Among patients with HIT, a buffer-positive SRA pattern was associated with more prolonged thrombocytopenia and increased mortality, though findings are hypothesis-generating because the assay used platelet-rich plasma and need confirmation with the classical washed-platelet SRA.
About 8% of confirmed HIT patients had a buffer-positive SRA pattern.
The buffer-positive group had significantly lower anti-PF4/heparin ELISA optical density.
Thrombosis incidence did not differ significantly between buffer-positive and buffer-negative patients.
The buffer-positive pattern was independently associated with longer time to platelet recovery.
The buffer-positive pattern was associated with higher 30-day mortality.
The authors characterize the findings as hypothesis-generating because of the assay type used.
Heparin-induced thrombocytopenia (HIT) is a dangerous reaction to the blood thinner heparin, in which platelet counts fall and clotting risk rises. The serotonin release assay (SRA) is the gold-standard lab test for it. Some patients' samples show platelet activation even without heparin (a 'buffer-positive' pattern), and it has been unclear what this means clinically. Researchers reviewed 207 patients with confirmed HIT at the University of Pennsylvania hospitals. About 8% (17 patients) had a buffer-positive pattern. These patients had lower levels of the HIT antibody on a screening test, took longer for platelet counts to recover (9 vs 5 days), and were more likely to die within 30 days (47% vs 17%). After adjustment for other factors, the risk of death was about 2.7 times higher. Rates of blood clots were not significantly different between groups. This research suggests a buffer-positive pattern might mark a sicker group of patients or a different disease process. However, the group was small, the study was retrospective, and the lab used a platelet-rich plasma version of the test rather than the classical washed-platelet method. The authors therefore describe the results as hypothesis-generating, needing confirmation in further studies.
Rungjirajittranon T, Warkentin T, Cuker A. (2026). A buffer-positive serotonin release assay pattern is associated with increased mortality in HIT: a retrospective cohort study.. Research and practice in thrombosis and haemostasis. https://doi.org/10.1016/j.rpth.2026.106995