Modification of the ProC Global assay using dilution of patient plasma in factor V-depleted plasma as a screening assay for factor V Leiden mutation.
The activated protein C (APC) resistant-factor V (factor V Leiden) has emerged as the most common inherited risk factor for thrombosis in the Caucasian population. Beside DNA analysis, the laboratory diagnosis is often based on the detection of a poor anticoagulant response to exogenous APC. The ProC Global assay (Dade Behring, Marburg, Germany) is a global clotting assay, which was primarily developed to evaluate the functionality of the protein C anticoagulant pathway. It is based on the ability of endogenous APC, generated by activation of protein C by an extract from Agkistrodon contortrix contortrix venom, to prolong an activated partial thromboplastin time. It was previously found to be highly sensitive for the factor V Leiden mutation and for protein C deficiency, but only moderately sensitivity for protein S deficiency. Here, we evaluated the performance of a modification of the ProC Global assay using a 1 : 5 pre-dilution of patient plasma in factor V-depleted plasma in the screening of the factor V Leiden mutation-related APC resistance. For that purpose, we investigated selected frozen plasma samples from 341 patients with a history of venous thromboembolism. The sensitivity for the factor V Leiden mutation of the modified assay was found to be 100%, as all the carriers of that mutation (five homozygotes and 77 heterozygotes) had a decreased response to the assay, i.e. a normalized ratio below 0.80. Its specificity was also 100% since none of the other tested patients had a decreased response, i.e. isolated protein C (n = 3) or protein S deficiency (n = 50), or without any abnormality of the protein C pathway (n = 143), even those on oral anticoagulant treatment (n = 76). However, it would be preferable that each laboratory defines both its reference range and its cut-off level. Finally, even if larger-scale multicentre studies are needed before definite recommendations could be made, these results suggest that the ProC Global performed using a 1 : 5 pre-dilution of the patient plasma in factor V-depleted plasma could be validly used as a screening assay of the factor V Leiden mutation-related APC resistance in patients with a history of thrombosis.
Quincampoix
J C
JC
Laboratoire d'Hématologie, Hôpital Cochin, Paris, France.
Legarff
M
M
Rittling
C
C
Andiva
S
S
Toulon
P
P
D020016:Activated Protein C Resistance / Q000175:diagnosis* / Q000235:genetics; D017836:Agkistrodon; D000818:Animals; D000925:Anticoagulants / Q000627:therapeutic use; D001778:Blood Coagulation Disorders / Q000097:blood; D001780:Blood Coagulation Tests / Q000379:methods*; D003435:Crotalid Venoms; D005165:Factor V / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008107:Liver Diseases / Q000097:blood; D009154:Mutation; D010314:Partial Thromboplastin Time; D011486:Protein C / Q000494:pharmacology; D020151:Protein C Deficiency / Q000097:blood; D018455:Protein S Deficiency / Q000097:blood; D012680:Sensitivity and Specificity; D013927:Thrombosis / Q000235:genetics
D000925:Anticoagulants; D003435:Crotalid Venoms; D011486:Protein C; C095381:factor V Leiden; D005165:Factor V