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. Author manuscript; available in PMC: 2010 Dec 1.
Published in final edited form as: Nat Biotechnol. 2010 May 23;28(6):595–599. doi: 10.1038/nbt.1641

Figure 4. Digital detection of PSA in serum samples of patients who had undergone radical prostatectomy.

Figure 4

Figure 4

Concentrations of PSA in serum samples from RP patients (Inline graphic), healthy control samples (Inline graphic), and Bio-Rad PSA control samples (▲) determined using digital ELISA. RP patient samples (SeraCare Life Sciences, Milford, MA) all had undetectable PSA levels as measured by a leading clinical diagnostic assay (ADVIA Centaur); the green line represents the detection limit of the ADVIA Centaur PSA assay (100 pg/mL or 3 pM). All 30 patient samples were above the detection limit of the PSA digital ELISA, shown by the red line (0.006 pg/mL or ~200 aM), with the lowest patient PSA concentrations measured at 0.014 pg/mL (~400 aM) using digital ELISA. Patient samples with the lowest PSA levels were detectable, but approached the LOD of the assay resulting in a large imprecision in the concentration determined (high dose %CV). The digital ELISA was validated for specificity to PSA using control standards (Bio-Rad) and serum from healthy individuals (ProMedDx) that had been assayed using the ADVIA Centaur PSA assay (See Supplementary Table 3).