Express diagnosis of acute coronary events
Velkov V.V., Reznikova O.I.
CJSC "DEACON", 142290, Pushchino, Moscow region, Prospekt Nauki, 5.
Acute myocardial infarctions: fast and accurate diagnosis is a matter of life and death
In 2003, 7.2 million cases of AMI were registered in the United States. At the same time, it is AMI that is a disease in the United States with a high frequency of misdiagnosis. As a result, some patients with valid AMI are unlawfully discharged from the hospital, which leads to high mortality, while patients without AMI are hospitalized in vain. In 2003 alone, the costs for patients with AMI in the United States amounted to $31.5 billion. A significant part of these costs is attributed to erroneous diagnoses (1).
Diagnosis of AMI is based on a comprehensive assessment of the patient's condition, which includes at least two of the three main definitions:
1) characteristic symptoms,
2) typical ECG changes,
3) determination of serum cardiomarkers (4).
This approach actually detects all patients with MI with and without ST-segment elevation.
Diagnosis of unstable angina is more difficult, because with it, tests for cardiomarkers usually give a negative result, and an ECG can be inconclusive. The frequency of missed cases of acute coronary syndromes (ACS) can range from 3% to 4%. (1). Moreover, for the effective diagnosis of patients with signs of ACS, an ECG interpretation is necessary within 10 minutes after the patient's admission and rapid receipt of information about the levels of cardiomarkers (2). The latter depends on how quickly a clinical laboratory is operating. Express diagnostics solves this problem. Thus, when 817 patients were observed who were admitted with suspected AMI, the average time from sampling to receiving results from the laboratory was 71 minutes (creatine kinase MV, CC-MV), and the time of rapid testing of CC-MV, myoglobin and troponin cTnI was 24 minutes. It has also been shown that rapid diagnostics of myoglobin and cTnI levels can exclude the diagnosis of AMI within the first 90 minutes after the patient's admission (3). Another study showed that rapid testing of cardiomarkers reduces the time required to confirm or exclude AMI from 83 minutes to 26.5 minutes (4).
Borderline levels of cardiomarkers:
the lower the number, the more false positive diagnoses,
the higher – the more false negatives
Obviously, if the boundary values are too low, the statistics of cases of MI will go up, the economic costs will unreasonably increase, but the mortality from AMI will decrease. If the borderline levels are too high, the statistics for THEM will go down, the cost of treatment will decrease, and the mortality from AMI will increase.
What should be the correct borderline level of the cardiomarker? When observing 11539 patients who had negative results of the troponin test (cTnT) at admission (with the borderline level accepted at that time), it was shown that in this cohort the 30-day mortality rate was 6.2% (5). As a result, stricter AMI criteria were proposed, with lower borderline levels of cardiomarkers (6,7). This immediately led to an increase in diagnosed cases of AMI. Thus, in Israel, the clinical data of patients with ACS admitted during 2000 were compared with the data of patients admitted during 2002, after the introduction of stricter criteria for the diagnosis of AMI. It turned out that in 2002 the number of patients with MI increased by 32%, and the 30-day mortality rate decreased by 33% (8,9). Therefore, the question of what should be the optimal borderline levels of cardiomarkers is truly vital, especially for domestic cardiology.
In general, rapid testing of cardiomarkers, as it has been repeatedly proven:
1) improves the diagnosis, risk assessment and stratification of cardiac patients;
2) increases the effectiveness of therapy;
3) reduces the number of complications;
4) reduces the time of hospitalization;
5) reduces treatment costs;
6) makes a favorable impression on patients.
To the chief physician – information for reflection:
why do rapid tests, which are more expensive than similar laboratory tests, lead to significant savings?
As an example of why this is the case – the results of a large special study, what exactly are the advantages of rapid determination of troponin I levels compared to its determination in the laboratory (10). In 274 patients admitted with symptoms of ACS, troponin I levels were determined by nurses using bedside rapid tests. In 271 similar patients who were admitted earlier, before the introduction of express diagnostics, troponin I levels were determined in the laboratory. The cost of laboratory analysis was $ 3.83, express test - $ 10.54.
The results obtained can be summarized as follows.
1. The average time from blood collection to the result was:
• for express diagnostics - 19.5 min,
• for laboratory analysis – 76 min.
2. Average total costs per patient:
• for laboratory analysis – $17,163.,
• for express testing - $ 12822 (a decrease of 25%).
Including reduced costs:
• other branches – by 58%;
• for pharmacological preparations – by 28%;
• for laboratory tests – for 28%;
• for non-cardiological procedures – for 28%,;
• for cardiological procedures – for 14%,
• for the maintenance of patients – by 21%.
3. Average period of hospitalization:
• for laboratory tests – 2.36 days,
• with express diagnostics - 2.19 days (a decrease of 8%).
4. Survival rate for one year:
4.1. When the borderline level of troponin I is less than 0.1 mcg/l:
• during rapid testing - 97.2%,
• in laboratory tests – 96.2%.
4.2. At a boundary level greater than 0.1 micrograms/l:
• during rapid testing - 75.5%;
• in laboratory tests – 77.7%.
The authors of this large study conclude: "rapid testing of troponin I in whole blood has demonstrated its cost-effectiveness and clinical efficacy" (10).
In conclusion, we emphasize that rapid testing brings real therapeutic and economic benefits only when its results are taken into account in clinical decisions. This means that attending physicians should be well informed about the characteristics and benefits of rapid testing.
Detailed information about rapid tests, especially quantitative immunochromatographic tests, can be found on the website of CJSC "DEACON".
Literature:1. Pope JH, Aufderheide TP, Ruthazer R, et al.
Missed diagnoses of acute cardiac ischemia in the emergency department. N Engl J Med 2000;342: 1163–1170.
2. Antman EM, Anbe DT, Armstrong PW, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: executive summary: a report of the ACC/AHA Task Force on Practice Guidelines. Circulation 2004;110(9):82–292. Accessed Jul 27, 2005.
3. McCord J, Nowak RM, McCullough PA, et al. Ninety-minute exclusion of acute myocardial infarction by use of quantitative point-of-care testing of myoglobin and troponin I. Circulation 2001;104:1483–1488.
4. Di Serio F, Antonelli G, Trerotoli P,et al. Appropriateness of point-of-care testing (POCT) in an emergency department. Clin Chim Acta 2003;333:185–189.
5. Ohman EM, Armstrong PW, White HD, et al. Risk stratification with a point-of-care cardiac troponin T test in acute myocardial infarction. Am J Cardiol 1999;84:1281–1286.
6. Panteghini M. The new definition of myocardial infarction and the impact of troponin determination on clinical practice. Int J Cardiol 2006;106: 298–306.
7. Wong C-K, White HD. Implications of the new definition of myocardial infarction. Postgrad Med J 2005;81:552–555.
8. Kontos MC, Fritz LM, Anderson FP et al. Impact of the troponin standard on the prevalence of acute myocardial infarction. Am Heart J 2003;146:446–452.
9. Zahger D, Hod H, Gottlieb S, et al. Influence of the new definition of acute myocardial infarction on coronary care unit admission, discharge diagnosis, management and outcome in patients with non-ST elevation acute coronary syndromes: a national survey. Int J Cardiol 2006;106:164–169.
10. Apple FS, Chung AY, Kogut ME et al. Decreased patient charges following implementation of point-of-care cardiac troponin monitoring in acute coronary syndrome patients in a community hospital cardiology unit. Clin Chim Acta. 2006; 370(1-2):191-195.
Portal "Eternal youth" www.vechnayamolodost.ru01.11.2008