Abstract:
The Human Immunodeficiency Virus infections have grown to pandemic
proportions with morbidity of more than 65 million people and mortality of over
25 million people. The health of infected individuals deteriorates rapidly to the
AIDS stage and consequent fast death when not treated. The advent of anti
retroviral treatment has brought hope for living longer lives for those who are
infected and living with the virus. In Kenya, the decision on when to start therapy
is largely based on the baseline CD4+ and CD8+ T-cell count whose reference
intervals are of a Caucasian population. Information on CD4+ and CD8+ T-cell
count reference values for the Kenyan population is seldom available.
A cross-sectional study was carried out to establish reference intervals for CD4+
and CD8+ T -cell subsets for select reference blood donors as a local guideline to
reference intervals. The study assumed there was no significant difference
between the Kenyan population living in Nairobi and Western countries
Caucasian CD4+ and CD8+ T-cell counts. These reference intervals could be used
to influence change in policy on when and how to treat people infected with HIV
among Nairobi residents. This can possibly be replicated to the whole country
after further studies for different regions in order to have a nationwide reference
interval guideline.
A total of 424 reference blood donors were recruited as study subjects after
passing a donor recruiting interview. After preliminary testing 17 (4.5%) blood
donor samples were excluded due to positive serological tests and a further
7(1.7%) were eliminated due to extreme values. Thus a total of 400 (215 (54%)
XIII
males, 185 (46%) females) were considered. The CD4+ and CD8+ T-cell count
values obtained from the study were subjected to statistical treatment and
reference intervals were determined using the mean±2SD based on a normal
distribution. Reference intervals obtained included CD4+:CD8+ 1.8 (0.7-4),
CD4+ % 40 (27 – 53), CD4+ absolute count 790 (392 – 1,405) cells/μL, and CD8+
absolute count 500 (202 – 1,131) cells/μL. The CD8+ % data did not attain a
Gaussian distribution and the reference interval was determined as the median
and the 2.5th and 97.5th interval at 95% CI i.e. 26% (15 – 50). Overall, Females
had a higher mean ratio, CD4+ % and absolute count than males and was
statistically significant (P<0.0001) whereas males had a higher CD8+ % than
females that was statistically significant (P<0.001). In both sexes, the CD4+
absolute mean counts were always higher than the CD8+ absolute mean counts
irrespective of age. There was no significant difference between the age groups
for all the T-cell subsets. Reference mean CD4+ values obtained in this study
were much lower than those of Burkina Faso but compared well with intervals
from Tanzania and current BD multiSET values from a Caucasian population
used in the FACsCalibur machine in Kenya. The reference intervals obtained in
this study though different, they are relatively comparable to the USA based
reference intervals and can be used to compliment these values. Country wide
reference intervals would add value to decision making about HIV/AIDS therapy