Patient-reported outcomes (PROs) are “any report 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,” according to the National Quality Forum (NQF).
Patient-reported outcome measures (PROMs) are the "tools or instruments used to measure PROs, often (patient) self-completed questionnaires. They may include instruments or tools that measure functional status, health related quality of life, symptom and symptom burden, personal experience of care, and health-related behaviors such as anxiety and depression. They can be either general in nature or disease-specific. Broader PROMs examine aspects that fit a variety of different conditions and allow comparison across these various medical conditions to assist in the evaluation and the implementation of new methods of providing care and equity of service delivery" (Weldring and Smith, 2013).
These statistically-valid patient-centered measures use validated questionnaires to turn a symptom into a numerical score. They complement traditional medical outcome measures, such as surgical complications and mortality rates, to help clinicians understand long-term patient results.
The Cochrane Library, available in the CORE Library, is an excellent source of systematic reviews and studies. However, Cochrane does not currently use "patient reported outcome" as a limiter or search field.
The savvy searcher will need to try out multiple search terms, and searches will likely take several iterations. In other words -- patience and persistence is the key.
For example, health status and quality of life outcomes are an important category of PROs. Published papers often use the terms ‘quality of life’ (QOL), ‘health status’, ‘functional status’, ‘health-related quality of life’ (HRQOL) and ‘well-being’ loosely and interchangeably. Your best bet is to include of these terms in your search strategy, and to examine the Suggested MeSH Terms box for the standard medical terms.