Performance characteristics of the Access® Inhibin A assay

Background: Second trimester maternal screening using AFP, uE3, hCG, and inhibin A has shown a detection rate for Down's syndrome of 81% with a 5% false positive rate. Inhibin A may also have utility as a serum tumor marker in postmenopausal women with ovarian cancer and men with testicular stromal tumors. Methods: The Beckman Coulter Access® Inhibin A assay was evaluated for limit of blank, dilution linearity, imprecision, interferences, reference intervals, and comparison to an inhibin A ELISA. Results: The limit of blank was 0.1 ng/l. The assay was linear from 0.2 to 1347 ng/l. Total inter-assay CVs were < 5% for control levels ranging from 24.6 ng/l to 811 ng/l. Interference studies showed recoveries of inhibin A within 10% of expected values at interferent concentrations of 10 g/l hemoglobin and 22 g/l triglycerides. No significant interference was observed at a bilirubin concentration of 400 mg/l. The 97.5th percentile upper reference limits were 6.8 ng/l for postmenopausal women and 3.0 ng/l for men. The Access assay compared to an ACTIVE ELISA showed a slope of 0.88, an intercept of - 3.7 ng/l, Sy/x = 40 ng/l, and r = 0.98. Conclusions: The analytical performance of the Access inhibin A assay is acceptable for routine laboratory testing. © 2008 Elsevier B.V. All rights reserved.