Risk factors for pulmonary tuberculosis: a clinic-based case control study in The Gambia.
BACKGROUND
The tuberculosis (TB) epidemic in Africa is on the rise, even in low-HIV prevalence settings. Few studies have attempted to identify possible reasons for this. We aimed to identify risk factors for pulmonary tuberculosis in those attending a general outpatients clinic in The Gambia, a sub-Saharan African country with relatively low HIV prevalence in the community and in TB patients.


METHODS
We conducted a case control study at the Medical Research Council Outpatients' clinic in The Gambia. Pulmonary TB cases were at least 15 years old, controls were age and sex matched clinic attendees. Participants were interviewed using a structured questionnaire.


RESULTS
100 sputum smear positive TB cases and 200 clinic controls were recruited. HIV prevalence was 6.1% in cases and 3.3% in controls. Multivariable assessment of host factors showed that risk of TB was increased among the Jola ethnic group and smokers, and decreased in those in a professional occupation. Assessment of environmental factors showed an increased risk with household crowding, history of household exposure to a known TB case, and absence of a ceiling in the house. In a combined multivariable host-environment model, the risk of TB increased with crowding, exposure to a known TB case, as well as amongst the Jola ethnic group.


CONCLUSIONS
In The Gambia, household crowding and past household exposure to a known TB case are the standout risk factors for TB disease. Further research is needed to identify why risk of TB seems to differ according to ethnicity.
Hill
Philip C
PC
Tuberculosis Division, Medical Research Council Laboratories, Banjul, The Gambia. phill@mrc.gm
Jackson-Sillah
Dolly
D
Donkor
Simon A
SA
Otu
Jacob
J
Adegbola
Richard A
RA
Lienhardt
Christian
C
D000293:Adolescent; D000328:Adult; D000368:Aged; D000554:Ambulatory Care Facilities / Q000706:statistics & numerical data; D016022:Case-Control Studies; D003441:Crowding; D004781:Environmental Exposure; D005191:Family Characteristics; D005260:Female; D005714:Gambia / Q000453:epidemiology; D015658:HIV Infections / Q000453:epidemiology / Q000208:ethnology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009790:Occupations; D018570:Risk Assessment; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000453:epidemiology* / Q000208:ethnology