Pelvic organ prolapse (POP) is a prevalent condition that, although not life-threatening, affects an individual’s quality of life, physical function, sexual function, body image and social function. [1] In measuring intervention impact, patient-reported outcome measures are recommended as they aim to capture what is most meaningful to patients. However, PROMs must have strong psychometric properties such as validity, reliability, and responsiveness to accurately reflect the impact of this condition as perceived by the patient. A previous review by Gray et al., 2021.[2] summarized the different PROMs used for POP. However, no study has systematically reviewed the measurement properties of PROMs used for POP based on the critical appraisal tool recommended by the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN).[3] This tool provides a systematic approach for assessing the methodological quality of studies used to evaluate the measurement qualities of a PROM, as well as the qualities of the PROM. As such, we aim to conduct the first systematic review (registered a priori in PROSPERO database) of studies that report on the psychometric properties of PROMs used for evaluating POP following the COSMIN guidelines.

The search strategy included controlled vocabulary and free-form text related to three search concepts: (Pelvic Organ Prolapse, Survey and Questionnaires/PROMs, and Validation Studies/Psychometrics) and the search terms and filters recommended by COSMIN.[3] Medline, EMBASE, CINAHL, Scopus, and Cochrane databases were searched from inception to May 2022. Studies were eligible if they involved 1) at least one group of female adults diagnosed with or presenting with symptoms of POP; 2) a self-reported outcome measure (PROMs, questionnaires) to evaluate POP-related domains; and 3) measurement of at least one psychometric property including PROM development, content validity, internal consistency, reliability, measurement error, concurrent validity, discriminative validity, and responsiveness. Studies were excluded if their analysis included patients with mixed conditions (i.e., patients with urinary incontinence and POP together) and/or if the PROM was not used in its original form. In addition, as no gold standard exists for PROMs, studies on criterion validity were excluded from this review, as well as cross-cultural validity. Two reviewers independently screened abstracts and conducted the full-text review using the Covidence software. Methodological quality was assessed using the COSMIN risk of bias (ROB) checklist, and measurement quality was determined using the COSMIN criteria for good measurement properties.

There were 2495 abstracts screened and 67 full-texts reviewed, from which 12 studies met the selection criteria and were included in this review (Figure 1). In those studies, 12 different PROMs were identified, including the Australian Pelvic Floor Questionnaire (APFQ), the Body Image in Pelvic Organ Prolapse Questionnaire (BIPOP), the electronic Personal Assessment Questionnaire-Pelvic Floor (ePAQ-PF), the International Consultation on Incontinence Questionnaire-Vaginal Symptoms (ICIQ-VS) module, Pelvic Floor Distress Inventory (PFDI) and its short form (PFDI-20), the Pelvic Floor Impact Questionnaire (PFIQ) and its short form (PFIQ-7), the Pelvic Organ Prolapse Symptom Score (POP-SS), the Pelvic Organ Prolapse-Urinary Incontinence (PISQ-IR) questionnaire, the Prolapse Quality of Life Questionnaire (P-QOL), and the Sheffield Prolapse Symptoms Questionnaire (SPS-Q). Most PROMs were only evaluated on one or two measurement properties; however, the ICIQ-VS was assessed on seven properties. The most evaluated measurement properties were internal consistency (6 PROMs, six studies) and responsiveness (11 PROMs, ten studies). 

Five of the included studies reported on PROM development methodologies; the BIPOP study was rated as having Adequate ROB, the P-QOL and the POP-SS were rated as having Doubtful ROB, and the ICIQ-VS and the SPS-Q were rated as having Inadequate ROB. The PROMs that were assessed for content validity were the BIPOP, ICIQ-VS, P-QOL, and SPS-Q. All studies were rated as having Doubtful ROB because of not conforming with the COSMIN standards of reporting at least two researchers in the analysis of relevance, comprehensiveness, and comprehensibility.

All other measurement properties are summarized in Table 1. Only two studies reported on structural validity (BIPOP and the ICIQ-VS). Internal consistency was the best-performing measurement property across PROMs, with all six studies on six different PROMs (BIPOP, ICIQ-VS, PFDI-20, PFIQ-7, POP-SS, and P-QOL) receiving the lowest ROB and the highest rating of Very Good.

All four studies on reliability (PROMs: BIPOP, ICIQ-VS, P-QOL, SPS-Q) received a ROB rating of Doubtful as the studies either did not report on how they confirmed the stability of the measured construct or of the testing conditions. Regarding the measurement quality, only the BIPOP and the ICIQ-VS provided results that met a Sufficient rating. No studies investigated measurement error.

The methodological quality of the studies assessing construct validity (concurrent validity, discriminative validity) and responsiveness varied across studies, with the high ROB ratings being primarily due to the incorrect or the incomplete reporting of interventions, statistical analysis, or results (see Table 1). Most PROMs received a Sufficient rating for the measurement quality of responsiveness in a surgical setting. Only five studies evaluated PROM responsiveness in a conservative management setting (PFDI, PFDI-20, PFIQ, POP-SS, PSIQ-IR).

Overall, the included studies spanned nearly two decades of research, during which time the standards for PROM reporting have expanded considerably. COSMIN provides a hierarchy when evaluating the measurement properties of PROMs. The first property to be considered is content validity, as this property assesses how well all items of the PROM are relevant to the construct being measured and the patient population. Only four of the 12 PROMs had evidence supporting this measurement property in the POP population. 

Next, the internal structure of the PROM should be evaluated. The BIPOP and ICIQ-VS had some evidence for sufficient structural validity in the POP population. They were the only PROMs to demonstrate a robust internal structure according to COSMIN standards. Lastly, the remaining measurement properties (reliability, measurement error, construct validity and responsiveness) are considered. Most studies found that the responsiveness of the identified PROMs was sufficient for use in a surgical setting. This was not the case for conservative management settings where only the PFDI, PFDI-20, and the POP-SS provided sufficient evidence for measurement quality.

This original work identified a gap in evidence in terms of the measurement quality of identified PROMs when used in the POP population. Few PROMs have empirical evidence supporting their content validity, as well as their responsiveness to conservative interventions. Further research is needed to assess the full spectrum of measurement properties identified by COSMIN when considering existing PROMs used for those with POP.

Sung VW, Rogers RG, Barber MD, Clark MA. Conceptual framework for patient-important treatment outcomes for pelvic organ prolapse. Neurourol Urodyn. 2014;33(4):414-9
Gray TG, Vickers H, Krishnaswamy P, Jha S. A systematic review of English language patient-reported outcome measures for use in urogynaecology and female pelvic medicine. International Urogynecology Journal. 2021;32(8):2033-92.
Prinsen CAC, Mokkink, L. B., Bouter, L. M., Alonso, J., Patrick, D. L., De Vet, H. C., et al. . COSMIN guideline for systematic reviews of Patient-Reported Outcome Measures. 2018 Available from: https://cosmin.nl/wp-content/uploads/COSMIN-syst-review-for-PROMs-manual_version-1_feb-2018.pdf

Continence 7S1 (2023) 101004
DOI: 10.1016/j.cont.2023.101004