Changing Concepts of “Latent Tuberculosis Infection” in Patients Living with HIV Infection
Table 1
Evidence that suggests the existing view of “latent tuberculosis infection” and active tuberculosis disease as binary compartmentalised states is oversimplistic.
(1) Risk of developing active tuberculosis in patients with “latent tuberculosis Infection” varies considerably over time, suggesting that “latent” infection is a heterogeneous state
(2) Isoniazid is active against actively replicating organisms and yet reduces TB risk in those with “latent tuberculosis infection”
(3) Isoniazid preventive therapy entails 6–12 months of therapy for good efficacy, possibly suggesting the pool of “latent” mycobacteria cycle through phases of metabolic activity and replication over time
(4) A significant proportion of patients with microbiologically proven pulmonary tuberculosis identified by prevalence surveys have no symptoms
(5) Serological markers are predictive of patients with different stages of tuberculosis infection and disease, including those with asymptomatic active disease
(6) Mycobacterial lesions within tissues from the same individual may represent a wide spectrum, ranging from sterility to multibacillary disease
(7) Discordance between tuberculin skin test and interferon-gamma release assay results cannot simply be explained by differences in specificity. These assays appear to reflect different aspects of immune sensitization which are as yet incompletely understood.
