[Challenges in determining red blood cell and platelet counts in severely burned patients]

The number of burned patients requiring hospital treatment in Hungary is between 4000 and 5000 per year. Complete blood count test is substantial in their care, but caution is needed in assessing the results. Cytoskeletal proteins of red blood cells can be damaged by strong heat, resulting in reduced cellular deformability, which can lead to the formation of spherocytes, fragmentocytes and microvesicles. In such cases, the peripheral blood smear exhibits an appearance similar to hereditary pyropoikilocytosis. During blood count analysis, depending on the measurement principle, interference can occur between red blood cell fragments, microvesicles and platelets. Therefore, the results can be misleading, particularly regarding platelet counts (pseudothrombocytosis). In our retrospective study, we describe this phenomenon through the cases of three patients who suffered severe (extensive, grade II–III) burns from different types of heat exposure. In two cases, marked thermal poikilocytosis was observed in the peripheral blood smears. In addition, platelet counts measured by the impedance principle which is commonly available in analyzers were strikingly different compared with the values determined by specific fluorescence staining. Only a few microvesicles were seen in the smear of the third patient, and platelet count values did not differ substantially. Our results suggest that severe burns are not necessarily associated with the development of thermal poikilocytosis, it may depend on the type of heat source, the duration of heat exposure and heat transfer. Our study points out the advantage of complete blood count analyzers having a channel for specific, fluorescent platelet counting in the care of severely burned patients. In their absence, peripheral blood smear preparation and evaluation is recommended. Since the reliability of results depends on the methodology, we also emphasize the importance of consultation between clinicians and the laboratory. Orv Hetil. 2025; 166(34): 1340–1346.