New Strategy in Patients with Suspected Heparin-Induced Thrombocytopenia Improves Diagnostic Accuracy
Clinical question: Can a diagnostic strategy that utilizes a clinical prediction rule combined with an immunoassay appropriately guide management for patients with suspected heparin-induced thrombocytopenia (HIT)?
Background: The appropriate and timely diagnosis of HIT can decrease the risks of thromboembolic and major bleeding events. Unfortunately, the reference standard tests for diagnosing HIT (e.g. serotonin release assay) are time-intensive. Immunoassays such as PF4/H-PaGIA provide a faster diagnostic approach but have been limited by poor specificity.
Study design: Single-group prospective cohort trial.
Setting: Four hospitals in Ontario, Canada between 2008 and 2013.
Synopsis: In 526 patients with suspected HIT, the results of a diagnostic strategy that combined the 4Ts score system and a PF4/H-PaGIA assay were compared to a HIT reference standard. For the identification of patients with HIT, the use of (1) an intermediate 4Ts score and negative PF4/H-PaGIA or (2) a low 4Ts score regardless of PF4/H-PaGIA result incorrectly excluded patients with HIT in 1.1% of cases (95% confidence interval 0.2-2.1%). For patients with low and intermediate 4Ts scores, however, a negative PF4/H-PaGIA result did not result in any incorrect exclusion.
Bottom line: In patients with low or intermediate 4Ts scores, a negative PF4/H-PaGIA assay may be used to exclude HIT, but further research into how to approach patients with a low 4Ts score and a positive PF4/H-PaGIA assay is needed.
Citation: Linkins LA, Bates SM, Lee AY, Heddle NM, Wang G, Warkentin TE. Combination of 4Ts score and PF4/H-PaGIA for diagnosis and management of heparin-induced thrombocytopenia: prospective cohort study. Blood. 2015;126(5):597-603.