Low tuberculosis notification in mountainous Vietnam is not due to low case detection: a cross-sectional survey.
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 (> or = 15 years) was carried out in twelve randomly selected districts in 2003. Three sputum specimens were microscopically examined of persons reporting a prolonged cough (> or = 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 > or = 15 years. The estimated case detection rate was 76%.


CONCLUSIONS
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.
Vree
M
M
KNCV Tuberculosis Foundation, The Hague, The Netherlands. vreem@kncvtbc.nl
Hoa
N B
NB
Sy
D N
DN
Co
N V
NV
Cobelens
F G J
FG
Borgdorff
M W
MW
D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D018563:Disease Notification; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification; D012424:Rural Population; D018571:Sentinel Surveillance; D013183:Sputum / Q000382:microbiology; D011795:Surveys and Questionnaires; D014397:Tuberculosis, Pulmonary / Q000517:prevention & control*; D014744:Vietnam / Q000453:epidemiology