Validity and Reliability of the Two-minute Step Test in Hemophilia

The aim of our study was to evaluate the psychometric properties of the 2-minute step test in hemophilia patients, assess its intra-rater and inter-rater reliability, and evaluate its convergent validity and construct validity supported by measurements of gait, balance, and functionality.

Hemophilia is a rare inherited bleeding disorder caused by a deficiency of factor (F) VIII or IX. It is a chronic group of diseases that primarily manifests as joint (hemarthrosis) and muscle (hematoma) bleeding, affecting quality of life. Easy bruising in early childhood, especially spontaneous joint and muscle bleeding, and a history of prolonged bleeding after procedures and trauma should raise suspicion of hemophilia. The severity of bleeding symptoms is directly related to the degree of FVIII or FIX deficiency. Although the clinical picture varies depending on the duration and frequency of bleeding, the severity of the disease is classified as severe (\<1 IU/dL), moderate (1-5 IU/dL), and mild (5-40 IU/dL). Hemophilia A occurs in 85% of the population (1 in 5,000 male births), while the rate for Hemophilia B is 15% (1 in 30,000 male births). Recurrent and resistant intra-articular bleeding in hemophilia patients leads to the development of hemophilic arthropathy as a result of progressive changes in the joint and bone. Physical performance is significantly affected, especially after recurrent bleeding in the lower extremities. Physical performance is a fundamental physiological indicator of health and functional fitness.Maintaining adequate physical performance is among the most important parameters for preventing social isolation in hemophilia patients, as it improves walking ability and ensures continued independence in daily living activities, participation in school and social activities. Physical performance in children is generally assessed using tests such as the 6-minute walk test, 10-meter walk test, 2-minute walk test, and Timed Up and Go test. However, these assessments may not be practical in routine clinical settings due to space limitations or the need for specialized equipment. The 2-Minute Step Test (2DAT) is a useful alternative that requires minimal equipment and space. This test measures the number of knee lifts (steps) completed during two minutes of steady walking. In addition to simulating walking, the 2DAT also mimics stair climbing, a fundamental activity of daily living. To ensure the test is suitable for both clinical and research settings, its psychometric properties must be evaluated in the relevant population. However, the validity and reliability of the 2DAT have not yet been sufficiently studied in pediatric hemophilia patients. Given the need for accessible and reliable tools to assess physical performance in hemophilia patients, further research is required on the relationship between the 2DAT and this population. In this context, the aim of our study was to evaluate the psychometric properties of the 2-minute walk test in patients with hemophilia, its intra-rater and inter-rater reliability, as well as its convergent validity and construct validity supported by measurements of walking, balance, and functionality.