Factor VIII Inhibitor Testing: Nijmegen Modifications, Experience and Recommendations

Transcription

1 Factor VIII Inhibitor Testing: Nijmegen Modifications, Experience and Recommendations Bert Verbruggen Radboud University Nijmegen Medical Centre The Netherlands

2 DISCLOSURE None

3 ECAT Surveys Factor VIII inhibitor (BU/mL) n Mean (range) BU/ml Number falsely pos Outliers Number falsely negative CV (%) Bethesda Nijmegen Sample A (2 67) / 28 Sample B (0 42) / 32 Sample C 2005 (neg) 127 -(0 8) Sample ( ) / 29 Sample (neg) 102 -(0 6.4) Sample (0.4 16) / 45 Sample (neg) (0 2.2) Sample ( ) / 40 Sample (neg) ( )? Sample ( ) / 38 Sample (0 7.6) - 3? 36 / 45 Sample ( ) - 3? 29 / 25 Sample ( ) / April

4 ECAT Surveys Factor VIII inhibitor (BU/mL) n Mean (range) BU/ml Number falsely pos Outliers Number falsely negative CV (%) Bethesda Nijmegen Sample A (2 67) / 28 Sample B (0 42) / 32 Sample C 2005 (neg) 127 -(0 8) Sample ( ) / 29 Sample (neg) 102 -(0 6.4) Sample (0.4 16) / 45 Sample (neg) (0 2.2) Sample ( ) / 40 Sample (neg) ( )? Sample ( ) / 38 Sample (0 7.6) - 3? 36 / 45 Sample ( ) - 3? 29 / 25 Sample ( ) / April

5 ECAT Surveys Factor VIII inhibitor (BU/mL) n Mean (range) BU/ml Number falsely pos Outliers Number falsely negative CV (%) Bethesda Nijmegen Sample A (2 67) / 28 Sample B (0 42) / 32 Sample C 2005 (neg) 127 -(0 8) Sample ( ) / 29 Sample (neg) 102 -(0 6.4) Sample (0.4 16) / 45 Sample (neg) (0 2.2) Sample ( ) / 40 Sample (neg) ( )? Sample ( ) / 38 Sample (0 7.6) - 3? 36 / 45 Sample ( ) - 3? 29 / 25 Sample ( ) / April

6 General Scheme Factor VIII Inhibitor Assay Patient plasma Factor VIII source Control sample without inhibitor Test mixture mix o C Control mixture Factor VIII activity assay Calculate inhibitor activity (U/ml) April

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8 37 degrees Room temperature April

9 Bethesda assay: Nijmegen assay: ph test mix and ph test mix and control control mix after mix after 2h i ncubation: 7.4 after 2h incubation: 8.4 resp. 7.4 Inhibitor activity:bu/ml Undiluted 1.6 Diluted: Inhibitor activity: NBU/ml ,9 Verbruggen et al, Lancet April

10 r.fviii in vwf deficient plasma 37 degrees Room temperature April

11 Inhibitor Assay in vwf-deficient System +/- Addition of Purified von Willebrand Factor vwf activity in control sample Inhibitor titre of positive sample (NB u/ml) 0 U/ml 0,34 (n=4) 0,32 U/ml 0,48,, 0,72 U/ml 0,62,, Verbruggen et al, Thrombosis and Haemostasis April

12 Inter-lab CV Factor VIII CV (%) Level (U/dL) Source: ECAT Surveys

13 Variables that Influence Test Performance Incubation time and temperature ph stability in incubation mixtures Type of used deficient plasma: vwf in assay matrix Type of control sample Inhibitor standard Lupus anticoagulant Dilution effect in type II Residual F.VIII in test plasma Ratio normal pool plasma and patiënt/control plasma F.VIII content of normal pool plasma Type of Factor VIII assay / Type of reagent Liquid handling April

14 How to differentiate between lupus anticoagulant and coagulation factor inhibitors? April

15 How to differentiate between lupus anticoagulant and coagulation factor inhibitors? Thrombocyte count: normal Bleeding time (Ivy) : 2 minutes INR : 1.1 APTT : 45 (38 ) PT : 16 F.VIII-activity : 55% F.IX-activity : 29% KCT (1:5) : 151 (120 ) APTT (1:2) : 45 (38 ) Staclot (lupus) : (borderline) F.VIII inhibitor : 1.3 NBU April

