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(6) QC and blood stabilizers. |
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The practical usefulness of blood stabilizers (fixatives) is astonishing [16] in two areas: |
|
1. to
provide stabilized cells to evaluate methods (a, below) and to
'quality-control' laboratories: these are the aims of the UK NEQAS [16]
and QASI [17] Quality
Control schemes operate in coordination with accreditation services. For
UK NEQAS these are the Royal College of Pathologists in the U.K., and
for QASI there is coordination with CDC in the USA and Canada. The
long-term stabilized cells last for months.
2. to provide fixatives for sample transport, e.g. when samples are sent through long routes and travel by slow postal services. For cellular analysis sample deterioration must be prevented for at least 7-14 days (b and c, below). |
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Can stabilized cells be used to standardize methods? |
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| Legend to above: The same batches of '98', '100' and '101' were also run on a volumetric flow cytometer (Cytoron-absolute) to check CD3, CD4 and CD8 counts with this particular FCM system. The correlation between the results of the volumetric Cytoron and the Mean absolute counts was proven to be >95%. |
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These batches were also run on a volumetric flow cytometer (Cytoron-absolute) to establish the CD3, CD4 and CD8 counts with this particular FCM system. |
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The good correlations
between the mean results of 200 samples and the Cytoron values lead to 3
conclusions: 1. The stabilized cells are useful for comparing the performance of methods / laboratories. 2. The methods used for clinical flow cytometry, in general, work reassuringly well. 3. The volumetric Cytoron-absolute provides precise absolute counts and can serve as a tool to check the precision of other, newly created volumetric flow cytometers. |
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Can the deterioration of whole blood be prevented by adding TransFix to the sample? |
| In rich countries, samples reach their destination relatively quickly, as they must be processed for flow cytometry within 6-12 hours in order to obtain optimal results. Such time limits are too short to operate in developing countries, where samples need to travel longer intervals and often in hot climates, to reach laboratories that are a distance away. |
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|
| Legend
to above: With TransFix both the immunological staining of lymphocyte subsets (b) and the haematological parameters (c) remain stable. In a number of collaborations between laboratories in the U.K. and on the African continent we have confirmed the reliability of CD4 absolute counting in samples transferred as whole blood fixed with TransFix ( [1], [12] and [15]). |
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Sending samples in a fixed condition in resource-poor countries is essential for effective operation for a number of reasons. |
| 1.
the establishment of large 'catchment-areas', 2. easier sample handling and evaluation in the laboratory, 3. possibility of good quality control (QC) on reliable samples that do not deteriorate within the time span of the study, 4. effective training. |
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2002.