Funnel plots, performance variation and the Myocardial Infarction National Audit Project 2003–2004

Table 1 Comparison of the numbers of hospitals achieving NSF goals and the number inside and outside 3 sigma limits.

	DTN	CTN	Aspirin	Beta-blocker	Statin
Analysis by attainment of NSF targets
Reaching the goal	163	102	191	151	180
Within 25% of the goal	51	0	16	46	24
More than 25% from the goal	8	116	0	3	2
Less than 20 cases	8	12	20	25	20
Total	230	230	227	225	226
Analysis by funnel plot
Above UCL	33	32	40	43	34
Within limits	182	170	187	152	164
Below LCL	15	28*	24	30	31
Total	230	230	227	225	226
Discrepancy between table and funnel plot assessment of performance
Within target and below LCL	0	0	8	0	5
Within 25% of target but below LCL	8	28*	16	27	24
Beyond 25% of target and below LCL	7	0	0	3	2
Within target but above UCL	27	32	37	44	35
Total discrepancy	42	60	61	74	66

DTN = door to needle time, CTN = call to needle time, Statin = HMG-CoA reductase inhibitor, NSF = National Service Framework for Coronary Heart Disease.
*The 'within 25% of target' did not apply to CTN 60. In total, 108 hospitals were above the 48% target and 122 below it, of which 28 were also below the LCL.

ISSN: 1471-2261