16 How to differentiate between lupus anticoagulant and coagulation factor inhibitors? Thrombocyte count: normal Bleeding time (Ivy) : 2 minutes INR : 1.1 APTT : 45 (38 ) PT : 16 F.VIII-activity : 55% 98% (with increased PPL conc.) / 75% (CS) F.IX-activity : 29% 103% (with increased PPL conc.) KCT (1:5) : 151 (120 ) APTT (1:2) : 45 (38 ) Staclot (lupus) : (borderline) F.VIII inhibitor : 1.3 NBU Conclusion: Medication related positive lupus anticoagulant April

17 How to Differentiate between Lupus Anticoagulant and Coagulation Factor Inhibitors? Factor assays with chromogenic substrates Factor assays with increased concentration phospholipids Detection of (non-) parallelism Confirmation tests of lupus with drvvt based assays April

18 Interference of FVIIII Inhibitors in DRVVVT-based Lupus Confirmationtest Purified Inhibitor type 1 in lupus negative sample: 0.5 NBU/ml 1.0 NBU/ml 5.0 NBU/ml 10.0 NBU/ml drvvt 1: sec 44.4 sec 44.3 sec 44.0 sec Lupus negatieve plasma sample with type 2 inhibitor: 7.0 NBU/ml 32 NBU/ml 124 NBU/ml drvvt 1: sec 42.6 sec 47.2 sec April

19 (Non-)parallelism of lupus-, FVIII inhibitorand normal plasma in one stage FVIII assay Lupus FVIII inhibitor Clotting time (seconds) Calibrator Plasma dilution factor April

20 Detection and Quantification of Type 2 FVIII Inhibitors Mixing study (APTT) Investigation of (Non-) parallelism April

21 Factor deficient Lupus April

22 Factor deficient Lupus FVIII inhibitor Type April

23 Factor deficient Lupus FVIII inhibitor Type April

24 National Quality Survey 1 Case of 56 year old woman: Haematoma and paresis of left leg followed by Hospitalisation Prolonged PT and APTT History: 4 years before a melanoma was diagnosed 2 years treatment with interferon No history of previous bleeding disorders 1 Organised by SKS and SKML, dr. Ton van de Besselaar April

25 Material and Question Material: freeze-dried plasma, dissolve in 1 ml aqua dest Normal platelet count, normal levels of protein C and S, no thrombophilia screening required Question: Which test do you perform What is your interpretation of the test April

26 Assay Results 80 laboratories reported results Assay n Result FVIII assay 30 0,01 0,08 u/ml Mixing test APTT 45 Negative: 24 Positive : 21 Lupus 7 Negative : 7 (Possible) FVIII:C inhibitor 8 0,7 1,6 BU/mL April

27 Reported Conclusions (80 laboratories) Conclusion Number (possible) FVIII inhibitor 12 FVIII deficiency and FVIII inhibitor 7 Lupus anticoagulant 2 Other inhibitor 5 FVIII deficiency 16 Other factor deficiency 21 Other or no conclusion April

28 Reported Conclusions (80 laboratories) Conclusion Number (possible) FVIII inhibitor 12 FVIII deficiency and FVIII inhibitor 7 Lupus anticoagulant 2 Other inhibitor 5 FVIII deficiency 16 Other factor deficiency 21 Other or no conclusion 36 Consensus: Aquired Haemophilia April

29 Potential of inhibitor detection by mixing studies is influenced by: Type of inhibitor (FVIII type 2 inhibitors may give normal mixing tests) Type of reagent (sensitivity) Time dependent action of inhibitor 5 seconds rule has to be used with care with particular factor inhibitors April

30 Overall Conclusions Factor VIII type 2 inhibitors may be missed in mixing studies even at high titres Measuring of non-parallelism in factor assays is not a tool for detecting particular factor inhibitors Quantification of Factor VIII inhibitors still is very cumbersome mainly because of the time dependent kinetics in VWF containing samples April

31 Acknowledgements Ingrid Stienissen Piet Meijer Ton van de Besselaar Waander van Heerde Technical support ECAT SKS /SKML Theoretical support April