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

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General discussion Table 11.1 Completeness of thee tuberculosis registers in the Netherlands, Italy and England, ascertained after record-linkage and estimated after capture-recapture analysis Ascertained completeness Estimated completeness Notification (%) Laboratory (%) Hospital (%) The Netherlands 86.6* 67.1 40.7 Piedmont region, Italy 84.1 43.3 61.8 England 84.1 54.3 41.6 The Netherlands 86.4 65.0 35.7 Piedmont region, Italy 79.1 40.5 57.7 England 56.2 36.2 27.7 * 89.9% for culture-confirmed and verified tuberculosis patients and 92.7% after correction for possibly imperfect record-linkage and possibly imperfect positive predictive value of the hospital register Laboratory: The ascertained completeness of the laboratory register in the Netherlands is high compared to the two other studies, indicating efforts to establish bacteriological confirmation of the diagnosis. The lowest proportion of bacteriologically confirmed tuberculosis patients is found in Italy, suggesting that fewer attempts are made to confirm the diagnosis and more patients are treated on empirical grounds. After capture-recapture analysis, the estimated completeness of the laboratory register in the Netherlands and Italy do not change much but it strongly decreases in England due to the high estimated total number of tuberculosis patients. Hospital: In the Netherlands and England, the ascertained completeness of the hospital register is low, likely reflecting common policies of preferably treating tuberculosis patients as outpatients, including isolation at home for infectious patients. The high proportion of hospitalised tuberculosis patients in Italy suggests a policy of (initial) clinical analysis, diagnosis, treatment or isolation. After capture-recapture analysis, the estimated completeness of the hospital register in the Netherlands and Italy slightly decrease but this effect is most profound in England due to the high estimated total number of tuberculosis patients. 167
Chapter 11 Question 3: What is the feasibility and validity of truncated population estimation models in infectious disease surveillance? For priority setting, service planning and resource allocation it is necessary to know the number of persons in a targeted group. This number can also be used to assess the coverage of an intervention. Often direct (enumeration) techniques are not feasible to estimate the size of hidden populations. Instead, indirect techniques such as capturerecapture analysis have to be used. Paradoxically, for hidden populations often the preferred three linked registers, allowing for log-linear capture-recapture analysis in order to reduce bias in the estimates, are not available. As an alternative, truncated models, related to capture-recapture analysis, and applicable to frequency counts of observations of individuals in a single source of information, are described in the literature. Two such truncated models are Zelterman’s Poisson mixture model and Chao’s heterogeneity model. 24-26 These models aim to estimate the number of unobserved persons in the (truncated) zero-frequency class based upon information from the lower observed frequency classes, assuming a specific truncated distribution of the observed data, e.g. Poisson in Chao’s model. Observed frequency distributions may not be strictly Poisson and to relax this assumption Zelterman based his model on a Poisson mixture distribution, allegedly allowing greater flexibility and applicability on real life data. The validity of truncated model estimates depends on the possible violation of the underlying assumptions, similar to capture-recapture analysis as described earlier, although the independent registers assumption is replaced by the constant (re)observation probability assumption when using a single data source. In addition, equiprobability (i.e. equal ascertainment probabilities of all registers) should be assumed when using multiple sources. This violation could be as much, possibly even more, as for capture-recapture analysis. 11 We estimated the coverage of a tuberculosis control intervention, a targeted mobile tuberculosis screening programme among illicit drug users and homeless persons in Rotterdam. Application of truncated models was feasible because this screening programme uses a single register. Although capture-recapture techniques for estimating the size of a population from a single register have been described occasionally, 27-29 for feasibility one prefers the simplest technique with almost similar assumptions. We could extract, check and prepare the required data from the existing routine dataset in two days and calculate the point estimates on a pocket calculator. Violation of the perfect recordlinkage assumption is considered minimal because of good computerised and visual identification of the clients in the screening programme. However, the closed population assumption is violated because every year a substantial number of people not previously screened enter the programme, resulting in under-estimation of the coverage. We cannot exclude heterogeneity among individuals belonging to the target group of the screening programme but this could cause limited bias in the model estimates. Truncated models are arguably more robust to violation of the homogeneity assumption since they are partly based upon the lower frequency classes, assumed to have more resemblance to the zero frequency class. The constant (re)observation probability assumption will be violated as well to some extent but this effect could be limited due to the nature and organisation of 168
