Simplifying CD4 Testing
Friday, 1:30 - 3:30 pm
Background: PointCare (Beckman Coulter) is a new CD4 testing system that is compact (30 cm3) and based on side-angle light-scatter detection of immunoconjugated CD4 gold particles on CD4+ lymphocytes. This non-fluorescent system is a fully automated cap piercing volumetric flow system complete with a user-friendly touch screen. A CD4 count, CD4 percentage of lymphocytes, and a white blood count, total lymphocyte count and lymphocyte percentage are reported in 17 minutes without any sample preparation.
Methods: An evaluation of this low throughput (± 20 specimens/day including cell controls) system was performed on 105 adult specimens (< 10 hours old) compared with 4-color TetraCHROME (Beckman Coulter) dual and single platform using Flow Count (Beckman Coulter).
Results: PointCare failed to generate a white blood cells in 20% cases (67cells/µL mean difference and 4.3% similarity CV), with more inaccuracies in the higher white blood cells range > 8.0 x 109 cells/L. Many cases still reported a CD4 count except 4.76% which is < 5.7% not generated by dual platform CD4 lymphocyte gating from this study. The mean difference between dual platform CD4 and PointCare CD4 is 55 cells/µL (19.9% similarity CV) compared with 38 cells/µL (4.8% similarity CV) single platform Flow Count CD4. Two outliers (2.4% of this data set excluding flags, n = 82) in the clinically relevant range (200 to 400 cells/µL CD4 counts) reported PointCare CD4 results > 500 cells/µL indicating these patients would receive incorrect treatment.
Conclusions: This is the first system that is operator independent to provide a CD4 count and haematological parameters. PointCare is well suited to the developing world where health care personnel in direct contact with a patient can provide immediate results. This complements ART roll-out programs by increasing the accessibility to CD4 monitoring. A longitudinal study performed in a field trial is still required
Keywords: Point Care CD4 testing; Operator independent; Evaluation