ObjectiveTo investigate the difference between electrochemiluminescent immunoassay (ECLIA) and radioimmunoassay (RIA) in the detection of serum cortisol.

MethodsA total of 188 patients were selected from healthy outpatients and inpatients. The serum cortisol of the patients and quality control serum cortisol were detected by ECLIA and RIA. The detection accuracy of the methods in the two batches and the coefficient of variation (CV) of within-batch and between-batch were calculated. To evaluate the precision of the test, quality control serum was added to low, medium, and high concentrations of serum cortisol for the evaluation of recovery rate and detection accuracy. The correlation between results was analyzed by regression.

ResultsThe sensitivity and specificity of the ECLIA method was higher than those of the RIA method. The CV of the ECLIA method was also lower than that of the RIA method, and the recovery rate of the ECLIA method was higher than that of the RIA method. The two methods showed good correlation and highly correlated results (r=0.991, P < 0.01).

ConclusionsThe two methods have their own advantages in the detection of serum cortisol. The degree of automation of ECLIA is high, whereas the RIA method is mature and inexpensive. Although ECLIA is the current and future development trend, RIA retains a certain advantage in terms of sensitivity and specificity. The two methods provide different reference intervals. RIA remains an indispensable method for clinical cortisol testing.