Enhanced diagnosis of HIV-1-associated tuberculosis by relating T-SPOT.TBand CD4 counts

Abstract

The sensitivity of the tuberculin skin test is impaired in HIV-1-infected persons. Enzyme-linked immunospot-based detection of immune sensitisation may be less affected. Furthermore, the quantitative response can be related to the CD4 count, potentially improving specificity for active disease.The T-SPOT.TBassay was performed on HIV-1-infected participants, 85 with active tuberculosis (TB) and 81 healthy patients (non-TB). The ratio of the sum of the 6-kDa early secretory antigenic target and culture filtrate protein 10 response to the CD4 count (spot-forming cell (SFC)/CD4) was calculated.Using the manufacturer's guidelines, active TB was diagnosed with 76% sensitivity and 53% specificity. Using an SFC/CD4 ratio of 0.12, sensitivity (80%) and specificity (62%) improved. The quantitative T-cell response increased with increasing smear-positivity in the active TB group (p = 0.0008). In the non-TB group, the proportion of persons scored positive by T-SPOT.TBassay was lower in the group with a CD4 count of 0.12 should prompt investigation for active disease. A strong association between the degree of sputum positivity and T-SPOT.TBscore was found. The sensitivity of the T-SPOT.TBassay in active disease may be less impaired by advanced immunosuppression.