Publication Date:
2020-11-05
Description:
INTRODUCTION: The serotonin release assay (SRA) is considered the gold standard for diagnosis of heparin-induced thrombocytopenia (HIT). While the SRA holds high sensitivity and specificity when results are definitive, up to 10% of samples from patients with suspected HIT yield "indeterminate" results. In classic HIT, the SRA typically reveals high levels of serotonin release when serum is mixed with low concentrations of heparin and low levels of serotonin release when serum is mixed with high concentrations of heparin. Results are considered "indeterminate" when high levels of serotonin release are seen at both low and high concentrations of heparin, indicating a failure of high-dose heparin to saturate the heparin binding sites of PF4 molecules and inhibit platelet activation. Explanations for indeterminate assays include the presence of heparin-binding proteins that interfere with the assay, high titers of HLA class I alloantibodies, or immune complexes. Since the diagnosis of HIT carries such significance and has so many ramifications, an indeterminate SRA may leave therapeutic indecision. The etiologies, platelet trends, clinical course and outcomes of patients that receive indeterminate SRA results are not well-understood. We conducted a retrospective review of 2,056 patients that underwent SRA testing as part of their evaluation for HIT. METHODS: Using the electronic medical record data extraction software Clinical Looking Glass, we identified patients that underwent SRA testing between 1/1/2014 and 12/31/2018. SRA results were considered "indeterminate" when serotonin release exceeded 19% at all heparin dilutions (0.1 U/mL, 0.5 U/mL and 10 U/mL). We conducted a retrospective chart review to study the clinical course among patients who had "indeterminate" SRA results, the trends in platelet count, the timing of platelet drops and the physician response to this result. Statistical analysis was performed using chi-square testing for categorical variables. RESULTS: We identified 2,056 patients that underwent SRA testing between 2014 and 2019. Of these, 90 patients (4.4%) had "positive" SRA results and 1,814 patients (88.2%) had "negative" SRA results. Among the 152 patients (7.4%) with "indeterminate" SRA results, the mean 4T score was just 2.9, corresponding to a HIT probability of
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
Permalink