Clinical features

• CK-MB at 0, 4, 8, 12 hours
• serial 12-lead ECGs
• clinical assessment at 0, 6, 12 hours
• exercise ECG: if all the above negative

Patients at low-risk for an MI who have no CK-MB rise or further pain within 12 hours are unlikely to have one

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
low-risk for MI a (pre-test probability: 7%)	myocardial infarction (typical change in cardiac enzymes or cardiac arrest)	cardiac enzyme rise or recurrent chest pain within 12 hours	6.8 (5.7 to 8.1)	34%	0.069 (0.027 to 0.18)	0.5%

• Patients admitted to a rapid assessment unit are not clearly less likely to be diagnosed with a myocardial infarction or unstable angina ^d but spend on average 40 hours less in hospital. ^d
• Half of patients are still admitted to hospital (45%: 95% CI: 34% to 56%). ^a