Content, face, and construct validity of the Irritable Bowel Syndrome Quality of Life (IBS-QOL) as a measure of bowel-related quality of life in spinal cord injury.

INTRODUCTION

Neurogenic bowel dysfunction is commonly encountered after a spinal cord injury (SCI), leading to a tremendous impact on quality of life (QOL). The neurogenic bowel dysfunction score (NBDS) is commonly used to measure the severity of bowel dysfunction and predict QOL. However, there is no comprehensive instrument to assess bowel-specific QOL for SCI patients. Instead, the Irritable Bowel Syndrome-Quality of Life (IBS-QOL) questionnaire evaluates the impact of bowel dysfunction on several aspects of QOL, although this questionnaire has not been validated for the SCI population. Motivated by the compelling need of instruments to accurately evaluate the QOL in patients who develope NBD after SCI, we aimed to assess the construct, content, and face validity of IBS-QOL in this population.

METHODS

Adult SCI patients with at least 3 months after their injury were recruited from the outpatient clinic of a national rehabilitation hospital. Patients completed the NBDS and IBS-QOL via telephone interview or paper survey in the clinic. Content and face validity were assessed via interviews with professionals with expertise in providing chronic care for SCI, as well as a subgroup of patients. Construct validity was assessed using the hypotheses testing method. Internal consistency was assessed using Cronbach's ⍺. Factor analysis was performed to assess the dimensionality of the IBS-QOL in the SCI population.

RESULTS

A total of 106 patients with a median age of 45.5 years (interquartile range: 21-79) participated in the study. The majority of the sample were men (n = 82, 77%) and had endured thoracolumbar injuries (n = 74, 71.2%). Twelve patients (seven English- and five Spanish speakers) and six professionals took part in content/face validation interviews. The median IBS-QOL total score was 15.91/100 (interquartile range: 4.55-33.14). IBS-QOL differentiated the subgroups of patients with severe bowel symptoms in terms of uneasiness, sweating, or headaches during bowel emptying (p = 0.0003), time spent on bowel emptying (p = 0.0065), flatus incontinence (p = 0.0076), and overall satisfaction with bowel function (p < 0.001), demonstrating its adequate construct validity. Interviews with the patients and professionals supported the comprehensiveness, comprehensibility, and relevance of IBS-QOL for assessment of bowel-related QOL in the SCI population. Item-level analysis of professional responses showed that 97% of questions were relevant to the construct and population of interest. Internal consistency analysis yielded a Cronbach's ⍺ of 0.9684. Exploratory factor analysis yielded six underlying factors which cumulatively accounted for 72.21% of the total variance, reflecting the dimensionality of bowel-related QOL in SCI population.

DISCUSSION

IBS-QOL questionnaire is a comprehensive measure of bowel-related QOL which encompasses the concerns of SCI patients. Our findings support the content, face and construct validity of IBS-QOL as a measure of bowel-related QOL in SCI. Further studies are warranted to assess the reliability and responsiveness of IBS-QOL, and to evaluate its performance across different patient populations.