Spatial distribution of people diagnosed with tuberculosis through routine and active case finding: a community-based study in Kampala, Uganda
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
Infectious diseases of poverty
Abstract
Routine tuberculosis (TB) notifications are geographically heterogeneous, but their utility in predicting
the location of undiagnosed TB cases is unclear. We aimed to identify small-scale geographic areas with high TB
notification rates based on routinely collected data and to evaluate whether these areas have a correspondingly
high rate of undiagnosed prevalent TB.
Methods: We used routinely collected data to identify geographic areas with high TB notification rates and
evaluated the extent to which these areas correlated with the location of undiagnosed cases during a subsequent
community-wide active case finding intervention in Kampala, Uganda. We first enrolled all adults who lived within
35 contiguous zones and were diagnosed through routine care at four local TB Diagnosis and Treatment Units. We
calculated average monthly TB notification rates in each zone and defined geographic areas of “high risk” as zones
that constituted the 20% of the population with highest notification rates. We compared the observed proportion
of TB notifications among residents of these high-risk zones to the expected proportion, using simulated estimates
based on population size and random variation alone. We then evaluated the extent to which these high-risk zones
identified areas with high burdens of undiagnosed TB during a subsequent community-based active case finding
campaign using a chi-square test. Results: We enrolled 45 adults diagnosed with TB through routine practices and who lived within the study area
(estimated population of 49 527). Eighteen zones reported no TB cases in the 9-month period; among the
remaining zones, monthly TB notification rates ranged from 3.9 to 39.4 per 100 000 population. The five zones with
the highest notification rates constituted 62% (95% CI: 47–75%) of TB cases and 22% of the population–significantly
higher than would be expected if population size and random chance were the only determinants of zone-to-zone
variation (48%, 95% simulation interval: 40–59%). These five high-risk zones accounted for 42% (95% CI: 34–51%) of
the 128 cases detected during the subsequent community-based case finding intervention, which was significantly
higher than the 22% expected by chance (P < 0.001) but lower than the 62% of cases notified from those zones
during the pre-intervention period (P = 0.02).
Conclusions: There is substantial heterogeneity in routine TB notification rates at the zone level. Using facilitybased
TB notification rates to prioritize high-yield areas for active case finding could double the yield of such casefinding
interventions.
Description
Keywords
Tuberculosis, Epidemiology, Health system, Geographic information systems
Citation
Robsky, K. O., Kitonsa, P. J., Mukiibi, J., Nakasolya, O., Isooba, D., Nalutaaya, A., ... & Dowdy, D. (2020). Spatial distribution of people diagnosed with tuberculosis through routine and active case finding: a community-based study in Kampala, Uganda. Infectious diseases of poverty, 9(1), 1-10. https://doi.org/10.1186/s40249-020-00687-2