Design and psychometric evaluation of the Quality of Life in patients with Anal Fistula Questionnaire

BACKGROUND: Quality of life is often considered when deciding and evaluating the treatment strategy for patients diagnosed with anal fistula.
OBJECTIVE: The purpose of this study was to develop and psychometrically test the Quality of Life in Patients with Anal Fistula Questionnaire.
DESIGN: This was an observational cross-sectional study for the development and validation of a psychometric tool.
SETTINGS: The study was conducted at a general hospital in the southeast of Spain.
PATIENTS: A convenience sample included 54 patients diagnosed with anal fistula.
MAIN OUTCOMES MEASURES: The reliability of the tool was assessed through its internal consistency (Cronbach α) and temporal stability (Spearman correlation coefficient (r) between test–retest). The content validity index of the items and the scale was calculated. Correlation analysis and an ordinal regression analysis between the developed tool and the Short Form 12 Health Survey examined its concurrent validity. Principal component analysis and known-group analysis using the Kruskal–Wallis test examined its construct validity.
RESULTS: The reliability of the developed questionnaire was very high (α = 0.908; r = 0.861; p < 0.01). Its content validity was excellent (all-item content validity index = 0.79–1.00; scale validity index = 0.92). Evidence of its concurrent validity included strong correlation between the developed tool and Short Form 12 Health Survey (r = 0.734; p < 0.001), and participant scores on the developed tool explained ≈46.2% of the between-subject variation for the participant scores on Short Form 12 Health Survey (Nagelkerke R2 = 0.462). Confirming its construct validity, principal component analysis revealed that 2 factors explained 81.63% of the total variance found. Known-group analysis evidenced the ability of the questionnaire to detect expected differences in patients presenting with different symptomatology.
LIMITATIONS: The major limitations of this study were the use of a small sample of Spanish-speaking patients, not including patients in the initial development of the questionnaire, and developing the scoring system using a summation method.
CONCLUSIONS: The Quality of Life in Patients with Anal Fistula Questionnaire has proven to be a valid, reliable, and concise tool that could contribute to the evaluation of quality of life among patients with an anal fistula. See Video Abstract at http://links.lww.com/DCR/A368.

This is a non-final version of an article published in final form in Ferrer-Márquez, M. et al., 2017. Design and Psychometric Evaluation of the Quality of Life in Patients With Anal Fistula Questionnaire. Diseases of the Colon & Rectum, 60(10), pp.1083–1091. Available at: http://dx.doi.org/10.1097/dcr.0000000000000877.