Use of World Wide Web-based directories for tracing subjects in epidemiologic studies

A successful implementation of e-epidemiology: the Danish pregnancy planning study 'Snart-Gravid'

The attraction of being able to use the internet for the recruitment of an epidemiologic cohort stems mainly from cost efficiency and convenience. The pregnancy planning study ('Snart-Gravid')-a prospective cohort study of Danish women planning a pregnancy-was conducted to evaluate the feasibility and cost efficiency of using internet-based recruitment and follow-up. Feasibility was assessed by examining patient accrual data over time, questionnaire-specific response rates and losses to follow-up. The relative cost efficiency was examined by comparing the study costs with those of an alternative non internet-based study approach. The target recruitment of 2,500 participants over 6 months was achieved using advertisements on a health-related website, supported by a coordinated media strategy at study initiation. Questionnaire cycle-specific response rates ranged from 87 to 90% over the 12-month follow-up. At 6 months, 87% of women had a known outcome or were still under follow-up; at 12 months the figure was 82%. The study cost of $400,000 ($160 per enrolled subject) compared favorably with the estimated cost to conduct the same study using a conventional non-internet based approach ($322 per subject). The gain in efficiency with the internet-based approach appeared to be even more substantial with longer follow-up and larger study sizes. The successful conduct of this pilot study suggests that the internet may be a useful tool to recruit and follow subjects in prospective cohort studies.

Predictors of locating women six to eight years after contact: internet resources at recruitment may help to improve response rates in longitudinal research

BACKGROUND

The ability to locate those sampled has important implications for response rates and thus the success of survey research. The purpose of this study was to examine predictors of locating women requiring tracing using publicly available methods (primarily Internet searches), and to determine the additional benefit of vital statistics linkages.

METHODS

Random samples of women aged 65-89 years residing in two regions of Ontario, Canada were selected from a list of those who completed a questionnaire between 1995 and 1997 (n = 1,500). A random sample of 507 of these women had been searched on the Internet as part of a feasibility pilot in 2001. All 1,500 women sampled were mailed a newsletter and information letter prior to recruitment by telephone in 2003 and 2004. Those with returned mail or incorrect telephone number(s) required tracing. Predictors of locating women were examined using logistic regression.

RESULTS

Tracing was required for 372 (25%) of the women sampled, and of these, 181 (49%) were located. Predictors of locating women were: younger age, residing in less densely populated areas, having had a web-search completed in 2001, and listed name identified on the Internet prior to recruitment in 2003. Although vital statistics linkages to death records subsequently identified 41 subjects, these data were incomplete.

CONCLUSION

Prospective studies may benefit from using Internet resources at recruitment to determine the listed names for telephone numbers thereby facilitating follow-up tracing and improving response rates. Although vital statistics linkages may help to identify deceased individuals, these may be best suited for post hoc response rate adjustment.

Characteristics of childhood cancer survivors predicted their successful tracing

OBJECTIVE

The Childhood Cancer Survivor Study is a retrospective cohort study that was initiated to explore late effects of childhood cancer and its therapies. We evaluated the characteristics of those requiring tracing and factors that influenced tracing success.

STUDY DESIGN AND SETTING

Medical record review identified 20,051 eligible individuals from 25 institutions in the United States and Canada. Of these, 13,021 had a current address in the medical record at the treating institution, and 7,030 had an incorrect address and required tracing by a commercial firm.

RESULTS

Tracing was successful for 4,188 persons (60%). Younger age at contact, shorter length of time since last contact, having a middle initial available, an uncommon last name, and socioeconomic factors were found to predict successful tracing. Compared to those with a current address available in medical records, subjects successfully traced were less likely to have accessed health care during the previous 2 years; and more likely to be current smokers, obese, and to report moderate to severe impairments (pain, functional status, and activity).

CONCLUSION

These findings provide an empirical basis concerning determinants and predictors of tracing success. If tracing had not been performed in this cohort, spurious associations may have been obtained for some health outcomes of interest.

Tracing and recruiting a cohort with community acquired hepatitis 25 years later

OBJECTIVE

We describe the methods used to trace and recruit a cohort (including injecting drug users) 25 years after admission to hospital in Melbourne with hepatitis.

METHODS

Information recorded in the original medical record was used for tracing purposes. Subjects were located using the electoral roll, CD-ROM telephone directory, the Health Insurance Commission database, Hepatitis Foundation newsletters, advertising and features in the press and local radio. Other approaches included contacting local medical officer or next of kin from the original admission, and the National Death Registry.

RESULTS

Tracing was undertaken on all members of the cohort; two-thirds were located. Methods were applied sequentially and 36% were found by CD-ROM telephone directory and the electoral roll, 33% from Health Insurance records, 15% by letter to last known address, 10% from contact of original next of kin, 3% from radio publicity and 1% from media advertisements. Of those who were located, 85% participated in the study.

CONCLUSIONS

Accurate ascertainment of birth date and full name from original case records was essential for tracing purposes. Use of Health Insurance records and CD-ROM telephone directory and the electoral roll were the most successful means of locating subjects while newspaper advertising was non-productive and expensive. History of IDU was the major association with failure to trace and unwillingness to enrol, but despite this tracing and recruitment was high in this group. The high participation rate in those located appears to be due to the experience of the staff member making the initial contact.