[Emergency blood picture].

Assessment of peripheral blood counts and blood film analysis are frequently performed as diagnostic procedures in emergency medicine. Far fewer situations exist, however, in which these analyses are the main clue in establishing an emergency diagnosis. Artifacts can lead to wrong diagnosis, e.g. pseudo-thrombocytopenia, which is defined as a low platelet count resulting from a laboratory artifact. Severe neutropenia (agranulocytosis) and extreme hyperleukocytosis, as well as suspicion of acute leukemia, require a rapid diagnostic work-up. A newly detected anemia should not necessarily be treated by packed red cell transfusions. The decision whether an anemic patient ought to receive transfusions should be based on the speed with which the anemia has developed, as well as on clinical judgement. As a rule a chronic anemia patient with hemoglobin above 70 g/l does not need transfusions. An uncritical transfusion policy can even cause emergencies, e.g. in patients with megaloblastic anemia or in anemic multiple myeloma patients with a hyperviscosity syndrome. An elevated hematocrit requires prompt further investigations. This is of utmost importance if one considers the diagnosis of polycythemia vera rubra, a disease in which patients are particularly prone to thrombotic complications. Fragmented red cells (schistocytes) on peripheral blood smears constitute a cardinal diagnostic clue for the detection of microangiopathic hemolytic anemias (MAHA), in particular for the diagnosis of the life-threatening thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). Malaria is another example for a chief role of blood smears examination in achieving a rapid diagnosis. If one encounters an unexpected severe thrombocytopenia, a marrow examination reveals whether it is due to rapid peripheral destruction, or due to a marrow failure. Furthermore, in any patients with an unanticipated thrombocytopenia, a disseminated intravascular coagulation and a MAHA should be ruled out. Heparin-induced thrombocytopenia is a rare, but possibly fatal complication of therapy with heparins.