Summary: Troponin T concentration in serum is usually measured by the automated method developed by Boehringer Mannheim for the ES-series of analysers. These instruments need at least 140 μΐ of serum and 700 μΐ of reagents for a single analysis, which takes 90 min. We describe an alternative procedure, using streptavidin-coated microtitre plates, troponin T reagents of Boehringer Mannheim and an ELIS Α-reader to measure the concentration of troponin T. The present assay needs only 30 μΐ of sample and 200 μΐ of reagents, and it takes 75 min; the detection limit is 0.10 μg/l. We also assessed the microtitre plate method for sensitivity and precision and compared the results with those measured by an ES-300 automatic analyser. Both methods have the same measurement range for troponin T of 0.1 to 15 μg/l. For daily routine use of the microtitre plate method we recommend duplicate determinations.

Three new rapid, qualitative bedside immunoassays were evaluated in the diagnosis of patients with acute chest pain. The subjects, 122 patients in group 1 (bedside tests for myoglobin, creatine kinase MB) and 233 patients in group 2 (bedside tests for troponin I and sensitive troponin T) were admitted to hospital with acute chest pain for less than 12 h. The bedside tests were performed on admission, and 2, 4, and 6 h later. The correlation between the two parts of the rapid creatine kinase MB/myoglobin test during the first 12 h after the onset of chest pain was moderate in all patients (kappa=0.401, 95% confidence interval 0.321-0.483). The highest correlation was seen with the patients with definite and probable myocardial infarction. The correlations were smaller but significant also in other diagnostic groups (unstable angina pectoris, prolonged chest pain, and non-cardiac chest pain). The correlation between the rapid sensitive test for troponin T and rapid test for troponin I was significant in all groups (kappa=0.776, 95% confidence interval 0.711-0.841). The myoglobin part of the rapid creatine kinase MB/myoglobin test may be too non-specific for clinical diagnostic purposes [in non-infarct patients the myoglobin part was significantly more often positive than creatine kinase MB or troponin tests (P<0.001)].

Summary:We describe an improved procedure using a standard microplate immunoassay reader to measure the concentration of troponin T in human serum. We also describe an immunoassay for troponin I in serum. Only 160 μΐ of serum are needed for a single analysis of each troponin. For comparison, creatine kinase MB mass analysis in serum was performed with a commercial luminometric method. From 95 apparently healthy people the following values were obtained: creatine kinase MB mass 2.6 ±1.2 μg/l, troponin Τ 0.027 ± 0.025 μg/l and troponin I 0.03 ± 0.031We compared the results of troponin Τ and troponin I methods with each other, as well as with those of creatine kinase MB mass measured in 48 patients with verified acute myocardial infarction and in 60 control patients with non-cardiac chest pain. The correlation between troponin Τ and troponin I values was 0.91 for the total material and 0.94 for 48 patients with acute myocardial infarction. Troponin I showed better earlier sensitivity than troponin Τ (ρ = 0.043). In nine patients in the control group, creatine kinase MB mass exceeded the reference limit of 5.0 μg/l, while in two patients the cut-off limit of 10.0 μ §/1 was also surpassed, pointing to non-specificity.In the group of infarct patients, the highest serum creatinine value was 193 μηιοΐ/ΐ, whereas in the control group it was 406 μιηοΙ/1. The sera of patients with impaired renal function without any cardiac failure showed no increase in troponin Τ and troponin I values.In conclusion, serum creatine kinase MB mass and troponin I seem to confirm an acute myocardial infarction more rapidly than does troponin T; troponin I has the highest cardiac specificity.

There is an increasing demand for the results of cardiac markers (troponin I or T, creatine kinase MB mass and myoglobin) to be made available promptly after sample-taking. In order to shorten the turnaround time, the possibility of using EDTA- or heparin-plasma instead of serum was investigated. The study population comprised 391 patients with acute chest pain. Four different instruments and systems routinely used in Finland giving quantitative results were studied for the assays of creatine kinase isoenzyme MB mass, myoglobin, and troponin I or troponin T. In addition to serum samples, heparin-plasma seems to be useful for all three assays using the Access and Immulite systems, while EDTA-plasma seems to be useful for all three assays with the Access and Elecsys systems. For the AxSYM assays, serum samples seem to be the best alternative. In conclusion, it is possible to use a single EDTA- or heparin-plasma sample for Access, Elecsys and Immulite analysers, and thereby to shorten the turnaround time. In this way the quantitative analyses from plasma can be performed 30 min after taking the sample.