Serum Samples Cannot Be Used for Fluorescence Immunoassay for detection of myocardial infarction triple

Background: Whole blood or plasma samples are recommended for use in triple-marker testing of myocardial infarction. Whether serum sample can be used for the diagnosis of myocardial infarction has not been compared and validated. Methods: Whole blood samples and serum samples were detected with CTnI, Mb and CK-MB simultaneously by using immunouorescence assay method. Results: Both CK-MB and TNI detection results were highly consistent for whole blood samples vs. serum samples. However, when Mb is tested, the positive rate of serum samples is relatively low, and there will be more false negative results, resulting in missed diagnosis. Conlusion: Serum samples cannot be used in replace of whole blood samples for triple-marker testing and diagnosis of myocardial infarction.


Background
Acute myocardial infarction is a clinically common critical illness caused by severe myocardial ischemia and myocardial necrosis caused by coronary artery disease [1]. Its testing and diagnosis are usually based on clinical symptoms, ECG ndings and test results of triple-marker diagnosis of myocardial infarction [2]. Because some patients with AMI have no typical clinical manifestations in the early stage of the disease, such patients have no characteristic ST segment changes on the electrocardiogram. Therefore, at present, early diagnosis of AMI mainly relies on the test results of the triple-marker testing of myocardial infarction at clinical laboratory. CTnI, Mb, CK-MB are three speci c biochemical markers of AMI [3][4][5][6]. The immuno uorescence assay for CTnI, Mb, CK-MB is a relatively advanced triple-marker testing method for myocardial infarction. Whole blood or plasma samples are recommended for use in triple-marker testing of myocardial infarction using certain matured commercial kits. Whether other samples can be used for the diagnosis of myocardial infarction by triple-marker testing indicators has not been compared and validated. In this study, we explored the possibility of triple-marker testing for myocardial infarction by replacing whole blood samples with serum samples based on the results of triple-marker testing for myocardial infarction with serum and whole blood samples.

Sample Collection
Whole blood samples and serum samples from a total of 30 patients who underwent triple-marker testing of myocardial infarction between July 24, 2018 and August 2, 2018 in Qianfoshan Hospital of Shandong Province were collected. CTnI, Mb and CK-MB were detected immediately after venous blood collection.

Assay method
Whole blood samples or serum samples were tested using myocardial infarction triple-marker test plates (Alere company). According to the instructions, blood samples or serum samples were added dropwise to the sample wells. After the sample has diffused to the frontmost mark line on the reagent cartridge, place the cartridge in a uorescence reader to read the uorescence values. All operations were carried out at room temperature.

Diagnostic thresholds
According to the instructions of Alere company kit, the sample can be diagnosed as CTnI positive when the test result is greater than 1.0 ng/mL, Mb positive when the test result is greater than 107 ng/mL, and CK-MB positive when the test result is greater than 4.3 ng/mL.

Statistical analysis
Student's t-test was further performed on the dataset using SPSS 19.0 software when a signi cant difference existed in the positive and negative results between whole blood samples and serum samples in the results of triple-marker testing for myocardial infarction of all the 30 cases.

Test results of CK-MB
The CK-MB testing results of whole blood and serum samples showed a high consistency. Twenty-nine of the 30 samples showed consistent results. Among them, 28 were positive, and 1 was negative. Only one sample showed a positive result for serum test and a negative result for whole blood test. The consistency of CK-MB detection in whole blood and serum samples was 96.7% (29 / 30) ( Table 1).  (Table 2). Student's t-test on the data set showed that p < 0.05. The difference in the test results was statistically signi cant.  Availability of data and materials The data supporting the conclusions are included in the article. Raw data are available upon request.

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