We have blogged previously about the limitations of urine hCG tests to detect pregnancy in a hospital setting and about the Abbott iSTAT, the first FDA approved device for detection of hCG in whole blood at the point-of-care.
Recently, Nerenz et al evaluated the NOWDiagnostics ADEXUSDx™ hCG test, a qualitative immunoassay device for the detection of hCG in anticoagulant-free whole blood, heparinized whole blood, or heparinized plasma. This device is read visually, like the urine/serum POC devices, but it is FDA approved for the use of whole blood samples.
Overall, the device performed very well for the detection of hCG using capillary fingerstick samples.
The device has several limitations.
- The ADEXUSDx product is a qualitative, not quantitative device. This is different than the iSTAT device, that we reported on previously, as the iSTAT is quantitative with a range of 5-2000 IU/L. However, since hCG concentrations in women rise so rapidly in early pregnancy, and with such a narrow dynamic range some would argue that the iSTAT device is almost a qualitative device.
- The authors reported that the device recognized 100% of samples at a concentration of 27 IU/L and approximately 50% of samples at a concentration around 10 IU/L. This analytical sensitivity is similar to the POC serum devices currently used in hospitals.
- Finally, the ADEXUSDx device showed susceptibility to the high-dose hook effect, as decreasing test line intensity was observed at concentrations ≥600,000 IU/L, but all devices were interpreted as positive. This limitation is similar to that seen with the iSTAT device.
Overall, this is a nice addition to the available POC hCG devices currently on the market. It should be pointed out that the Abbott iSTAT and the NOWDiagnostics ADEXUSDx are the only two devices currently available for the diagnosis of pregnancy using whole blood at the point of care.
Whole blood should not be used on devices that are only FDA approved for urine and/or serum, as we have pointed out in previous publications.