Evaluation of a new silica clotting time in the diagnosis of lupus anticoagulants.
BACKGROUND
A new commercial silica clotting time (SCT), the HemosIL SCT assay (Instrumentation Laboratory, Milan, Italy) was evaluated in the laboratory diagnosis of lupus anticoagulants (LAC). This integrated test system for screening and confirmation was compared with the frequently used aPTT-based PTT-LA and Staclot-LA (Diagnostica Stago, Asnières, France) in a patient population investigated for LAC and in a subpopulation who met the clinical criteria for antiphospholipid syndrome (APS).


METHODS
201 samples were analysed with the HemosIL SCT assay. Own reference values were calculated. Results are expressed as measured clotting times in seconds or as normalised ratios.


RESULTS
SCT screen and PTT-LA had a sensitivity of, 61.1% and 63.8%, respectively. Normalising the results gained sensitivity up to 72.2% and 90%, respectively. The confirmation SCT and the Staclot-LA had a sensitivity of 30.6% and 63.9% with a specificity of 86.7% and 100%, respectively. Sensitivity of SCT for detecting LAC in clinical criteria positive patients was lower compared to aPTT and dRVVT (45.8% versus 66.7% and 65%). Combination of SCT/dRVVT and aPTT/dRVVT gave a sensitivity of 51.2% and 63.6%, with a specificity of 50.0% and 52.3%, respectively.


CONCLUSIONS
In comparison with PTT-LA as screening test, the SCT screen shows an acceptable sensitivity. However, the HemosIL SCT assay including the confirmation step, has a much lower sensitivity in the diagnosis of LAC in comparison with the Staclot-LA test. Combining the HemosIL SCT assay with dRVVT results in a better sensitivity, although lower than the combined aPTT/dRVVT based method as usually performed in our lab.
Devreese
Katrien M J
KM
Coagulation Laboratory, Department of Clinical Chemistry, Microbiology and Immunology, Ghent University Hospital De Pintelaan, 185 (2P8) B-9000 Gent Belgium.
D016736:Antiphospholipid Syndrome / Q000097:blood* / Q000175:diagnosis*; D001780:Blood Coagulation Tests / Q000379:methods; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000097:blood*; D010314:Partial Thromboplastin Time; D012372:ROC Curve; D012016:Reference Values; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide
D016682:Lupus Coagulation Inhibitor; D012822:Silicon Dioxide