Irritable bowel syndrome: diagnostic approaches in clinical practice

Irritable bowel syndrome (IBS), a functional gastrointestinal disorder long considered a diagnosis of exclusion, has chronic symptoms that vary over time and overlap with those of non-IBS disorders. Traditional symptom-based criteria effectively identify IBS patients but are not easily applied in clinical practice, leaving >40% of patients to experience symptoms up to 5 years before diagnosis.

To review the diagnostic evaluation of patients with suspected IBS, strengths and weaknesses of current methodologies, and newer diagnostic tools that can augment current symptom-based criteria.

The peer-reviewed literature (PubMed) was searched for primary reports and reviews using the limiters of date (1999-2009) and English language and the search terms irritable bowel syndrome, diagnosis, gastrointestinal disease, symptom-based criteria, outcome, serology, and fecal markers. Abstracts from Digestive Disease Week 2008-2009 and reference lists of identified articles were reviewed.

A disconnect is apparent between practice guidelines and clinical practice. The American Gastroenterological Association and American College of Gastroenterology recommend diagnosing IBS in patients without alarm features of organic disease using symptom-based criteria (eg, Rome). However, physicians report confidence in a symptom-based diagnosis without further testing only up to 42% of the time; many order laboratory tests and perform sigmoidoscopies or colonoscopies despite good evidence showing no utility for this work-up in uncomplicated cases. In the absence of diagnostic criteria easily usable in a busy practice, newer diagnostic methods, such as stool-form examination, fecal inflammatory markers, and serum biomarkers, have been proposed as adjunctive tools to aid in an IBS diagnosis by increasing physicians' confidence and changing the diagnostic paradigm to one of inclusion rather than exclusion.

New adjunctive testing for IBS can augment traditional symptom-based criteria, improving the speed and safety with which a patient is diagnosed and avoiding unnecessary, sometimes invasive, testing that adds little to the diagnostic process in suspected IBS.