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OBJECTIVE: To analyse the demographic, clinical and laboratory data of Beninese patients with haemophilia. METHOD: A prospective survey was conducted in three different hospitals of Benin from April 2021 to March 2022, to analyse clinical and biological features of patients with haemophilia previously diagnosed or identified based on personal/family history. RESULTS: A total of 101 patients were studied, 97 with haemophilia A and 4 with haemophilia B, including 26 new cases identified after family investigation. Their median age was 11 years, and the most frequent initial manifestations were cutaneous-mucosal haemorrhages (29.70%) and post-circumcision haemorrhages (25.74%). Previous joint bleedings were present in 77% of them, with an arthropathy in 65 cases, which particularly affected the knees (75%), elbows (41%) and ankles (29%). Factor VIII (FVIII) levels combined with activated partial thromboplastin time (APTT) values did not always enable, as would be expected, the distinction between severe and moderate haemophilia, since they were >1 IU/dl in 31 of 74 patients with APTT > 80 s, and between 1 and 2 IU/dl in 26 other cases with previous joint haemorrhages, including 18 with chronic arthropathy. Therefore, for these patients, severe haemophilia could not be excluded, and this uncertainty probably reflects technical difficulties affecting the pre-analytical and analytical stages of the APTT and FVIII/IX assays. CONCLUSION: Our study proved that haemophilia is a significant reality in Benin, but also remains under-diagnosed in some districts of the country. In addition, more reliable biological tests are needed in the future to better define the severity of the disease and improve treatment of patients.
RESUMEN
BACKGROUND: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a complication of adenoviral-based vaccine against SARS-CoV-2 due to prothrombotic immunoglobulin (Ig) G antibodies to platelet factor 4 (PF4) and may be difficult to distinguish from heparin-induced thrombocytopenia (HIT) in patients treated with heparin. OBJECTIVES: We assessed the usefulness of competitive anti-PF4 enzyme immunoassays (EIAs) in this context. METHODS: The ability of F(ab')2 fragments of 1E12, 1C12, and 2E1, 3 monoclonal anti-PF4 antibodies, to inhibit the binding of human VITT or HIT antibodies to PF4 was evaluated using EIAs. Alanine-scanning mutagenesis was performed to define the amino acids involved in the interactions between the monoclonal antibodies and PF4. RESULTS: A strong inhibition of VITT IgG binding to PF4 was measured with 1E12 (median inhibition, 93%; n = 8), whereas it had no effect on the binding of HIT antibodies (median, 6%; n = 8). In contrast, 1C12 and 2E1 inhibited VITT (median, 74% and 76%, respectively) and HIT antibodies (median, 68% and 53%, respectively) binding to PF4. When a competitive anti-PF4 EIA was performed with 1E12 for 19 additional VITT samples, it strongly inhibited IgG binding to PF4, except for 1 patient, who had actually developed HIT according to the clinical history. Epitope mapping showed that 1E12 interacts with 5 key amino acids on PF4, of which 4 are also required for the binding of human VITT antibodies, thus explaining the competitive inhibition. CONCLUSION: A simple competitive anti-PF4 EIA with 1E12 could help confirm VITT diagnosis and distinguish it from HIT in patients when both diagnoses are possible.