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Capture-recapture Methods in Survei
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Colofon Capture-recapture methods i
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Promotiecommissie Promotor: Prof.dr
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Contents Page 1 Introduction 9 2 Me
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Chapter 1 1.1 Assessing completenes
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Chapter 1 94% among AIDS patients w
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Table 1.1 Objectives, methods, data
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Researchers Objective Method Data-s
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Chapter 1 source capture-recapture
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Chapter 1 32. Bradley BL, Kerr KM,
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2 Methodology of capture-recapture
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Methodology of capture-recapture an
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Chapter 3 3.1 Application of captur
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Table 3.1 Published capture-recaptu
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Disease Authors Objective Method Da
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Chapter 3 3.3 References 1. Hook EB
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Chapter 3 52. Reintjes R, Termorshu
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Chapter 4 Abstract The aim of this
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Chapter 4 Methods Nearly all Dutch
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Chapter 4 Table 4.2 The number of m
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Chapter 4 diagnosis. Other patients
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Chapter 4 stratify the population i
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Chapter 4 25. Lambeth, Southwark an
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Chapter 5 Abstract To estimate inci
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Chapter 5 patients. Capture-recaptu
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Chapter 5 Figure 5.1 Four regions o
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Chapter 5 Hospital records From 385
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Chapter 5 Table 5.1 Epidemiological
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Table 5.2 Number and proportion of
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Chapter 5 cautious about the associ
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Chapter 5 Incidence of community-ac
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Chapter 6 Abstract The aim of this
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Chapter 6 3. Hospitalised patients
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Chapter 6 Record-linkage of all 537
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Chapter 6 Figure 6.1 Schematic view
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Chapter 6 Table 6.2 Total and strat
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Chapter 6 administrative discrepanc
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Chapter 6 the patients, and complet
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7 Undetected burden of tuberculosis
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Introduction Underreporting of tube
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Underreporting of tuberculosis in t
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Table 7.1 Total and subset numbers
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Table 7.2 Capture-recapture estimat
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Chapter 8 Abstract In 1999 the Enha
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Chapter 8 bacteriological confirmat
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Chapter 8 Results Table 8.1 shows t
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Page 119 and 120: Table 8.4 Annual and overall estima
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Page 126 and 127: 9 Estimating the coverage of tuberc
Page 128 and 129: Introduction Estimating targeted mo
Page 130 and 131: Estimating targeted mobile tubercul
Page 136 and 137: References Estimating targeted mobi
Page 138 and 139: 10 Estimating infectious diseases i
Page 140 and 141: Introduction Estimating infectious
Page 142 and 143: Estimating infectious disease incid
Page 144 and 145: Study Disease and number of patient
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Page 148 and 149: Table 10.3 Comparison of the variou
Page 150 and 151: Discussion Estimating infectious di
Page 156: Estimating infectious disease incid
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Page 161 and 162: Chapter 11 overestimation of the nu
Page 163 and 164: Chapter 11 clinicians to the Public
Page 165 and 166: Chapter 11 operation with the chest
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Page 171 and 172: Chapter 11 11.2 Some findings of th
Page 173 and 174: Chapter 11 • To improve timelines
Page 176 and 177: Summary Summary Surveillance is an
Page 178 and 179: Summary linkage of notification and
Page 180 and 181: Samenvatting Samenvatting Surveilla
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Page 184 and 185: Acknowledgements Acknowledgements W
Page 186 and 187: Curriculum vitae Rob van Hest was b
Page 188 and 189: Publications This thesis Van Hest N
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