A new algorithm based on
components of a complete blood cell count (CBC) gives a better estimate
of CD4 cell count in HIV patients than estimates using the total
lymphocyte count (TLC), recommended by the World Health Organization,
according to a report in the April 15th issue of the Journal of
Acquired Immune Deficiency Syndromes.A TLC of 1,200 cells/mL or less has been used as a surrogate for a
CD4 cell count of 200 cells/microliters or less in settings where
resources are limited and there is no ability to measure CD4 cell
count. However, some studies have shown that TLC-based estimates can
have a poor correlation with actual CD4 cell count.
Dr. Ray Y. Chen and colleagues at the University of Alabama at
Birmingham (UAB) and elsewhere developed a decision tree based on
multiple components of the CBC -- including TLC, hemoglobin and
platelet count -- and adjusted for gender, body mass index (BMI) and
antiretroviral therapy status.
The algorithm was developed from complete blood counts obtained from
1,189 patients attending the UAB Outpatient HIV Clinic since 1994.
Results were compared with blood samples from Zambia and the Birmingham
Veterans Affairs Medical Center.
Dr. Chen and colleagues report that the "UAB-based decision tree
performed better than the TLC cutpoint of 1,200 cells/mL" in the BVAMC
and Zambian samples.
The investigators caution that "a given model is not always
applicable in another population." They say additional studies may show
that "the best model to identify a low CD4 cell count may be one based
on local data."
This or a similar model provides a reliable, affordable method of
estimating CD4 cell counts in HIV-infected patients in resource-limited
areas, the team concludes.
J Acquir Immune Defic Syndr 2007;44:525-530.
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