Effect of a thrombopoietin receptor agonist on use of intravenous immune globulin in patients with immune thrombocytopenia.

BACKGROUND: Thrombopoietin receptor agonists are new treatments for patients with chronic immune thrombocytopenia (ITP). How one of these agent, romiplostim, has impacted practice patterns, especially the use of intravenous immune globulin (IVIG), has not been evaluated outside of clinical trials. STUDY DESIGN AND METHODS: This was a retrospective cohort study of adult ITP patients treated with romiplostim in four Canadian centers. Patients had primary or secondary ITP and were followed for 1 year before starting weekly romiplostim treatment. We compared IVIG use, clinical outcomes, and cost before and after romiplostim. RESULTS: Twenty-nine patients with ITP received romiplostim. Median age was 54 years (interquartile range [IQR], 45-63 years) and patients had a median of two prior ITP treatments (IQR, 1-4) including splenectomy (n = 7). Median platelet (PLT) count was 23 × 10(9) before and 124 × 10(9) after romiplostim. Median duration of romiplostim treatment was 3.7 months. Patients used a median of two IVIG infusions per year before and 0.7 per year after starting romiplostim (p = 0.16). For patients who received weekly romiplostim for at least 1 month (n = 19), IVIG infusions were three (IQR, 1-5) per year before and 0.7 (IQR, 0.4-1.6) per year after romiplostim. Results were squewed by two high IVIG users. Nineteen (66%) patients discontinued romiplostim treatment during follow-up because of lack of response (n = 8), sustained response (n = 5), toxicities (n = 4), or response to splenectomy (n = 2). Overall health care costs were similar before and after romiplostim when concomitant treatments, nursing resources, and hospitalizations were considered. CONCLUSIONS: Romiplostim was associated with improved PLT counts and fewer IVIG infusions for most ITP patients. In practice, romiplostim was generally not continued long term and was cost neutral for overall ITP management.

Correlation of ELISA optical density with clinical diagnosis of heparin-induced thrombocytopenia: a retrospective study of 104 patients with positive anti-PF4/heparin ELISA.

BACKGROUND: Enzyme-linked immunosorbent assay (ELISA) for antiplatelet factor 4 (anti-PF4)/heparin antibodies is expressed in terms of optical density (OD). Previous studies have shown correlation between OD and heparin-induced thrombocytopenia (HIT) diagnosis. However, these were mainly laboratory based. OBJECTIVE: Retrospective correlation of clinical HIT to ELISA OD. PATIENTS/METHODS: We conducted a retrospective study involving 104 patients with a positive ELISA for anti-PF4/heparin antibodies between 2008 and May 2012. For each patient, a clinical diagnosis was adjudicated based on different features including "4T scores," laboratory results, and a 3-month clinical follow-up. RESULTS: In this study, 28.8% of the patients were HIT positive, and 71.2% HIT negative. Patients with positive diagnosis had significantly higher mean OD (2.15 ± 0.76 vs 0.83 ± 0.62). Patients with OD <1.0 only had 3.4% positive diagnosis versus 45.5% for OD 1.0 to 2.0 and 78% for >2.0 units. CONCLUSION: This study is a clinical confirmation that ELISA OD results are correlated with the probability of a clinical diagnosis of HIT.