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TOTAL LYMPHOCYTE COUNT AS A SURROGATE MARKER FOR CD4+ T CELL COUNT IN INITIATING ANTIRETROVIRAL THERAPY AT KENYATTA NATIONAL HOSPITAL, NAIROBI
Abstract
ABSTRACT
Objective: To evaluate the utility of Total Lymphocyte Count (TLC) as a surrogate marker for CD4
+ T cell count in antiretroviral (ARV) treatment initiation in a Kenyan population of HIV seropositive
patients at Kenyatta National Hospital.
Design: Cross-sectional descriptive study.
Setting: Kenyatta National Hospital, HIV treatment and follow-up outpatient facility; Comprehensive
Care Centre, Nairobi, Kenya.
Subjects: Two hundred and twenty fi ve HIV Elisa positive, ARV naive patients visiting the
Comprehensive Care Centre between january 2006 to March 2006.
Results: A signifi cant linear correlation was found between TLC and CD4 cell count for the whole
group with a Spearman rank correlation of 0.761 ( p < 0.01); and was also independently observed
in the four WHO clinical stages. The classifi cation utility of TLC 1200 cells/mm3 cut-off was suboptimal;
sensitivity 37% specifi city of 99% and the NPV of 56%. The receiver operator characteristics
(ROC) curve generated an optimal TLC cut-off of 1900cells/mm3 cut-off to be of greatest utility
with a sensitivity of 81.1%, specifi city of 90.3%, PPV of 90.8% and NPV of 80.2%. This implies that
a TLC cut-off of 1900cells/mm3 correctly classify eight out of ten HIV positive patients as having
a CD4 < 200 cells/mm3 and only misclassify two such patients. Serial CD4 testing can then be
performed on the minority of patients who despite a TLC≥1900 cells/mm3 are, on basis of clinical
data, suspect of more advanced disease warranting ARV therapy. This would reduce the number
of patients tested for and focus the application of CD4 testing and thus reduce attendant cost in
care provision in CD4 resource poor settings.
Conclusion: Our data showed a good positive correlation between TLC and CD4 cell count, however
the WHO recommended TLC cuto-ff of 1200/mm3 was found to be of low sensitivity in classifying
patients as having a CD4 counts < 200 cells/mm3. This would result in underestimation of advanced
stage of disease and to withholding ARVs treatment to persons who need treatment. We recommend
a TLC cut-off of 1900 cells/mm3 for our population to classify patients as either above or below the
CD4 count cut-off of 200 cells/mm3 as an indicator of when to start antiretroviral therapy.
Objective: To evaluate the utility of Total Lymphocyte Count (TLC) as a surrogate marker for CD4
+ T cell count in antiretroviral (ARV) treatment initiation in a Kenyan population of HIV seropositive
patients at Kenyatta National Hospital.
Design: Cross-sectional descriptive study.
Setting: Kenyatta National Hospital, HIV treatment and follow-up outpatient facility; Comprehensive
Care Centre, Nairobi, Kenya.
Subjects: Two hundred and twenty fi ve HIV Elisa positive, ARV naive patients visiting the
Comprehensive Care Centre between january 2006 to March 2006.
Results: A signifi cant linear correlation was found between TLC and CD4 cell count for the whole
group with a Spearman rank correlation of 0.761 ( p < 0.01); and was also independently observed
in the four WHO clinical stages. The classifi cation utility of TLC 1200 cells/mm3 cut-off was suboptimal;
sensitivity 37% specifi city of 99% and the NPV of 56%. The receiver operator characteristics
(ROC) curve generated an optimal TLC cut-off of 1900cells/mm3 cut-off to be of greatest utility
with a sensitivity of 81.1%, specifi city of 90.3%, PPV of 90.8% and NPV of 80.2%. This implies that
a TLC cut-off of 1900cells/mm3 correctly classify eight out of ten HIV positive patients as having
a CD4 < 200 cells/mm3 and only misclassify two such patients. Serial CD4 testing can then be
performed on the minority of patients who despite a TLC≥1900 cells/mm3 are, on basis of clinical
data, suspect of more advanced disease warranting ARV therapy. This would reduce the number
of patients tested for and focus the application of CD4 testing and thus reduce attendant cost in
care provision in CD4 resource poor settings.
Conclusion: Our data showed a good positive correlation between TLC and CD4 cell count, however
the WHO recommended TLC cuto-ff of 1200/mm3 was found to be of low sensitivity in classifying
patients as having a CD4 counts < 200 cells/mm3. This would result in underestimation of advanced
stage of disease and to withholding ARVs treatment to persons who need treatment. We recommend
a TLC cut-off of 1900 cells/mm3 for our population to classify patients as either above or below the
CD4 count cut-off of 200 cells/mm3 as an indicator of when to start antiretroviral therapy.
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