Smock, Kristi J

ABSTRACT Background Platelet factor 4‐polyanion enzyme‐linked immunosorbent assays (ELISAs) are considered highly sensitive for diagnosing heparin‐induced thrombocytopenia (HIT), such that current practice guidelines recommend use of ELISA‐negative results to exclude HIT. Once HIT is ruled out, alternative, non‐heparin‐based anticoagulant treatments are ceased, and heparin reintroduction frequently occurs. Methods Antigen‐based and PF4‐dependent functional testing were used to study PF4/polyvinylsulfonate ELISA‐negative platelet‐activating antibodies in HIT‐suspected patients. Results Three patients with clinical presentations consistent with HIT tested negative in an ELISA using PF4‐polyvinylsulfonate (PF4/PVS), an antigenic target very commonly used for HIT antibody screening. All three patients demonstrated PF4‐dependent platelet activation in functional testing that was sensitive to blockade of platelet FcγRIIa receptors and inhibited by high concentrations of heparin, consistent with pathogenic HIT antibodies. Functional testing‐based screening of 500 ELISA‐negative patients identified three additional patients whose sera activated platelets in a PF4‐ and FcγRIIa‐dependent manner and had clinical histories consistent with HIT. Five of the six ELISA‐negative HIT patients were re‐exposed to heparin, which precipitated a decrease in platelet counts in all re‐exposed patients, and one patient developed a new thrombus. Conclusions Recognition of ELISA‐negative HIT is critical to avoid harm due to the cessation of alternative anticoagulation therapy and re‐exposure of these patients to heparin.

Abstract Background There have been conflicting messages about the influence of female sex hormones on women's health, with historical messaging indicating that use of estrogen and/or progesterone in peri- or postmenopause poses a significant clinical risk to cisgender women. More recent guidance indicates that the benefit of hormone therapy (HT) outweighs the risks for symptomatic women. Exogenous estrogen use is also indicated for contraception and gender-affirming care. Despite the potential for broad applications, robust reference intervals for estradiol, progesterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are lacking, and guidelines indicate that measurement of 17-β-estradiol (E2), progesterone, LH, or FSH does not facilitate care in women who may be experiencing menopausal symptoms or women taking exogenous HT. Content Here we review the physiological roles of estrogen, progesterone, LH, and FSH. We examine the modes of administration for estrogen and progesterone, clarify the nomenclature related to exogenous hormone use, and comprehensively review the literature for studies evaluating normal concentrations of these female gonadal axis hormones during the menstrual cycle. The content primarily focuses on cisgender women, but some aspects of these hormones in transgender women will also be discussed. Summary Currently, E2, LH, FSH, and progesterone reference intervals for women remain incomplete. Although there are a variety of clinical indications that benefit women using HT, symptoms and shared decision-making should guide care. Collaborative efforts between clinicians and laboratory professionals to better define therapeutic or reference intervals for these hormones can advance women's health globally.

Kanack and colleagues analyze anti-platelet factor 4 antibodies from 5 patients with vaccine-induced thrombotic thrombocytopenia (VITT) secondary to COVID-19 adenoviral vaccination and antibodies from patients with spontaneous heparin-induced thrombocytopenia (HIT) and classical HIT. VITT antibodies are monoclonal or oligoclonal, similar to spontaneous HIT, whereas classical HIT antibodies are polyclonal. Heparin inhibits antibody-induced platelet activation in VITT, suggesting that heparin should be considered for the treatment of VITT.