References in the content below refer to the PBMEF Guide.
Definitions
The number needed to screen (NNS) is the number of people that must be screened for symptoms of active TB disease to identify one person with TB during the reporting period.
"Screening" is defined at a minimum as verbal screening for TB symptoms to identify people to be referred for further clinical evaluation or testing for TB disease. It may include mobile chest X-ray (CXR), an increasingly important intervention in high TB burden settings.
Calculation: Numerator/Denominator
Numerator
Denominator
Ref # |
NNS
(Previously AF-7) |
Tier Level |
Project Level Indicators
|
Category |
Reach
|
Type |
Output
|
Unit of Measure |
Number of people
|
Data Type |
Integer
|
Disaggregations |
Age
Sex
Setting
|
Reporting Level |
National, subnational
|
Reporting Frequency |
Quarterly, monthly
|
The data sources are basic management unit TB register, screening register, presumptive TB register, laboratory register, or electronic management information systems available at tbe health facility and district level.
USAID invests in a variety of case finding approaches with the goal of closing the gap between estimated and notified people with TB. This indicator is important to help identify how effective these case finding strategies are.
The screening procedure used influences the percentage of evaluated people who are diagnosed with TB. A screening procedure that identifies only people at high risk for TB (e.g. cough lasting more than 2 weeks) may result in a low number NNS, but it also misses many people with TB that do not have such strong signs of TB risk. A screening procedure that identifies more people for testing (e.g., any TB symptom and/or abnormal CXR) may result in a higher number NNS, but it may also be successful in diagnosing more people.
As the incidence of TB falls, it should become more difficult to find active TB. As a result, it is reasonable to expect that if the comprehensive approach to TB succeeds in reducing TB incidence over time, the percentage of people diagnosed with TB will decrease. This is not to say that active case finding efforts should be halted.
Example charts/graphs:
- Trends over time comparisons
- Comparisons public vs private, rural vs urban and high risk subgroups
Indicator Visualizations
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