Elevated FVIII levels in hereditary hemorrhagic telangiectasia:Implications for clinical management

Abstract

Objectives: The objective of this study was twofold: to determine the prevalence of arterial and venous thromboembolic events in the Norwegian Hereditary Hemor- rhagic Telangiectasia (HHT) population, and to explore potential factors linked to such events, with particular emphasis on FVIII. Methods: Patients with an HHT diagnosis attending the Otorhinolaryngology Department at Oslo University Hospital—Rikshospitalet were included consecutively between April 2021 and November 2022. We recorded the participants' medical his- tory with an emphasis on thromboembolic events. Measurements of blood constitu- ents, including FVIII, FIX, vWF, hemoglobin, iron, ferritin, and CRP were performed. Results: One hundred and thirty-four patients were included in the study. The total prevalence of thromboembolic events among the participants was 23.1%. FVIII levels were high (>150 IU/dL) in the majority of HHT patients (n = 84) (68.3%) and were significantly associated with thromboembolic events (p < .001), as was age. Of the patients with high FVIII levels, 28 (33%) had experienced a thromboembolic event. Furthermore, FVIII levels were measured consecutively in 51 patients and were found to fluctuate above or below 150 IU/dL in 25% of these cases. Conclusion: Thromboembolic events are highly prevalent in the Norwegian HHT popula- tion and are significantly associated with FVIII levels. FVIII levels can fluctuate, and measure- ments should be repeated in HHT patients to assess the risk of thromboembolic events. Level of Evidence: 4.