Received on May 3, 2007
Accepted on August 29, 2007

General Clinical Chemistry

Ultrasensitive Flow-based Immunoassays by Use of Single-Molecule Counting

¹ Singulex, Inc., Hayward, CA

^* To whom correspondence should be addressed. E-mail: j.todd{at}singulex.com.

Background: Immunoassay (IA) technology has expanded the clinical utility of protein biomarkers, but demands for increased sensitivity, dynamic reporting ranges, and small sample volumes has limited the potential clinical usefulness of many biomarkers. We assessed the performance, including limits of detection (LODs) and the dynamic reporting range of an IA-based technology, Erenna Immunoassay System, for a series of biomarkers, including cardiac troponin I (cTnI).

Methods: Erenna IAs were used with 10 different and clinically important biomarkers to ascertain the LOD with various sample sizes (10 µL to 200 µL).

Results: The Erenna Immunoassay System generated LODs of 10–100 pg/L using 100 µL of sample. For cTnI, the LOD was 0.2 ng/L and a 10% CV was seen between 0.78 and 1.6 ng/L.

Conclusions: The Erenna IA-based technology reproducibly measures protein biomarkers with detection limits of 10–100 pg/L, with a dynamic range of >4.5 logs in sample volumes of 50–150 µL.