Territory Stories

The Northern Territory Disease Control Bulletin



The Northern Territory Disease Control Bulletin

Other title

Disease Control Bulletin


Territory Health Services, Centre for Disease Control


Northern Territory disease control bulletin; E-Journals; PublicationNT; Northern Territory disease control bulletin






Date:2002-03; This publication contains may contain links to external sites. These external sites may no longer be active.; Made available via the Publications (Legal Deposit) Act 2004 (NT).




Communicable diseases; Reporting; Northern Territory; Statistics; Periodicals

Publisher name

Northern Territory Government

Place of publication



Northern Territory disease control bulletin


v. 9 no. 1

File type





Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government



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The Northern Territory Disease Control Bulletin Vol 9, No.1, March 2002 6 Introduction Mantoux screening of school-aged children in the Northern Territory (NT) has been carried out for decades, but the purpose and target groups of the screening have changed. Initially Mantoux screening determined whether a student was Mantoux negative and should be offered a BCG vaccination. Gradually the emphasis was placed on identifying those who were Mantoux positive for evaluation. In 1991 the policy of giving BCG to Mantoux negative students was stopped and BCG was only recommended for Aboriginal newborns or those up to 5 years of age living in Aboriginal communities or travelling/living for more than 3 months in high risk TB countries. However, screening continued from 1991 with the aim of determining levels of latent TB infection (LTBI) in the school population and offering treatment as appropriate to those students with LTBI (as reflected by a positive Mantoux and clinical examination). From 1991 to 1997 the screening program included all 10 year old students in rural communities. In the urban schools it included initially all Year 9 students and then switched to Year 8 students. A review in 1996 revealed that in the years 1991-94 Australian born non-Aboriginal students had significantly lower prevalence of positive Mantoux reactions (2.0%) regardless of where their parents were born, while Aboriginal students and children born overseas had a significantly higher prevalence (4.3% and 8.6% respectively). On this basis Australian born nonAboriginal students (except those living in Aboriginal communities) were excluded and efforts were directed towards screening Aboriginal children and those born overseas. CDC coordinated the program and collected data from the outset. A brief review of the 1991 to 2000 data was undertaken, with the aim of determining the trends in Mantoux status over time, whether the 1997 change to targeted screening was successful and to assess outcomes of screening for the year 2000. Method An extract of the database was analysed in EpiInfo. Included were all students aged 9-16 years inclusive who underwent Mantoux testing between 1991 and 2000. This range was chosen to include all children in the target age-groups (those aged 10 years in rural schools and Year 8 and 9 students - 12 to 15 years in urban schools) but also accepting those one year either side of the target group. Students outside this age group or whose ages were unknown were excluded (n=51). There were a number of students (n=464 or 3.0% of total) whose results were entered on the adult Mantoux database because they were outside the target age group and these were not included in the analysis. For the purposes of analysis the population was divided into three groups; Aboriginal students, Australian born non-Aboriginal students and overseas born students. Mantoux positive was defined as having a Mantoux reading of 10 mm or over without a history (or scar) of BCG vaccination or a Mantoux reading of 15 mm or over with a history (or scar) of BCG vaccination. Those 0 9 mm or 0 14 mm respectively were defined as Mantoux negative. A small number of students in whom BCG status was unknown with Mantoux readings between 10 and 14 mm were classified as negative (n=43). Outcome data, separate from the database, was collected for the 2000 calendar year. This included reviewing records to ascertain whether a student who was Mantoux positive in 2000 had been followed up appropriately (a clinical review and chest x-ray), offered treatment for LTBI and, if accepted, had completed treatment. An estimate of the number of students to be screened (ie the denominator) was derived from data from the Australian Bureau of Statistics (ABS). It was assumed that the target population for the years 1991-96 was a yearly cohort of children in the 10-14 year age bracket according to ABS estimates. The denominator for the years 1997-2000 was calculated using an extract of 1996 census data of the NT population by ethnicity and country of birth (requested from ABS for this purpose). The proportion of the 1996 cohort which would have been screened using the revised criteria (ie overseas born, Aboriginal or living in an Aboriginal community)a was applied to the subsequent years cohorts to give an estimate for each year. NT Mantoux school screening 1991 - 2000 Peter Markey, Lyn Barclay and Vicki Krause, CDC Darwin a According to the ABS 1996 census figures, 46.1% of children aged 10-14 years would have been the target group. This proportion was applied to future ABS estimates of the yearly cohort to calculate the denominator in subsequent years.