The attenuation of a light beam by a suspension of platelets in plasma was examined theoretically and experiments were performed to confirm this analysis. Interfering and modifying inputs were identified and their effects quantified. Recommendations for instrument design are made which minimise the effects of spurious inputs and enable platelet concentration in plasma to be estimated by simple optical methods. The most important recommendations are: (i) the use of light in the range 850–1000 nm so that water may be used instead of isologous platelet-free plasma as a blank and (ii) the emphasis on the need for the calibration of the system and the necessity for re-calibration if the optical system is disturbed or adjusted.
Keywords
Platelet (thrombocyte) concentration, plasma - Attenuation of light, plasma turbidity, light scatter - Wavelength, infrared - Optical density, error analysis
