Evaluating the measurement properties of patient-reported outcome measures in radiotherapy-induced xerostomia.

OBJECTIVE: Radiotherapy-induced xerostomia (RIX) is one of the most common adverse effects of radiotherapy to the head and neck, and a major determinant of survivors' quality of life. A number of patient-reported outcome measures (PROMs) have been used in clinical trials of therapeutic interventions for RIX; however, little is known regarding their measurement properties and methodological quality. METHODS: We conducted a systematic literature search in Embase, MEDLINE and PsycINFO for articles published up to May 2019 and evaluating at least one measurement property of PROMs relevant to RIX. The COSMIN guidelines were used to assess relevant measurement properties and methodological quality. RESULTS: Nine validations studies were identified reporting on four PROMs relevant to RIX. The Xerostomia Questionnaire (XQ) showed overall high-quality evidence for structural validity and internal consistency, but low-quality evidence supporting reliability. The methodological quality of the Groningen Radiotherapy-Induced Xerostomia scale (GRIX), Xerostomia Inventory (XI) and the Xerostomia Quality of Life Scale (XeQoLS) was relatively low for all measurement properties. CONCLUSIONS: The XQ was found to have the highest potential to capture changes in RIX according to COSMIN guidelines. Additional validation studies are required to further understand the methodological quality of the XI, GRIX and XeQoLS.

Measurement properties of patient-reported outcome measures in radiotherapy-induced trismus.

Trismus or lockjaw is the reduction in mouth opening. Radiotherapy-induced trismus occurs when the masticatory muscles are within range of radiation treating head and neck cancer, resulting in muscular fibrosis and trismus. We aim to assess the measurement properties of available validated patient-reported outcome measures relevant to radiotherapy-induced trismus in head and neck cancer patients. Systematic electronic searches were performed in MEDLINE and EMBASE databases to identify studies validating radiotherapy-induced trismus with patient-reported outcome measures up to January 2018. Two reviewers independently rated the methodological quality of identified validation studies, using the consensus-based standards for the selection of health status measurement instrument (COSMIN) checklist. The level of evidence for measurement properties was then summarised based upon pre-defined criteria. Only one of the 280 retrieved studies were deemed fit for inclusion. The Gothenburg Trismus Questionnaire was assessed and found to have a good methodological quality of measurement properties except for reliability, which was poor. There was a moderate level of evidence supporting internal consistency, content validity, structural validity and hypothesis testing. The evidence for test-retest reliability remains unknown in the population of interest. The Gothenburg Trismus Questionnaire is the only patient-reported outcome measure in the field of showing some good measurement properties, and it may therefore represent a useful instrument for the assessment of radiotherapy-induced trismus in head and neck cancer patients. However, further validation studies are needed especially with respect to the reliability, measurement error and the responsiveness of this instrument.