Diagnosing heparin-induced thrombocytopenia in mechanical circulatory support device patients.

BACKGROUND: Mechanical circulatory support device (MCSD) patients with positive heparin-induced thrombocytopenia (HIT) screening pose a unique challenge, as clinicians must make rapid decisions about their anticoagulation and whether they can safely undergo cardiopulmonary bypass. We identified screening practices at our institution and other institutions nationwide that differed from American Society of Hematology (ASH) guidelines. This discovery prompted a data review to confirm the applicability of guidelines to this unique population and to highlight complications of "gestalt" screening. METHODS: Our study included MCSD patients with HIT testing from April 2014 to August 2020. We evaluated 510 PF4 IgG ELISA results. RESULTS: HIT was confirmed in 4.2% of patients. There was an increased prevalence of HIT in patients with nondurable (5.3%) vs durable devices (2.9%) or those in the preimplantation setting (1.3%), however this difference was not statistically significant (p = 0.26). None of the patients with a low probability 4T Score had HIT. All patients with a high probability 4T Score and PF4 immunoassay OD >2.0 had HIT. False positive results occurred in 22% of assays ordered for patients with a low probability 4T Score. Twelve patients with a low probability 4T Score and a false positive immunoassay were switched to a direct thrombin inhibitor (DTI) while awaiting confirmatory results. Two patients experienced clinically significant bleeding after conversion to a DTI. An organ was refused in one patient with false positive HIT screening. CONCLUSIONS: Our findings demonstrate that an opportunity exists to improve clinical outcomes by re-emphasizing the utility of established guidelines and highlighting their safe use in the MCSD patient population.

Turoctocog alfa for the treatment of hemophilia a.

Hemophilia A (HA) represents one of the most common genetic bleeding disorders worldwide and results from a deficiency in factor VIII (FVIII). The mainstay of treatment for HA is repletion of FVIII. Numerous plasma-derived and recombinant factor concentrates are available, each with clinical advantages and disadvantages. Nonfactor products including desmopressin and antifibrinolytic agents can also be used, depending on the clinical situation and severity of FVIII deficiency. Turoctocog alfa is the most recent addition to recombinant FVIII concentrates available for the treatment of HA. Pharmacokinetic trials in animals and humans have demonstrated characteristics similar to those of other recombinant FVIII concentrates. Clinical trials have supported efficacy and safety in the management of HA in treatment-experienced patients; study results of turoctocog alfa in treatment-naïve patients are pending. A smaller study in hemophilic patients undergoing surgery has demonstrated positive results. Although turoctocog alfa was approved by the U.S. Food and Drug Administration in 2013, it will not be available on the market until 2015. Turoctocog alfa appears to be a safe and effective alternative to currently available recombinant FVIII concentrates; however, its place in therapy among these products has yet to be elucidated.

Overdiagnosis of heparin-induced thrombocytopenia in surgical ICU patients.

BACKGROUND: Heparin use in surgical patients places them at increased risk for developing heparin-induced thrombocytopenia (HIT). The false positive rate of HIT using the current standard criteria is unknown in surgical ICU patients, who often have confounding factors that cause thrombocytopenia. STUDY DESIGN: Surgical ICU patients, admitted over a 2-year period with a positive screening test for HIT (platelet factor [PF] 4 ≥ 0.4 optical density [OD]), were reviewed retrospectively at a single institution. Correlation of the Warkentin 4-T score and commercial heparin PF4 ELISA with serotonin releasing assay (SRA) was performed. Logistic regression was used to determine independent risk factors associated with the development of HIT. RESULTS: PF4 tests were requested in 643 patients based on a clinical suspicion of HIT. Of these, 104 patients had a PF4 result, an SRA value (%), and a 4-T score available. Twenty patients (19%) had true positive HIT, defined as a positive PF4 and positive SRA (SRA ≥ 20%). Eighty-four patients (81%) were false positive, defined as a positive PF4 and negative SRA. Five of 58 patients with Warkentin score of 0 to 3, and 6 of 14 patients with Warkentin score of 6 to 8 were HIT positive by SRA. CONCLUSIONS: In surgical ICU patients, clinical suspicion for HIT necessitates PF4 and SRA analysis. Testing for HIT or treatment with a direct thrombin inhibitor should not depend on the Warkentin 4-T score alone. Although a PF4 ≥ 0.4 OD is considered a positive screening test for HIT, a PF4 ≥ 2.0 OD is preferable in surgical ICU patients.