Evaluation of a cost-effective ADAMTS13 antigen assay

Abstract

Thrombotic thrombocytopenic purpura (TTP) is life-threatening and is characterised by platelet deposition in the microvasculature with thrombus formation in particular organs. This results in thrombocytopenia, microangiopathic haemolytic anaemia, kidney failure and neurological symptoms. It is a rare disorder, but can occur in patients infected with the human immunodeficiency virus (HIV). ADAMTS13 is the 13 th member of a disintegrin and metalloprotease with thrombospondin type motifs. Its deficiency causes TTP. Therefore, the measurement of the ADAMTS13 levels in plasma is vital in the diagnosis of TTP and also important in distinguishing it from other thrombotic microangiopathies (TMA’s). Unfortunately, commercial ADAMTS13 antigen assays are expensive for healthcare service providers in developing countries. However, several antibodies and antibody pairs have been produced against ADAMTS13 and are commercially available. In this study, we evaluated an in-house ADAMTS13 antigen assay using two different commercial antibodies and compared the outcomes to that of a commercial ADAMTS13 antigen kit by using the plasma of 40 patients with possible HIV-associated TTP and 40 healthy subjects. The Intra- and inter-assay coefficients of variation were calculated as 8% and 7% respectively. The assay gave linear results between 0.78 to 12.5% ADAMTS13. The limit of detection was 0.2%, and the limit of quantification was 0.8%. The correlation of our assay compared to the commercial test kit was excellent, with a R 2 value of 0.9. In addition, the cost of our ADAMTS13 antigen assay was lower than that of the commercial ADAMTS13 antigen test kit. Our cost-effective in-house ADAMTS13 antigen test also produced reliable results. We therefore recommend that this assay be used to diagnose HIV-associated TTP.