Tuberculosis (TB) infection is one of the most common infectious diseases in the world. And although TB is less common in the United States, many people still get infected every year or are at risk of getting sick and spreading the infection to others.
So on March 8, the U.S. Preventive Services Task Force (USPSTF) posted a draft recommendation statement(www.uspreventiveservicestaskforce.org) and draft evidence review(www.uspreventiveservicestaskforce.org) on screening for latent tuberculosis infection (LTBI) and recommended physicians screen adults at increased risk. This is a "B" recommendation.(www.uspreventiveservicestaskforce.org)
The USPSTF said patients considered at increased risk for LTBI include those who were born in or who have lived in countries with a high prevalence of TB, including Mexico, the Philippines, Vietnam, India, China, Haiti and Guatemala. Also, people who have lived in group settings where exposure to TB is more likely, such as homeless shelters or correctional facilities, are considered at increased risk for LTBI.
It's also important to note that about 30 percent of patients exposed to TB bacteria will develop LTBI, which means they are infected but do not have any symptoms. While these patients cannot spread TB to others, if they remain untreated, about 5 percent to 10 percent will eventually develop active TB.
- On March 8, the U.S. Preventive Services Task Force (USPSTF) issued a draft recommendation that physicians screen adults at increased risk for latent tuberculosis infection (LTBI).
- The USPSTF found effective screening tests that detect LTBI and also effective treatments to prevent patients from progressing from LTBI to active tuberculosis (TB) disease.
- The USPSTF last issued a recommendation on screening for TB in 1996. At that time, the task force recommended screening for TB infection with the Mantoux tuberculin skin test in asymptomatic, high-risk patients -- an "A" recommendation.
Screening Tests and Treatment
The USPSTF found effective screening tests that detect LTBI and also effective treatments to prevent patients from progressing from LTBI to active TB disease.
Two types of screening tests for LTBI are currently available in the United States: the Mantoux tuberculin skin test (TST) and interferon-gamma release assays (IGRAs). TST requires intradermal placement of purified protein derivative and interpretation of response 48 to 72 hours later. IGRA requires a single venous blood sample and laboratory processing within 8 to 30 hours after collection.
The CDC recommends screening with either TST or IGRA. IGRA tests may be preferred for patients who have received a Bacillus Calmette-Guérin vaccination or those who may be unlikely to return for TST interpretation.
The USPSTF found no evidence on the optimal frequency of screening for LTBI, explaining that depending on specific risk factors, screening frequency could range from one-time only screening in patients at low risk for future exposure to annual screening in patients who are at continued risk of exposure.
As for treatments, the CDC recommends(www.cdc.gov) four different treatment regimens for LTBI. Medications include rifampin, isoniazid or isoniazid plus rifapentine. Treatment duration ranges from three to nine months. If a nondaily dosing regimen is offered, the CDC recommends directly observed therapy.
Update of 1996 Recommendation
The USPSTF last issued a recommendation on screening for TB in 1996. At that time, the task force recommended screening for TB infection with TST in asymptomatic, high-risk patients -- an "A" recommendation. It also recommended the consideration of Bacillus Calmette-Guérin vaccination for selected high-risk individuals only -- a "B" recommendation.
According to the task force, this updated draft recommendation came about due to the changes in the epidemiology of the disease, the development of newer screening technologies and newer methods for developing evidence-based recommendations.
So the USPSTF commissioned a systematic review of the evidence on screening for LTBI in asymptomatic adults who are seen in primary care settings.
Family Physician's Take
Family physician Kenneth Lin, M.D., M.P.H., of Washington, D.C., told AAFP News that he generally does TB testing in his office only when asked. These test usually are for patients who work in health care settings where testing is a work requirement, or for recent immigrants from countries with high TB prevalence.
"In terms of what's changed since 1996, we now have a blood test for TB (IGRA) which is more convenient for patients since they don't have to come back in 48 to 72 hours to have it read," he said.
The USPSTF is providing an opportunity for public comment on this draft recommendation statement(www.uspreventiveservicestaskforce.org) and draft evidence review(www.uspreventiveservicestaskforce.org) until April 4.
The AAFP is reviewing the USPSTF's draft recommendation and will release its own recommendation after the task force publishes its final recommendation statement.