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



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.



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.



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.
TB and Chest Service, Centre for Health Protection. cc_leung@dh.gov.hk.
Chi Chiu
CC
Leung
Special Preventive Programme, Centre for Health Protection, Department of Health.
Kenny
K
Chan
Centre of Infection and Department of Microbiology, Queen Mary Hospital, The University of Hong Kong.
Wing Cheong
WC
Yam
Department of Medicine, Queen Elizabeth Hospital, Hong Kong, China.
Man Po
MP
Lee
TB and Chest Service, Centre for Health Protection.
Chi Kuen
CK
Chan
Special Preventive Programme, Centre for Health Protection, Department of Health.
Ka Hing
KH
Wong
Centre of Infection and Department of Microbiology, Queen Mary Hospital, The University of Hong Kong.
Pak Leung
PL
Ho
TB and Chest Service, Centre for Health Protection.
Ida
I
Mak
TB and Chest Service, Centre for Health Protection.
Cheuk Ming
CM
Tam
D000328:Adult; D000368:Aged; D018791:CD4 Lymphocyte Count; D003955:Diagnostic Tests, Routine; D005260:Female; D015658:HIV Infections / Q000150:complications* / Q000382:microbiology; D006723:Hong Kong; D006801:Humans; D015994:Incidence; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014374:Tuberculin Test; D019562:Viral Load; D055815:Young Adult
human immunodeficiency virus; interferon-gamma release assay; latent tuberculosis infection; tuberculin skin test