Author(s): Vincenzo Stanghellini [*] 1
constipation; diagnostic criteria; functional gastrointestinal disorder; irritable bowel syndrome; linaclotide; prevalence; Rome III
The definition and diagnosis of irritable bowel syndrome (IBS) remains challenging in the absence of validated biomarkers and, until recently, IBS was often dismissed as a purely psychosomatic condition where the diagnosis was made by exclusion. However, the advancement of a biopsychosocial concept for the pathogenesis of IBS and the development of symptom-based international consensus criteria for diagnosis and treatment [1-4] have led to a growing acceptance that IBS exists as a coherent entity, requiring a symptom-based, positive diagnosis.
The international Rome III guidelines published in 2006 define IBS as "a functional bowel disorder in which abdominal pain or discomfort is associated with defecation or a change in bowel habit, and with features of disordered defecation"  . Diagnosis of a functional bowel disorder requires characteristic symptoms during the last 3 months with an onset of at least 6 months before diagnosis. Importantly, the Rome III guidelines state that the diagnosis of IBS should be achievable using symptom-based criteria, careful history taking and examination, with limited or no laboratory or structural evaluations unless the patient exhibits alarm features, including fever, blood in stool, unexplained weight loss, onset after the age of 50 years, and a family history of colorectal cancer or inflammatory bowel disease. Specific diagnostic criteria for IBS are recurrent abdominal pain or discomfort at least 3 days per month in the last 3 months associated with two or more of the following: improvement with defecation; onset associated with a change in frequency of stool or onset associated with a change in form (appearance) of stool. Predominant stool pattern is a useful approach for subtyping IBS as follows: IBS with constipation (IBS-C); IBS with diarrhea (IBS-D); mixed IBS and unsubtyped IBS. Subtyping is aided using the Bristol Stool Form Scale in which a type 1-2 stool indicates IBS-C, whereas IBS-D is typically associated with a Bristol Stool Form Scale type 6-7 stool [1,5] .
A community survey of more than 40,000 subjects in eight European countries found that 9.6% of respondents met IBS diagnostic criteria, with a higher prevalence in females (12%) compared with males (7.1%)  . Prevalence was also higher in young adults (18-34 years: 12.2%) compared with older adults (35-54 years: 9.9%; [greater than or equal]55 years: 7%). In a meta-analysis of 81 population-based studies that reported the prevalence of IBS in 80 discrete study populations containing more than 260,000 subjects, the pooled global prevalence of IBS was reported as 11.2% (95% CI: 9.8-12.8)  . Again, the prevalence was higher for women compared with men (odds ratio [OR]: 1.67; 95% CI: 1.53-1.82) and lower for subjects older than 50 years compared with those younger than 50 years (OR: 0.75; 95% CI: 0.62-0.92). IBS prevalence varied markedly according to country (range: 1.1-45.0%) (Figure 1), but the effects of socioeconomic status are not well described. Prevalence also differed according to diagnostic criteria, with a prevalence of 14% (95% CI: 10.0-17.0) obtained when...