Stability of specimens for use in the Centers for Disease Control and Prevention assays for factor VIII and IX inhibitors

Abstract

The Centers for Disease Control and Prevention (CDC) Nijmegen-Bethesda Assay (NBA) 1 is a modification of traditional methods 2,3 for measurement of factor VIII (FVIII) and factor IX (FIX) inhibitors that includes a 30-minute preanalytical heat treatment (PHT) step to remove endogenous and infused FVIII or FIX. Specimens for inhibitor tests using PHT thus do not require the stringent conditions needed to maintain clotting factors during shipping and storage, as we have previously documented by split-sample analysis showing that results of the CDC-modified NBA on specimens shipped cold correlated well with those of frozen specimens. 1

International Council for Standardization in Haematology recommendations for laboratory measurement of factorVIIIandFIXtypeIinhibitors

“…A recent study has demonstrated that both FVIII and FIX inhibitor positive sample can be stored at room temperature for 1 week, while stored at À70 C inhibitor positive samples can be stored for up to 15 years after their original analyses. 55 For FVIII:C and FIX:C it has been demonstrated that clotting activity should be measured within 2 and 4 h, respectively. 56 Storage of frozen plasma at À70 C for the measurement of FVIII:C and FIX:C is possible for 18 and 24 months, respectively.…”

“…Standard centrifugation conditions for blood coagulation samples can be used (15 min at 1500× g ). A recent study has demonstrated that both FVIII and FIX inhibitor positive sample can be stored at room temperature for 1 week, while stored at −70°C inhibitor positive samples can be stored for up to 15 years after their original analyses 55 . For FVIII:C and FIX:C it has been demonstrated that clotting activity should be measured within 2 and 4 h, respectively 56 .…”