Should absolute lymphocyte count be used as a surrogate marker for CD4+ count in patients with HIV/AIDS?

The World Health Organization (WHO) has recommended the use of absolute lymphocyte count (ALC) as a potential marker for immunosuppression where CD4+ count is unavailable. However, there are conflicting reports on the usefulness of ALC as a surrogate marker for CD4+ counts in patients with HIV/AIDS, more so, in patients with HIV-associated tuberculosis (TB). To evaluate the usefulness of ALC as an alternative to CD4+ counts and to see whether TB affects the correlation of ALC with CD4+ counts in patients with HIV-associated TB. A total of 66 consecutive patients (33 with and 33 without TB) with a diagnosis of HIV infection were recruited into the study as cases. Another group of 66 subjects (33 subjects each) age- and sex-matched HIV-negative controls were recruited as controls and stratified in to two: a) HIV-negative PTB patients. b) apparently healthy HIV and PTB negative individuals. The age range was from 15-60 years (median: 32 years). The highest percentage (39%) of subjects fell in the age range of 25-29 years. The mean ALC for HIV-associated PTB was 3906 +/- 1092 cells/microl and for patients with HIV infection only. 4755 +/- 1049 cells/microl. There was no significant difference in mean ALC between males and females in both groups (P > 0.05). Patients with dual infection by M. tuberculosis and HIV had the lowest mean ALC (3906 +/- 1092 cells/microl). Healthy controls had mean ALC (+/- SD) of 5249 +/- 101 cells/microl. There was significant difference between the healthy controls and the other three groups. The observed difference was more in patients with HIV/ TB co-infection (P < 0.005) compared with patients with HIV alone (P < 0.05). No significant correlation was observed between CD4+ cell counts and ALC in all the age groups of the study population. When the CD4+ counts were divided into < 200 and > or = 200 cells/microl and the ALC into < 2000 and > or = 2000 cells/microl, the sensitivity, specificity and positive predictive values of the diagnostic usefulness of ALC in HIV-associated PTB were 52%. 56.3% and 78.8% while for HIV only patients the same values were 56.3%. 55.9% and 54.5%, respectively. We cannot recommend the use of ALC as a surrogate for CD4+ count in our environment as this study has clearly shown that the correlation between the two is weak. Patients with dual infection by HIV and M. tuberculosis are more likely to have lower CD4+ cell and AL counts than those with HIV infection occurring alone.