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Letters to the Editor |
1 St George’s Hospital, London, UK
2 Helsinki University Hospital, Helsinki, Finland
3 Aarhus University Hospital (Aalborg), Aalborg, Denmark
4 University of Zagreb, Zagreb, Croatia
5 Innsbruck Medical University, Innsbruck, Austria
6 Kliniken Ludwigsburg-Bietigheim, Germany
7 University Hospital Maastricht, Maastricht, the Netherlands
8 Oulu University Hospital, Oulu, Finland
aAddress correspondence to this author at: Laboratory, Oulu University Hospital, PO Box 500, FIN-90029 OYS, Oulu, Finland, Fax: 358-8-3154474, e-mail paivi.h.laitinen{at}ppshp.fi
To the Editor:
Evidence-based medicine is recognized as underlying good clinical practice. Similarly, evidence-based laboratory medicine should be used to guide and monitor laboratory testing. One area where laboratory testing has undergone a revolutionary change is in the diagnosis of acute coronary syndrome (ACS)1 , as underscored in the American College of Cardiology (ACC) and the European Society of Cardiology (ESC) consensus document on the definition of and diagnostic approach of myocardial infarction in 2000, updated in 2007. Since the original reports, the measurement of cTnT and cTnI has been recommended in many guidelines, (1)(2) and they have formed a part of the redefinition of myocardial infarction (3).
The CARdiac MArker Guideline Uptake in Europe study (CARMAGUE) was a pilot study to provide baseline data and validate a web-based audit tool to assess compliance of cardiac marker testing in current clinical practice. The study was sponsored by the European Federation of Clinical Chemistry and Laboratory Medicine (EFCC) in conjunction with the national societies in 8 participating countries (Austria, Croatia, Denmark, Finland, Germany, Hungary, the Netherlands, and the U.K.). Laboratories were invited to participate by emailing a weblink to an electronic questionnaire. The questionnaire developed by the CARMAGUE study group comprised 123 questions covering all aspects of cardiac marker testing, concentrating on choice of markers and clinical decision making. The questionnaire can be viewed at www.carmague.fi/1. In a first analysis, we focused on the application of cardiac markers of myocardial necrosis used in ACS.
Responses were received from 220 laboratories (22% of those invited), with response rates varying from 12% to 80% of potential participants in each country.
The majority of the hospitals (94%) used a cardiac troponin (cTn), either cTnT (51%) or cTnI (49%), as their preferred test for diagnosis of acute myocardial infarction. All the other participants used creatine kinase MB isoenzyme (CK-MB) but were planning to change. Although troponin was the preferred marker, it was used in combination with a second marker in 34% of the laboratories, usually CK, CK-MB mass, or CK-MB activity, whereas only 2 laboratories used myoglobin. Of the 58.9% of laboratories with a written protocol, 90% used the same protocol in the emergency department and for inpatients. The protocols were developed jointly with clinicians in 80% of cases.
Turnaround time was reported as <60 min in most cases of urgent tests. Seven percent of laboratories did not participate in external quality assessment for cTnI and 11% for cTnT. The clinical decision limits chosen by the laboratories were split between 10% CV (39%), 99th centile (35%), and others. Information was obtained from assay package by more than half (52%), with only 4% of laboratories independently assessing manufacturers’ claims. Peer-reviewed literature was cited by 16%. Actual guidelines were directly cited as the source by only 9%.
The study shows that guidelines are used less consistently than expected. Although cTnT and cTnI are the preferred markers, as recommended in all of the guidelines, they are combined with other markers. A defined protocol for cardiac biomarkers was one of the earliest recommendations. The absence of such a protocol in a large number of laboratories is a cause for concern, as is the lack of clinician involvement in protocol development in 20% of cases. Thus there is a clear need to improve the dialog between clinicians and laboratory.
Considering laboratory aspects, reported turnaround time was good and in accordance with recommendations. However, this may not be truly representative, as the questionnaire requested analytical turnaround time and not time from sample draw to the result being acted on. This will be addressed in the next audit. A serious concern is the fact that external quality assessment was not 100%. The reason for the selection of 10% CV or 99th centile was arbitrary, as it was seen for both troponin T and troponin I. The study also indicated that it was mainly the information given by the manufacturer that guided the selection of decision limits, not any in-house verification or guidelines.
In conclusion, the CARMAGUE study demonstrates the rapid transformation to using troponin measurement as standard. It also reveals some challenges, such as lack of dialog between the laboratory and clinicians and failure of laboratories to participate in external quality assurance schemes. A more extensive survey is required to confirm and extend these findings. A policy of encouragement and education, combined with further audit, should help to encourage more evidencebased practice and implementation of guidelines (4)(5).
Acknowledgments
Grant/funding Support: None declared.
Financial Disclosures: None declared.
Footnotes
1 Nonstandard abbreviations: ACS, acute coronary syndrome; CARMAGUE, Cardiac Marker Guideline Uptake in Europe study; cTn, cardiac troponin; CK, creatine kinase; CK-MB, creatine kinase MB isoenzyme. 
References
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