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COVID-19 contact tracing at work in Belgium - how tracers tweak guidelines for the better
Jerome Kieltyka1, Jinane Ghattas2, Sandrine Ruppol3
1CESI ASBL, Avenue Konrad Adenauer 8, 1200, Woluwe-Saint-Lambert, Belgium. jerome.kieltyka@gmail.com.
Insights
COVID-19 contact tracers in Belgium did not consistently follow guidelines for classifying high-risk contacts (HRC) and low-risk contacts (LRC). However, their practical risk stratification better predicted infection risk than guidelines alone.
Area of Science:
- Public Health
- Epidemiology
- Infectious Disease Control
Background:
- COVID-19 contact tracing relies on pre-defined criteria to distinguish high-risk contacts (HRC) from low-risk contacts (LRC).
- Evaluating the adherence of contact tracers to these established criteria is crucial for effective infection control.
Purpose of the Study:
- To assess whether contact tracers in Belgium applied the official criteria for HRC and LRC classification in practice.
- To determine if deviations from guidelines by contact tracers improved the accuracy of infection risk assessment.
Main Methods:
- A retrospective cohort study was conducted in Belgium using an anonymous online survey distributed to 111,763 workers.
- Concordance between guideline-based and tracer-based risk classifications was evaluated using positive and negative agreement metrics.
- Multivariate Poisson regression analyzed the risk ratio (RR) of testing positive based on both classification methods.
Main Results:
- Positive agreement between guideline-based and tracer-based HRC/LRC classification was 0.53, with negative agreement at 0.70.
- Contact tracers' risk stratification showed a higher RR of testing positive (3.10) compared to guideline-based criteria (2.24).
- The type of contact tracer did not significantly impact the classification results.
Conclusions:
- Contact tracers in Belgium did not consistently adhere to pre-defined criteria for classifying high and low-risk contacts.
- The practical risk stratification by contact tracers demonstrated a superior ability to predict infection risk compared to guidelines alone.
- Findings suggest a need to re-evaluate and potentially adapt current contact tracing guidelines to incorporate the insights gained from experienced tracers.
Background:
When conducting COVID-19 contact tracing, pre-defined criteria allow differentiating high-risk contacts (HRC) from low-risk contacts (LRC). Our study aimed to evaluate whether contact tracers in Belgium followed these criteria in practice and whether their deviations improved the infection risk assessment.
Method:
We conducted a retrospective cohort study in Belgium, through an anonymous online survey, sent to 111,763 workers by email. First, we evaluated the concordance between the guideline-based classification of HRC or LRC and the tracer's classification. We computed positive and negative agreements between both. Second, we used a multivariate Poisson regression to calculate the risk ratio (RR) of testing positive depending on the risk classification by the contact tracer and by the guideline-based risk classification.
Results:
For our first research question, we included 1105 participants. The positive agreement between the guideline-based classification in HRC or LRC and the tracer's classification was 0.53 (95% CI 0.49-0.57) and the negative agreement 0.70 (95% CI: 0.67-0.72). The type of contact tracer (occupational doctors, internal tracer, general practitioner, other) did not significantly influence the results. For the second research question, we included 589 participants. The RR of testing positive after an HRC compared to an LRC was 3.10 (95% CI: 2.71-3.56) when classified by the contact tracer and 2.24 (95% CI: 1.94-2.60) when classified by the guideline-based criteria.
Conclusion:
Our study indicates that contact tracers did not apply pre-defined criteria for classifying high and low risk contacts. Risk stratification by contact tracers predicts who is at risk of infection better than guidelines only. This result indicates that a knowledgeable tracer can target testing better than a general guideline, asking for a debate on how to adapt the guidelines.
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