This Guide to Statistics and Methods provides an overview of patient-reported outcome measures for clinical research, emphasizes several important considerations when using them, and points out their limitations.
Health conditions may cause patients to feel ill and have impaired functioning in their daily lives. Thus, it is important to assess how patients are feeling and functioning when evaluating the effects of interventions to prevent or treat health conditions. Aspects of health that patients can report on directly, such as the severity of pain or limitations in physical functioning, are patient-reported outcomes.
The recommended quantitative approach to measure these aspects of health status is to ask patients directly using a standardized questionnaire. Patient-reported outcome measures are reports of “the status of a patient’s health condition that comes directly from the patient without interpretation of the patient’s response by a clinician or anyone else.”1 An example of a patient-reported outcome measure, the Short Form 36 (SF-36), was used in a randomized clinical trial conducted by Ghogawala et al2 to compare 2 surgical approaches (ventral or dorsal) for the treatment of cervical spondylotic myelopathy, which is a condition that can cause significant impairments in physical functioning.
EXPLANATION OF THE CONCEPT
What Is a Patient-Reported Outcome Measure?
A patient-reported outcome measure is a questionnaire designed to assess a patient-reported outcome; the outcome being assessed is referred to as the concept, construct, or domain; and the individual questions of the patient-reported outcome measure are called items. Some patient-reported outcome measures are designed to measure only a single concept (eg, a 4-item measure of fatigue), whereas others are designed to measure multiple concepts (eg, the SF-36, which measures 8 health concepts and includes 36 items). A patient’s score on the concept is estimated by their answers to 1 or more questions (or items), using standardized response options for the patient-reported outcome measure.
For example, an item from the Patient-Reported Outcomes Measurement Information System SexFS3 intended to measure interest in sexual activity asks, “In the past 30 days, how interested have you been in sexual activity?” The response options are not at all, a little bit, somewhat, quite a bit, or very much. Ordered sets of response options such as these that are expressed as words are typically converted to numbers to compute a score (eg, not at all = 0; a little bit = 1). Some response options integrate numbers in the scale, such as the 11-point pain intensity numeric rating scale in which 0 = no pain and 10 = worst pain imaginable. Based on responses to the items, a patient-reported outcome measure generates a numeric score that represents the patient’s level on the health concept of interest.
Designing a new patient-reported outcome measure and collecting validity evidence involves a rigorous multistep process that includes both qualitative and ...