Evaluating test-retest reliability in patient-reported outcome measures for older people: A systematic review

When researchers plan to assess the test-retest reliability of patient-reported outcome measures for older people, they need to consider an adequate time interval of approximately 13 days and the sample size of about 5 times the number of items. Particularly, statistical methods should not only be selected based on the types of scores of the patient-reported outcome measures, but should also be described clearly in the studies that report the results of test-retest reliability.