Assessment of risk factors for development of active pulmonary tuberculosis in northern part of Ethiopia: a matched case control study.

Background: Understanding the role of various determinants of tuberculosis (TB) is particularly important in countries like Ethiopia where TB is endemic and the resources available to public health intervention are limited However, little information is available on risk factors of TB to be able to effectively and efficiently control TB.

Objective: To identify and determine the potential host and environmental-related risk factors for development of active pulmonary tuberculosis (PTB) in the Tigray region of Ethiopia.

Methods: A matched case-control study was conducted from April-August 2011. Cases were defined as all newly diagnosed of PTB patients aged 15 years and above, who were registered by directly observed treatment short-course (DOTS) program health centers found in the randomly selected 16 districts in the region. Controls were age matched with no previous history of TB and chronic cough. For each case, two controls were recruited. Trained nurses collected data using structured and pre-tested questionnaire. Predictors of caseness were identified using conditional logistic regression method. Odds ratio were calculated with 95% confidence intervals to assess the strength of association.

Results: Data was collected from 463 cases and 860 controls. The mean age of the cases and controls were 37 +/- 14.9 and 39 +/- 14.5 years, respectively. In the multivariable analysis significant risk factors for active PTB were illiteracy (OR = 1.90, 95% CI: 1.24, 2.93), household food shortage (OR = 2.38, 95% CI: 1.52, 3.73), HIV seropositivity (OR = 2.7, 95% CI: 1.42, 5.13), and past alcohol consumption (OR = 2.44, 95% CI: 1.08, 5.50). Marriage (OR = 95% CI: 0.37, 0.89) was identified as protective factor. Consumption of raw milk, history of imprisonment, having a separate kitchen, history of asthma and history of TB contact were significant risk factors on crude analysis but their significance was not maintained in multivariable analysis.

Conclusion: Our study results indicated that household food shortage, HIV sero-positivity, illiteracy, being married, smoking and alcohol consumption before six months have a substantially increased risk of developing tuberculosis, independent of other risk factors in adults in the Tigray region of Ethiopia. Hence, prevention and control efforts must target on this identified factors toward facilitating and effective and efficient TB control program in the study area.