Global Programme to Eliminate Lymphatic Filariasis (GPELF)
Training in monitoring and epidemiological assessment of mass drug administration for eliminating lymphatic filariasis
TAS
Module 3 Evaluation unit

By the end of this module, you should understand:
 How to define a survey area, known as an evaluation unit (EU).
Slide 2 Module 3 Evaluation unit

 Survey area for a TAS
 Defining an EU

Combining IUs

Dividing IU

Geographical area of an EU
Slide 3 Module 3 Evaluation unit

 If all the data from relevant IUs confirm that they are eligible for a TAS, planning can begin.
 The first step in designing a TAS is to define the survey area.
1. Survey area Evaluation unit
2. Survey site School Community
3. Sampling strategy Cluster-based sampling Systematic sampling
4. Sample size Sample size and critical cut-off
Census
Slide 4 Module 3 Evaluation unit

 Implementation unit (IU) : The administrative unit in a country used for MDA
 Evaluation unit (EU) : An area selected for a TAS
Slide 5 Module 3 Evaluation unit

IUs within an EU can be combined, divided or remain the same, but all IUs in a country in which MDA is conducted must be included in a TAS.
 IUs in an EU are usually contiguous.

All IUs in an EU should have had at least five effective rounds of
MDA (i.e. ≥ 65% total population) and meet all the eligibility criteria for conducting a TAS .

All areas in the EU should have similar epidemiological features and
LF transmission dynamics (e.g. epidemiological drug coverage, baseline prevalence, prevalence of Mf or Ag in sentinel and spotcheck sites, principal parasites, vector abundance).
 The population should not exceed 2 million.
Slide 6 Module 3 Evaluation unit

1
2
3
Unit
Total population
Baseline Mf prevalence (%)
MDA coverage (%)
Sentinel site Mf prevalence (%)
(after fifth round)
Spot-check site
Mf prevalence
(%)
32 983
101 438
52 138
2.1
3.4
2.9
#1 #2 #3 #4 #5
81 69 79 76 76
78 67 77 72 76
75 70 72 76 68
1
2
3
0
0.3
0.1
Endemic IU
MDA
0
0.1
0.1
Slide 7 Module 3 Evaluation unit

Total population
Baseline Mf prevalence (%)
MDA coverage (%)
Sentinel site Mf prevalence (%)
(after fifth round)
Spot-check site
Mf prevalence
(%)
#1 #2 #3 #4 #5
79 66 71 74 72 2 647 953 2.8
0.2
0.3
1
3
2
Endemic IU
MDA
Sub-district Total population
1
2
3
798 234
989 436
860 283
Baseline Mf prevalence (%)
1.8
5.4
1.2
Slide 8 Module 3 Evaluation unit

 Although there is no upper limit to the geographical area of an EU, the following considerations should be taken into account when combining IUs:

The probability that foci of infection will be missed increases as the geographical area of the EU increases.

Covering a larger area during the survey may increase logistical requirements (e.g. transport costs).
Slide 9 Module 3 Evaluation unit

Using existing data (e.g. maps, list of IUs, population sizes, number of rounds of MDA and coverage).
1.
Define an appropriate EU(s).
Note: Some of the data will have been reported on the
‘ELIGIBILITY’ worksheet of the TAS Eligibility and Reporting Form
2.
Present the defined EU(s) to the group.
Slide 10 Module 3 Evaluation unit