Australia Trachoma Surveillance Report 2011

Appendix 3: Methods for estimating number of people requiring treatment

Page last updated: 09 April 2013

As stated in the Methods section, two approaches are used to estimate the denominator of the number of people requiring treatment for each region. The methods are based on the following assumptions:

Method 1 (targeted treatment) assumes that if a community has reported the number of contacts requiring treatment then this number is correct, and contacts are only estimated when this number is not reported. In the case that community treatment is required, it is assumed that all children in the community aged six months to 14 years as well as household contacts of active cases require treatment.

Method 2 (whole community treatment) additionally estimates the number of contacts requiring treatment, assuming that all members of the community require treatment if community treatment is required, rather than just those aged six months to 14 years and household contacts of active cases.

Each approach follows the following steps but the two methods only differ in points d and e of Step 2.

Step 1: Estimate the average number of contacts of each active case in jurisdiction

  • For each community where household treat-ment is reported, calculate the average number of contacts requiring treatment per active case by dividing total number of contacts by total number of active cases.
  • Calculate the unweighted average number of contacts per active case in each jurisdiction by averaging over each the estimates in (a) for each community in the jurisdiction.

Step 2: Estimate the number of community and household contacts requiring treatment

a. If trachoma prevalence in children aged 1-9 years is less than 10% go to (b), otherwise go to (d).

b. If number of household and community contacts requiring treatment is given, take this number as the true number of household and community contacts requiring treatment and exit algorithm, otherwise go to (c).

c. Estimate number of contacts requiring treatment as (Number of active cases of trachoma in the community) multiplied by (average number of contacts per active case in communities which used household treatment strategy in the jurisdiction) and exit algorithm.

Method 1

d. If number of household and community contacts requiring treatment is given, take this number as the true number of household and community contacts requiring treatment and exit algorithm, otherwise go to (e).

e. Estimate number of contacts requiring treatment as Reported (during screening) number of children in community aged 1-14 years plus (Number of active cases if trachoma in the community) multiplied by (average number of contacts per active case in communities which used household treatment strategy in the juris-diction) and exit algorithm.

Method 2

d. If community reports clustering of cases and the number of household contacts is reported, take this number as the true number of household and community contacts requiring treatment and exit algorithm, otherwise go to (e).

e. Estimate the total number of persons (active cases and contacts) in the community who require treatment as the total population of the community using ABS data and exit algorithm.