Minimum and Optimal Factor Levels in Physically Active Hemophiliacs

Introduction

Low levels of coagulation factors can be associated with an increased risk of bleeding. The goal of classic prophylaxis in the treatment of severe hemophilia is therefore to achieve and maintain a factor VIII or IX activity level > 1% of normal. This treatment setup already leads to a significant reduction in bleeding frequency and improves musculoskeletal functions in hemophiliacs.

However, recently a number of opinions have emerged suggesting that during physical activity, bleeding can still occur even with higher factor levels (e.g., > 20%), exacerbating existing joint morbidity, and that the factor level during physical activity also affects bleeding risk (Soucie et al., Blood Adv 2018; den Uijl et al., Blood Transfus 2013). Due to these reasons, a study was conceived whose authors sought to gain further insights.

Estimated Mean Factor Levels

To determine the minimum acceptable and ideal factor levels important for protection against bleeding considering various risk categories, the Sheffield Elicitation Framework (SHELF) method was used. Researchers utilized the NHF physical activity risk classification (created by the American National Hemophilia Foundation − NHF), which includes 5 categories, from low to high risk.

The estimated mean factor levels for various physical activities ranged as follows:

• Minimum factor levels from 4.17 for low-risk to 38.07% for high-risk
• Ideal factor levels from 8.36 for low-risk to 52.05% for high-risk

As the intensity (risk) of physical activity increased, the minimum and ideal factor levels also increased.

For hemophiliacs without joint damage, the mean level (standard deviation; range) for moderately risky physical activity was 11.44% (2.16; 2.53–51.55). For patients with joint damage, it was 12.33% (1.81; 3.87–39.27).

Discussion

The expert team stated that particularly the range of the determined levels was broader than expected. It was confirmed that it is always important to consider the individual characteristics of the patient and their risk factors. The used model also allowed for understanding the need to focus not only on achieving the clinical norm of prophylaxis (i.e., a factor level of at least 1%), but also taking into account the specific patient and the extent of their physical activity.

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Source: Martin A. P., Burke T., Asghar S. et al. Understanding minimum and ideal factor levels for participation in physical activities by people with haemophilia: an expert elicitation exercise. Haemophilia 2020 Apr 8, doi: 10.1111/hae.13985 [Epub ahead of print].