Depending on the nature of the Detection system assays can be based on:
#Colony forming or virtual colony count: e.g. by multiplying bacteria or proliferating cells.
#Photometry / spectrophotometry When the absorbance of a specific wavelength of light while passing through a fixed path-length through a cuvette of liquid test sample is measured and the absorbance is compared with a blank and standards with graded amounts of the target compound. If the emitted light is of a specific visible wavelength it may be called colorimetry, or it may involve specific wavelength of light e.g. by use of laser and emission of fluorescent signals of another specific wavelength which is detected via very specific wavelength optical filters.
#Transmittance of light may be used to measure e.g. clearing of opacity of a liquid created by suspended particles due to decrease in number of clumps during a platelet agglutination reaction.
#Turbidimetry when the opacity of straight-transmitted light passing through a liquid sample is measured by detectors placed straight across the light source.
#Nephelometry where a measurement of the amount of light scattering that occurs when a beam of light is passed through the solution is used to determine size and/or concentration and/or size distribution of particles in the sample.
#Reflectometry When color of light reflected from a (usually dry) sample or reactant is assessed e.g. the automated readings of the strip urine dipstick assays.
#Viscoelastic measurements e.g. viscometry, elastography (e.g. thromboelastography)
#Counting assays: e.g. optic Flow cytometric cell or particle counters, or coulter/impedance principle based cell counters
#Imaging assays, that involve image analysis manually or by software:
##Cytometry: When the size statistics of cells is assessed by an image processor.
#Electric detection e.g. involving amperometry, Voltammetry, coulometry may be used directly or indirectly for many types of quantitative measurements.
#Other physical property based assays may use
##Osmometer
##Viscometer
##Ion Selective electrodes
##Syndromic testing