The NRL conducts quality control (QC) and quality assurance (QA) activities for all levels of the network laboratories at regular intervals. The NRL also participates in the WHO-AFRO External Quality Assessment (EQA) scheme for enteric and meningitis pathogens, TB and malaria. External quality assurance for HIV, measles and selected bacterial diseases is carried out through designated international partner or disease-specific collaborating laboratories. As an example, in 2003, 100% concordance was reported for the unlinked, anonymous HIV testing in a total of 288 samples sent to CDC-Atlanta.