Year: 2002
Type: article
Study design: Observational Study
Abstract: Background: Lupus anticnagulants (LA) are aoquired heterogeneous groups of antibodies that cause prolongation of the phospholipid-dependent coagulation tests. Due to the beterogeneity of LA and the diferences in the reagents and tests, the diagnosis of LA vanies from laboratory to laboratory. Objective: To study the pattern of LA positivity by different coagulation tests and the prevalence of LA among blood samples sent for LA screening to our laboratory. Methods: Blood samoles from a group of 278 Thai patients sent for LA screening were analyzed. Criteria for the diagnosis of LA were based on prolongation of at least one of the screening coagulation tests, endence of inhibitor mixing study and evidence of phosphoid dependendency. The screening tests included activated partial thromboplastin time (APTT), kaolin clotting time KCT), dilute activated partial thromboplastin time (dAPIT), and diute Russel's viper venom time (dRVVT). Mixing study was performed if an individual screening coagulation test was abnormal. If the initial mixing study showed correction of the abnormal clotting time, then assay for time-dependent inhibition was perfomed. There presence of a circulating inhibitor. The confirmatory studies consisted of platelet neutralization procedure (PNP) and tissue thromboplastin inhibition time ITTITIT). Results: Of the 278 blood samples, 12 (4.3%) were LA positive. The prevalence would have been higher (9:5% or 12/126 if the tests had been done only in patients clinically more likely have LA. The results of screening dAPIT. APTT. KCT and dRVVT were abnomal in 12/12 (100%), 11/12 (91.7%), 10/12 (83.3%) and patients (75.0%), respectively. However, only 8/12 (66.7%), 9/11 (81.8%), 610 (60%)and 6/9 (68.7%) of the afore-mentioned abnomal screening tests gave positive results with the immediate 1:1 mixing studies. One sample each showed time-dependent inhibition in the dAPTT and dRVVT. For confimatory sten, the PNP-APTT PNP-dRVVT. and TITI were positive in 8/11 (727%), 89 (88.9%), and 11/11 patients (100%) respectively. Conclusion: The prevalence of the LA positivity was quite low in this group of Thai patients. The dAPTT was the most sensitive screening test while the TTIT was the most sensitive confimatory test. About 10% of our LA showed time-dependent inhibitition. This study also confirmed the need of various tests to detect LA.
Language: English
Subfield: Rheumatology
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W2187684087