title: Discrepant test findings in early infant diagnosis of HIV in a national reference laboratory in Kenya: challenges and opportunities for programs.
abstract: BACKGROUND
  In Kenya, the availability of a cheap diagnostic service for HIV-exposed infants has helped scale-up access to treatment, and provided a means by which programs that support Prevention of Mother to Child Transmission of HIV can be evaluated. As expected for any large testing program, discrepant and indeterminate results present a significant challenge.
  
  
  METHODS
  Dried Blood Spots were collected from health centers countrywide and couriered to four laboratories for tests. Results were dispatched either by email, telephone, GSM SMS printer or courier. Between 2006 and 2009, tests were conducted with the Manual Roche v. 1.5 Assay. In 2010 the labs switched fully to the Cobas® AmpliPrep/ Cobas® TaqMan® HIV-1 Qual automated Roche Test.
  
  
  RESULTS
  Between 2006 and 2010, the KEMRI CVR EID Lab conducted 64 591 HIV tests in on children <18 months of age. HIV tests (38 834) used the manual assay, while 17 133 tests used the automated assay. Overall, 10.7% (6915) of the samples tested positive, while 86.6% (55 967) tested negative. A total of 1.6% (1041) tested indeterminate and required a re-bleed of the infant. Two hundred positive tests by the manual assay were retrieved randomly and retested using the automated assay. Among them, 192 (96%) remained positive, 5 (2.5%) were negative while 3 (1.5%) failed. A total of 160 negative samples by the manual assay were retrieved and retested with the automated assay. Among them, 154 (96.24%) remained negative, 3 (1.88%) tested positive while 3 (1.88%) failed. A total of 215 samples that gave indeterminate results by the manual assay were retested using the automated system. Among them, 62 (28.8%) gave positive results, 144 (66.97%) negative and 6 (2.8%) samples still gave discrepant results. Three (1.4%) did not amplify successfully. A few infants who were apparently positive appeared to test HIV negative with age.
  
  
  CONCLUSIONS
  Indeterminate results are a significant challenge for HIV diagnostic services, as seen in the Kenyan EID Program. In our experience, they are more often negative than they are positive. False positive and false negative results can arise from clerical error, contamination and limitations of the technologies available. To forestall the consequences of such outcomes, the sensitivity and specificity of available assays must be further improved. All HIV positive samples should be retested for confirmation, and if confirmed, a new sample must be drawn and tested for DNA at the time the infant receives their initial results or starts antiretroviral therapy. Viral clearance is a phenomenon that requires further studies.
authors: Centre for Virus Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya.
authors: Sheila
authors: S
authors: Kageha
authors: Vincent
authors: V
authors: Okoth
authors: Silvia
authors: S
authors: Kadima
authors: Stella
authors: S
authors: Vihenda
authors: Elphas
authors: E
authors: Okapesi
authors: Elizabeth
authors: E
authors: Nyambura
authors: Alex
authors: A
authors: Maiyo
authors: Nancy
authors: N
authors: Ndung'u
authors: Samoel
authors: S
authors: Khamadi
authors: Matilu
authors: M
authors: Mwau
mesh_terms: D001800:Blood Specimen Collection / Q000379:methods; D002648:Child; D002675:Child, Preschool; D004279:DNA, Viral / Q000235:genetics; D042241:Early Diagnosis; D005189:False Positive Reactions; D005260:Female; D006678:HIV / Q000235:genetics; D015658:HIV Infections / Q000097:blood / Q000175:diagnosis* / Q000821:virology; D015497:HIV-1 / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D007223:Infant; D007630:Kenya; D016133:Polymerase Chain Reaction / Q000379:methods; D015397:Program Evaluation; D012367:RNA, Viral / Q000097:blood*; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling; D019562:Viral Load
chemical_list: D004279:DNA, Viral; D012367:RNA, Viral; D011933:Reagent Kits, Diagnostic