Physical function in patients with cancer: Psychometric characteristics and clinical usefulness of a physical performance test battery

This study investigated the psychometric properties of a battery of physical performance tests, characterized physical function in patients with cancer referred for rehabilitation, and provided normative standards against which to compare disease progression and/or future treatment effectiveness. A total of 109 patients with cancer (55 women and 54 men) and 105 control subjects (66 women and 39 men) participated. Subjects completed self-report questionnaires regarding pain, physical function, and fatigue, and also performed nine physical performance tests: the time taken to complete various tasks (picking up coins, tying a belt, reaching up, putting on a sock, standing from sitting, a 50-foot fast walk, a 50-foot walk at preferred speed), the distance walked in 6 minutes, and the distance reached forward while standing were measured. Inter-tester and test-retest reliability was good to excellent for all tests (ICC₁₁ 0.69 to 0.99). Known group analyses controlling for age were significant (P < 0.001) for all physical performance tests. Control subjects significantly and systematically outperformed those with cancer by a factor of two or three. Examination of the correlation matrices showed relatively low correlations between performance and external measures (r = 0.01 to 0.45). In contrast, correlations among performance measures were generally in the range of r = 0.25 to 0.85. Correlations between self-report of function and performance of functional tests were moderate, suggesting that the two methods of measuring function are complementary and both should be used for assessment and as outcome measures.