Interpreting Patient Reported Urinary and Sexual Function Outcomes across Multiple Validated Instruments

Abstract

Purpose: Comparing patient reported outcomes such as urinary and erectile function across institutions is critical for prostate cancer research and quality assurance. Such comparisons are complicated due to the use of different questionnaires. We aimed to develop a method to convert scores among 4 commonly used instruments.

Materials and methods: Patient reported data on urinary and sexual function were collected on 1,284 men with localized prostate cancer using the EPIC-26 (Expanded Prostate Index Composite), PCI (UCLA Prostate Cancer Index), SHIM (Sexual Health Inventory for Men) and I-PSS (International Prostate Symptom Scale) questionnaires. We investigated several methods to convert scores among questionnaires.

Results: Conversion between EPIC and PCI urinary and sexual function subscales was best achieved using only the subset of questions asked on both questionnaires. For the conversion between EPIC or PCI erectile function scores and SHIM scores, we defined thresholds of poor, intermediate and good function as EPIC/PCI 0 to 40 and SHIM 1 to 7, EPIC/PCI 41 to 59 and SHIM 8 to 16, and EPIC/PCI 60 to 100 and SHIM 17 to 25, respectively. Urinary continence scores highly correlated for PCI and EPIC (r = 0.94). No comparison was possible for I-PSS with EPIC and PCI due to differences in the domains addressed by these questionnaires.

Conclusions: We have introduced methods to convert scores among the EPIC, PCI and SHIM questionnaires. While these conversion methods may introduce minor imprecision, to our knowledge they represent the best available tools to combine and compare patient reported outcomes that are assessed using different instruments in men undergoing radical prostatectomy or active surveillance.

Keywords: erectile dysfunction; patient outcome assessment; prostatic neoplasms; surveys and questionnaires; urinary incontinence.