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Evaluation of Surveillance Systems
St Lukes-Roosevelt
Problems with our field
Programs often do more harm than good
Programs don’t collect data, so no benefit shown
The data we do collect is often not useful for improving program quality or guiding policy
How do we show benefit, impact, change?
Surveillance Ongoing
Surveys One point in time
Definition
Public health surveillance is the ongoing, systematic collection, analysis, interpretation, and dissemination of data regarding a health-related event for use in public health action to reduce morbidity and mortality to improve health
*CDC, Atlanta GA
Key concept
Ongoing Action
Why evaluate a surveillance system?
Ensure that problems of public health importance are being monitored efficiently and effectively
Recommendations about the system should focus on improving quality, efficiency, and usefulness
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality Acceptability Sensitivity Predictive value positive Representativeness Timeliness Stability
What should be evaluated?
System attributes: determine priorities Simplicity: combine a practical structure with ease of use Flexibility Data quality Acceptability Sensitivity Predictive value positive Representativeness Timeliness Stability
Figure 1: Monthly attendance by diagnosis following December drug distribution, Matoumbou Clinic, Kinkala
Dist., R.O.Congo
0
50
100
150
200
250
300
Jan. Feb. Mar. Apr.
Pa
tie
nt
Vis
its Other
Para.
Dia.
ARI
Mal./Fev.
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility: ability to adapt to changing information needs or
operating conditions with minimal time, effort, cost Data quality Acceptability Sensitivity Predictive value positive Representativeness Timeliness Stability
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality: completeness and validity Acceptability Sensitivity Predictive value positive Representativeness Timeliness Stability
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality Acceptability: willingness of persons or organizations to
participate Sensitivity Predictive value positive Representativeness Timeliness Stability
Contraceptive prevalence rates in Afghanistan, WHO
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality Acceptability Sensitivity: ability to detect cases OR ability to detect outbreaks Predictive value positive Representativeness Timeliness Stability
Incidence* of Shigella Dysentery
Central Bosnia, 1991-1993
Region Prewar May-July 1993
Sarajevo City 0.3 4.0 (+1250%)
Zenica City 0.3 4.4 (+1690%)
Tuzla Region 0.5 0.4 (-10%)
*Cases per 100,000 per month
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality Acceptability Sensitivity Predictive value positive: proportion of persons identified as
cases who truly are cases Representativeness Timeliness Stability
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality Acceptability Sensitivity Predictive value positive Representativeness: system accurately describes events over
time and space (time, person, place) Timeliness Stability
Causes of death, Kenema District, 2000 N=197
Febrile Illness39%
Chronic Conditions
4%
Unknown/Others18%
Trauma/Viol.3%
Bloody Diarrhoea
3%Diarrhoea
12%
Maternal deaths
2%
Miscellaneous Infections
5%
Neonatal deaths
5%
Resp. Infect.9%
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality Acceptability Sensitivity Predictive value positive Representativeness Timeliness: speed between steps; appropriateness in delays Stability
Epidemic curve, outbreak of mumps, Montreal
Epidemic curve, cholera
What should be evaluated?
System attributes: determine priorities Simplicity Flexibility Data quality Acceptability Sensitivity Predictive value positive Representativeness Timeliness Stability: reliability and availability; resources
Steps in evaluating a surveillance system
Stakeholder engagement
Describe the system: importance, purpose, resources
Focus the evaluation design
**Gather evidence regarding performance
Justify and state conclusions, make recommendations
Malaria Surveillance
Purpose (CDC): (a) identify local transmission; (b) guide prevention recommendations for travelers
Additional benefits (JE) Identify emerging species; treatment failures; local outbreaks
Historically Tracking elimination
Case definition Malaria cases confirmed by blood film, rapid diagnostic tests,
PCR
Malaria Surveillance
The system **National Malaria Surveillance System National Notifiable Disease Surveillance System
(1878 cholera, smallpox, plague, yellow fever at overseas consules)
Direct CDC consultation