SENSITIVE RAPID DETECTION OF MYOGLOBIN IN SERUM OF PATIENTS WITH MYOPATHY BY IMMUNOTURBIDIMETRIC ASSAY

Objective. To study immunoturbidimetry, a new technique for the quantitative determination of myoglobin in serum. Methods. Correlation with the standard technique of radioimmunoassay in sera of patients with and without myopathy. Results. Immunoturbidimetry was found to have a close correlation with the radioimmunoassay (RIA) method (r = 0.97, p = < 0.001), although it was slightly less sensitive. Compared to RIA, sensitivity was 87.8% and specificity, 98.6%. The turbidimetric method was performed considerably more rapidly than RIA. Using this method to assess patients with dermatomyositis and polymyositis, a close relationship to clinical findings was noted. However, of 64 samples with myoglobin level greater than 50 ng/ml, there were 3 instances (4.7%) where elevated myoglobin in the presence of normal CK suggested active disease, and there were 9 instances (14.1%) where myoglobin was normal in the presence of elevated CK. Seven of these cases were felt to reflect a lower sensitivity of the turbidimetric method. The other 2 are not explained. Serial measurements of serum myoglobin correlated well with clinical state in the course of 2 patients illustrated. Conclusions. Assay of serum myoglobin by immunoturbidimetry may provide a rapid and easily performed method without reliance on radiochemicals. It can be useful in clinical assessment of patients with myopathies, although sensitivity is not quite as high as that of RIA.