These recommendations are mainly based on the National Institute for Health and Clinical Excellence (NICE) clinical guideline Management of chronic obstructive pulmonary disease in adults in primary and secondary care (partial update) [National Clinical Guideline Centre, 2010; NICE, 2010].

• The statement that referral to a community or hospital spirometry service may be necessary is based on expert opinion and evidence of low-quality delivery and interpretation of spirometry in primary care, discussed in guidelines on diagnostic spirometry in primary care by the GP Airways Group [Levy et al, 2009].
• The recommendation that spirometry should be post-bronchodilator is new in the updated 2010 NICE guideline. This recommendation by NICE is based on limited evidence from a cross-sectional study and a case series study of increased diagnostic accuracy compared with pre-bronchodilator spirometry, and on the consensus of the guideline development group. The major limitation of the evidence is the lack of a gold (reference) standard for chronic obstructive pulmonary disease (COPD).
• The recommendations on the choice, dose, and delivery of bronchodilator, and how long after inhalation spirometry should be done, are based on expert opinion from CKS reviewers and on extrapolations from recommendations in guidelines on diagnostic spirometry in primary care by the GP Airways Group on how to do reversibility testing using a short-acting bronchodilator [Levy et al, 2009].
• The statement that a slow or relaxed vital capacity (SVC) may be used instead of forced vital capacity (FVC) to calculate the ratio if either the SVC is higher than the FVC, or the person cannot perform a forced manoeuvre to full exhalation, is derived from guidelines on diagnostic spirometry in primary care by the GP Airways Group [Levy et al, 2009] and a consensus statement in the NICE COPD guideline [National Clinical Guideline Centre, 2010].
• Routine spirometric reversibility testing is not recommended by NICE on the basis of evidence from mainly observational studies and one randomized controlled trial indicating that:
• Repeated measurements of the forced expiratory volume in 1 second (FEV₁) can show small spontaneous fluctuations.
• The results of a reversibility test performed on different occasions can be inconsistent and not reproducible.
• Over reliance on a single reversibility test may be misleading unless the change in FEV₁ is greater than 400 mL.
• Response to long-term therapy is not predicted by acute reversibility testing.
• Other recommendations by NICE are based on expert opinion or extrapolations from higher levels of evidence.