title: Affordable pediatric CD4 counting by flow cytometry in Malawi.
abstract: BACKGROUND
  Rapid expansion of antiretroviral therapy in Malawi has occurred in the relative absence of suitable pediatric CD4 counting facilities. We have recently validated in adults a simplified affordable flow cytometric CD4 counting method, the Blantyre count. There is a need for this technology to transfer to government laboratories run by local staff, and to be validated in children, where %CD4/lymphocyte values are required.
  
  
  METHODS
  We assessed agreement of %CD4/lymphocyte values determined by the Blantyre count and Panleucogate methods on an EPICS XL-MCL flow cytometer on 113 venous blood samples from HIV-seropositive children in Blantyre, Malawi. All assays were performed by two Malawian laboratory technicians.
  
  
  RESULTS
  Overall bias between the two methods was -0.13% (95% CI -0.37 to 0.11) and limits of agreement were -2.69 to 2.43% (95% CI -3.11 to -2.27 and 2.01 to 2.85). Limits of agreement were within -3.00 and 3.00 for each laboratory technician. Coefficient of variation for the Blantyre count assay was 2.0% and samples showed good stability over 5 days.
  
  
  CONCLUSIONS
  The Blantyre count method can accurately determine %CD4/lymphocyte values in blood of HIV-seropositive children on an EPIC XL-MCL flow cytometer at a reagent cost of US $0.21 per test or less. The assay can be competently carried out by local laboratory technicians.
authors.affiliation: Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, University of Malawi, Blantyre, Malawi. c.maclennan@bham.ac.uk
authors.forename: Calman A
authors.initials: CA
authors.lastname: Maclennan
authors.forename: Felix
authors.initials: F
authors.lastname: Dzumani
authors.forename: Alinane
authors.initials: A
authors.lastname: Namarika
authors.forename: Peter
authors.initials: P
authors.lastname: Moons
authors.forename: Edward
authors.initials: E
authors.lastname: Senga
authors.forename: Malcolm E
authors.initials: ME
authors.lastname: Molyneux
authors.forename: Mark T
authors.initials: MT
authors.lastname: Drayson
authors.forename: James E G
authors.initials: JE
authors.lastname: Bunn
mesh_terms: D015982:Bias; D001800:Blood Specimen Collection; D018791:CD4 Lymphocyte Count / Q000191:economics* / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry / Q000191:economics* / Q000379:methods*; D006801:Humans; D007223:Infant; D008295:Malawi; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D012984:Software