  Immunoassay formats applicable for clinical or point-of-care diagnostics fall
into two broad classes. One which uses labeled secondary antibodies for signal
transduction and the other which does not require the use of any labels.
Comparison of the limits of detection (LoD) reported by these two sensing
approaches over a wide range of detection techniques and target molecules in
serum revealed that labeled techniques achieve 2-3 orders of magnitude better
LoDs. Further, a vast majority of commercial tests and recent examples of
technology translations are based on labeled assay formats. In light of this
data, it is argued that extension of traditional labeled approaches and
enhancing their functionality may have better clinical impact than the
development of newer label-free techniques.
