Lupus anticoagulant: a multicenter study for a standardized and harmonized reporting.

Laboratory assessment of Lupus anticoagulant (LAC) is very challenging because of inter and intralaboratory variability, which makes it difficult to standardize and harmonize results expression. Five hospital laboratories in North-eastern Italy shared their efforts and their experience in a cross-laboratory study, conducting the diagnostic process as homogeneously as possible and providing a better interpretation for LAC positivity. Hundred normal samples from healthy subjects (20 from each center) were processed to confirm negative upper limits and calculate positivity cutoffs of LAC integrated assays, that is dilute Russell's viper venom time (dRVVT) and silica clotting time (SCT).

Cooperation experience in a multicentre study to define the upper limits in a normal population for the diagnostic assessment of the functional lupus anticoagulant assays.

Background: Phospholipid-dependent coagulation tests for lupus anticoagulant (LA) are considered an important step for the diagnosis of anti-phospholipid syndrome; however, LA laboratory detection is difficult because of many variables. Five hospital laboratories, located in a North-Italy area and using the same method for LA testing, cooperated to standardise sample treatment and analytical procedure in order to define the upper values for LA negativity.

Methods: In total, 200 normal subjects (40 for each centre) were studied for six LA functional assays, using the same procedure, reagent lot and analyser type.