Measuring and maximizing coverage in the World Trade Center Health Registry

Abstract

The World Trade Center Health Registry (WTCHR) is a database for following people who were exposed to the disaster of 11 September 2001. Hundreds of thousands of people were exposed to the immense cloud of dust and debris, the indoor dust, the fumes from persistent fires, and the mental trauma of the terrorist attacks on the WTC on 9/11. The purpose of the WTCHR is to evaluate the potential short- and long-term physical and mental health effects of the disaster. The definitions of the exposed groups are broad and defined based on an understanding of which groups had the highest exposures to the WTC disaster and its aftermath. The four exposure groups include rescue and recovery workers, residents, students and school staff, and building occupants and passersby in Lower Manhattan. While one goal of the WTCHR was to maximize coverage overall and for each exposure group, another was to ensure equal representation within exposure groups. Because of the multiple sample types pursued, several approaches were required to determine eligibility. Estimates of the number of eligible persons in each of the exposed populations were based on the best available information including Census, entity-specific employment figures, and public and private school enrollment data, among other publicly available sources. To address issues of undercoverage and overcoverage a variety of methods were assessed or applied, including a capture-recapture analyses test of overlapping sample building list sources and automated deduplication of sample records. Estimates of the true eligible population indicate that over 400,000 unique individuals were eligible for the baseline health survey. Interviewer-administered surveys were completed with more than 71,000 persons, resulting in an overall enrollment rate of approximately 17 per cent. Coverage was highest among rescue and recovery workers, followed by residents, students and school staff, and building occupants. Both the accuracy of coverage estimates and the raw number and representativeness of enrollees were maximized by our approach to coverage. In designing a registry which relies on multiple pathways and sources of data to build the sample, it is important to develop a comprehensive approach that considers all sources of error and minimizes bias that may be introduced through the methodology.

Risk factors for and consequences of persistent lower respiratory symptoms among World Trade Center Health Registrants 10 years after the disaster

“…Extrapolating the prevalence of symptoms to the estimated 400 000 adults exposed to the WTC disaster, ∼25 000 experienced persistent LRS during the 12-month interval before W320 32 (see online supplementary appendix table S2). This generalisation, however, may be affected by study selection factors (see limitations below).…”

Asthma and Posttraumatic Stress Symptoms 5 to 6 Years Following Exposure to the World Trade Center Terrorist Attack

“…The methods and findings of W1 have been previously published. 4,7,9,11,12,25,27 The potential impact of selfselection bias in W1 registry enrollment has been described in other reports. Wave 1 studies examining either asthma or probable PTSD included subanalyses of list-identified participants to measure self-selection influences.…”

“…25 Disease rates for self-and listidentified enrollees from W2 were multiplied by the respective estimated population exposed. To address potential selection bias attributable to the higher prevalence of disease among selfvs list-identified persons, the midpoint estimate was based on disease rates among list-identified enrollees only.…”

Cigarette smoking and 9/11-related posttraumatic stress disorder among World Trade Center Health Registry enrollees, 2003–12

“…Details on Registry eligibility criteria, recruitment methods, and findings have been published elsewhere (Brackbill et al, 2009;Farfel et al, 2008;Murphy et al, 2007). In summary, Registry enrollees comprise rescue/recovery workers and volunteers; lower Manhattan residents; area workers; passers-by; and school children and staff.…”