Window periods and classification of individuals with long-standing infection as positive, for the BED-CEIA alone, the avidity assay alone, a two-assay multi-assay algorithm (MAA) and two 4-assay MAAs*.

*Window periods are shown in years for four testing algorithms for subtype A, subtype C, subtypes A and C combined, and subtype D. BED: the BED capture immunoassay (results are expressed as normalized optical density units); Avidity: the avidity assay (results are expressed as a percentage, avidity index); CD4: CD4 cell count (results are expressed as cells/mm3); VL: HIV viral load (results are expressed as HIV RNA copies/mL). The lower two rows show results for MAAs (see text); for these MAAs, individuals are classified as MAA positive if they have results for all for assays that are below/above the cutoffs indicated.aND: not determined; MAAs that include viral load could not be evaluated for subtype D due to missing viral load data.