Diagnostic value of thrombin generation using different trigger reagents in patients with bleeding disorder of unknown cause
The majority of patients with an increased bleeding tendency remain undiagnosed after extensive laboratory testing and are classified as having a bleeding disorder of unknown cause (BDUC). Global hemostasis assays, such as the plasma thrombin generation assay (TGA), may provide enhanced sensitivity and provide a rationale for the diminished coagulation profile. The aim was to assess whether TGA can identify a bleeding tendency in BDUC patients and to determine the most sensitive TGA trigger reagent for this patient population.
BDUC patients (n=83) from the Predictors of Bleeding Evaluation in Adult Hematologic Patients (ProBe-AHP) study were analyzed. Patients had clinically relevant bleeding symptoms (elevated ISTH-BAT scores or based on clinical gestalt) and normal standard hemostasis test results. TGA was performed using the Calibrated Automated Thrombography (CAT) method (Stago BNL) with three different trigger reagents: PPP Reagent INT (intrinsic activation), PPP Reagent LOW (low tissue factor (TF) activation), and PPP Reagent LOW 1:5 PL (low TF and diluted phospholipids). Reference values were obtained from 107 healthy volunteers.
TGA was performed in a total of 83 BDUC patients and the lag time (LT), velocity index (VI), peak height (PH), and endogenous thrombin potential (ETP) were analyzed. Compared with healthy volunteers, BDUC patients had a longer LT in all three trigger reagents, and in PPP Reagent LOW 1:5 PL, ETP, PH, and VI were also decreased. Overall, 21/83 (25%) BDUC patients had one or more abnormal TGA parameters suggestive of a bleeding tendency. All three reagents demonstrated comparable sensitivity in detecting a bleeding phenotype. PPP Reagent INT and PPP Reagent LOW each identified 10 patients with abnormalities suggestive of a bleeding tendency, while PPP Reagent LOW 1:5 PL identified 8 patients. Multiple coagulation factors demonstrated moderate to strong correlations with TGA parameters: fibrinogen correlated with LT and PH across reagents, FII showed the strongest associations with PH and VI (PPP Reagent INT), and FVIII, FIX, and FXI correlated moderately with ETP and PH.
While TGA identified hemostatic abnormalities in one-quarter of BDUC patients, trigger reagent modifications provided no added diagnostic advantage in this patient population.