title: Field evaluation of PIMA point-of-care CD4 testing in Rakai, Uganda.
abstract: OBJECTIVE
  To assess the accuracy of PIMA Point-of-Care (POC) CD4 testing in rural Rakai, Uganda.
  
  
  METHODS
  903 HIV positive persons attending field clinics provided a venous blood sample assessed on site using PIMA analyzers per manufacturer's specifications. The venous samples were then run on FACSCalibur flow cytometry at a central facility. The Bland-Altman method was used to estimate mean bias and 95% limits of agreement (LOA). Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated for a CD4 threshold of <350 and <500 cells/uL for antiretroviral eligibility.
  
  
  RESULTS
  There was a high correlation between PIMA and FACSCalibur CD4 counts (r = 0.943, p<0.001). Relative to FACSCalibur, the PIMA POC CD4 had negative mean bias of -34.6 cells/uL (95% LOA: -219.8 to 150.6) overall. The dispersion at CD4<350 cells/uL was 5.1 cells/uL (95% LOA: -126.6 to 136.8). For a threshold of CD4<350 cells/uL, PIMA venous blood had a sensitivity of 88.6% (95%CI 84.8-92.4%), specificity of 87.5% (95%CI 84.9-90.1%), NPV of 94.9% (95%CI 93.1-96.7%), and PPV of 74.4% (95%CI 69.6-79.2%). PIMA sensitivity and PPV significantly increased to 96.1% and 88.3% respectively with increased threshold of 500 cells/uL.
  
  
  CONCLUSIONS
  Overall, PIMA POC CD4 counts demonstrated negative bias compared to FACSCalibur. PIMA POC sensitivity improved significantly at a higher CD4 threshold of 500 than a 350 cells/uL threshold.
authors.affiliation: Rakai Health Sciences Program, Kalisizo, Uganda.
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Galiwango
authors.affiliation: Rakai Health Sciences Program, Kalisizo, Uganda.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Lubyayi
authors.affiliation: Rakai Health Sciences Program, Kalisizo, Uganda.
authors.forename: Richard
authors.initials: R
authors.lastname: Musoke
authors.affiliation: Rakai Health Sciences Program, Kalisizo, Uganda.
authors.forename: Sarah
authors.initials: S
authors.lastname: Kalibbala
authors.affiliation: Rakai Health Sciences Program, Kalisizo, Uganda.
authors.forename: Martin
authors.initials: M
authors.lastname: Buwembo
authors.affiliation: Rakai Health Sciences Program, Kalisizo, Uganda.
authors.forename: Jjingo
authors.initials: J
authors.lastname: Kasule
authors.affiliation: School of Public Health, Makerere University College of Health Sciences, Kampala, Uganda.
authors.forename: David
authors.initials: D
authors.lastname: Serwadda
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Ronald H
authors.initials: RH
authors.lastname: Gray
authors.affiliation: Laboratory of Immunoregulation, Division of Intramural Research, National Institute for Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America; Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Reynolds
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Larry W
authors.initials: LW
authors.lastname: Chang
mesh_terms: D023241:Antiretroviral Therapy, Highly Active; D018791:CD4 Lymphocyte Count / Q000295:instrumentation* / Q000379:methods*; D005434:Flow Cytometry; D006801:Humans; D019095:Point-of-Care Systems; D011237:Predictive Value of Tests; D012016:Reference Values; D012680:Sensitivity and Specificity; D014454:Uganda