Table 2. Change in compliance with NICE quality indicators for patients before and after intervention for comparing the intervention with the control practices.

Quality indicator	Control			Intervention			Difference in differences: Intervention—control	P-value
	Baseline (CB)	Post intervention (CP)	Difference (CP)−(CB)	Baseline (IB)	Post intervention (IP)	Difference (IP)−(IB)
Post-BD spirometry confirmed diagnosis	6.7	3.3	−3.4	11.3	12.6	1.3	4.7	0.001
Annual review performed	65.2	57.9	−7.3	63.1	60.5	−2.6	4.7	0.22
Self-management plan received	4.5	6.2	1.7	4.8	9.7	4.9	3.2	0.12
MRC 3+ referred for rehabilitation	0.9	2.2	1.3	1.2	8.6	7.4	6.1	0.03
Patients quit smoking	21.8	20.1	−1.7	22.0	22.0	0.0	1.7	0.58

Generalised linear clustered model estimates, allowing for the cluster effects of GP practices, back transformed (from logits) to percentages.

Abbreviations: BD, bronchodilator; MRC, Medical Research Council.