Disease detection at the molecular level is driving the emerging revolution of early diagnosis and treatment. A challenge facing the field is that protein biomarkers for early diagnosis can be present in very low abundance. The lower limit of detection with conventional immunoassay technology is the upper femtomolar range (10 −13 M). Digital immunoassay technology has improved detection sensitivity three logs, to the attomolar range (10 −16 M). This capability has the potential to open new advances in diagnostics and therapeutics, but such technologies have been relegated to manual procedures that are not well suited for efficient routine use. We describe a new laboratory instrument that provides full automation of single-molecule array (Simoa) technology for digital immunoassays. The instrument is capable of single-molecule sensitivity and multiplexing with short turnaround times and a throughput of 66 samples/h. Singleplex and multiplexed digital immunoassays were developed for 16 proteins of interest in cardiovascular, cancer, infectious disease, neurology, and inflammation research. The average sensitivity improvement of the Simoa immunoassays versus conventional ELISA was >1200-fold, with coefficients of variation of <10%. The potential of digital immunoassays to advance human diagnostics was illustrated in two clinical areas: traumatic brain injury and early detection of infectious disease.

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