Establishment of the WaS-ALD50 method for novel APTT cross-mixing test determination

Abstract

We established the numerical parameters ALD50 and WaS of the cross-mixing test in APTT prolongation and proposed the WaS-ALD50 method. ALD50 is the parameter that is measured immediately after mixing, and WaS is the parameter that is measured after warming. ALD50 (%) is obtained by dividing the actual value of mixed plasma by the linear value between plasma from a normal person (normal plasma) and plasma from a patient (patient plasma). WaS is the value obtained by calculating the rate of change from immediately after mixing to after warming and subtracting the rate of change in patient plasma from the mixed plasma. We examined 100 plasma samples with prolonged APTT. Of these samples, 38 had the lupus anticoagulant, 14 had coagulation factor deficiency, and 48 had the factor VIII inhibitor. APTT was examined with thrombocheck APTT-SLA using the Coapresta2000 instrument. ALD50 had a sensitivity of 94.7% and a specificity of 92.9% when the cutoff value was calculated with ROC curves of the lupus anticoagulant and the factor deficiency WaS was set to 87.8%. WaS had a sensitivity of 95.8% and a specificity of 96.2% when the cutoff value was calculated with the ROC curves of factor VIII inhibitor and the lupus anticoagulant/factor deficiency WaS was set to 10.2%. The discrimination rate was determined by the WaS-ALD50 method using a matrix table, which showed the discrimination rates to be 94.7% for the ALD50 and WaS LA group, 85.7% for the factor deficiency group, and 95.8% for the VIII inhibitor group as 95.8%, with a mean of 94.0%. In conclusion, the WaS-ALD50 method examined in this study can contribute to the precise analysis of the cause of APTT prolongation.