Chest Radiograph Screening for Detecting Subclinical Tuberculosis in Asymptomatic Household Contacts, Peru

Abstract

The World Health Organization's end TB strategy promotes the use of symptom and chest radiograph screening for tuberculosis (TB) disease. However, asymptomatic early states of TB beyond latent TB infection and active disease can go unrecognized using current screening criteria. We conducted a longitudinal cohort study enrolling household contacts initially free of TB disease and followed them for the occurrence of incident TB over 1 year. Among 1,747 screened contacts, 27 (52%) of the 52 persons in whom TB subsequently developed during follow-up had a baseline abnormal radiograph. Of contacts without TB symptoms, persons with an abnormal radiograph were at higher risk for subsequent TB than persons with an unremarkable radiograph (adjusted hazard ratio 15.62 [95% CI 7.74-31.54]). In young adults, we found a strong linear relationship between radiograph severity and time to TB diagnosis. Our findings suggest chest radiograph screening can extend to detecting early TB states, thereby enabling timely intervention.

Keywords: Peru; bacteria; chest radiography; contact tracing; global health; mass chest x-ray; pulmonary; subclinical infections; tuberculosis and other mycobacteria.

Figure 1

Flowchart of enrollment in study of chest radiograph screening for detection of subclinical TB in asymptomatic household contacts, Peru. CXR, chest radiograph; SX–, no symptoms; SX+, symptoms; TB, tuberculosis; TST–, tuberculin skin test negative; TST+, tuberculin skin test positive.

Figure 2

Associations between chest radiograph and symptom screening results and time to incident TB among tuberculin skin test–positive adults, Peru. N = 1,747, incident events = 52. CXR–, unremarkable chest radiograph; CXR+, abnormal chest radiograph; SX–, no symptoms; SX+, symptoms; TB, tuberculosis.

Figure 3

Associations between abnormal chest radiographs and time to incident TB among tuberculin skin test–positive adults in 3 age groups, Peru. A) 16–24-year age group (N = 370, incident events = 25); B) 25–44-year age group (N = 709, incident events = 13); C) >45-year age group (N = 668, incident events = 14). CXR–, unremarkable chest radiograph, CXR+, abnormal chest radiograph; SX–, no symptoms; SX+, symptoms; TB, tuberculosis.

Figure 4

Association between degree of baseline chest radiograph severity and time to developing incident TB among persons with abnormal radiograph findings by age group, Peru. Gray shading indicates 95% CIs. A) 16–24-year age group (n = 12). Mean difference −0.004 (95% CI −0.007 to −0.001); p<0.001, ρ = −0.71; B) 25–44-year age group (n = 6). Mean difference −0.0002 (95% CI −0.015 to 0.015); p = 0.96, ρ = −0.025; C) >45-year age group (n = 9). Mean difference 0.0006 (95% CI −0.004 to 0.005); p = 0.73, ρ = 0.14. ρ, Pearson correlation coefficient.