Background and ObjectiveFor people with cystic fibrosis, validated patient-reported outcome measures for the assessment of the complex abdominal involvement are lacking. The objective of this study was to examine whether the CFAbd-Score, a novel questionnaire consisting of 28 items, meets the essential requirements (validity and reliability) for a patient-reported outcome measure according to US Food and Drug Administration recommendations. Methods Content validity was assessed by recording the frequencies and severity of symptoms that occurred during the prior 2 weeks in patients with cystic fibrosis (n = 116; aged ≥ 6 years). Comparing the CFAbd-Score results obtained from patients with cystic fibrosis and healthy controls (n = 88), we determined known-groups validity. To explore the structure of the patient-reported outcome measure, a factor analysis was conducted. Internal consistency of the five extracted score domains was assessed using Cronbach's alpha. For test-retest reliability, a subgroup of patients (n = 43) was reevaluated and intra-class correlation coefficients were determined. ResultsThe CFAbd-Score differentiated patients with cystic fibrosis from healthy controls with a large effect size (17.3 ± 1.1 vs. 8.0 ± 0.7 points; p < 0.001; Cohen's d = 0.85). Items, domains, and scores reflected the relevance to patients with cystic fibrosis and allowed a differentiation between subgroups of patients with cystic fibrosis (e.g., patients with and without abdominal pain, pancreatic sufficiency, and age groups). High item-domain loadings as well as good to excellent internal consistency and reproducibility (Cronbach's α = 0.70-0.92; intra-class correlation coefficient = 0.932, 95% confidence interval 0.874-0.963) indicated construct validity and reliability. Conclusions The CFAbd-Score has successfully passed through key steps of the iterative process of patient-reported outcome measure development. Prospectively, the CFAbd-Score is proposed as a patient-centered instrument for monitoring abdominal symptoms and, most interestingly, for evaluating changes in symptoms with novel treatments such as cystic fibrosis transmembrane regulator modulators. Trail Registration ClinicalTrials.gov: NCT03052283.

Objectives:This prospective study evaluated the relationship between fecal markers of intestinal inflammation and cystic fibrosis (CF)-associated abdominal symptoms. These were assessed using the CFAbd-Score, a CF-specific patient-related outcome measure developed and validated, following FDA guidelines.Methods:In feces from patients with CF (n = 41) and healthy volunteers (n = 27), concentrations of fecal calprotectin (FC), M2-pyruvate kinase (M2-PK), interleukins IL-1β, IL-6, IL-8, and neutrophilic elastase (NE) were measured. Abdominal symptoms during the 2 preceding weeks were recorded using the CFAbd-Score. This patient-reported outcome measure (PROM) for assessment of the multi-organic abdominal involvement in CF includes 28 items in five domains.Results:Inflammatory parameters FC, IL-1β, M2-PK, and NE in feces, as well as CFAbd-Scores resulted significantly higher in CF patients than in healthy controls (all P < 0.01). Furthermore, significant differences between both groups were found for pain-symptoms, disorders of bowel movement, impaired quality of life, as well as disorders of eating and appetite. With 83% sensitivity and 74% specificity, FC was the most reliable measure for CF-related intestinal inflammation, which, in the CFAbd-Score, was associated to significantly higher rates of abdominal pain, as well as to general quality of life items such as gastrointestinal-related impaired sleep and frustration.Conclusion:Using the CFAbd-Score as a CF-specific PROM for identification and quantification of abdominal symptoms revealed that abdominal pain and impaired quality of life are associated with intestinal inflammation in CF.