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Pain and Urinary Symptoms Should Not be Combined into a Single Score: Psychometric Findings from the MAPP Research
James W Griffith1, Alisa J Stephens-Shields1, Xiaoling Hou1
1Northwestern University (JWG, RBL), Chicago, Illinois; NorthShore University HealthSystem (FT), Chicago, Illinois; University of Chicago (FT), Chicago, Illinois; University of Pennsylvania (AJS-S, XH, JRL), Philadelphia, Pennsylvania; Temple University (MP), Philadelphia, Pennsylvania; University of California-Los Angeles (BDN), Los Angeles, California; Cedars-Sinai Medical Center (JK), Los Angeles, California; University of California-San Diego and Veterans Affairs Center of Excellence for Stress and Mental Health, San Diego (NA), California; University of Washington (TCE, JNK), Seattle, Washington; University of Michigan (DAW, JQC), Ann Arbor, Michigan; National Institute of Diabetes and Digestive and Kidney Disease, National Institutes of Health (CM, JWK), Bethesda, Maryland; Washington University in St. Louis (SS, BAH, HHL), St. Louis, Missouri; University of Iowa (CSB), Iowa City, Iowa.
Purpose:
The purpose of this study was to create symptom indexes, that is scores derived from questionnaires to accurately and efficiently measure symptoms of interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome, collectively referred to as urological chronic pelvic pain syndromes. We created these indexes empirically by investigating the structure of symptoms using exploratory factor analysis.
Materials And Methods:
As part of the MAPP (Multi-Disciplinary Approach to the Study of Chronic Pelvic Pain) Research Network 424 participants completed questionnaires, including GUPI (Genitourinary Pain Index), ICSI (Interstitial Cystitis Symptom Index) and ICPI (Interstitial Cystitis Problem Index). Individual items from questionnaires about bladder and pain symptoms were evaluated by principal component and exploratory factor analyses to identify indexes with fewer questions to comprehensively quantify symptom severity. Additional analyses included correlating symptom indexes with symptoms of depression, which is a known comorbidity of patients with pelvic pain.
Results And Conclusions:
Exploratory factor analyses suggested that the 2 factors pain severity and urinary severity provided the best psychometric description of items in GUPI, ICSI and ICPI. These factors were used to create 2 symptom indexes for pain and urinary symptoms. Pain, but not urinary symptoms, was associated with symptoms of depression on multiple regression analysis, suggesting that these symptoms may impact patients with urological chronic pelvic pain syndromes differently (B ± SE for pain severity = 0.24 ± 0.04, 95% CI 0.16-0.32, β = 0.32, p <0.001). Our results suggest that pain and urinary symptoms should be assessed separately rather than combined into 1 total score. Total scores that combine the separate factors of pain and urinary symptoms into 1 score may be limited for clinical and research purposes.