title: A meta-analysis of the performance of the Pima™ CD4 for point of care testing.
abstract: BACKGROUND
  The Alere point-of-care (POC) Pima™ CD4 analyzer allows for decentralized testing and expansion to testing antiretroviral therapy (ART) eligibility. A consortium conducted a pooled multi-data technical performance analysis of the Pima CD4.
  
  
  METHODS
  Primary data (11,803 paired observations) comprised 22 independent studies between 2009-2012 from the Caribbean, Asia, Sub-Saharan Africa, USA and Europe, using 6 laboratory-based reference technologies. Data were analyzed as categorical (including binary) and numerical (absolute) observations using a bivariate and/or univariate random effects model when appropriate.
  
  
  RESULTS
  At a median reference CD4 of 383 cells/μl the mean Pima CD4 bias is -23 cells/μl (average bias across all CD4 ranges is 10 % for venous and 15% for capillary testing). Sensitivity of the Pima CD4 is 93% (95% confidence interval [CI] 91.4% - 94.9%) at 350 cells/μl and 96% (CI 95.2% - 96.9%) at 500 cells/μl, with no significant difference between venous and capillary testing. Sensitivity reduced to 86% (CI 82% - 89%) at 100 cells/μl (for Cryptococcal antigen (CrAg) screening), with a significant difference between venous (88%, CI: 85% - 91%) and capillary (79%, CI: 73% - 84%) testing. Total CD4 misclassification is 2.3% cases at 100 cells/μl, 11.0% at 350 cells/μl and 9.5 % at 500 cells/μl, due to higher false positive rates which resulted in more patients identified for treatment. This increased by 1.2%, 2.8% and 1.8%, respectively, for capillary testing. There was no difference in Pima CD4 misclassification between the meta-analysis data and a population subset of HIV+ ART naïve individuals, nor in misclassification among operator cadres. The Pima CD4 was most similar to Beckman Coulter PanLeucogated CD4, Becton Dickinson FACSCalibur and FACSCount, and less similar to Partec CyFlow reference technologies.
  
  
  CONCLUSIONS
  The Pima CD4 may be recommended using venous-derived specimens for screening (100 cells/μl) for reflex CrAg screening and for HIV ART eligibility at 350 cells/μl and 500 cells/μl thresholds using both capillary and venous derived specimens. These meta-analysis findings add to the knowledge of acceptance criteria of the Pima CD4 and future POC tests, but implementation and impact will require full costing analysis.
authors.affiliation: Department of Molecular Medicine and Haematology, Faculty of Health Science, School of Pathology, University of the Witwatersrand, 7 York Road Parktown, Johannesburg, South Africa. lesley.scott@nhls.ac.za.
authors.forename: Lesley E
authors.initials: LE
authors.lastname: Scott
authors.affiliation: Clinton Health Access Initiative, Boston, MA, USA. jcampbell@clintonhealthaccess.org.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Campbell
authors.affiliation: US Centers for Disease Control, Atlanta, GA, USA. lew2@cdc.gov.
authors.forename: Larry
authors.initials: L
authors.lastname: Westerman
authors.affiliation: Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium. LKestens@itg.be.|Laboratory of Immunology, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium. LKestens@itg.be.
authors.forename: Luc
authors.initials: L
authors.lastname: Kestens
authors.affiliation: Clinton Health Access Initiative, Boston, MA, USA. lvojnov@clintonHealthAccess.org.
authors.forename: Lara
authors.initials: L
authors.lastname: Vojnov
authors.affiliation: US Centers for Disease Control, Atlanta, GA, USA. iee2@cdc.gov.
authors.forename: Luciana
authors.initials: L
authors.lastname: Kohastsu
authors.affiliation: US Centers for Disease Control, Atlanta, GA, USA. jcn5@cdc.gov.
authors.forename: John
authors.initials: J
authors.lastname: Nkengasong
authors.affiliation: Clinton Health Access Initiative, Boston, MA, USA. tpeter@clintonhealthaccess.org.
authors.forename: Trevor
authors.initials: T
authors.lastname: Peter
authors.affiliation: Department of Molecular Medicine and Haematology, Faculty of Health Science, School of Pathology, University of the Witwatersrand, 7 York Road Parktown, Johannesburg, South Africa. wendy.stevens@nhls.ac.za.|National Health Laboratory Service, Johannesburg, South Africa. wendy.stevens@nhls.ac.za.
authors.forename: Wendy
authors.initials: W
authors.lastname: Stevens
mesh_terms: D000328:Adult; D018791:CD4 Lymphocyte Count / Q000295:instrumentation*; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy; D006801:Humans; D008875:Middle Aged; D000067716:Point-of-Care Testing; D012680:Sensitivity and Specificity