Antigen/biological-activity ratio for factor VIII

Problems in the detection of carriers of hemophilia A: the influence of stress and thrombin

After exposure to stress, factor VIII coagulant activity and factor VIII antigen were determined in healthy volunteers for about 3 days. Three out of four volunteers at different time showed results resembling a carrier state. In vitro incubation of plasma with thrombin in decreasing concentrations showed increased factor VIII coagulant activity, although no fibrin clot or fibrin monomers were formed. The concentration of factor VIII antigen remained constant. The action of thrombin can explain the misclassification of known carriers.

[Problems of conductor demonstration in haemophilia A: error possibilities in the determination of factor-VIII-associated antigen]

Difficulties in the detection of haemophilia A carriers by the determination of the ratio factor VII coagulation activity to factor VII antigen concentration are shown in part one of our investigations. The second part evaluates methodical parameters of the quantitative immunoelectrophoretic technique. According to our results reliable data can only be obtained under the following conditions: 1. At least three determinations of each sample are required and the mean value should be used as the final result. 2. Each gel plate should be calibrated separately 3. The calibration line should include values less than 100%. Factor VIII concentrates are not suitable for determination of the calibration curve, as higer dilution results in lower calculated concentration of the undiluted concentrate. Storage of pooled normal plasma at--25 degrees C is possible without significant loss of antigen concentration over 5 months. However, plasma samples of a single person show an unpredictable variation in the antigen concentration during storage over the same time.

Factor VIII and factor-VIII-related antigen in multiple myelomatosis and related conditions

Factor VIII and factor-VIII-related antigen (FVIIIRA) were estimated in 19 patients with paraproteinaemia. The FVIIIRA levels were above the normal range in 12 cases with II of these showing an abnormal FVIII/FVIIIRA ratio. The patients could be subdivied into three groups according to their FVIIIRA levels: normal levels, levels greater than normal but less than 200%, greater than 200%. This subdivision correlated with the degree of bone involvement as assessed by radiological skeletal survey.

Detection of carriers of haemophilia: a 'blind' study

A 'blind' study has been made to try to find out if it is possible to diagnose carriers of haemophilia. A group of 34 obligatory carriers of haemophilia were compared with 34 normal women. Levels of factor VIII activity, factor VIII-related antigen, factor V and ratio of factor VIII activity to factor VIII-related antigen were measured. In the carrier group the mean level of factor VIII activity and the mean level of the ratio of activity to antigen were each approximately half of those found in the normal women. The mean level of factor V was the same in both groups of women. By setting the lower limit of normal at the lowest level of the different factors found in the normal women, 12 out of 34 (35%) carriers could be distinguished on the basis of their factor VIII level alone; 24 out of 34 (71%) could be detected on the basis of the ratio of factor VIII activity to factor VIII related antigen and 25 out of 34 (73%) could be detected if both factor VIII activity and the ratio were taken into account. It is concluded that consideration of both the level of factor VIII activity and the ratio of factor VIII activity to factor VIII-related antigen is of some value in detecting carriers of haemophilia. The number of carriers detected (73%) in the present study is not as high as that found by other workers.