TB Study: African-Americans Diagnosed More Quickly Than Whites

The time from onset of tuberculosis to diagnosis is longer in whites versus African-Americans, according to a study presented Monday during “Update from CDC’s TB Epidemiologic Studies Consortium and TB Trials Consortium.”

Determinants of Early Diagnosis, Prevention, and Treatment of TB in African-Americans was one of four trials presented during the session. Other trials examined tests for diagnosis of tuberculosis, new treatment options, and treating latent TB to prevent the disease from becoming active.

The goal of the first study was to find reasons for racial differences in occurrence of TB, says Dolly Katz, PhD, co-principal investigator of the Tuberculosis Epidemiologic Studies Consortium.

“African-Americans have consistently higher rates of TB compared to whites. They have five times higher rates,” she says. “The study purpose was to understand the TB disparity in the African-American Community.

“We wanted to quantify the time from symptom onset to reaching care and receiving a TB diagnosis among African-Americans and whites, and understand the factors associated with the delays.”

The study collected data from eight states in the South and Southeast, which reported 35.5 percent of all TB cases in African-Americans born in the United States and 16.5 percent of cases of whites born in the U.S. Interviews of the study population gathered information about age, education, income, whether they smoked, incarceration, HIV/AIDS, diabetes, or health insurance.

The mean time from first medical care to diagnosis was 2.2 months for African-Americans compared with 6.1 months for whites.

“There seems to be a longer time to care driven by a concentration of whites who were longer to diagnosis,” Dr. Katz says. “The African-American race was forced into every one of 12 models, and in nine, the African-American time to diagnosis was shorter than whites.”

Another interesting finding was that study participants with health insurance who were receiving antibiotics took longer to receive a diagnosis compared with those with other predictors, such as excess alcohol use, fever, cough, and race.

Dr. Katz speculated that people with health insurance “may tend to go to clinicians not familiar with TB. Emergency department physicians may be more familiar with TB.”

“The overall distributions of time to getting care and getting diagnosed do not appear to fuel the TB disparity between African-Americans and whites,” she says when discussing the public health implications of the results. “Because of the rarity of TB as a diagnosis among U.S.-born persons in the United States, efforts focused on prevention may be more fruitful than attempts to reduce delays in diagnosis of TB disease.”

Jennifer Flood, MD, MPH, presented the results of Comparison of TST and IGRAs in Diagnosing TB Infection and Predicting Progression to Tuberculosis. There is no gold standard for tuberculosis infection diagnosis, so the study examined the tuberculin skin test and two interferon-gamma release assay tests.

The study enrolled more than 8,000 patients, mostly foreign-born, and the majority had concordant test results of triple negatives or positives, she says. The study also found that positive test results increased with age until age 40 for all three tests, and incident disease occurred in persons who had concordant positive TST and IGRAs.

No incident TB cases have thus far developed in a single-test, TST-positive group so far, says Dr. Flood, chief of the TB Control Branch, California Department of Public Health.

Susan E. Dorman, MD, presented Current Status of Ultra-Short Therapy for TB Disease, which looked at shorter tuberculosis treatments using existing drugs. The duration of treatment for most forms of drug-susceptible TB is six months.

The study looked at the use of fluorquinolones and rifapentine. In phase 3 studies of fluorquinolones, the regimens were not potent enough to achieve a durable cure in acceptably high proportions of participants and shorten the therapy to four months, she says.

For rifapentine, the robust antimicrobial activity and observed good tolerability and safety justify assessment of daily high doses in regimens of shorter than six months in a phase 3 clinical trial, Dr. Dorman says.

Carol D. Hamilton, MD, MHS, professor of medicine at Duke University, presented an update on latent tuberculosis interventions. The principles behind the treatments are that they must be effective, safe, affordable, have few side effects, and short in duration so patients would be more likely to complete treatment.

The TB Trials Consortium continues to look at treatment options and also is working to develop LTBI testing and treatment guidelines, she says.

See the schedule of upcoming sessions by outside organizations