For details of diagnosing irritable bowel syndrome and excluding other causes of symptoms, see Diagnosis.

• Assess the type and severity of symptoms.
• Assess the person for the presence of red flag indicators (see Differential diagnosis).
• Assess the person's diet and nutrition:
• Is there anything in the diet that triggers symptoms?
• Review fibre intake. (What type of fibre and how much?)
• Assess the person's physical activity levels, ideally using the the General Practice Physical Activity Questionnaire (GPPAQ).
• Assess the person's lifestyle and psychological status.
• Have they recently experienced any psychological or physical stress?
• Are they depressed or anxious?

• The General Practice Physical Activity Questionnaire (GPPAQ) is intended for use in adults (16–74 years of age) in routine general practice to provide a simple, 4-level Physical Activity Index (PAI) reflecting an individual's current physical activity. The index can be used to help inform the decision as to when interventions to increase physical activity might be appropriate.
• The GPPAQ can be downloaded from the Department of Health website (www.dh.gov.uk).

Basis for assessing red flag indicators

• The National Institute for Heath and Clinical Excellence (NICE) guidance Irritable bowel syndrome in adults recommends that all people with possible irritable bowel syndrome (IBS) should be assessed for red flag indicators and referred to secondary care for further investigation if any are present [NICE, 2005; National Collaborating Centre for Nursing and Supportive Care, 2008; NICE, 2008].

Basis for assessing symptoms

• Assessment of bowel habits and stool characteristics will enable the healthcare professional to determine whether the person has diarrhoea-predominant IBS, constipation-predominant IBS, or mixed IBS [Mayer, 2008]. This will guide the person's management.

Basis for assessing diet

• The NICE guidance Irritable bowel syndrome in adults recommends that diet and nutrition should be assessed in all people with IBS [National Collaborating Centre for Nursing and Supportive Care, 2008; NICE, 2008].
• The role of dietary modification in the management of IBS is uncertain. Dietary manipulation in the form of avoidance of specific foods may offer improvement for up to two-thirds of people with IBS [National Collaborating Centre for Nursing and Supportive Care, 2008].
• Single food avoidance diets and exclusion diets should only be undertaken on the advice of a dietitian [National Collaborating Centre for Nursing and Supportive Care, 2008; NICE, 2008].
• The NICE guidance Irritable bowel syndrome in adults recommends that healthcare professionals should review the fibre intake of all people with IBS [National Collaborating Centre for Nursing and Supportive Care, 2008; NICE, 2008].

Basis for recommending assessment of physical activity using the General Practitioner Physical Activity Questionnaire (GPPAQ)

• Public health intervention guidance from NICE recommends that primary care practitioners should use a validated tool (such as the Department of Health's GPPAQ) to identify inactive individuals [NICE, 2006].

Basis for assessing lifestyle

• IBS is often associated with psychological distress. Both initial presentations and exacerbations of IBS are often preceded by psychological stressors or physical stressors (e.g. gastrointestinal infection) [Spiller, 2007; Mayer, 2008].