[PD Test]New diagnostic tools, better treatments needed for TB

Currently available immunodiagnostic tests as well as widely used treatments for tuberculosis (TB) are not particularly effective, according to a new study.

“With the huge problem scale and the number of persons to be treated to prevent one case of TB, further research efforts are required in the development of new diagnostic tools with better disease-predicting ability, as well as shorter and safer regimens, preferably applicable to latent infection by both drug-sensitive and drug-resistant TB,” said study investigator Dr. Chi-Chiu Leung, consultant chest physician with the Tuberculosis and Chest Service, Department of Health, Hong Kong.

Leung and colleagues have reported the results of a meta-analysis of data from 15 studies involving a total of 26,680 subjects in low- and middle-income countries.

Amongst their findings – evidence that commonly used TB diagnostic tools such as interferon-gamma release assay (IGRA) and tuberculin skin test (TST) were not able to identify or predict the development of TB in subjects latently infected with live Mycobacterium tuberculosis without active disease.

The research further found that the effectiveness of widely used TB treatments is often limited in real- life settings or in different patient subtypes.

In evaluating patterns of use of several isoniazid-based therapies in patients with latent TB infection, there appeared to be little consistency in terms of optimal duration of treatment, and field efficacies appear to have often been compromised by hepatotoxicity as well as suboptimal patient acceptance and adherence.

Randomized controlled trials of isoniazid therapy have demonstrated efficacy rates of up to 90 percent (for 12 months) of compliance. Prolonged isoniazid therapy among HIV-infected individuals remains controversial with conflicting results in two published trials [Lancet 2011;377:1588-98; N Engl J Med 2011;365:11-20], whereas it has been proven to be not useful among the non-HIV-infected individuals. Primary isoniazid prophylaxis has also been found to be non-effective among HIV-infected and non-HIV-infected children immunized with BCG vaccine. [N Engl J Med 2011;365:21-31] There is also no clear evidence to support the use of chemoprophylaxis for TB patients previously treated and subsequently put on immunosuppressive therapy.

The study also looked at the use of other types of anti-TB regimens, such as those using isoniazid in combination with other medications and non-isoniazid-based regimens, and found these to offer varying degrees of effectiveness and tolerability in preventing or treating latent TB infection.