[Platelet volume in essential thrombopenia]. / Problèmes posés par la mesure des volumes plaquettaires dans les grandes thrombopénies.

The electronic method for measuring platelet volume using the Coulter Z BI Counter coupled with a Channelyser C 1000 has been standardized. The distribution of platelet volumes was studied in 28 cases of idiopathic thrombocytopenic purpura (ITP) and in 59 cases of thrombocytopenia attributed to a failure of platelet production. Results showed that the volumetric distribution curve of platelet rich plasma (PRP) was altered in 40 cases, by the presence of small particles interfering with platelets of small volume and/or by residual red cells modifying its terminal segment. These abnormalities seem linked to the degree of thrombopenia, but independent of its central or peripheral origin. A method of isolation and concentration of platelets in an albumin gradient allowed the restoration of the classical volume distribution in 24 cases out of 40. Simulated thrombopenias obtained by dilution of platelets in their own platelet poor plasma (PPP) showed that the abnormalities in the small volume range could be reproduced in vitro by modifying the proportion of platelets and of small residual elements in the PRP. When the albumin gradient method was used, the classical distribution of platelet volumes was found. Preliminary electron-microscopy studies show that the small elements in the PRP of thrombopenic subjects could be formed by red cell fragments. Cytoenzymologic studies should be able to confirm this. Volumetric parameters were determined from the asymmetric and unimodual distribution of platelets, either directly on PRP or after concentration and separation of platelets in an albumin gradient. They showed that platelet volumes were very often increased in ITP but also occasionnally in thrombopenia of attributed to a failure of production.

[Volume distribution studies on the platelet populations (author's transl)]. / Etude sur la distribution des volumes des populations plaquettaires.

The volume distribution into human platelet populations was investigated in order to determine if thereis a relationship between the cell density and the cell size and if the isolated platelets are homogeneous populations of cells. The platelet populations were isolated from platelet rich plasma or from washed platelets by isopycnic centrifugation on sucrose density gradients. Platelet volume was measured electronically with Coulter F or Coulter Z Bic coupled with Channelyser C 1000. The results show that there exists a direct relationship between platelet density and size, since the volumetric parameters gradually increase from the small platelets of lower density to the larger ones isolated at higher density. Evidence was also obtained that the isolated populations of platelets were heterogeneous and their volume distribution was log-normal. Both the heavy and the light platelet populations were found as a mixture of mainly large or mainly small platelets respectively.