Patent GB-1400640-A (GB)
Title: Blood analysis
IPC: G01N21/47
Filed: 1973-07-26
Abstract: 1400640 Blood analysis J P MERIC 26 July 1973 [10 Aug 1972] 35625/73 Heading G1A Blood components are analyzed by investigating the diffraction patterns generated by two samples when arranged in a convergent coherent beam of radiation, the red cells of one sample being haemolyzed and of the other being spherized. The radiation diffracted at angles which lie between specified pairs of limits related to the diameter of the particles being analyzed, the distance of the sample from the focal plane of the system, and the wavelength of the radiation, are measured photo-electrically and utilized to determine the number of red cells, platelets and white cells, the haematocrit value and the average corpuscular volume. As shown, Fig. 1, a laser 1 generates a beam of radiation which is expanded by lenses 4 and 5 and focused on to a central pinhole in a screen 9 behind which is located a light trap 11. A plate 7 having an aperture 8 is placed between the lenses and acts as a spacial filter. The screen 9 has four concentric arcuate windows 12, 13, 14, 15 behind each of which is located a vacuum photodiode 16, 17, 18, 19. The sample is placed in or flows through a vessel 20 spaced a distance D from the screen 9 so that radiation diffracted at various angles, defined by the radii of the windows and the distance D, are detected. The inner and outer radii of windows 12, 13 and 14 are selected according to first formulae to accept radiation diffracted according to the number of objects present of average diameter 6Á (red cells), 3Á (platelets) and 12Á (white cells) respectively, while those of window 15 are selected according to second formulae to accept diffracted radiation representing the total volume of the red cells. Two blood samples are used, the first being haemolyzed to convert the red cells into stromas by removing the haemoglobin to enable the much smaller numbers of white cells and platelets to be determined. The signals produced by detectors 17 (platelets) and 18 (white cells) are in part affected by other components in the sample and these signals are corrected by combining the signals in suitable proportions together with appropriate proportions of the signal from detector 16 (stromas) and background (noise) constants to produce signals representing the concentration of platelets and white cells. The proportionality constants are determined by preliminary calibration. The second blood sample is treated to spherize the red cells and the signals from detectors 16 (red cells) and 19 (haematocrit) are used to determine the concentration of red cells and the haematocrit value respectively. The ratio of the haematocrit value and the number of red cells may be obtained to give the average corpuscular volume. Instead of using two blood samples a single sample may be circulated through the vessel 20 a reagent first being added to spherize the red cells for the determination of their concentration and volume and the haematocrit value and then more of the reagent being added to haemolyze the red cells for the determination of platelet and white cell concentrations. Instead of four windows and detectors only three need be used since a single window can be selected satisfying the given formulae for the white cell concentration and for the haematocrit value. The number of windows and detectors may be reduced to two since the ratio of window positions for the platelet and white cell determinations is the same as for the red cell and haematocrit value determinations so that the desired diffraction angles can be obtained by using different distances D of the sample vessel from the mask 9 for the spherized and haemolyzed samples.