title: Evaluation of a low-cost method, the Guava EasyCD4 assay, to enumerate CD4-positive lymphocyte counts in HIV-infected patients in the United States and Uganda.
abstract: OBJECTIVE
  To evaluate the EasyCD4 assay, a less expensive method to enumerate CD4+ lymphocytes, in resource-limited settings.
  
  
  METHODS
  Cross-sectional study conducted in the United States and Uganda.
  
  
  METHODS
  We compared CD4+ cell counts obtained on replicate samples from HIV-infected patients by the EasyCD4 assay, a microcapillary flow-based system, and by standard flow cytometry or FACSCount with linear regression and the Bland-Altman method.
  
  
  RESULTS
  Two hundred eighteen samples were analyzed (77 in the United States and 141 in Uganda). In the United States, mean +/- SD CD4 was 697 +/- 438 cells/microL by standard flow cytometry and 688 +/- 451 cells/microL by EasyCD4. In Uganda, the mean +/- SD CD4 was 335 +/- 331 cells/microL by FACSCount and 340 +/- 327 cells/microL by EasyCD4. The 2 methods were highly correlated (US cohort, r2 = 0.97, slope = 1.0, intercept = -18; Ugandan cohort, r2 = 0.92; slope = 0.95; intercept = 23). The mean differences in CD4 cell counts were 9.0 and -4.6 cells/microL for the US and Ugandan cohorts, respectively, and they were not significant in either cohort. In the Ugandan cohort, sensitivity and specificity of the EasyCD4 for CD4 below 200 cells/microL were 90% and 98%, respectively. Positive predictive value was 96%; negative predictive value was 93%.
  
  
  CONCLUSIONS
  Our results suggest that EasyCD4 may be used with high positive and negative predictive value in resource-limited settings.
authors.affiliation: School of Medicine, Johns Hopkins Medical Institutions, Rm. 456, 1830 East Monument Street, Baltimore, MD 21287, USA. l.spacek@jhmi.edu
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Spacek
authors.forename: Hasan M
authors.initials: HM
authors.lastname: Shihab
authors.forename: Fred
authors.initials: F
authors.lastname: Lutwama
authors.forename: Jean
authors.initials: J
authors.lastname: Summerton
authors.forename: Harriet
authors.initials: H
authors.lastname: Mayanja
authors.forename: Moses
authors.initials: M
authors.lastname: Kamya
authors.forename: Allan
authors.initials: A
authors.lastname: Ronald
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Margolick
authors.forename: Tricia L
authors.initials: TL
authors.lastname: Nilles
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Quinn
mesh_terms: D018791:CD4 Lymphocyte Count; D005434:Flow Cytometry; D015658:HIV Infections / Q000276:immunology*; D006801:Humans; D015166:Monitoring, Immunologic; D014454:Uganda; D014481:United States