using a single batch of ly ophilized plasmas at three anti-Xa activities. The two automated syste ms tested [SE 300 (Gilford) and ACL (IL)] and the two semiautomated sy stems [ST 888 (D. Stago) and Chromotimer Behring)] gave similar mean v alues, Dispersion of results was lower with the automated systems than with the semiautomated ones, especially at low anti-Xa activities, a tendency that also was observed for reproducibility. Because each anal ytical system gave linear results for activities as great as 1000 IU/L , suitable sample dilution is advisable for higher anti-Xa activities, Accuracy was greater in the automated systems. We conclude that this protocol is feasible and is applicable to validation of other analytic al hemostasis instruments, in particular the latest generation of full y automated instruments.