ABSTRACT
Laboratory-based CD4 monitoring of HIV patients presents challenges in resource limited settings (RLS) including frequent machine breakdown, poor engineering support and limited cold chain and specimen transport logistics. This study assessed the performance of two CD4 tests designed for use in RLS; the Dynal assay and the Alere PIMA test (PIMA). Accuracy of Dynal and PIMA using venous blood was assessed in a centralised laboratory by comparison to BD FACSCount (BD FACS). Dynal had a mean bias of -50.35 cells/µl (r(2) = 0.973, p<0.0001, n = 101) and PIMA -22.43 cells/µl (r(2)= 0.964, p<0.0001, n = 139) compared to BD FACS. Similar results were observed for PIMA operated by clinicians in one urban (n = 117) and two rural clinics (n = 98). Using internal control beads, PIMA precision was 10.34% CV (low bead mean 214.24 cells/µl) and 8.29% (high bead mean 920.73 cells/µl) and similar %CV results were observed external quality assurance (EQA) and replicate patient samples. Dynal did not perform using EQA and no internal controls are supplied by the manufacturer, however duplicate testing of samples resulted in r(2) = 0.961, p<0.0001, mean bias = â-1.44 cells/µl. Using the cut-off of 350 cells/µl compared to BD FACS, PIMA had a sensitivity of 88.85% and specificity of 98.71% and Dynal 88.61% and 100%. A total of 0.44% (2/452) of patient samples were misclassified as "no treat" and 7.30% (33/452) "treat" using PIMA whereas with Dynal 8.91% (9/101) as "treat" and 0% as "no treat". In our setting PIMA was found to be accurate, precise and user-friendly in both laboratory and clinic settings. Dynal performed well in initial centralized laboratory evaluation, however lacks requisite quality control measures, and was technically more difficult to use, making it less suitable for use at lower tiered laboratories.
Subject(s)
CD4 Lymphocyte Count/standards , CD4-Positive T-Lymphocytes/pathology , HIV Infections/diagnosis , Hematology , Laboratories , Point-of-Care Systems/standards , Adult , CD4 Lymphocyte Count/economics , CD4 Lymphocyte Count/instrumentation , CD4-Positive T-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/virology , Developing Countries , Female , HIV Infections/economics , HIV Infections/immunology , HIV Infections/virology , Humans , Male , Papua New Guinea , Point-of-Care Systems/economics , Quality Control , Sensitivity and SpecificityABSTRACT
There are few data from tuberculosis (TB) endemic settings of the performance and outcome predictors of the QuantiFERON-TB Gold in Tube assay (QFT) in children with suspected TB. A prospective cross-sectional study was conducted in Papua New Guinea children with suspected TB evaluated at Port Moresby General Hospital (Port Moresby, Papua New Guinea). Two hundred sixteen children were enrolled including 106 probable TB, 87 possible TB and 23 without TB. Concordance between QFT and tuberculin skin test results was 86% (P < 0.001, κ = 0.70). QFT was significantly more likely to be positive than tuberculin skin test, overall and within the probable or possible TB categories, with no difference in prevalence of positivity between these 2 categories. The role of QFT in supporting the clinical diagnosis of TB in endemic settings, where resources are limited, remains uncertain especially as cost and technical requirements remain considerable.
