Laboratory prediction of the carrier state in hemophilia B: role of replication of assays.

The authors studied the effect of averaging replicated assays of Factor IX coagulation activity and Factor IX antigen on each plasma specimen in improving the ability to detect carriers of hemophilia B. The improvement resulting from this procedure is particularly marked in tests depending on the linear regression of one characteristic on another to diagnose the carrier state. The effects of averaging assays on the ratio of Factor IX coagulation activity to Factor IX antigen were also explored. The benefits of averaging replications were not greatly increased by use of more than four replications.