Development and validation of processed foods questionnaire (PFQ) in adult inflammatory bowel diseases patients

Background Processed foods have been implicated in the pathogenesis of inflammatory bowel diseases (IBD). Our goal was to develop a validated processed foods frequency questionnaire (PFQ) and assess its reliability and validity. Methods We recruited adult IBD patients to fill-in a PFQ in this prospective single-center study. Food intake was categorized into three groups of processed food levels: unprocessed, processed, and ultra-processed. Reliability was assessed by comparing the PFQ results of each patient at 2 time points. Validity was assessed by comparing the PFQ results to a 3–7 day food diary (FD), and by comparing urine sodium as a biomarker for the high intake of sodium that is mostly present in processed food. Results Eighty-six IBD patients were enrolled. Good test–retest reliability was indicated by intraclass correlation of 0.75–0.88 for the different food processing levels. Validity was fair-to-strong as assessed by correlations for different levels of processed food intake between FDs and PFQ, ranging between 0.43 and 0.64 (Pearsonr, P