Case Definition in Epidemiologic Studies of AD/HD

https://doi.org/10.1016/j.annepidem.2004.12.004Get rights and content

Purpose

Propose a five-step multigating, multimodal procedure for research case definition and identification of attention-deficit/hyperactivity disorder (AD/HD) in population-based epidemiologic studies.

Methods

Subjects included a birth cohort of all children born between 1976 and 1982 who remained in Rochester after age 5. Screening for AD/HD required 4 steps, using these sources: school/medical records, computerized diagnostic index, and private psychiatry records. In step 5, research criteria were applied to potential cases. The model for defining cases used combinations of three categories of information (DSM-IV, questionnaire, clinical diagnosis). Validity was tested by comparing medication treatment, substance abuse, school outcomes, and comorbidities between cases who did or did not meet DSM-IV criteria.

Results

Among 5718 subjects, 1344 potential cases were identified; 379 met research criteria. No difference in gender, treatment, school outcome, or professional making clinical diagnoses was found between cases who did (N = 228) and did not (N = 151) meet DSM-IV criteria. However, cases not meeting DSM-IV criteria were more inattentive (33.8% vs. 17.1%; p < 0.001), older (age 12.8 vs. 10.5 years; p = 0.01), with less substance abuse (15.2% vs. 26.3%; p < 0.001) and psychiatric comorbidities (43.1% vs. 54.4%; p = 0.031).

Conclusions

If only DSM-IV criteria were applied, 151 cases would not have been identified. This study underscores the importance of using multiple sources and combinations of documented information for case definition and identification.

Introduction

Attention-deficit/hyperactivity disorder (AD/HD) is the most common neurobehavioral disorder of childhood 1, 2. It is often chronic in nature, with symptoms which may continue into adulthood. AD/HD is a significant public health concern and represents a costly public health problem 3, 4, 5.

Epidemiologic studies of AD/HD help to address important, but not yet agreed upon, issues related to AD/HD frequency, distributions, and determinants. To address these closely interrelated components requires clearly described and applied AD/HD definitional and assessment methods. Goldman et al. (6) stated that a combination of different types of information (e.g., from several sources, careful examination, appropriate testing, several visits, teacher's reports, a multidisciplinary team approach) is needed to establish the diagnosis of AD/HD. Our proposed research model of identifying AD/HD cases resembles, to a certain degree, current recommended clinical practice (7). A combination of different types of information is required to identify an AD/HD case and most importantly, to avoid overlooking a case for both clinical and research purposes. This article provides details of the methods used in retrospectively identifying and defining incident cases of AD/HD utilizing a population-based birth cohort and the unique resources of the Rochester Epidemiology Project (REP) (8).

Section snippets

Study Setting

Rochester, Minnesota, is located 90 miles southeast of Minneapolis-St. Paul, the closest major urban center. Using census data from 1990, the years the children from this birth cohort were in school, there were 70,745 residents who were 96% white, fairly young (75% ≤ 45 years old), and primarily middle class. With the exception of the place of employment (predominantly health care and computer industries), characteristics of the Rochester population are similar to those of the US white

Results

Among our population-based birth cohort of 5718 children, we identified 379 AD/HD incidence cases using research criteria for AD/HD case definition (Table 2). Of the 379, only 31 (8.2%) moved prior to age 16. The display of numbers of AD/HD cases who satisfied five different combinations of three different categories of information is given in Table 1. Of particular interest were the 228 AD/HD cases who met DSM-IV criteria and the 151 AD/HD cases who did not meet DSM-IV criteria. The median

Discussion

Population-based epidemiologic studies of AD/HD are limited in numbers. Most of the AD/HD research is based on clinic-referred samples of children 17, 18, which may not reflect the spectrum of AD/HD in the population at large. Therefore, population-based, non-referred samples of children with AD/HD are critically needed in order to increase our understanding of AD/HD and increase the generalizability and comparability among studies 4, 16, 19. A population-based birth cohort is a powerful tool

Conclusion

In summary, epidemiologic studies of AD/HD and other developmental and psychiatric disorders, even though difficult and challenging, are feasible when properly planned and implemented. Our approach of developed research criteria for defining AD/HD cases by combining three different categories of information (meets DSM-IV criteria, positive questionnaire results, and recorded clinical diagnosis of AD/HD) is especially appropriate for retrospective, population-based research with reliable,

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      We have previously published descriptions of the identification of the 5718 members of the 1976 to 1982 birth cohort in Rochester, Minnesota, who remained in the community at least until 5 years of age and who were included as subjects for this study.1,15,16

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    This project was supported by research grant HD29745 and AR30582 from the Public Health Service of the National Institutes of Health (Bethesda, MD) and Mayo Foundation (Rochester, MN).

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