Sensitivity of sixteen APTT reagents for the presence of lupus anticoagulants.

Activated partial thromboplastin time (APTT) is the most common assay used to screen for lupus anticoagulant (LA). For some years, manufacturers have been proposing APTT reagents that were more sensitive to LA. In this study, we evaluated the sensitivity and responsiveness of 16 APTT reagents in 40 LA and 46 normal plasmas. Sensitivity was established using a 1:1 mixture of normal and LA plasma that optimized the most sensitive reagent. The same pool of normal plasma was used for the assay of mixtures and daily APTT values for the determination of ratios. The results show that new commercially available APTT reagents are more sensitive and responsive to LA. The different sensitivities of APTT reagents might be partly due to the heterogeneity of LAs and several APTT reagents should be used for LA detection. The choice of APTT reagents constitutes an important preliminary step for LA evaluation.