Irritable bowel syndrome subtypes according to bowel habit: revisiting the alternating subtype.

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Disturbed bowel habit, diarrhoea or constipation is a key manifestation of irritable bowel syndrome (IBS). In some patients, diarrhoea and constipation alternate, giving rise to the so-called alternating subtype. To assess IBS subtype breakdown (constipation (C-IBS), diarrhoea (D-IBS) or alternating (A-IBS)) according to the Rome II criteria and patients' self-assessment, the predominance in the alternating subtype (i.e. constipation, diarrhoea or neither), and the medical and personal impact, including health-related quality of life (HRQoL), of the different IBS subtypes. Two thousand individuals selected randomly to represent the general population were classified as potential IBS subjects (n = 281) or as non-potential IBS subjects (n = 1719) according to a validated questionnaire. Bowel habit classification was determined using the Rome II IBS supportive symptoms. Among 201 subjects meeting the Rome I criteria, 15% presented with D-IBS, 44% presented with C-IBS, 19% presented with A-IBS, and 22% presented with normal bowel habit. Among the 63 subjects meeting the Rome II criteria, 23% presented with A-IBS. According to the subjects' self-assessment, of those meeting the Rome I criteria, 16% considered themselves to have D-IBS, 66% to have C-IBS and 18% to have A-IBS. In subjects meeting the Rome II criteria, 24% considered themselves to have A-IBS. Among those classified with A-IBS by the Rome II criteria, most considered themselves to be constipated. Regardless of the subtype self-classification, most subjects reported a normal frequency of bowel movements. Clinical manifestations in A-IBS were very similar to those of C-IBS but with the added presence of defecatory urgency. Abdominal discomfort/pain and frequency of visits to physicians were greater in the A-IBS subtype than in the other two IBS subtypes. HRQoL was affected similarly in all IBS subtypes. Approximately one-quarter of subjects with IBS belong to the A-IBS subtype by the Rome II criteria, although the majority consider themselves to be constipated; indeed, clinical manifestations are more akin to the C-IBS subtype than to the D-IBS subtype. Abdominal discomfort/pain and frequency of visits to physicians are greater in the A-IBS subtype than in the other two IBS subtypes, while HRQoL is impaired similarly.