Venous blood, taken with EDTA-NaCl solution according to Schulz et al (1971, Z. Klin. Chem. Klin. Biochem. 9, 329-333) is used. The blood is centrifuged at IQOg for 10 min and 10 μΐ of the supernatant is added to 3000 μΐ of a suspending medium (dilution 1:80); 300 μΐ platelet suspension are read in a nephelometer cuvet or tube against blank. The number of platelets per liter blood are determine...