title: Using BD Vacutainer CD4 Stabilization Tubes for Absolute Cluster of Differentiation Type 4 Cell Count Measurement on BD FacsCount and Partec Cyflow Cytometers: A Method Comparison Study from Zimbabwe.
abstract: BACKGROUND
  Blood collected in conventional EDTA tubes requires laboratory analysis within 48 hours to provide valid CD4 cell count results. This restricts access to HIV care for patients from rural areas in resource-constraint settings due to sample transportation problems. Stabilization Tubes with extended storage duration have been developed but not yet evaluated comprehensively.
  
  
  OBJECTIVE
  To investigate stability of absolute CD4 cell count measurement of samples in BD Vacutainer CD4 Stabilization Tubes over the course of 30 days.
  
  
  METHODS
  This was a laboratory-based method comparison study conducted at a rural district hospital in Beitbridge, Zimbabwe. Whole peripheral blood from 88 HIV positive adults was drawn into BD Vacutainer CD4 Stabilization Tubes and re-tested 1, 2, 3, 5, 7, 14 and 30 days after collection on BD FacsCount and Partec Cyflow cytometers in parallel. Absolute CD4 cell levels were compared to results from paired samples in EDTA tubes analysed on BD FacsCount at the day of sample collection (references methodology). Bland-Altman analysis based on ratios of the median CD4 counts was used, with acceptable variation ranges for Limits of Agreements of +/-20%.
  
  
  RESULTS
  Differences in ratios of the medians remained below 10% until day 21 on BD FacsCount and until day 5 on Partec Cyflow. Variations of Limits of Agreement were beyond 20% after day 1 on both cytometers. Specimen quality decreased steadily after day 5, with only 68% and 40% of samples yielding results on BD FacsCount and Partec Cyflow at day 21, respectively.
  
  
  CONCLUSIONS
  We do not recommend the use of BD Vacutainer CD4 Stabilization Tubes for absolute CD4 cell count measurement on BD FacsCount or Partec Cyflow due to large variation of results and decay of specimen quality. Alternative technologies for enhanced CD4 testing in settings with limited laboratory and sample transportation capacity still need to be developed.
authors: Operational Centre Barcelona, Médecins Sans Frontières / Doctors Without Borders, Barcelona, Spain.
authors: Florian
authors: F
authors: Vogt
authors: Operational Research Unit Luxembourg, Médecins Sans Frontières / Doctors Without Borders, Luxembourg, Luxembourg.
authors: Rafael
authors: R
authors: Van den Bergh
authors: Operational Centre Barcelona, Médecins Sans Frontières / Doctors Without Borders, Barcelona, Spain; Department of Field Epidemiology and Training, Epicentre, Paris, France.
authors: Andrea
authors: A
authors: Bernasconi
authors: Beitbridge Project, Médecins Sans Frontières / Doctors Without Borders, Beitbridge, Zimbabwe.
authors: Buhlebenkosi
authors: B
authors: Moyo
authors: Zimbabwe Mission, Médecins Sans Frontières / Doctors Without Borders, Harare, Zimbabwe.
authors: Liberty
authors: L
authors: Havazvidi
authors: Department of Clinical Research, Epicentre, Paris, France.
authors: Mathieu
authors: M
authors: Bastard
authors: Operational Centre Barcelona, Médecins Sans Frontières / Doctors Without Borders, Barcelona, Spain.
authors: Laurence
authors: L
authors: Flevaud
authors: Zimbabwe Mission, Médecins Sans Frontières / Doctors Without Borders, Harare, Zimbabwe.
authors: Fabian
authors: F
authors: Taziwa
authors: Laboratory Department, Beitbridge District Hospital, Ministry of Health and Child Welfare, Beitbridge, Zimbabwe.
authors: Eliphas
authors: E
authors: Makondo
authors: National Microbiology Reference Laboratory, Ministry of Health and Child Welfare, Harare, Zimbabwe.
authors: Sekesai
authors: S
authors: Mtapuri-Zinyowera
mesh_terms: D000328:Adult; D001800:Blood Specimen Collection / Q000295:instrumentation* / Q000592:standards; D018791:CD4 Lymphocyte Count / Q000295:instrumentation* / Q000592:standards; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000473:pathology* / Q000821:virology; D005260:Female; D005434:Flow Cytometry / Q000592:standards*; D015658:HIV Infections / Q000175:diagnosis / Q000276:immunology / Q000473:pathology* / Q000821:virology; D006767:Hospitals, District; D006801:Humans; D008297:Male; D008875:Middle Aged; D012424:Rural Population; D014186:Transportation; D015030:Zimbabwe