Tuberculosis Remains a Serious Global Health Issue
Saturday, March 24 is World Tuberculosis Day, a day dedicated to raising public awareness that tuberculosis remains a serious global health issue, causing the deaths of several million people each year, and one that is becoming increasingly significant in the United States.
1. What are the most important current issues and "hot topics" in the treatment of tuberculosis, from both the screening and patient management perspectives?
The introduction of new, sophisticated interferon gamma release assays (IGRAs) over the last several years, which have been very effective in detecting latent TB, is a significant advance, although there have been some challenges to the broad adoption of these assays.
The development of multi-drug resistant tuberculosis is a significant emerging treatment concern. Accordingly, the rapid molecular diagnosis of drug-resistant TB strains will be an important future development in controlling the spread of tuberculosis and assisting clinicians with treatment plans for infected patients.
Lastly, while there has been a dearth in new drug development for tuberculosis treatment over the last 50 years or so, there currently is a promising development pipeline consisting of a number of new drugs being investigated in trials from Phases 1 through 3.
2. What are the most important risk factors for active TB?
- Close contact with persons infected with TB
- Prior, untreated TB with fibrotic lesions on chest x-ray
- Skin test or IGRA conversion within 2 years
- Immigrating from endemic countries (within 5 years of arrival)
- Children <5 years with a positive purified protein derivative (PPD) or IGRA
- HIV infection
- Being underweight and/or malnourished
3. Why is the detection of latent tuberculosis infection (LTBI) a key element in strategies to detect, manage and treat tuberculosis?
- The rate of active tuberculosis in the United States has declined, which makes it more important to identify and treat high-risk patients with latent infection, in order to eliminate TB.
- Treatment of LTBI can prevent the development of active TB in high-risk patients. The focus should be on high-risk (as opposed to low-risk) patients, as defined by targeted testing.
- It is important to remember that all testing should include a follow-up care plan for treating TB.
4. What is the role of IGRAs in the management of TB? How do they compare with the tuberculin skin test (TST)?
- The 2010 CDC guidelines indicate that IGRAs may be used in place of (but not in addition to) a TST in all situations in which CDC recommends tuberculin skin testing.
- These FDA-approved assays use antigens not found in BCG or MAC (ESAT-6 CFP-10 TB-7.7) and are more specific, with no cross reactors.
- IGRAs rely on specific antigens, do not involve boosting, require only one patient visit with results possible in 24 hours, and display minimal inter-reader variability -- all advantages compared with TST.
- IGRAs may offer major operational and biologic advantages over the TST and, when used on a large scale, their accuracy could result in reductions in patient costs and in inappropriate treatment. Although the cost for an IGRA is greater than that for a TST, cost savings may occur because of reduced physician involvement and minimal false positives. Fewer false positives means fewer patients placed on isoniazid therapy, where they would need to be monitored.
- TST is the preferred test for children under age 5, although IGRAs are acceptable.