Poor agreement between diagnostic tests for latent tuberculosis infection among HIV-infected persons in Hong Kong.

BACKGROUND AND OBJECTIVE: The tuberculin skin test (TST), T-Spot.TB (T-Spot) and QuantiFERON-TB Gold-In Tube (QFT) were compared in diagnosing latent tuberculosis infection (LTBI) among human immunodeficiency virus (HIV)-infected persons. METHODS: Human immunodeficiency virus-infected persons without previous history of tuberculosis or LTBI were simultaneously tested by TST, T-Spot and QFT annually and followed up for tuberculosis. RESULTS: Among 110 HIV-infected subjects with 85% previous TST screening coverage, 75% on anti-retroviral therapy, well-preserved median CD4 count (414/µL) and low median viral load (<75/µL), baseline TST, T-Spot and QFT were positive in 5.5%, 5.6% and 4.9%, respectively, with almost complete discordance of positive results. Among 91 (83%), 66 (60%) and 26 (24%) subjects successfully undergoing the first, second and third annual retesting, TST, T-Spot and QFT were, respectively, positive in 11/123 (8.9%), 13/173 (7.5%) and 21/182 (11.5%) on retesting, with similar discordance of positive results. There was no significant association with the concurrent CD4 count or viral load. Conversion occurred in 11/123 (8.9%), 8/160 (5.0%) and 18/168 (10.7%) of TST, T-Spot and QFT, respectively, and none was associated with changes in CD4 count or viral load. More than half of the positive T-SPOT and QFT results reverted to negative on follow-up. None of these tests picked up the single case of culture-confirmed tuberculosis observed after 798 person-years of follow-up. CONCLUSION: Major discordance in positive results, high reversion rates and low tuberculosis incidence among test-positive subjects cast serious doubt on the utility of the currently available LTBI tests in the annual screening of HIV-infected persons in an intermediate tuberculosis burden area.

The epidemiology and clinical manifestations of human immunodeficiency virus-associated tuberculosis in Hong Kong.

OBJECTIVE: To evaluate the epidemiology and clinical manifestations of human immunodeficiency virus-associated tuberculosis in Hong Kong. DESIGN: Retrospective study. SETTING: Tuberculosis and Chest Service and Special Preventive Programme, Public Health Services Branch, Centre for Health Protection, Department of Health, Hong Kong Special Administrative Region. PATIENTS: Cases reported to the TB/HIV Registry jointly kept by the Tuberculosis and Chest Service and Special Preventive Programme from 1996 to 2006 were reviewed. The Registry includes cases of human immunodeficiency virus-associated tuberculosis diagnosed in the two services, and cases referred from regional hospitals under the Hong Kong Hospital Authority and the private sector. RESULTS: Tuberculosis has become an increasingly important acquired immunodeficiency syndrome-defining illness in Hong Kong, and overtook Pneumocystis jiroveci pneumonia for the first time as the most common primary acquired immunodeficiency syndrome-defining illness in 2005 (accounting for 39% and 31% of all such illnesses, respectively in that year). The presentation of human immunodeficiency virus-associated tuberculosis is often atypical. In these patients moreover, there was a slightly higher rate of multidrug-resistant tuberculosis (2%) than in the general population (range, 0.7-1.5%). CONCLUSIONS: Programmes for the provider-initiated human immunodeficiency virus testing policy to reduce diagnostic delays should continue and be enhanced. Continual surveillance of both conditions is imperative, especially in view of a possible link between human immunodeficiency virus and multidrug-resistant tuberculosis.