Enumeration of CD4 and CD8 T-cells in HIV infection in Zimbabwe using a manual immunocytochemical method.
OBJECTIVE
To enumerate CD4 and CD8 T-cells using the simple and cheap immuno-alkaline phosphatase (IA) method and to compare it with flow cytometry (FC); and to study the effects of duration of sample storage on the IA method results.


METHODS
Method comparison study.


METHODS
Blair Research Laboratory, Harare, Zimbabwe.


METHODS
41 HIV positive and 11 HIV negative men and women from Harare participating in HIV studies at Blair Research Laboratory, Zimbabwe.


METHODS
CD4 and CD8 T-cell counts by FC and the IA method.


RESULTS
The IA method and FC were highly correlated for CD4 counts (Spearman rs = 0.91), CD4 percentage (rs = 0.84), CD8 count (rs = 0.83), CD8 percentage (rs = 0.96) and CD4/CD8 ratio (rs = 0.89). However, CD4 cell counts and percentage measured by the IA method were (mean difference +/- SE) 133 +/- 24 cells/microL [corrected] and 6.7 +/- 1.1% higher than those measured by the FC method (p < 0.0001) respectively. CD8 counts and percentages by the IA method were lower than those by the FC method (p < 0.01). Accordingly, the IA method gave a higher CD4/CD8 ratio (p < 0.01). IA method CD4 counts < 300/mL best predicted FC CD4 counts < 200/mL while IA CD4% < 25 best predicted FC CD4% < 14%. IA method CD4/CD8 ratio < 0.8 best predicted FC CD4/CD8 ratio < 0.5. Smears stored for up to 18 months gave results similar to fresh smears.


CONCLUSIONS
The IA method correlates well with but gives CD4 counts and percentages that are higher than those determined by FC. On the contrary, the IA method gives CD8 counts and percentage that are lower than FC values. The method is a cheap and reliable alternative to FC and allows storage of samples for extended periods before analysis, making it an appropriate technology for resource poor countries.
Gomo
E
E
Blair Research Laboratory, Ministry of Health, PO Box CY573, Causeway, Harare, Zimbabwe. gomo@blair.co.zw
Ndhlovu
P
P
Vennervald
B J
BJ
Nyazema
N
N
Friis
H
H
D000469:Alkaline Phosphatase / Q000276:immunology; D018791:CD4 Lymphocyte Count / Q000379:methods*; D016516:CD4-CD8 Ratio / Q000379:methods*; D018414:CD8-Positive T-Lymphocytes; D005260:Female; D005434:Flow Cytometry; D006679:HIV Seropositivity / Q000097:blood* / Q000276:immunology; D015497:HIV-1 / Q000276:immunology; D006801:Humans; D008297:Male; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D015030:Zimbabwe
D000469:Alkaline Phosphatase