Mater Pathology

Routine confirmation of platelet counts at Mater Pathology

April 3, 2017

Sysmex pathology analyser

At Mater Pathology, platelet counts less than 50x10^9/L will now routinely be confirmed by the PLT-F method as this is the preferred method to make better decisions on platelet transfusions.

Platelet counts are usually performed by an impedance (of an electrical current) and/or optical method. The latter method is more accurate for platelet counts below 100x10^9/L; however, for samples from patients undergoing chemotherapy, the impedance count will be more accurate. Deviations may be explained by the presence of white cell fragments after apoptosis.

Mater Pathology recently obtained the newly developed XN-2000 haematology analyser that employs a third method of platelet counting that is especially accurate at counts less than 50x10^9/L. The PLT-F (fluorescence) channel can be selected for testing on any sample or only used as a reflex test if red cell fragments are flagged, large platelets are present, or if the platelet count is below a preset limit (for example, the level close to which platelet transfusion may be considered). Compared with the optical method, platelets are more clearly distinguished from other blood cells using the difference in forward scattered light and fluorescence intensity.

Principle of PLT-F Channel.

(A) Platelets stained with the dedicated reagent. The staining pattern of platelets by the flourescent dye is localised, reflecting its specific binding to nucleiec acid-rich organelles.

(B) PLT-F scattergram. After platelets are stained with fluorescent dye, they are differentiated using information from the forward scattered light and side fluorescence intensity.

Correlation studies have found that, if a transfusion threshold is set at 20x10^9/L, the very reproducible PLT-F method does not result in unnecessary transfusions. However, using the impedance and optical methods may result in cases not receiving proper transfusion due to the presence of interfering entities (red cell fragments, etc.). At a transfusion threshold of 10x10^9/L, only slight differences are observed.

For further information please contact the Mater Pathology Haematology laboratory at 07 3163 8506 or 07 3163 1793.

*Sources: Am J Clin Pathol 2013; 140:495-499; J Clin Lab Anal. 28:341-348 (2014)