Construction and validation of a questionnaire distinguishing a chronic abdominal wall pain syndrome from irritable bowel syndrome

OBJECTIVE: The irritable bowel syndrome (IBS) population is heterogeneous, harbouring a variety of abdominal symptoms. Therefore, IBS is often termed a ‘diagnosis of exclusion’. Chronic abdominal wall pain (CAWP) is a poorly recognized entity, frequently caused by the anterior cutaneous nerve entrapment syndrome (ACNES). Some patients may be misdiagnosed because IBS and CAWP share symptoms. Aim of this study was to construct and validate a questionnaire to distinguish patients with CAWP (including ACNES) patients with IBS. DESIGN: A questionnaire was designed of 17 ACNES characteristic items obtained from ACNES patients (n=33) and expert opinion of two specialized surgeons. Eleven IBS-related items (‘Rome III’ criteria) were added leading to a questionnaire containing 28 items. This was validated in a ‘gold standard’ ACNES group (successfully operated ACNES patients, n=68) and a ‘prospective’ IBS group (n=64) as well as in a ‘prospective’ ACNES group (n=47). Distinctive power of individual items was analyzed by χ(2). Reliability was tested with Crohnbach's α. ROC curve was used to determine cut-off values. RESULTS: Eighteen of 28 items were significantly distinctive (p<0.01) between ACNES and IBS patients leading to an 18-point ACNES score with good internal consistency (α=0.85). Cut-off value of 10 points resulted in 94% sensitivity, 92% specificity and areas under the curve (AUC) of 0.98. Evaluation of the prospective ACNES group led to 85% sensitivity, 92% specificity and AUC 0.95 indicating high discriminative properties of the questionnaire. CONCLUSIONS: This novel questionnaire may be useful and valid as a simple tool distinguishing patients harbouring a CAWP syndrome from those having IBS.