Rob van Hest Capture-recapture Methods in Surveillance - RePub ...

General discussion
Homogeneous population assumption
Possible heterogeneity of the patient population, i.e. the presence of categorical covariates
associated with the probability of capture in a register, causing bias in the capturerecapture
estimate, cannot be excluded in the three infectious diseases studies and was
examined in three different ways. For the malaria study we performed a stratified capturerecapture
analysis by Plasmodium species which showed limited variety in capture-recapture
probabilities. However, we cannot exclude the possible presence of other (but
unmeasured) sources of heterogeneity,
For the tuberculosis data, after conventional log-linear capture-recapture
analysis, we applied alternative truncated population estimation models, arguably more
robust in the presence of heterogeneity, and these models gave identical results.
Because regional differences in the incidence rate of Legionnaires’ disease were
described in the Netherlands and abroad, 6,14 and observed in our data after recordlinkage,
alternative to conventional log-linear capture-recapture analysis a log-linear
covariate capture-recapture model was specified, with region as covariate, to reduce bias
due to geographical heterogeneity. The better goodness-of-fit and narrow confidence
interval suggest a more valid estimate with less statistical uncertainty compared to the
outcome of the conventional saturated model. Unfortunately, the data-quality of the
hospital episode register prevented meaningful inclusion of other covariates in the model,
possibly causing bias, such as the method of laboratory diagnosis, described as a relevant
covariate elsewhere. 6 At the time of the malaria and tuberculosis studies we were not
familiar with covariate capture-recapture techniques and did not explore this
methodology to investigate the impact of possible heterogeneity.
Question 2
How do the characteristics of tuberculosis surveillance systems in different
countries influence the feasibility and validity of capture-recapture analysis?
Different characteristics of tuberculosis surveillance systems can influence the feasibility
and validity of capture-recapture analysis. In this thesis we describe three three-source
log-linear capture-recapture studies on tuberculosis incidence and completeness of
notification in three different European countries, the Netherlands, the Piedmont region
of Italy and England, at a different scale, both administrative and regarding the number of
patients involved, and with different tuberculosis surveillance systems. The feasibility and
validity of these studies will be discussed by country, after a short introduction to
tuberculosis surveillance in each country, followed by a comparison of the results of the
three tuberculosis capture-recapture studies.
The Netherlands
In the Netherlands the annual national tuberculosis incidence has been decreasing during
the last decade. This can be partially explained by the nation-wide system of Public Health
Tuberculosis Clinics, with public health tuberculosis physicians and nurses, performing
diagnostic, curative, preventive and screening activities, parallel to and in good co-
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