Godfrey, AnnaSousos, NikolaosFrewin, RebeccaPrahladan, MaheshGreen, AnnaMcGregor, AndrewKhan, AlesiaMilne, KateAmin, FaisalTorre, ElenaGudgin, EmmaLambert, JonathanWilson, AndrewRoyston, DanielHarrison, ClaireMead, Adam2025-07-012025-07-012024-07-14Godfrey, A. L., Sousos, N., Frewin, R., Prahladan, M., Green, A. C., McGregor, A., Khan, A., Milne, K., Amin, F., Torre, E., Gudgin, E. J., Lambert, J., Wilson, A. J., Royston, D., Harrison, C. N., & Mead, A. J. (2024). Clinical utility of investigations in triple-negative thrombocytosis: A real-world, multicentre evaluation of UK practice. British journal of haematology, 205(4), 1411–1416. https://doi.org/10.1111/bjh.1964310.1111/bjh.19643https://hdl.handle.net/20.500.14709/162Diagnosis of essential thrombocythaemia (ET) is challenging in patients lacking JAK2/CALR/MPL mutations. In a retrospective evaluation of 320 patients with 'triple-negative thrombocytosis', we assessed utility of bone marrow histology (90.9% of patients) and myeloid gene panel (MGP, 55.6%). Supportive histology ('myeloproliferative neoplasm-definite/probable', 36.8%) was associated with higher platelet counts and varied between centres. 14.6% MGP revealed significant variants: 3.4% JAK2/CALR/MPL and 11.2% other myeloid genes. Final clinical diagnosis was strongly predicted by histology, not MGP. 23.7% received cytoreduction (17.6% under 60 years). Real-world 'triple-negative' ET diagnosis currently depends heavily on histology; we advocate caution in MGP-negative cases and that specific guidelines are needed.enHaematologyDiagnosisJournal Article