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Evaluation of Cyto-Chex® reagent on the stability of T CD4+ and T CD8+ cell markers in whole blood samples
Abstract Content:
Background: In Brazil and other moderately resourced settings flow cytometry can be made available in central laboratories to monitor immune status in HIV-infected patients. However, specimens must typically be analyzed within 24 hours after phlebotomy, which dramatically limits availability of this testing. We evaluated the Cyto-Chex® reagent, a stabilizer that preserves the white blood cells markers.
Methods: The samples were obtained from three clinical centers located in south Brazil, during June-July/2008, with separate aliquots stored in EDTA and Cyto-Chex BCT at room temperature (12°C-27°C) until the moment of analysis. CD4+ and CD8+ T cell counts were performed on EDTA specimens within 24 hours; Cyto-Chex® BCT (CCBCT) samples were analyzed over different time periods (3 to 5, 7, 9-11 days post collection). Assays were performed using BD Facs Count equipment.
Results: Of forty-eight samples collected into CCBCT, forty-six (95.8%) gave valid CD4/CD8 results. Both CD4 and CD8 on fresh specimens were highly correlated whether in CCBCT or EDTA (CD4 r2=.965; CD8 r2=.958, p< .001); Fresh blood CD4 counts were similar but fresh blood CD8 counts were significantly lower on CCBCT specimens than on EDTA (mean difference: -34.81 CD8 cells/mm3; p< .001). We detected no change in CD4 or CD8 counts over time.
Conclusions: The Cyto-Chex® reagent appears to maintain integrity of white blood cell antigens for CD4 and CD8 enumeration for up to 11 days, providing additional time for sample shipment and processing to a flow cytometry laboratory. This could be an important tool in resource-poor settings where refrigeration and other ancillary laboratory equipment may not be available at collection sites.
Methods: The samples were obtained from three clinical centers located in south Brazil, during June-July/2008, with separate aliquots stored in EDTA and Cyto-Chex BCT at room temperature (12°C-27°C) until the moment of analysis. CD4+ and CD8+ T cell counts were performed on EDTA specimens within 24 hours; Cyto-Chex® BCT (CCBCT) samples were analyzed over different time periods (3 to 5, 7, 9-11 days post collection). Assays were performed using BD Facs Count equipment.
Results: Of forty-eight samples collected into CCBCT, forty-six (95.8%) gave valid CD4/CD8 results. Both CD4 and CD8 on fresh specimens were highly correlated whether in CCBCT or EDTA (CD4 r2=.965; CD8 r2=.958, p< .001); Fresh blood CD4 counts were similar but fresh blood CD8 counts were significantly lower on CCBCT specimens than on EDTA (mean difference: -34.81 CD8 cells/mm3; p< .001). We detected no change in CD4 or CD8 counts over time.
Conclusions: The Cyto-Chex® reagent appears to maintain integrity of white blood cell antigens for CD4 and CD8 enumeration for up to 11 days, providing additional time for sample shipment and processing to a flow cytometry laboratory. This could be an important tool in resource-poor settings where refrigeration and other ancillary laboratory equipment may not be available at collection sites.