A rapid latex agglutination test for detection of elevated levels of myoglobin in serum and its value in the early diagnosis of acute myocardial infarction.

A latex agglutination test for detection of elevated levels of myoglobin in serum has been studied, and its clinical value in diagnosis of acute myocardial infarction (AMI) has been evaluated on a retrospective material of fifty-five patients consecutively admitted to hospital on suspicion for AMI within 4 h after onset of symptoms. The analysis time was less than 10 min. There was no evidence of interference with other related proteins, as judged from analysis of sera with high content of aspartate and alanine aminotransferase, lactate dehydrogenase and creatine kinase, nor was the test sensitive to haemolysis. However, unspecific agglutination was seen with some sera containing a high concentration of rheumatoid factors. In sera with known concentrations of myoglobin, quantitated by a radioimmunoassay, the test was negative in all sera below 80 micrograms/l (n = 187), and positive in all sera above 140 micrograms/l (n = 209). In the range 80-140 micrograms/l the latex test could be either positive or negative (n = 105). The day-to-day reproducibility was high in the ranges below 80 micrograms/l and above 140 micrograms/l, but range 80-140 micrograms/l. In the diagnosis of AMI the predictive value of a positive result was 0.64, and the predictive value of a negative result was 1.0. The latex agglutination test is therefore clinically useful as an emergency test, and as a very early and sensitive indicator for AMI. Patients with a negative test result during the first 12 h after debut of symptoms can with great certainty be identified as not suffering from AMI, whereas patients with a positive test result should be monitored by further laboratory analyses.