Analytical evaluation of the Radiometer AQT90 FLEX βhCG assay

Many hospitals cannot afford an hCG assay on a central lab analyzer and turn to point of care testing (POCT) solutions. The Radiometer AQT90 FLEX is a small benchtop immunoareement between the AQT90 and comparator methods for samples with hCG ssay analyzer for use in the laboratory or at the patient bedside. This study evaluated the analytical performance of the AQT90's βhCG assay.

Precision was assessed using whole blood patient samples and two levels of quality control. Linearity was assessed by dilution of a high hCG plasma sample. Carryover and hook effect were assessed using high and low hCG samples. Method comparisons were done against Abbott i-STAT Total βhCG, Beckman Coulter Total βhCG (5th IS), and Roche hCG+β. Sample concentrations ranged from<2 IU/L to 4,973 IU/L.

Repeatability and within-laboratory precision passed most manufacturer's claims and allowable error criteria. Linearity was validated from<2 IU/L to 4,741 IU/L. Hook effect was not observed up to 2,446,448 IU/L. Carryover was<4.0 ppm. A linear relationship was observed with i-STAT, Beckman and Roche methods. At>20 IU/L, biases were apparent against all three comparator assays (i-STAT: +20%, Roche: +30%, Beckman: +5 to 15%). At ≤20 IU/L, the acceptability of agreement varied according to TAE specifications. Concordance between AQT90 and comparator assays using 5 IU/L as the medical decision level ranged from 69% to 81%.

Overall, the AQT90 hCG assay performed well and would be suitable for smaller suburban or rural hospitals. Some limitations have been noted and should be kept in mind during clinical testing.