Automated microfluidic electrochemical biosensor for the detection of immune-mediated thrombotic disorders.

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a new disorder that emerged in the wake of COVID-19 vaccination. It is a rare but life-threating condition that requires aggressive course of treatment to improve patient outcomes. To date, there has not been an effective diagnostic assay for detecting VITT. Instead, definitive diagnosis requires satisfying several criteria including history of recent vaccination, platelet count, positive ELISA result for a closely related thrombotic disorder, heparin-induced thrombocytopenia (HIT) and PF4-dependent functional assays. Our study describes a technically simple antigenic assay for direct diagnosis of autoimmune antibodies (Abs) associated with VITT. We first show that cross-linked platelet factor 4 (PF4) represents an antigenic target specific for VITT Abs. We then incorporate this antigenic target into a microfluidic electrochemical biosensor and demonstrate specific and sensitive detection of VITT Abs in a fully automated manner while using microliter volumes of patient sera. We tested 51 patient samples using the microfluidic electrochemical biosensor and demonstrated 100% sensitivity and specificity for VITT sera compared to healthy controls and HIT patients.