New electrochemiluminescent immunoassay for the determination of CYFRA 21-1: Analytical evaluation and clinical diagnostic performance in urine samples of patients with bladder cancer

Background: A new electrochemiluminescent immunoassay (ECLIA) has been deve loped for the determination of cytokeratin 19 (CYFRA 21-1) in the Elecsys 2 010 immunoassay system. Urinary CYFRA 21-1 might have a role in the diagnos is of bladder cancer. Methods: We performed an analytical evaluation of the CYFRA 21-1 ECLIA for serum and urine samples. The clinical value of urinary CYFRA 21-1 for the d etection of bladder cancer was evaluated through its measurement in 226 uri ne samples from symptomatic and asymptomatic controls. Results: At concentrations of 2-30 mu g/L, within-assay imprecision (CV) wa s below 2.1% for sera and 3.3% for urines, with interassay CVs below 3.3% f or sera and 4.9% for urines. The day-to-day CV was <20% at concentrations > 0.2 mu g/L (functional sensitivity). Measurement of diluted samples showed that the assay estimated CYFRA 21-1 between 98% and 103% for sera and 98% a nd 105% for urines. Recovery of added CYFRA 21-1 was 99-105% for sera and 9 6-115% for urines. We separately compared serum and urine CYFRA 21-1 ECLIA results with those obtained with an IRMA (CIS bio international). Regressio n analysis for sera was: CYFRA 21-1 (ECLIA) = 0.520 + 1.018 CYFRA 21-1 (IRM A); [95% confidence interval (CI) (y-intercept), -0.260 to 1.309]; 95% CI ( slope), 0.978-1.060; n = 100; S-y \ x = 3.242; r(2) = 0.987. For urine samp les it was: CYFRA 21-1 (ECLIA) = 0.716 + 0.966 CYFRA 21-1 (IRMA); 95% CI (y -intercept), 0.009-1.422; 95% CI (slope), 0.956-0.976; n = 100; S-y \ x = 4 .136; r(2) = 0.986. In urine samples voided by patients with and without bl adder cancer, the best ROC analysis discrimination provided 81.0% (95% CI, 72.7-87.7%) sensitivity and 97.2% (95% CI, 90.2-99.6%) specificity at a thr eshold value of 5.7 mu g/L. Conclusions: Our initial evaluation showed reliable analytical performance for urinary CYFRA 21-1, which might assist urologists in the detection of b ladder cancer as a noninvasive adjunct to cystoscopy. (C) 1999 American Ass ociation for Clinical Chemistry.