Participation Bias and Its Impact on the Assembly of a Genetic Specimen Repository for a Myocardial Infarction Cohort

Abstract

Objective-To assess participation bias in the assembly of a specimen repository for genetic studies and to examine the association of participation with outcome within the Olmsted County myocardial infarction (MI) cohort. January 1, 1979, to May 31, 2006, 3081 persons had MI in Olmsted County, MN. Face-to-face contact was used to recruit patients who were hospitalized for an acute event. Persons who had had an MI before establishment of this repository were contacted by mail. At initial contact, we sought consent to use blood samples for genetic studies. Persons who refused were contacted by mail and were asked to consent to the use of stored tissue samples. For deceased subjects, stored tissue was collected when available. Participants and Methods-FromResults-Of the 3081 persons in the Olmsted County MI cohort, 1994 participated in the study; 1007 (50.5%) blood and 987 (49.5%) tissue specimens were provided. Participants were more likely to be younger men with hypertension, comorbidities, and non-ST-segment elevation MI (all, P<. 05). Participants who provided blood specimens were more likely to have non-ST-segment elevation MI and lower Killip class than those who provided tissue. After adjustment for age, sex, hypertension, ST-segment elevation, Killip class, and comorbidities, participation was not associated with outcome. Participants who provided blood specimens were less likely to have heart failure (hazard ratio, 0.49; 95% confidence interval, 0.40-0.59; P<.01) or to die (hazard ratio, 0.16; 95% confidence interval, 0.12-0.21; P<.01) than those who provided tissue.Conclusions-A variety of sources can be used to assemble community specimen repositories. Baseline characteristics differed between participants and nonparticipants and, among participants, by specimen source. Participants who provided blood specimens had better outcomes than those who provided tissue specimens. No survival advantage was observed for participants after combining blood and tissue specimens.Participation bias occurs when comparisons are made between groups of patients who differ in determinants of outcome and when the differences are themselves related to the outcome. 1 Studies that require enrollment of participants are inherently affected by participation bias. 2 Because selective participation can threaten the external validity of studies, assessment of the magnitude of participation bias is essential to optimize the inference from these studies.Few studies in the community have examined the effect of participation bias. In one populationbased study of myocardial infarction (MI), nonparticipants were older, had greater comorbidity, and experienced poorer survival than participants. 3 A population-based study of left ventricular function reported that participation rates were lowest among the oldest, the youngest, and those with chronic obstructive pulmonary disease. 4 However, those studies did not examine the effects of participation on genetic studies of heart diseases.Population-based studies, using both established...

Factors influencing patient willingness to participate in genetic research after a myocardial infarction

“…Further clouding the literature is that most genetic studies have not adequately described populations from which samples were recruited, precluding an assessment of participation bias and potentially affecting internal and external validity [5]. The only study we are aware of examining genetic participation rates in an MI registry found significant clinical differences between participants and non-participants [13], calling into question the external validity of this study. A better understanding of the variability in patients' willingness to participate in genetic studies of acute cardiovascular disease is needed to assess for selection biases and to identify opportunities to improve participation and optimize the generalizability of such studies.…”

Frequency, comprehension and attitudes of physicians towards abbreviations in the medical record

“…In addition, when we assessed the benefits of taking the lesson, a difference (0.91 in mean correct answers) was found in favour of those who opted to participate in that second part of the survey. Despite the differences being small, it may still affect our results due to a participation bias 26. Finally, no mechanism existed to prevent the physicians surveyed from using reference materials, though it was written in the instructions not to.…”

Association of TNFSF8 Polymorphisms With Peripheral Neutrophil Count

“…Therefore, we investigated the association between 347 single-nucleotide polymorphisms (SNPs) within candidate genes of the proinflammatory cytokine families, including TNF (18 genes), IL-1 (10 genes), and IL-6 (12 genes), and peripheral neutrophil count in a nested case-control study from the Olmsted County, Minnesota, cohort of incident MI. 28 This study tests the hypothesis that variants within candidate genes of these proinflammatory cytokine families are associated with peripheral neutrophil count in patients with MI.…”

“…29 Details of assembly of the DNA repository that was used for the identification and recruitment of participants in this study have been previously published. 28 The current study design was a case-control study of white patients nested in the incident MI cohort. The case group consisted of 400 patients with MI and post-MI HF (HF within 90 days after MI), and the control group consisted of 694 MI patients who did not experience post-MI HF (within 90 days after MI).…”