BMC Infectious Diseases (Sep 2007)

Low tuberculosis notification in mountainous Vietnam is not due to low case detection: a cross-sectional survey

  • Sy DN,
  • Hoa NB,
  • Vree M,
  • Co NV,
  • Cobelens FGJ,
  • Borgdorff MW

DOI
https://doi.org/10.1186/1471-2334-7-109
Journal volume & issue
Vol. 7, no. 1
p. 109

Abstract

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Abstract Background Studies show that tuberculosis notification declines with increasing altitude. This can be due to declining incidence or declining case detection. In Vietnam notification rates of new smear-positive tuberculosis in the central mountainous provinces (26/100,000 population) are considerably lower than in Vietnam in general (69/100,000 population). In order to clarify whether this is explained by low incidence or low case detection, we aimed to assess the prevalence of new smear-positive tuberculosis among adults with prolonged cough in three mountainous provinces in central Vietnam. Methods A house-to-house survey of persons (≥ 15 years) was carried out in twelve randomly selected districts in 2003. Three sputum specimens were microscopically examined of persons reporting a prolonged cough (≥ 3 weeks). Case detection was assessed by the ratio between notification and prevalence. Results Of 68,946 included persons (95% response), 1,298 (1.9% 95%CI 1.8–2.2) reported a prolonged cough. Of these, eighteen were sputum smear-positive of whom two had had anti-tuberculosis treatment. The prevalence of new smear-positive tuberculosis was 27/100,000 (95%CI 11–44/100,000) and the notification rate was 44/100,000 among persons ≥ 15 years. The estimated case detection rate was 76%. Conclusion Low tuberculosis notification in this mountainous setting is probably a true reflection of low tuberculosis incidence. Possible causes for low incidence in mountainous areas include low transmission rates or altitude-related differences in pathology.