Abstract
OBJECTIVE: This study aims to investigate the prevalence of heparin-induced thrombocytopenia among hospitalized patients with antiphospholipid syndrome or systemic lupus erythematosus with antiphospholipid antibodies. METHODS: A retrospective cohort study was performed on patients hospitalized at a tertiary care medical center who met criteria for antiphospholipid syndrome or lupus with antiphospholipid antibodies and were evaluated for heparin-induced thrombocytopenia with anti-platelet factor 4 or serotonin release assay. Pretest probabilities of heparin-induced thrombocytopenia were estimated using a 4T score. Proportions of patients with positive anti-platelet factor 4 and serotonin release assay tests were calculated, and the number of patients meeting clinical criteria for heparin-induced thrombocytopenia was determined. RESULTS: Of 33 patients identified in screening, 23 met inclusion criteria. Pretest probability for heparin-induced thrombocytopenia based on 4T scores was intermediate in 9 (39%) and high in no patients. Only 1 patient (4%) tested positive for anti-platelet factor 4. Serotonin release assay was tested in 4 patients (17%) and was negative in all cases. CONCLUSION: Among 23 hospitalized patients with antiphospholipid syndrome or lupus with antiphospholipid antibodies who were tested, none were diagnosed with heparin-induced thrombocytopenia. Most patients had low pretest probability for heparin-induced thrombocytopenia based on 4T scores but were still tested for anti-platelet factor 4. Our study suggests that heparin-induced thrombocytopenia is rare among hospitalized patients with antiphospholipid syndrome or lupus with antiphospholipid antibodies.