Issn Print: 1077-9450

Publication Date: 1996/04/01


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Authors' Reply: Total Lymphocyte Count as a Surrogate for CD4+ Lymphocyte Count in African Patients Coinfected With HIV and Tuberculosis

D. J. Martin; J. G. M. Sim

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To the Editor: We thank Drs. Wood and Post for their response to our article. Further data in this area can only help establish the value of total lymphocyte count (TLC) as a useful clinical tool in developing countries. The data presented by Wood and Post-show that, in patients with tuberculosis (TB) and HIV infection, a TLC of <1,250 cells/mm3 is predictive of a CD4+ lymphocyte count of <200/mm3. This finding is not at variance with our own results, which predict that a TLC of 1,300-1,500 cells/mm3 is a surrogate for a CD4 count of <200 cells/mm3.
It is difficult to comment on Wood and Post's findings regarding the predictive value of a TLC of 1,250-1,500 cells/mm3 for a CD4+ count of <200 cells/mm3, as their sample size (n = 15) was small (see their Table 2).
Wood and Post also presented data on 831 HIV-positive patients, 128 of whom had pulmonary TB (see their Fig. 1). These data showed that, in the absence of TB, positive predictive values decline rapidly at TLCs >1,000 cells/mm3. It should be stressed that the data we presented were derived from patients coninfected with HIV and TB, as was clearly stated. However, we also demonstrated a fall-off in the positive predictive values at the higher TLC range.
The aim of our study was to define a surrogate cutoff for a CD4+ count in the lower range of 200-500 cells/mm3—a range we consider to be of greater clinical significance in patient management. We thoroughly endorse the sentiments of Wood and Post that the TLC as a surrogate for the CD4+ lymphocyte count is particularly relevant in developing countries where access to flow cytometry is limited and TB is the most common opportunistic infection in HIV disease.

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