Trop tops?

Role of troponin in patients with chronic kidney disease and suspected acute coronary syndrome: a systematic review.

Sylvie R. Stacy, et al

Ann Intern Med. Published online 12 August 2014 doi:10.7326/M14-0746

http://annals.org/article.aspx?articleid=1895305 (Full text)

 Reviewed by Dr Helen Prescott CT1

Background

  • Timely diagnosis of cardiac injury is crucial
  • Troponins found almost exclusively in myocardium
  • Troponin measurement is widespread
  • Elevated troponin does not always imply ACS
  • Checking troponin in CKD is problematic
  • Troponin levels are often elevated even in apparent absence of cardiac disease
  • Possible reasons:
  • Impaired renal excretion of troponin
  • Non-ischaemic cardiac disorders e.g. LVH

 

Rationale and Study methods

 “To evaluate the utility of troponin in ACS diagnosis, treatment and prognosis among patients with CKD”

Meta analysis of Studies looking at raised troponin levels and diagnostic utility in detection of ACS, subsequent ACS management, and prognosis of mortality or cardiovascular morbidity among patients with CKD.

 

Literature search strategy

  • All Major databases searched
  • Search terms can be viewed at;

http://annals.org/DownloadImage.aspx?image=/data/Journals/AIM/0/912tta1.jpeg&sec=54479662&ar=1895305&imagename=

  • ClinicalTrials.gov searched
  • Manufactures of troponin assays contacted
  • Two independent reviewers

 

Methods and Population

  • Inclusion and exclusion criteria explained
  • 23 studies selected in total
  • Diagnostic performance of elevated troponin: 14 studies
  • Effect of treatments: 0 studies
  • Prognostic value of elevated troponin in ACS: 14 studies
  • Sample sizes ranged from 31 to 31 586 patients
  • Publication dates ranged from 1990 to 2013
  • Downs and Black Checklist of all papers
  • Quality assessed as good, fair or poor
  • Third party adjudicator employed

 

Results

  • Overall strength of evidence graded for each set of studies as high, moderate, low or insufficient
  • Low strength evidence for diagnostic accuracy
  • No studies examined how troponin levels affect management strategies
  • Low strength evidence for prognostic accuracy

 

Utility of troponin in diagnosis

 Troponin T

Sensitivity 71 – 100%

Specificity 31 – 86%

Troponin I

Sensitivity 43 – 94 %

Specificity 48 – 100%

  • Marked heterogeneity between studies
  • Different settings and populations
  • No universal definition of ACS
  • Different troponin assays and cut-offs
  • Only 1 study investigated the accuracy of a change in troponin level

 

Utility of troponin in prognosis

  • Differences between studies prevented pooled analysis
  • Elevated levels of troponin I & T associated with higher risk for short term death and cardiac events
  • Increased long-term mortality with elevated troponin I
  • Patients with advance CKD tend to have worse prognosis with elevated troponin I levels

 

Strengths of the review

  • Clear purpose for the review
  • Extensive literature search
  • Inclusion and exclusion criteria explained
  • Two independent reviewers
  • Quality of studies assessed with a pre-validated checklist

Limitations of the review

  • Related to limitations of the individual studies
  • Heterogeneity in study methods
  • Lack of blinding of assessors to troponin results
  • Variation in definitions of ACS
  • Different troponin cut offs and assay manufacturers
  • Variability in length of follow-up
  • No studies examined how troponin levels affect management strategies

 

What does this review add?

  • Summarizes what is known about the topic
  • Diagnostic utility is limited by varying estimates of sensitivity and specificity
  • Serial measurements remain preferable
  • Can aid in identifying those with a poor prognosis
  • Indicates further research is needed

Clinical Correlation

  • Only test when clinically indicated
  • Serial results preferable to a single value – although evidence base for this is poor
  • Elevated troponin associated with poorer prognosis
  • Risk vs. benefit to treating elevated troponin levels is not known

 

Reviewed by Dr Helen Prescott CT1

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