Osmotische Resitenz der Thrombozyten

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Abstract
Introzzi and De Nicola''s procedure for determining osmotic fragility of platelets by means of the recalcification time requires a normal factor 3 level and unimpeded release. Moreover there are too great variations in the individual results by this method, so that a critical limit for osmotic changes in the platelets cannot be given. The results are somewhat better if, instead of washed thrombocytes, platelet-rich plasma with dilute saline solutions is incubated before recalcification. Feissly''s method determines the critical limit of osmotic fragility of the thrombocytes by the absence of clot retraction. This method is impracticable, however, on account of the varying plasma components (plasma cofactors). Thrombocytes from children with infectious diseases usually did not present retraction in the patient''s plasma, but only when the latter was replaced by normal plasma. Inhibition of retraction in the osmotic series in infectious diseases is due not to the thrombocytes but to the plasma, and may be mistaken for increased osmotic fragility in the thrombocytes. Results with the method of Gurevitch and Nelken, using morphological criteria (swordlike processes, platelet shadows) to determine osmotic changes in the thrombocytes, may be considerably influenced by subjective errors. With practive, however, the range of osmotic fragility of thrombocytes can be determined by this means (0.44-0.34% NaCl).