PB1092 - Performance evaluation and comparison of two diluted Russell viper venom time systems for lupus anticoagulant detection in systemic lupus erythematosus patients

Background: Lupus anticoagulant (LA) testing in clinical laboratory is very crucial for diagnosis of antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). However, there is no single or gold standard test that can detect all LA. Diluted Russell viper venom time (dRVVT) is the most common method which is adopted in clinical laboratories for LA detection in Taiwan but variabilities in the sensitivity were exist in several commercial reagent products. The performance and limitation should be well evaluated when laboratories choose a testing platform.

Aims: This study aimed to evaluate two dRVVT systems for lupus anticoagulant detection in suspected SLE patients.

Methods: We collected eighty-five routine specimens from suspected SLE patients. LA measurements were performed by using Siemens LA1/LA2 reagents and Stago STACLOT LA reagent on Sysmex CS-5100 and Stago STA-R Max automatically coagulation analyzers, respectively. The results were calculated as normalized LA ratio (normalized LA screen/normalized LA confirmation).

Results: Twenty-nine patients were finally diagnosed SLE disease from eighty-five collected patients in this study. The agreement rate was 91.8% between two different dRVVT system. The sensitivity, specificity, PPV and NPV were 55%, 77%, 55% and 77% in Siemens system, respectively. The sensitivity, specificity, PPV and NPV were 59%, 80%, 61% and 79% in Stago STA-R Max, respectively. These five test results all fall near the threshold values, and we discovered that the other autoimmune antibody tests for these specimens were positive. The differences between these two platforms have minimal impact on clinical diagnosis.

Conclusion(s): The diagnosis of SLE should involve a comprehensive approach, incorporating symptom assessments, physical examinations, X-rays, and laboratory tests. Based on our findings, specimens showing weak positive results for LA should be subject to careful consideration, necessitating additional tests or examination of clinical syndromes for an accurate diagnosis of SLE.