An evaluation of screening tests for defects in the protein C pathway: commercial kits lack sensitivity and specificity.

A comparative evaluation of four commercial coagulation test kits for screening the protein C pathway kits was performed at two centres. The tests were Acticlot V-OUT (V-OUT), the PCA test (PCA), the GradiThrom PCP test (PCP) and ProC Global (ProC). Reference ranges were established in 40 normal subjects and, with the exception of V-OUT and ProC, significant differences were observed between males and females.

Fluctuations in levels of antiphospholipid antibodies and increased coagulation activation markers in normal and heparin-treated antiphospholipid syndrome pregnancies.

Antiphospholipid antibodies (aPL) are associated with an increased risk of thrombosis and recurrent miscarriage. We assessed levels of coagulation activation markers and aPL during normal pregnancy and in women with the antiphospholipid syndrome (aPS). Fluctuations in aPL levels were observed in all patients with aPS.

The importance of locally derived reference ranges and standardized calculation of dilute Russell's viper venom time results in screening for lupus anticoagulant.

Three commercial dilute Russell's viper venom time (DRVVT) kits were evaluated at four UK centres experienced at performing lupus anticoagulant (LA) tests. Each centre established a normal reference range for the DRVVT ratio calculated against local pooled normal plasma from 20 healthy normal subjects. Plasma from LA-positive patients and LA-negative thrombophilia patients was also tested.

Recombinant and tissue extract thromboplastins for determination of international normalised ratio in over-anticoagulated patients.

The international normalised ratio (INR)/international sensitivity index (ISI) system is established for calibration of thromboplastins for laboratory monitoring of oral anticoagulant therapy. The calibration procedure employs patients stabilised on oral anticoagulants, and is therefore validated for patients within the therapeutic range. For practical reasons, the system is used for patients at all levels of therapy, including over-anticoagulated patients with particularly low levels of factors II, VII and X.

Marked variation in antiphospholipid antibodies during pregnancy: relationships to pregnancy outcome.

Variations in blood concentrations of antiphospholipid antibodies (APA) were investigated through the course of pregnancy in women who had a history of recurrent pregnancy loss, and were related to changes in pregnancy outcome. Serial measurements of APA were made in 16 women with antiphospholipid syndrome (APS) and 16 with negative APA tests pre-pregnancy. There was considerable intraindividual variation in test results through pregnancy.