Revision to PNH screen by flow cytometry
From the 26th February the current PNH screen will be updated.
The revised protocol will include analysis of monocytes in addition to neutrophils and red cells. Monocyte analysis provides additional evidence for PNH, and in some cases gives a truer reflection of PNH clone size.
The sensitivity of the assay has been determined and the lower limit of quantitation is 0.01% for both red cell and neutrophil analysis. To achieve this level of sensitivity we need to count a large number of cells.
In cases of neutropenia it can be difficult to acquire sufficient cells for the desired sensitivity. We therefore recommend that freshly taken, full EDTA tubes are sent. It may still not be possible to provide a result in severely neutropenic cases.
Monocyte analysis is less sensitive to small populations due to the lower number of monocytes available in samples.
Red cell analysis is performed to allow recognition of PNH type II and PNH type III clones and should not be used as a definitive measure of clone size. Please supply details of transfusion history.
It is possible to recognise tiny rbc and neutrophil clones at <0.01%, but these are not quantifiable.
The format of reports will be updated to reflect the changes and provide greater clarity of the results.
This will be reviewed during our October UKAS inspection.
Please contact the Haematology Cell Markers laboratory on 0121 424 0704 if you require further information.