Table 2.
Specificity of third- and fourth-generation immunoassays in 19 public health laboratoriesa participating in the nucleic acid testing referral program
| Immunoassay (Laboratories) | Median Specificityb (Minimum, Maximum) |
Median Specificity, Sensitivity Analysisc (Minimum, Maximum) |
|---|---|---|
| ARCHITECT HIV Ag/Ab Combo (6) | 99.9% (99.9%, 100%) | 99.9% (99.7%, 99.9%) |
| GS HIV Combo Ag/Ab EIA (8) | 100% (99.8%, 100%) | 99.9% (99.8%, 100%) |
| GS HIV-1/HIV-2 Plus O EIA (5) | 100% (99.8%, 100%) | 99.9% (98.7%, 100%) |
Specificity of the Advia Centaur could not be calculated as the site using it did not submit data. Specificity of the two screening immunoassays could not be assessed in the site that switched assays as the site did not separate testing data by screening assay. One site using the ARCHITECT did not submit data required to calculate specificity.
Specificity (for screening immunoassay (IA) at each submitting laboratory)= IA negative/ [IA negative +(IA false positive)] where IA false positive=number with repeatedly reactive IA, negative or indeterminate supplemental antibody test, and negative NAT. The median, minimum and maximum were calculated based on the specificity in laboratories using the specified assay.
Calculated as specificity in which IA false positive= (number with repeatedly reactive IA, negative or indeterminate supplemental antibody test, and negative NAT) PLUS (number specimens eligible for NAT testing that did not receive it). The median, minimum and maximum were calculated based on the specificity in laboratories using the specified assay.