[Latex myoglobin: a fast early marker in acute myocardial infarction]

To evaluate the diagnostic power of serum myoglobin (Mgb) by latex agglutination as a marker in the first hours of acute myocardial infarction (AMI).

Two hundred forty-eight serum samples from 53 patients admitted to the Coronary Unit (CU) from the Emergency Department (ED) for suspected AMI were studied. The extractions were carried out upon admission and at 4, 8, 12, 18, 24 and 36 hours after the initiation of symptoms. Myoglobin was analyzed by radioimmunoassay (RIA) and by a semiquantitative method of latex agglutination (Rapitex), in addition to creatine kinase (CK) and MB fraction (CK-MB). Sensitivity (S), specificity (E), positive and negative predictive value (PPV) (NPV) and standard efficacy (SE) of the different markers were measured along with the correlation between RIA and latex methods for Mgb.

For a prevalence of 83%, the latex test provided S = 81%, E = 8%, PPV = 97%, NPV = 50%, ES = 0.85; CK S = 43% (*), E = 88%, PPV = 97%, NPV = 24% (*) and ES = 0.31 (*) (* = p less than 0.01) and CK-MB S.63% (*), E = 100%, PPV = 100%, NPV = 34% (*) and ES = 0.31 (*) (* = p less than 0.05). The correlation between latex and RIA in the first 4 hours was r = 0.8243 (p less than 0.0001). On performing the 2 tests separated by 2 in the first 4, latex NPV was 100%.

Mgb - latex is the earliest AMI indicator and has greater diagnostic strength in the first hours than CK and CK-MB. It has a good correlation with Mgb-RIA and is simple and rapid to carry out making it specially useful in Emergency Departments and Coronary Units.