Investigations

• troponin T ^{a b c} or troponin I ^{b c}

Why?

A normal troponin T at 20 hours makes a myocardial infarction unlikely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected myocardial infarction c (pre-test probability: 18%)	myocardial infarction (history, ECG, CK-MB act)	elevated troponin T at 3 hours after symptom onset	6 (4 to 9)	57%	0.67 (0.59 to 0.76)	13%
		elevated troponin T at 4 hours after symptom onset	11 (7 to 16)	71%	0.59 (0.52 to 0.67)	9%
		elevated troponin T at 6 hours after symptom onset	7 (4 to 10)	61%	0.37 (0.31 to 0.43)	8%
		elevated troponin T at 8 hours after symptom onset	9 (6 to 13)	66%	0.23 (0.19 to 0.27)	5%
		elevated troponin T at 12 hours after symptom onset	9 (7 to 12)	66%	0.078 (0.064 to 0.094)	2%
		elevated troponin T at 20 hours after symptom onset	9 (6 to 13)	66%	0.022 (0.019 to 0.027)	0.5%

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected acute myocardial infarction b (pre-test probability: 37%)	myocardial infarction (CK-MB at 24 hours)	troponin I > 0.1 ng/ml at 1 hour after onset	2.7	61%	0.9	35%
		at 2 hours	6.8	80%	0.7	29%
		at 3 hours	10	85%	0.5	23%
		at 4 hours	13	88%	0.34	10%
		at 5 hours	16	90%	0.2	11%
		at 6 hours	18	91%	0.1	6%
suspected acute myocardial infarction  (pre-test probability: 37%)	myocardial infarction (CK-MB mass at 24 hours)	troponin I at 18 hours	15 (11 to 19)	67%	0.045 (0.019 to 0.11)	1%