Do Patient-Reported Quality-of-Life (QoL) Scales Provide an Adequate Assessment of Patients with Cryptoglandular Anal Fistulae? A Systematic Review of Measurement Instruments and Their Content Validity

Background: Cryptoglandular anal fistulae can significantly affect patient quality of life (QoL), making it essential to ensure that any study of fistula treatment assesses the impact on QoL. The aim of this systematic review was to evaluate the content validity of Patient-Reported Outcome Measures (PROMs) that assess QoL in patients with a fistula. Methods: MEDLINE, EMBASE, PsycINFO, and Scopus were searched and studies assessing the content validity of patient-reported QoL measurement instruments, or PROM development studies in patients with cryptoglandular anal fistulae, were included. Data were extracted from eligible studies to determine the instruments’ relevance, comprehensiveness, and comprehensibility, and their quality was assessed according to COnsensus-based Standards for the Selection of health Measurement Instruments (COSMIN). Results: Two PROM development studies were identified, both of which described the development of a disease-specific QoL measurement instrument for patients with cryptoglandular anal fistulae. The overall content validity of these instruments was inconsistent and supported by very low-quality evidence. There were no studies assessing the content validity of established QoL measurement instruments in patients with fistulae. Conclusions: This systematic review could not establish the content validity of the available QoL PROMs for patients with anal fistulae, due either to the absence of designated content validity studies or a lack of comprehensiveness of the available PROMs. This highlights an important gap in the literature that needs to be addressed to ensure high-quality outcome assessment in patients with fistulae.