{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,16]],"date-time":"2026-04-16T23:06:37Z","timestamp":1776380797188,"version":"3.51.2"},"reference-count":25,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2024,6,24]],"date-time":"2024-06-24T00:00:00Z","timestamp":1719187200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Haemophilia"],"published-print":{"date-parts":[[2024,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Introduction<\/jats:title><jats:p>Diagnosing hemophilia B (HB) carrier status is important to manage bleeding in carriers and to prevent bleeding in potential offspring. Without a family history of hemophilia, diagnosing HB carrier status is challenging. Genetic testing is the gold\u2010standard, however it is reserved for individuals with a high suspicion of carrier status.<\/jats:p><\/jats:sec><jats:sec><jats:title>Aims<\/jats:title><jats:p>To describe the distribution of activated partial thromboplastin time (aPTT) and factor IX coagulant (FIX:C) levels in HB carriers and assess the ratio of FIX:C to other Vitamin K dependent factors (FII:C, FVII:C, FX:C) as an indicator of HB carrier status.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>In this retrospective, single\u2010centre cohort study, subjects were included if they were obligate or genetically proven HB carriers. Distributions of aPTT and FIX:C were described and the relationship between FIX:C levels in carriers and severity of familial HB was analysed. Ratios of FIX:C to FII:C, FVII:C, FX:C were calculated.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Seventy\u2010two female HB carriers (median age: 34 years; IQR 24\u201343) were included. Median aPTT and FIX:C levels were 33.0\u00a0s [IQR 30.0\u201337.0] and 57\u00a0IU\/dL [IQR 43\u201374]. Fifteen carriers (21%) had mild HB (FIX:C levels of 10\u201340\u00a0IU\/dL). FIX:C levels trended higher in carriers of mild HB versus carriers of moderate\/severe HB. In six carriers, the median ratio of FIX:C to other Vitamin K dependent factors was 0.44, with 92% of ratios being \u2264 0.75.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>aPTT and FIX:C levels were unreliable in diagnosing HB carrier status. A low ratio of FIX:C to other Vitamin K dependent factors may be a useful marker of HB carrier status.<\/jats:p><\/jats:sec>","DOI":"10.1111\/hae.15068","type":"journal-article","created":{"date-parts":[[2024,6,25]],"date-time":"2024-06-25T03:57:59Z","timestamp":1719287879000},"page":"1003-1009","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Identifying hemophilia B carriers: Utility of aPTT, factor IX levels and ratios of factor IX to other Vitamin K dependent factors"],"prefix":"10.1111","volume":"30","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1940-3734","authenticated-orcid":false,"given":"Michael","family":"Shu","sequence":"first","affiliation":[{"name":"Division of Haematology\/Oncology Department of Paediatrics The Hospital for Sick Children  Toronto Ontario 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