Affordable pediatric CD4 counting by flow cytometry in Malawi.

Area of Science:

• Clinical Immunology
• Flow Cytometry
• Pediatric Infectious Diseases

Background:

• Antiretroviral therapy expansion in Malawi lacks adequate pediatric CD4 counting facilities.
• A simplified, affordable Blantyre count flow cytometry method was validated in adults.
• Need to validate the Blantyre count method for pediatric use in government labs.

Purpose of the Study:

• To assess the agreement of the Blantyre count method with the Panleucogate method for pediatric CD4+ T-lymphocyte percentage (%CD4) determination.
• To validate the Blantyre count method for use by local laboratory technicians in Malawi.

Main Methods:

• 113 blood samples from HIV-seropositive children in Malawi were analyzed.
• Comparison of %CD4 values using the Blantyre count and Panleucogate methods on an EPICS XL-MCL flow cytometer.
• Assays were performed by two Malawian laboratory technicians.

Main Results:

• The Blantyre count showed minimal bias (-0.13%) and acceptable limits of agreement (-2.69% to 2.43%) compared to Panleucogate.
• Results were consistent across laboratory technicians, with limits of agreement within -3.00% and 3.00%.
• The Blantyre count assay demonstrated good sample stability over 5 days with a 2.0% coefficient of variation.

Conclusions:

• The Blantyre count method accurately determines pediatric %CD4/lymphocyte values using an EPICS XL-MCL flow cytometer.
• The assay is cost-effective at $0.21 per test and can be competently performed by local laboratory technicians.
• This validated method supports improved pediatric HIV care in resource-limited settings.