A patient-reported outcome or PRO is a questionnaire used in a clinical trial or a clinical setting, where the responses are collected directly from the patient. PRO is an umbrella term that covers a whole range of potential types of measurement but is used specifically to refer to questionnaires completed by the patient. PRO data may be collected via self-administered questionnaires completed by the patient or via interviewer-administered questionnaires. The latter will only qualify as a PRO where the interviewer is gaining the patient’s views, not where the interviewer uses patient responses to make a professional assessment or judgment of the impact of the patient’s condition. Thus, PROs are a means of gathering patient rather than clinical or other views on the content covered by the questionnaire.
The term PRO should not be confused with patient-based outcomes. The latter implies that questionnaire covers issues of specific concern to the patient. However, patient-reported implies only that the patient provides the information. This information may, or may not, be of concern to the patient.
A well-designed PRO questionnaire should assess either a single underlying characteristic or, where it addresses multiple characteristics, should be a number of scales that each address a single characteristic. These measurement “characteristics” are termed constructs and the questionnaires used to collect them, termed instruments, measures, scales or tools.
A questionnaire that measures a single construct is described as unidimensional. Items (questions) in a unidimensional questionnaire can be added to provide a single scale score. However, it cannot be assumed that a questionnaire is unidimensional simply because the author intended it to be. This must be demonstrated mathematically (for example, by Rasch analysis) . A questionnaire that measures multiple constructs is termed multi-dimensional. A multi-dimensional questionnaire is used to provide a profile of scores; that is, each scale is scored and reported separately. It is not appropriate to produce an overall single summary score for a multi-dimensional questionnaire (akin to adding apples and pears together). Each scale within a multidimensional questionnaire should have been shown by the authors to be unidimensional.
The most commonly used PRO questionnaires assess one of the following constructs:
- Symptoms (impairments)
- Functioning (disability)
- Health related quality of life (HRQL)
- Quality of life (QoL).
Measures of symptoms may focus on a range of impairments or on a specific impairment such as depression or pain. Measures of functioning assess activities such as personal care, activities of daily living and locomotor activities. HRQL instruments are generally multi-dimensional questionnaires assessing a combination of aspects of impairments and/or disability and reflect a patient’s health status. In contrast, QoL goes beyond impairment and disability by asking about the patient’s ability to fulfil their needs and also about their emotional response to their restrictions. The most widely used model of QoL is the needs-based model.
It is essential that a PRO questionnaire meets certain development, psychometric and scaling standards if it is to provide useful information. Specifically, questionnaires should have a sound theoretical basis and should be relevant and well targeted to the patient group with which they are to be used. They should also be reliable, valid and responsive and the structure of the scale (whether it possesses a single or multiple domains) should have been thoroughly tested using appropriate methodology in order to justify the use of scale or summary scores.
Questionnaires may be generic (designed to be used in any disease population and cover a broad aspect of the construct measured) or condition-specific (developed speficially to measure those aspects of outcome that are of importance for a people with a particular medical condition).
Many of the common generic PRO tools assess HRQL. For example, the SF-36 Health Survey (SF-36 Health Survey), SF-12 Health Survey (SF-12 Health Survey), the Sickness Impact Profile and the Nottingham Health Profile.
Condition specific tools may capture any of the constructs listed above, depending on the purpose for which they were designed. Examples include the Adult Asthma Quality of Life Questionnaire (AQLQ), Migraine Specific Quality of Life (MSQOL), the Ankylosing Spondylititis Quality of Life questionnaire (ASQoL) and the Seattle Angina Questionnaire (SAQ), to name a few.
Reliability and Validity of Dyax's Novel Patient Reported Outcome Measures PROs Affirmed in Published Study.
Sep 23, 2009; Dyax Corp. (NASDAQ:DYAX) announced a study published evaluating the Company's novel Patient Reported Outcome Measures (PROs) used...