Screening for latent TB may miss higher-risk patients

Screening for latent tuberculosis (TB) may miss patients at higher risk, according to a recent study.

Latent TB screening is often done for employment, in schools, and in settings such as nursing homes. In addition, the California Department of Health recommends screening based on birth, travel, or residence in a country with elevated TB rates for more than one month; immunosuppression; and close contact with active TB. Researchers used data from Kaiser Permanente Southern California to evaluate factors associated with testing for latent TB and with positive results. The study was conducted between Jan. 1, 2008, and Dec. 31, 2019, and included adults with no history of active TB. Testing was defined as a tuberculin skin test or interferon gamma release assay. The results were published Jan. 11 by Clinical Infectious Diseases.

Overall, 3,816,884 adults were included in the testing-eligible cohort. Over half (52%) were female, 37% were White, and 37% were Hispanic. The mean age was 43.5 years. Of these, 706,367 (19%) were tested for latent TB and made up the tested cohort. Positive results on at least one test were found in 60,393 (9%). There were 1,211,971 patients in the testing-eligible cohort who met at least one screening criteria for latent TB according to the California Department of Health's guidelines, and of these, 210,025 (17%) were tested. Latent TB testing was done in 88,088 of 183,741 patients (48%) who were immunosuppressed any time during follow-up, 157,405 of 1,087,237 (14%) who were born in a country with an elevated TB rate, 6,704 of 24,803 (27%) with a history of at least 30 days of travel to a country with an elevated TB rate, and 4,297 of 5,406 (79%) with a history of close contact with TB.

An association with higher odds of a positive TB result occurred for male sex (adjusted odds ratio [OR], 1.32; 95% CI, 1.30 to 1.35), Asian/Pacific Islander ethnicity (adjusted OR, 2.78; 95% CI, 2.68 to 2.88), current smoking (adjusted OR, 1.24; 95% CI 1.20 to 1.28), diabetes (adjusted OR, 1.13; 95% CI, 1.09 to 1.16), hepatitis B (adjusted OR, 1.45; 95% CI, 1.34 to 1.57), hepatitis C (adjusted OR, 1.54; 95% CI, 1.44 to 1.66), and birth in a country with an elevated TB rate (adjusted OR, 3.40; 95% CI, 3.31 to 3.49). However, none of these factors were associated with higher odds of being tested.

The researchers noted that some misclassification of latent TB infection was possible and that some diagnoses could have been missed, among other limitations. They concluded that although some high-risk patients are being tested appropriately for latent TB, current testing strategies are missing other high-risk groups. The authors called for prioritizing increased testing in these patients and said that screening guidelines should be updated. “Additional work is needed to refine guidelines that are feasible to operationalize and more appropriately target populations with highest [latent TB infection] risk, as well as to identify strategies to support guideline implementation,” they wrote.