Applications of clinical pathology: from the practice lab to the research bench

Abstract

Applications of clinical pathology: from the practice lab to the research bench IN-HOUSE clinical pathology in now common-place, with many practices using bench top haematology and biochemistry analysers. This does not appear to be at the expense of the commercial laboratories, which continue to be busy with haematological and biochemical samples as well as in areas that cannot be served by the practice laboratory such as microbiology, cytology and histopathology. Thus the use of laboratory testing, whether in house or in a commercial laboratory, increases to be a key part of clinical investigation of our patients. It is important for practitioners to have an understanding of the methodology and limitations of their practice analysers, so that further testing (e.g. blood film examination or mailing to a commercial laboratory) is performed when required. Bertazzolo and others (2007) compare methods for determining platelet counts and platelet volume in cavalier King Charles Spaniels (CKCSs) and provide a helpful review of the methodology used by various analysers to count platelets and distinguish them from red cells. Their study clearly illustrates the problems encountered in obtaining platelet counts in this breed. They describe how impedance counters distinguish these cells based on their cell size, with the result that laboratory error can be expected when red cells are small or platelets are large. The latter is often the case with feline platelets and in this species evaluation of a blood film is crucial in validating the analyser count. Likewise in CKCSs large platelets may be misclassified as red cells, giving rise to a spuriously low platelet count. Laser cell counters (flow cytometers) distinguish cells based on differences in the amount of forward and side scatter generated when the laser light encounters a cell. Side scatter depends on cell granularity or complexity whilst forward scatter depends on cell size. Thus two parameters are used to distinguish red cells and platelets. However Bertazzolo and others (2007) show that large platelets may also be misclassified using this methodology. Quantitative buffy coat analysis (QBC) measures the width of different cell layers after centrifugation with a cylinidrical float which lengthens cell layers, and staining with a fluorescent dye. Thus the QBC produces a haematoctrit, a leucocrit and a platelet crit and then calculates the cell number by dividing by a standard mean volume for each cell type. The study illustrates how the platelet crit may be a better indicator of platelet mass/function than the platelet counts determined by other methods. Platelet clumping also leads to errors in platelet counts, and again the platelet crit may be less influenced by this.Accompanying an increase in investigation of haematological diseases in practice is an increase in the use of blood transfusions for treating anaemia and coagulation disorders. The importance of blood typing of cats prior to transfusion is well established and studies have shown important geographi...

Petechien, Hämatome, Epistaxis – Was nun? Ein diagnostischer Leitfaden

“…Die vollständige diagnostische Aufarbeitung von Thrombozytopenien würde den Rahmen dieses Artikels übersteigen. Es ist jedoch zu bedenken, dass hochgradige Thrombozytopenien (< 25 000/µl) v. a. bei immunmediierten Geschehen beobachtet werden, während erhöhter Verbrauch oder Sequestration i. d. R. zu einer milden oder moderaten Reduktion der Thrombozytenzahl führt 3 , 8 .…”

“…Diese sollte im Normalfall über 70% liegen. Von deutlichen Abweichungen spricht man ab einer Aktivität von unter 50%, wobei wiederum bei einer Aktivität unter 25 – 35% (je nach Quelle unterschiedliche Angaben) das Auftreten von Blutungen wahrscheinlich ist 8 . Dieser Test kann nur Typ I und III des vWS diagnostizieren, weil beim Typ II ein qualitativer und (nicht zwingend auch) ein quantitativer Mangel vorliegt 4 .…”

“…Ein angeborener Mangel von Faktor VII ist für den Beagle und Alaskan Klee Kai beschrieben 8 , 30 , 31 .…”

“…Deutlich seltener tritt diese Veränderung auch unter Heparintherapie oder bei Vorliegen einer Hypofibrinogenämie (Mangel an Fibrinogen) auf 1 , 3 , 4 , 8 . Diese kann primär (kongenital) oder sekundär, beispielsweise im Rahmen einer Infektion mit Angiostrongylus vasorum oder nach einem Schlangenbiss, sein.…”