Development of a quantitative lateral-flow assay for rapid detection of fatty acid-binding protein.

Using human heart-type fatty acid-binding protein (H-FABP) as an early cardiac marker to confirm or exclude a diagnosis of acute myocardial infarction (AMI) soon after admission requires a rapid assay system. Due to the requirement of skillful technicians and complicated assay procedures, most immunochemical assays for H-FABP are of limited use for routine clinical practice. In the present study, we describe a rapid lateral-flow assay for detection of H-FABP. Fifty-one human samples were evaluated using a conventional ELISA and a newly developed lateral-flow assay. A good agreement between the two methods was found according to Bland and Altman plot. The correlation found was y=0.9685 x -0.6270 (r(2)=0.9585). The detector antibody labeled with colloidal gold was mixed with those without label to extend the linear range of the calibration curve up to 125 microg/l H-FABP with r(2)=0.9832. The detection limit of the assay was 2.8 microg/l. The test-strips can be stored either at 4 degrees C and room temperature for up to 1 year without significant loss of activity. Finally, a one-step FABP test so-called CardioDetect(R), which was derived from the serum lateral-flow assay has been designed for qualitative determination of H-FABP in whole blood samples. It requires no sample pretreatment and gives results within 15 min. Thirty-eight patients presenting with chest pain and suspected AMI were studied. Using an upper reference level of 7 microg/l, the specificity of the rapid test was 94%. Both sensitivity and negative predictive value (NPV) were 100%, implying that 100% of non-AMI patients could be excluded with no false-negative results. With this rapid and sensitive immunotest, H-FABP could soon be introduced into clinical practice.