Myocardial infarction: biochemical markers helped to diagnose.

Clinical bottom line (level 1b)

  1. A tenth of patients with suspected myocardial infarction had one.
  2. In patients with suspected myocardial infarction, creatine kinase-MB subforms, myoglobin and troponin T or I at 6 hours after symptom onset, all helped to rule myocardial infarction in or out, but creatine kinase-MB subforms were most sensitive and specific.
  3. Creatine-kinase-MB subforms, myoglobin and troponin T at 10 hours after symptom onset, all helped to rule myocardial infarction in or out.
  4. Troponin I at 18 hours after onset helped to rule myocardial infarction in or out.
Zimmerman et al: Circulation 1999; 99: 1671-1677
Expires March 2003

The study

Setting: multicentre, USA

955 patients (aged mean 55 years, 60% male) chest pain = 15 minutes suspected to be of myocardial origin and occurring within 24 hours of presentation

Excluded if
  • <21 years old

?independent blinded reference standard, applied in all patients from a consecutive appropriate spectrum.
Reference standard:
  • Creatine kinase-MB mass = ng/mL and creatine kinase-MB index = 2.5% determined in two or more samples obtained in the first 24 hours after presentation or in one sample if only one sample was available.
Diagnostic test: Analysis of creatine kinase-MB subforms, myoglobin, troponin T and troponin I.

The evidence

pre-test probability of myocardial infarction: 12.5%, (95% CI: 10.4% to 14.6%)

diagnostic test myocardial infarction no myocardial infarction LR+
(95% CI)		 post-test probability LR-
(95% CI)		 post-test probability
creatine kinase subforms- early diagnosis (6 hours) 109 10 8.32
(6.81 to 10.2) 		54.0% 0.09
(0.05 to 0.17) 		1.00%
myoglobin- early diagnosis (6 hours) 94 25 7.42
(5.97 to 9.22) 		51.0% 0.24
(0.17 to 0.33) 		3.00%
troponin T- early diagnosis (6 hours) 73 46 15.5
(10.8 to 22.4) 		69.0% 0.40
(0.32 to 0.50) 		5.00%
troponin I- early diagnosis (6 hours) 68 51 9.95
(7.26 to 13.7) 		59.0% 0.45
(0.37 to 0.56) 		6.00%
creatine kinase-MB subforms- late diagnosis (10 hours) 114 5 9.77
(7.92 to 12.0) 		58.0% 0.05
(0.02 to 0.11) 		1.00%
myoglobin- late diagnosis (10 hours) 103 16 8.82
(7.10 to 11.0) 		56.0% 0.15
(0.09 to 0.24) 		2.00%
troponin T- late diagnosis (10 hours) 103 16 24.1
(16.9 to 34.5) 		77.0% 0.14
(0.09 to 0.22) 		2.00%
troponin I- late diagnosis (18 hours) 114 5 14.6
(11.3 to 18.9) 		67.0% 0.04
(0.02 to 0.11) 		1.00%
total 119 836

Comments

  1. Diagnosis using creatine kinase-MB subforms, myoglobin, troponin T or I are less accurate before 6 hours and, all markers except troponin I, are less accurate after 10 hours.
  2. A restructuring of the accepted diagnostic standard for myocardial infarction makes the troponin tests likely to be more effective

Citation

  1. Zimmerman J, Fromm R, Meyer D, et al: Diagnostic Marker Cooperative Study for the diagnosis of myocardial infarction. Circulation 1999; 99: 1671-1677
Contributor: Clare Wotton and Musab Hayatli, January 2000
Reviewer: Christian Torp-Pedersen

Clinical Question.
Patient chest pain
Intervention or Exposure positive results with biochemical markers, CK, CK-MB, troponin T, troponin I
Comparison negative results
Outcome diagnosis of myocardial infarction