Early Diagnosis of Acute Myocardial Infarction Using Immunosensors and Immunotests

Various biochemical markers are available to detect cardiac tissue injury after an acute myocardial infarction (AMI) and to estimate the extent of this injury. One of the markers used to detect AMI early after onset of symptoms is heart-type fatty acid-binding protein (H-FABP). To make it clinically applicable it is important to develop rapid diagnostic sensors to assess its concentration. Due to the requirement of skilled technicians and lengthy assay procedures, most immunochemical assays for H-FABP are of limited use for routine clinical practice. A rapid and quantitative immunotest for the detection of H-FABP in serum samples has been successfully developed with a performance time of 10 min. Fifty-one serum samples from patients were evaluated using a conventional ELISA and the newly developed test. A good correlation was found with r 2 = 0.9585. The detection limit of the test was 2.8 µg/L. For the pooled serum sample with a lower H-FABP concentration (4 µg/L), the calculated intra-assay coefficient of variation (CV) was 10%, and the inter-assay CV was 15%; for the pooled serum sample with a high H-FABP concentration (103 µg/L), the intra-assay CV was 8% and the inter-assay CV was 10%. Furthermore, the immunotest can be stored either at 4°C and room temperature for up to one year without significant loss of activity. Finally, a one-step FABP test so-called CardioDetect® which was derived from the serum immunotest has been designed for qualitative determination of H-FABP in whole blood samples. It requires no sample pretreatment and gives result within 15 min. Thirty-nine patients presenting with chest pain and suspected AMI were studied. Using an upper reference level of 7 µg/L, the specificity of the rapid test was 94%. Both sensitivity and negative predictive value (NPV) were 100% implying that 100% of nonAMI patients can be excluded with no false negative results. With this rapid and sensitive immunotest, H-FABP will be soon introduced to clinical practice.