Myocardial infarction: a normal troponin at 8 hours after symptom onset makes an MI unlikely

Clinical bottom line (level 2a)

  1. An elevated troponin T (> 0.1 ng/ml) makes a myocardial infarction more likely at 1 hour after onset of symptoms (LR + 3.7) .
  2. Neither a normal troponin T or troponin I can safely rule out a myocardial infarction if taken within 3 hours of onset of symptoms.
  3. A normal troponin T (< 0.2 ng/ml) at 8 hours makes a myocardial infarction much less likely (LR - 0.05).
  4. Troponin I may be better at diagnosing a myocardial infarction after 3 hours than troponin T.
Ebell et al: J Fam Pract 2000; 49 : 550-556
Expires February 2004

The study

Systematic review of all prospective diagnostic studies of
  • Patients: with a suspected acute myocardial infarction
  • Intervention: troponin T or troponin I compared with WHO reference standard for diagnosing myocardial infarction (at least 2 of clinical history, characteristic ECG changes, and an increase in CK or CK-MB)
  • Outcome: acute myocardial infarction
Articles found in English, French, German, Spanish using Medline, 1966 to December 1999 (search terms: troponin and diagnosis )

Selection criteria: by 2 independent reviewers
Appraisal criteria: by 2 independent reviewers based on blinding and reference standard used. Patients could be enrolled consecutively or non-consecutively. Disagreements were resolved by consensus.
Articles excluded if:
  • non-human subjects
  • children


11 studies with consecutive enrollment, and 8 studies with non-consecutive enrollment were found.
A random-effects model was used to combined data.

The evidence

 
diagnostic test number of patients sensitivity for
MI
(95% CI)		 specificity for
MI
(95% CI)		 LR+ LR-
Troponin T > 0.1 ng/ml at 1 hour from onset 47%
(% to %) 		87%
(% to %) 		3.7 0.6
Troponin T > 0.1 ng/ml at 2 hours 53%
(% to %) 		87%
(% to %) 		3.9 0.5
Troponin T > 0.1 ng/ml at 3 hours 58%
(% to %) 		86%
(% to %) 		4.1 0.5
Troponin T > 0.1 ng/ml at 4 hours 64%
(% to %) 		85%
(% to %) 		4.2 0.4
Troponin T > 0.1 ng/ml at 6 hours 74%
(% to %) 		83%
(% to %) 		4.4 0.3
Troponin T > 0.1 ng/ml at 8 hours 84%
(% to %) 		81%
(% to %) 		4.5 0.2
Troponin T > 0.1 ng/ml at 10 hours 93%
(% to %) 		80%
(% to %) 		4.6 0.1
Troponin T > 0.2 ng/ml at 1 hour from onset 14%
(% to %) 		87%
(% to %) 		1.1 1.0
Troponin T > 0.2 ng/ml at 2 hours 33%
(% to %) 		87%
(% to %) 		2.5 0.8
Troponin T > 0.2 ng/ml at 3 hours 50%
(% to %) 		86%
(% to %) 		3.5 0.6
Troponin T > 0.2 ng/ml at 4 hours 65%
(% to %) 		85%
(% to %) 		4.3 0.4
Troponin T > 0.2 ng/ml at 6 hours 86%
(% to %) 		83%
(% to %) 		5.1 0.2
Troponin T > 0.2 ng/ml at 8 hours 96%
(% to %) 		81%
(% to %) 		5.2 0.05
Troponin T > 0.2 ng/ml at 10 hours 96%
(% to %) 		80%
(% to %) 		4.7 0.05
Troponin I > 0.1 ng/ml at 1 hour after onset 13%
(% to %) 		95%
(% to %) 		2.7 0.9
Troponin I > 0.1 ng/ml at 2 hours 34%
(% to %) 		95%
(% to %) 		6.8 0.7
Troponin I > 0.1 ng/ml at 3 hours 52%
(% to %) 		95%
(% to %) 		10 0.5
Troponin I > 0.1 ng/ml at 4 hours 67%
(% to %) 		95%
(% to %) 		13 0.34
Troponin I > 0.1 ng/ml at 5 hours 80%
(% to %) 		95%
(% to %) 		16 0.2
Troponin I > 0.1 ng/ml at 6 hours 90%
(% to %) 		95%
(% to %) 		18 0.1
total

  • The data for troponin I involved only 78 patients in one study.

Comments

  1. By limiting the search to Medline, important articles may have been missed.

Citation

  1. Ebell MH, Flewelling D, Flynn CA: a systematic review of Troponin T and I for diagnosing acute myocardial infarction. J Fam Pract 2000; 49 : 550-556
Search Terms: from ACP Journal Club
Contributor: Chris Ball, February 2002
Reviewer:

Clinical Question.
Patient suspected acute myocardial infarction
Intervention or Exposure troponin T or troponin I
Outcome acute myocardial infarction