Rapid determination of serum myoglobin with a routine chemistry analyzer

A turbidimetric immunoassay system (Turbitime system, Behringwerke AG) allows rapid determination of myoglobin in serum. We adapted the reagents for this myoglobin assay (Turbiquant myoglobin) for use with a Hitachi 717 analyzer. No high-dose hook effect was observed up to 15,000 micrograms/L. Interassay CVs were 4.6% (mean = 72.0 micrograms/L; n = 9) and 2.5% (mean = 365.6 micrograms/L; n = 11). The calibration curve was stable for at least 1 month. Hemolysis did not interfere, and turbidity from lipemia interfered only when absorbance exceeded 2.0 A. Results of this method (y) correlated well with those by the Turbitime method (y = 1.256x - 44.1 micrograms/L; n = 91; r = 0.991) and by a commercially available radioimmunoassay (Byk-Sangtec; y = 0.739x - 42.2 micrograms/L; n = 94; r = 0.991). The upper limit (95th percentile) of the reference interval for myoglobin was estimated at 57.9 micrograms/L. The positive predictive value for results of myoglobin at admission was 89% with this upper reference limit and 99% with 100 micrograms/L, whereas the negative predictive value was about 60% for both limits.