Digital chest X-ray, symptom-based screening doubled yield of undiagnosed TB in inmates

The addition of a digital chest X-ray to symptom-based screening doubled the yield of undiagnosed tuberculosis among inmates in South Africa compared with symptom-based screening alone, researchers reported.

“South Africa remains a high tuberculosis burden county despite recent progress in reducing incidence. Diagnosis and treatment of TB among key populations, including inmates within correctional facilities, is important for TB elimination. In particular, early and effective diagnosis of TB disease among inmates is critical to control TB in this population,” Kavindhran Velen, MD, senior TB program manager in the implementation research division at The Aurum Institute in Johannesburg, and colleagues wrote in the Annals of the American Thoracic Society.

Symptom-based screening is routinely used to find active TB cases in correctional facilities in South Africa. However, alternatives, such as digital chest X-ray, may be more accurate than symptom-based screening only, according to the researchers.

Researchers screened 3,576 adult inmates (median age, 34 years; 99.6% men) at four correctional facilities in South Africa for TB using symptoms and digital chest X-ray. Participants with at least one symptom or computer-aided detection of 50 or more provided two sputa for liquid culture and GeneXpert MTB/RIB Ultra (Xpert Ultra; Cepheid) testing. Xpert Ultra testing was also performed in a sample of 800 inmates without symptoms.

TB yield was defined as the proportion of new bacteriologically confirmed patients with TB identified.

Of those screened, 24.2% required investigation, with 11.2% symptomatic, 19.1% on abnormal computer-aided detection and 24.2% with either.

Researchers collected sputum from 86.2% of participants. Twenty-eight new TB cases were identified, resulting in 7.8 TB cases per 1,000 population, according to the results.

TB yield would have been 3.6 per 1,000 population when assessing symptoms alone and 7 per 1,000 population when assessing digital chest X-ray alone based on hypothesized screening modalities, the researchers wrote.

In the 800 inmates who were initially without symptoms, researchers diagnosed five new TB cases.

The researchers reported no difference in TB yield with Xpert Ultra compared with culture (5.6 vs. 4.8 per 1,000 population; P = .21).

“The roadmap to TB elimination, which emphasizes the importance of screening and treating key populations, will require that we innovate and optimize current approaches,” the researchers wrote. “Our study found that using [digital chest X-ray] and symptom-based TB screening doubled the yield of undiagnosed TB among inmates.”