Assessing severity of illness and outcomes of treatment in children with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME): a systematic review of patient-reported outcome measures (PROMs). 
Chronic Fatigue Syndrome or Myalgic Encephalomyelitis (CFS/ME) in children is characterized by persistent or recurrent debilitating fatigue which results in a substantial reduction in activity.  There is a growing interest in the use of questionnaires, or patient-reported outcome measures (PROMs), to assess how patients function and feel in relation to their health and associated healthcare.  However, guidance for PROM selection for children with CFS/ME does not exist.  We reviewed the quality and acceptability of PROMs used with children with CFS/ME to inform recommendations for practice.  We conducted a systematic review of PROMs completed by children with CFS/ME.  The quality of the evaluative studies and the reviewed measures were assessed against recommended criteria using an appraisal framework and the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist.  We sought evidence of measurement (reliability, validity, responsiveness, interpretability, data quality) and practical properties (acceptability, relevance, feasibility).  Sixteen articles were included in the review, providing evidence of reliability and/or validity for 13 PROMs.  Of these, five were child-specific (one health-related quality-of-life; four emotional well-being) and eight were not (four emotional well-being, three fatigue-specific; and one generic).  All measures had limited evidence of measurement properties and no evidence of practical properties.  Recommendations for patient-reported assessment are difficult to make because of limited evidence of the quality and acceptability of PROMs for children with CFS/ME.  The appraisal method highlighted significant methodological and quality issues which must be addressed in future research.  There is a lack of qualitative evidence describing the outcomes of healthcare that are important to children with CFS/ME, and the relevance or appropriateness of available measures.  Future PROM development and evaluation in this group must seek to involve children collaboratively to ensure that the outcomes that children care about are assessed in an acceptable way.