patient-reported outcome patient-reported outcome a patient-reported outcome (pro) is a health outcome directly reported by the patient who experienced it. it stands in contrast to an outcome reported by someone else, such as a physician-reported outcome, a nurse-reported outcome, and so on. pro methods, such as questionnaires, are used in clinical trials or other clinical settings, to help better understand a treatment's efficacy or effectiveness. the use of digitized pros, or electronic patient-reported outcomes (epros), is on the rise in today's health research setting. terminology pros should not be confused with pcos, or patient-centered outcomes. the latter implies the use of a questionnaire covering issues and concerns that are specific to a patient. instead, patient-reported outcomes refers to reporting situations in which only the patient provides information related to a specific treatment or condition; this information may or may not be of concern to the patient. further, pros should not be confused with prems (patient reported experience measures), which focus more on a patient's overall experience versus a focus on specific treatment outcomes. the term pros is becoming increasingly synonymous with "patient reported outcome measures" (proms). overview pro is an umbrella term that covers a whole range of potential measurements, but it specifically refers to "self-reporting" by the patient. pro data may be collected via self-administered questionnaires, which the patient completes themselves, or through patient interviews. the latter will only qualify as a pro, however, if the interviewer is gaining the patient's views and not using the responses to make a professional assessment or judgment of the impact of a treatment on the patient's condition. thus, pros are used as a means of gathering patient- rather than clinical- or other outcomes perspectives. the patient-reported perspective can be an important asset in gaining treatment or drug approval. there is no incentive for patients to report their outcome data other than to "pay it forward" to the community and help the health industry prevent unnecessary suffering in other patients. characteristics 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. typically, pro tools must undergo extensive validation and testing. 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 empirically (for example, by confirmatory factor analysis or 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 possible to create an overall (single summary) score from a multi-dimensional measure using factor analysis or preference-based methods but some may see this as akin to adding apples and oranges together. questionnaires may be generic (designed to be used in any disease population and cover a broad aspect of the construct measured) or condition-targeted (developed specifically to measure those aspects of outcome that are of importance for a people with a particular medical condition). the most commonly used pro questionnaires assess one of the following constructs: symptoms (impairments) and other aspects of well-being functioning (disability) health status general health perceptions quality of life (qol) health related quality of life (hrqol) reports and ratings of health care. 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. health-related quality of life 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 fulfill their needs and also about their emotional response to their restrictions. a new generation of short and easy-to-use tools to monitor patient outcomes on a regular basis has been recently proposed. these tools are quick, effective, and easy to understand, as they allow patients to evaluate their health status and experience in a semi-structured way and accordingly aggregate input data, while automatically tracking their physio-emotional sensitivity. as part of the national institute of health's roadmap initiative, the patient-reported outcomes measurement information system (promis) uses modern advances in psychometrics such as item response theory (irt) and computerized adaptive testing (cat) to create highly reliable and validated measurement tools. the literature suggests increasing consistency in recommendations to guide prom selection for clinical trials. validation and quality assessment it is essential that a pro instrument satisfy certain development, psychometric and scaling standards if it is to provide useful information (e.g.). specifically, measures should have a sound theoretical basis and should be relevant to the patient group with which they are to be used. they should also be reliable and valid (including responsive to underlying change) 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. the validation of the pro measures should incorporate not only short-term but also long-term success in order to be able to reflect sustainability of interventions. classic examples of such tools and methods are noted in commonly used oncology tools, such as fact or eortc tools. these standards must be maintained throughout every target language population. in order to ensure that developmental standards are consistent in translated versions of a pro instrument, the translated instrument undergoes a process known as linguistic validation in which the preliminary translation is adapted to reflect cultural and linguistic differences between diverse target populations. preference-based preference-based pros can be used for the computation of a quality-adjusted life year. a preference based pro has an algorithm attached to the pro instrument which can 'weigh' the outcomes reported by patients according to the preferences for health outcomes of a group of individuals such as the general public or of patient groups. the purpose of this 'weighing' is to make sure that elements of health that are very important receive larger weight when computing sum scores. for example, individuals may consider problems with their mood to be more important than limitations in usual activities. examples of generic preference-based pros are the health utilities index and the eq-5d. condition-targeted preference-based pros also exist, but there are some questions regarding their comparability to generic pros when used for the computation of quality adjusted life years. examples