Prevalence of tuberculosis in adolescents, western Kenya: implications for control programs

Objective: The aim of this study was to determine the prevalence of tuberculosis (TB) in adolescents in western Kenya. Methods: A cohort study of 5004 adolescents aged 12–18 years was conducted. Adolescents were screened for prevalent TB using clinical criteria, history of TB contact, and a Mantoux test. Cases of suspected TB were investigated through two sputum examinations (microscopy and liquid culture) and chest radiography. Results: Out of 5004 adolescents enrolled, 1960 (39.2%) were identified with suspected TB, including 1544 with a positive Mantoux (prevalence 1544/4808, 32.1%), 515 with symptoms suggestive of TB (10.3%), and 144 (2.9%) with household TB contact. Sixteen culture-confirmed (definite) and 18 probable pulmonary TB (PTB) cases were identified, reflecting a prevalence estimate of 3.2/1000 (definite) and 6.8/1000 all PTB, respectively. Only one smear-positive case was detected. The case notification rate among 12–18-year-old adolescents for all TB was 101/100 000, yielding a patient diagnostic rate of 0.13 (95% confidence interval 0.03–3.7) cases detected per person-year for all TB. Conclusion: The prevalence of PTB among adolescents is high, with the majority of cases not detected routinely. Innovative active case finding including the wider use of Xpert MTB/RIF is needed to detect smear-negative TB among adolescents

Incremental Cost-Effectiveness Ratios (ICERs) of Xpert on all persons with presumptive TB compared to triage algorithms for various sensitivity, specificity and cost combinations of a triage test.

<p>The figure shows the Uganda setting.</p

Combinations of cost and specificity of a triage test with 100% relative sensitivity.

<p>These combinations result in equal or reduced diagnostic cost of a triage pathway, compared to Xpert on all persons with presumptive TB. Panel 2A shows the Uganda setting, 2B the India setting and 2C the South African setting.</p

Simplified schematic presentation of the two pathways in the model.

<p>Simplified schematic presentation of the two pathways in the model.</p

Case detection, total cohort cost and costs per patient diagnosed for Xpert-for-all and 3 example triage pathways.

<p>% prevalence of smear-positive TB. For a cohort of 10 000 persons with presumptive TB with 5</p><p> =  multi-drug resistant tuberculosis. MDR TB</p><p> =  GeneXpert MTB/RIF assay. Xpert</p

Total cohort cost, DALYS, cost per DALY and ICER for Xpert on all compared to triage pathways as the base case.

<p>% prevalence of smear-positive TB. For a cohort of 10 000 persons with presumptive TB with 5</p><p> = incremental cost-effectiveness ratio. ICER</p><p> = disability adjusted life year. DALY</p><p> =  multi-drug resistant. MDR</p><p> =  GeneXpert MTB/RIF assay. Xpert</p><p> Fixed values for the sensitivity, specificity and cost of the triage test.</p

Sensitivity analyses.

<p> The effect of assumptions on the ICER of Xpert-for-all compared to triage pathway with different triage test examples.</p><p> per-patient test cost including cost to acquire, apply and maintain the test.</p><p> = incremental cost-effectiveness ratio. ICER</p><p> = disability adjusted life year. DALY</p><p> =  multi-drug resistant. MDR</p><p> =  GeneXpert MTB/RIF assay. Xpert</p><p>+  = HIV positive; HIV–  =  HIV negative; spec = specificity. HIV</p