48
ICCS 2011
P12
EVALUATION OF FIXATIVES COMPATIBILITY
WITH CD4 T CELL TECHNOLOGIES
Tao Ding, Peggy Seely, Christian Chabot, Alexandre
Martel, Xuefen Yang, Dragica Bogdanovic, Michele
Bergeron
National Laboratory for HIV Immunology, Public
Health Agency of Canada, Ottawa, ON, Canada
Background/Objective
CD4 T-cell enumeration
remains the best surrogate marker for staging
and monitoring the immune status of HIV patients
under treatment in resource-limited countries.
QASI, an international external Quality Assessment
Program (EQAP), evaluates the performance of
à 600 clinical laboratories and assists national
reference laboratory with implementation process
of independent national EQAP. The selection of
adequate testing material is critical to that process.
This preliminary study is evaluating the compatibility
of commercial fxatives with various CD4 counting
platforms.
Method
Compatibility was assessed on
the capacity of each platform: (1) to measure CD4 in
fxed blood; (2) to generate an accurate measurement
and; (3) the degree of similarity between fxed and
unfxed samples (cluster resolution). “Streck Cell
Preservative” and “TransFix” fxatives solution were
used as recommended. One day old fxed HIV-
specimens were prepared in triplicate according
to manufacturers’ instruction and tested on their
respective platforms: FACSCalibur, Epic-XL,
FACSCount, Guava, CyFlow Counter, PointCare
Now and PIMA. The reference method was based on
4-color reagent using FACSCalibur with Flowcount
beads.
Results
All platforms tested could measure
CD4 except PointCare. Accuracy (% difference)
was less than 15% as compared to reference
method. Fixed preparations had various degree
of similarity.
Conclusion
The results showed that
fxatives are not fully compatible across the whole
array of CD4 technologies and EQA provider must
be aware of these limitations. The next phase of
the study will involve fxed HIV+ blood preparations
and the evaluation of their stability in sub-optimal
environmental condition.
POSTER ABSTRACTS