Videlis Nduba
Kenya Medical Research Institute, Kenya
Title: Incidence of tuberculosis and cohort retention among adolescents in Western Kenya
Biography
Biography: Videlis Nduba
Abstract
Setting: Karemo division, Siaya County, Western Kenya, with the highest TB notification rates in Kenya (400/100,000). Objective: To determine the incidence of tuberculosis and one year cohort retention in 12–18 year adolescents, in preparation for Phase III TB vaccine trials. Design: Adolescents were enrolled and followed up for 1-2 years to determine TB incidence. Adolescents who had a positive tuberculin skin test, history of cohabitation with a TB case within the previous 2 years, or at least one TB symptom received clinical examination, sputum examination, and a chest X-ray. TB cases were defined as definite if bacteriologically confirmed and clinical if diagnosed by a clinician based on a suggestive chest X-ray scored using Chest Radiograph Review System (CRRS) and having at least one clinical symptom. Risk factors were explored using Poisson regression. Results: Among 4965 adolescents without TB at baseline, 26 TB cases were found during follow up with a corresponding incidence density of 4.4 (95% CI, 3.0-6.4) events per 1000 person years of observation. Tuberculin skin test (TST) conversion (RR=3.5; CI 1.5, 7.7) and history of previous tuberculosis (RR=12.5; CI 1.8, 100) were the strongest predictors of incident TB. Overall (4086/4957) 82.4% of adolescents were retained in the study after 1 year of follow up. Being female, older, out of school and being orphaned were significant risk factors for lower retention rates. Conclusion: Given the high incidence of tuberculosis and good cohort retention, this setting is suitable for TB vaccine trials targeting adolescents.