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

Area of Science:

• Hematology
• Clinical Chemistry
• Immunology

Background:

• Laboratory assessment of Lupus anticoagulant (LAC) faces significant challenges due to inter- and intra-laboratory variability.
• This variability hinders standardization and harmonization of LAC test results expression.
• Accurate LAC detection is critical for diagnosing thrombotic disorders.

Purpose of the Study:

• To address the challenges in LAC laboratory assessment by proposing a standardized approach.
• To establish reliable positivity cutoffs and interpretative criteria for LAC assays.
• To improve the objectivity and clarity of LAC reporting through a collaborative study.

Main Methods:

• A cross-laboratory study involving five hospital laboratories in North-eastern Italy.
• Analysis of 100 normal samples to determine negative upper limits and positivity cutoffs for dRVVT and SCT assays.
• Evaluation of 311 previously diagnosed LAC-positive samples to characterize positivity levels.

Main Results:

• Negative upper limits were established at 1.17 for dRVVT screen ratio and 1.19 for SCT screen ratio.
• Positivity cutoffs were set at 1.20 for dRVVT and 1.23 for SCT (Test Ratio).
• A proposed scoring system categorized positive LAC results into weak, moderate, and strong levels.

Conclusions:

• The combined use of dRVVT and SCT assays, with defined positivity levels, enhances LAC reporting objectivity.
• An interpretative table for a proposed LAC score aids in clearer interpretation of positive results.
• All participating centers have adopted the proposed interpretative table for LAC reporting.