Rapid estimation of serum myoglobin concentration during rhabdomyolysis with a latex-agglutination test (Rapi-Tex)

A latex-agglutination test (Rapi-Tex) was used for semiquantitative estimation of myoglobin concentration in 89 serum samples obtained from ten patients undergoing lower-limb arterial embolectomy. Each serum sample was tested with Rapi-Tex both undiluted and after 1:50 dilution with saline. The myoglobin concentration was additionally measured with enzyme-immunoassay. In the undiluted samples there were five 'false negative' Rapi-Tex results--two in the myoglobin concentration interval 0-300 micrograms and three in the samples with myoglobin exceeding 25,000 micrograms/l--and four 'false positive' results. None of the diluted samples gave rise to false classification. Using 1:50 diluted serum, the negative predictive value of the Rapi-Tex test for identification of a myoglobin concentration greater than 5,000 micrograms/l was 0.99 (95% confidence limits 0.94-1.00), and the positive predictive value was 1.00 (0.61-1.00). Rapi-tex is concluded to be a useful emergency test for severe hypermyoglobinemia.