Analytical and Clinical Evaluation of the NOWDiagnostics ADEXUSDx Human Chorionic Gonadotropin Test Using Whole Blood

Abstract

Background Point-of-care (POC) urine qualitative human chorionic gonadotropin (hCG) devices are used to rapidly assess pregnancy status, but many of these devices are susceptible to false-negative results caused by increased concentrations of hCG β core fragment (hCGβcf) that does not contain hCGβcf. Methods Purified hCG was added to hCG-negative heparinized whole blood to generate samples with known hCG concentrations, and the resulting samples were used to evaluate device sensitivity, low-end reproducibility, high-dose hook effect, intermediate range performance, acceptable sample volume, acceptable hematocrit range, and lot-to-lot variation. Device performance was also prospectively evaluated in 40 pregnant and 40 nonpregnant women aged 18–44 years in a hospital-based clinic or an academic hospital emergency department. Results All device observations were positive using a whole blood sample containing a plasma hCG concentration of 2.2 × 106 IU/L, and all device observations were positive from18 IU/L to 1.2 × 103 IU/L and from 2.5 × 104 IU/L to 2.2 × 106 IU/L. Three invalid results were observed in the intermediate range because of decreased control line intensity. The minimum sample volume was 30 μL, and maximum hematocrit was 46%. In 40 pregnant and 40 nonpregnant women aged 18–44 years, the device generated 100% concordance with urine qualitative and plasma quantitative test results. Conclusions The ADEXUSDx™ hCG test demonstrates acceptable performance for the determination of pregnancy status using capillary fingerstick samples.

Inappropriate Off-label Use of a Qualitative, Point-of-care hCG Device

“…In addition to receiving FDA approval, the performance characteristics of both of these devices have been independently evaluated in academic medical centers. 4 , 5 We strongly recommend that the authors engage with laboratory professionals at their institution to discuss available testing options and select appropriate test methods that meet the clinical need without jeopardizing patient care.…”