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

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Underreporting of tuberculosis in England likely to be managed by clinicians familiar with notification of infectious diseases. Apart from under-estimating the burden of tuberculosis, the implications for public health are limited as extrapulmonary tuberculosis patients are rarely infectious. 2. We tested our data using Zelterman’s truncated Poisson mixture model, which is also vulnerable to possible violation of underlying assumptions. 34 This estimator and similar ones have been used in social sciences to estimate the size of hidden populations such as illicit drug users and homeless persons. 33,35-37 A recent publication compares three-source capture-recapture model estimates with the estimates of truncated models, including Zelterman’s model, for 19 datasets of infectious disease incidence and discusses the conditions where these estimates are similar or dissimilar. 38 The results of this study suggest that for estimating infectious disease incidence and completeness of notification independent (i.e. without pair-wise interdependencies between the data sources) and parsimonious (i.e. incorporating one or two pair-wise interdependencies between the data sources) three-source loglinear capture-recapture models are preferable. However, when saturated models are selected as best fitting model and the estimates are unexpectedly high and seem implausible the data should be re-examined with truncated models as a heuristic tool, in the absence of a gold standard, to identify possible failure in the saturated loglinear model. When the truncated models produce a lower and more plausible estimated number of infectious disease patients arguments are given that the estimates of the truncated models could be preferable. Table 8.5 shows the annual and overall estimated numbers of unobserved and total tuberculosis cases. The estimated numbers of unobserved tuberculosis cases were low compared to the structural source model, especially in 1999. From 2000 onwards the estimates reduce every year. According to Zelterman’s model estimated completeness of Notification was 68.5%, 63.8%, 73.6% and 76.4% for the years 1999-2002 respectively. The confidence intervals do not overlap with the other models but include expected values of under-notification in 2001 and 2002. Hook and Regal state that “In no sense is there any proof or re-assurance that application of multiple-source log-linear estimators for any particular observed data on real populations results in a valid estimate, nor even necessarily produce an estimate closer to the true value than some alternative approach” and “if the saturated log-linear model is selected by any criterion the investigator should be particularly cautious about using the associated outcome”. 12 Confidence in the validity of capture-recapture results may reflect publication bias in favour of successful capture-recapture studies rather than the inherent strength of this methodology. 39 Conclusion Record-linkage, as performed in Enhanced Tuberculosis Surveillance, improves accuracy of surveillance data as well as completeness of case-ascertainment of tuberculosis. Hospital-derived data added a limited number of possible true tuberculosis patients. Since the introduction of Enhanced Tuberculosis Surveillance the annual observed completeness of notification has increased. This is most likely due to improvements in case-reporting combined with improved data collection and record-linkage. This study 121
Chapter 8 shows that observed under-notification of tuberculosis cases in England might be as high as 10.4% as these cases were laboratory-confirmed but not notified. The overall observed under-notification was 15.9% which is consistent with prior reports. Overall undernotification estimated by a saturated log-linear capture-recapture model is highly inconsistent with prior reports and could be an over-estimate due to violation of the underlying assumptions, especially the homogeneity assumption as suggested by the alternative models. Instead of capture-recapture analysis including hospital episode registers, record-linkage and case-ascertainment using the two most relevant sources for infectious disease surveillance, namely notification and laboratory, both with an expected high specificity and hence positive predictive value, as performed in Enhanced Tuberculosis Surveillance, will often already considerably improve the knowledge of the number of patients and infectious disease incidence rates, as well as the completeness of information on specific demographic, diagnostic or epidemiological variables. All unlinked laboratory cases in addition to the notifications are by definition tuberculosis cases. According to Zelterman’s truncated model, in England and Wales the estimated completeness of the notification and laboratory records combined was 78.2%, 74.1%, 81.0% and 83.8% for the years 1999 - 2002 respectively, all within the expected range of under-notification and consistent with the results of parsimonious capture-recapture model estimates in some other European countries. 9,20 Approaching and encouraging the clinicians treating the culture-positive tuberculosis cases not linked to Notification to notify these patients, considering the unlinked MycobNet cases as “pre-notifications”, would increase the completeness of the notifications register. Acknowledgements We thank David Quinn for designing the record-linkage software and processing the record-linkage procedures, Charlotte Anderson for providing the MOTT data and Valerie Delpech and Filip Smit for their suggestions on alternative models. References 1. Health Protection Agency. Tuberculosis cases reported, England and Wales, 1988, 1993, 1998 – 2005 (http://www.hpa.org.uk/infections/topics_az/tb/epidemiology/ table14.htm). Accessed 23 May 2007. 2. Rose AM, Gatto AJ, Watson JM. Recent increases in tuberculosis notifications in England and Wales – real or artefact? J Public Health Med 2002: 24: 136-37. 3. Pillaye J, Clarke A. An evaluation of completeness of tuberculosis notification in the United Kingdom. BMC Public Health 2003; 1: 31. 4. Van Buynder P. Enhanced surveillance of tuberculosis in England and Wales: circling the wagons? Commun Dis Public Health 1998; 1: 219-20. 5. Sheldon CD, King K, Cock H, Wilkinson P, Barnes NC. Notification of tuberculosis: how many cases are never reported. Thorax 1992; 47: 1015-8. 6. Roderick PJ, Connelly JB. The problems of monitoring tuberculosis in an inner-city health district: integrated information is required. Public Health 1992; 106: 193-201. 7. Devine MJ, Aston R. Assessing the completeness of tuberculosis notification in a health district. Comm Dis Rep 1995; 5: R137-140. 8. Mukerjee AK: Ascertainment of non-respiratory tuberculosis in five boroughs by comparison of multiple data source Commun Dis Public Health 1999; 2: 143-4. 9. International Working Group for Disease Monitoring and Forecasting. Capture-recapture and multiplerecord estimation I: History and theoretical development. Am J Epidemiol 1995; 142: 1047-58. 10. Fienberg SE. The multiple-recapture census for closed populations and the 2 k incomplete contingency table. Biometrika 1972; 59: 591-603. 11. Bishop YMM, Fienberg SE, Holland PW. Discrete Multivariate Analysis. Cambridge: MIT-Press, 1975. 122
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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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Page 98 and 99: Introduction Underreporting of tube
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Page 128 and 129: Introduction Estimating targeted mo
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Page 136 and 137: References Estimating targeted mobi
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Page 140 and 141: Introduction Estimating infectious
Page 142 and 143: Estimating infectious disease incid
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Page 150 and 151: Discussion Estimating infectious di
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Chapter 11 • To improve timelines
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Summary Summary Surveillance is an
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Summary linkage of notification and
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Samenvatting Samenvatting Surveilla
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Acknowledgements Acknowledgements W
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Curriculum vitae Rob van Hest was b
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Publications This thesis Van Hest N
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