School and household TB contact investigations in Swaziland: Active TB case finding in a high HIV/TB burden setting
Abstract
Background
Investigation of
household contacts exposed to infectious tuberculosis (TB) is
widely recommended by international guidelines to identify
secondary cases of TB and limit spread. There is little data to
guide the use of contact investigations outside of the
household, despite strong evidence that most TB infections occur
outside of the home in TB high burden settings. In older
adolescents, the majority of infections are estimated to occur
in school. Therefore, as part of a project to increase active
case finding in Swaziland, we performed school contact
investigations following the identification of a student with
infectious TB.
Methods
The Butimba Project
identified 7 adolescent TB index cases (age 10–20) with
microbiologically confirmed disease attending 6 different
schools between June 2014 and March 2015. In addition to
household contact investigations, Butimba Project staff worked
with the Swaziland School Health Programme (SHP) to perform
school contact investigations. At 6 school TB screening events,
between May and October 2015, selected students underwent
voluntary TB screening and those with positive symptom screens
provided sputum for TB testing.
Results
Among 2015 student contacts
tested, 177 (9%) screened positive for TB symptoms, 132 (75%)
produced a sputum sample, of which zero tested positive for TB.
Household contact investigations of the same index cases yielded
40 contacts; 24 (60%) screened positive for symptoms; 19
produced a sputum sample, of which one case was confirmed
positive for TB. The odds ratio of developing TB following
household vs. school contact exposure was significantly lower
(OR 0.0, 95% CI 0.0 to 0.18, P = 0.02) after exposure in school.
Conclusion
School-based contact
investigations require further research to establish best
practices in TB high burden settings. In this case, a
symptom-based screening approach did not identify additional
cases of tuberculosis. In comparison, household contact
investigations yielded a higher percentage of contacts with
positive TB screens and an additional tuberculosis case.
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Source:
PLOS ONE
