Performance evaluation of heparin-induced platelet aggregation vs serotonin release assay

Area of Science:

• Clinical immunology
• Hematology
• Diagnostic testing

Background:

• Heparin-induced thrombocytopenia (HIT) is a critical condition necessitating prompt diagnosis.
• Platelet factor 4 (PF4) enzyme-linked immunosorbent assay (ELISA) serves as a screening tool, requiring confirmation via highly specific tests like heparin-induced platelet aggregation (HIPA) or serotonin release assay (SRA).

Purpose of the Study:

• To evaluate the diagnostic performance of HIPA compared to SRA.
• To establish PF4 ELISA cutoffs for predicting HIPA/SRA positivity.
• To assess mortality differences in suspected HIT cases based on confirmation status.

Main Methods:

• Analysis of 232 cases with positive or indeterminate anti-PF4 IgG ELISA and confirmatory HIPA/SRA testing.
• HIPA performance evaluation against SRA (gold standard) before and after a 2022 interpretation guide update.
• Chart reviews for mortality data collection.

Main Results:

• HIPA sensitivity increased from 55.4% (2018-2021) to 73.8% (2022) post-update.
• Specificity remained high (94.9% vs 87.5%), with improved negative predictive value (NPV) in 2022.
• PF4 optical density cutoffs were established for SRA, HIPA, and combined testing; no significant mortality difference was found between confirmed HIT positive and negative patients.

Conclusions:

• A new standardized interpretation guide enhanced HIPA's sensitivity and NPV in 2022, despite lower sensitivity than SRA.
• Further refinements are necessary for HIPA to function as a standalone confirmatory test, aiming to reduce hospital stays and optimize anticoagulation management.