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Title: Derivation and validation of an accurate estimation of CD4 counts from the absolute lymphocyte count in virologically suppressed and immunologically reconstituted HIV infected adults
Authors: Young, B
Ng, O.T 
Lye, D.C 
Leo, Y.S 
Keywords: stavudine
blood examination
CD4 CD8 ratio
CD4 lymphocyte count
CD8+ T lymphocyte
cohort analysis
controlled study
flow cytometry
full blood count
hospital admission
Human immunodeficiency virus infection
major clinical study
measurement accuracy
middle aged
predictor variable
retrospective study
validation study
virus load
case control study
highly active antiretroviral therapy
HIV Infections
lymphocyte count
regression analysis
Antiretroviral Therapy, Highly Active
Case-Control Studies
CD4 Lymphocyte Count
HIV Infections
Lymphocyte Count
Middle Aged
Regression Analysis
Reproducibility of Results
Retrospective Studies
Viral Load
Issue Date: 2015
Citation: Young, B, Ng, O.T, Lye, D.C, Leo, Y.S (2015). Derivation and validation of an accurate estimation of CD4 counts from the absolute lymphocyte count in virologically suppressed and immunologically reconstituted HIV infected adults. BMC Infectious Diseases 15 (1) : 330. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: Background: A simple method to estimate CD4 counts in stable, HIV infected virologically-suppressed and immune-reconstituted adults could save the expense of unnecessary formal testing. Methods: Using a baseline CD4 percent, CD4 counts were estimated from subsequent absolute lymphocyte counts (ALC) measured by an automated FBC machine (CD4 estimate calculated by the ALC multiplied by the baseline CD4 percent). The accuracy of this approach was established in a large, retrospective clinical laboratory dataset of virologically-suppressed HIV infected subjects. A case-control study explored important clinical factors for accurate estimates, and a heuristic algorithm was derived and validated in a random sample. Results: Data from 3,630 subjects were available. CD4 counts were generally accurately estimated, with a mean 6.1 % underestimation. Overall 83.3 % of CD4 estimates were within 25 % of the actual values, with 12.1 % CD4 counts underestimated by more than 25 %, and 4.5 % overestimated. The CD4 count was increasingly underestimated with time from baseline, and the degree of underestimation correlated with baseline CD4 percent (p < 0.0001). From the case-control study, baseline CD4 percent of ?20, no illness requiring hospitalization and more than a year since starting or switch of anti-retroviral therapy were identified as significant predictors of inaccurate estimates. Employing this simple algorithm, CD4 estimate accuracy improved to a mean 1.3 % underestimation, and the proportion of estimates within 25 % of the actual value increased to 93.4 %. Conclusions: In virologically-suppressed and immune-reconstituted HIV-infected adults, the CD4 count can be accurately estimated from the ALC using a baseline CD4 percent for at least 2 years after measurement. © 2015 Young et al.
Source Title: BMC Infectious Diseases
ISSN: 14712334
DOI: 10.1186/s12879-015-1079-5
Rights: Attribution 4.0 International
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