Impact Of Selection Bias Research Articles

Juvenile transfer and recidivism: a propensity score matching approach

There has been research conducted which focused on the topic of juvenile transfer to adult court. However, less research has been done focusing on the effectiveness of juvenile transfer in reducing recidivism for transferred offenders. Of the research that has been done, most may not have adequately addressed selection bias. The current study investigates the impact of juvenile transfer on subsequent recidivism, using an eight-year follow-up period. The research is based on 308 violent youth legislatively waived to adult court in Pennsylvania. Propensity score matching is used to minimize the impact of selection bias, and sensitivity analysis is performed to determine the effect of hidden bias on the results. The findings indicate that youth processed in juvenile court have a higher recidivism rate than youth processed in adult court. Implications for subsequent research and policy are discussed.

Commentary: Decreasing response rates require investigators to quantify and report the impact of selection bias in case-control studies

A high response rate has long been regarded as one of the hallmarks of a ‘good’ epidemiological study. However, the validity of results from studies that require participants to complete questionnaires, have an interview or provide a biological specimen is becoming increasingly jeopardized by decreasing participation. One analysis showed that cooperation rates (participants interviewed/number eligible that were contacted) in published population-based case–control studies declined by 3.33% per year in cases and 5.15% per year in controls from 1991 to 2003. In such studies, cooperation rates of 70% and response rates [participants interviewed/(participants interviewedþ eligible non-participantsþ people of presumed but unconfirmed eligibility)] of 50% are not uncommon today. Furthermore, and maybe because of declining rates, only a minority of studies published sufficient information for either cooperation or response rates to be calculated. A fundamental tenet of a case–control study design is that the controls should be selected randomly, and independently of exposure status, from the source population from which the cases were drawn and thus be representative of the exposure experience of the source population. Poor response rates by themselves do not create selection bias any more than high response rates guarantee unbiased estimates, but by endangering representativeness, low participation can provide more opportunity for bias to occur. Selection bias develops if the selection probabilities are different for cases and controls based on their exposure status. Since odds ratios maybe biased due to low participation, should we discard case–control studies as a valid study design?

Adjusting for Selection Effects in Epidemiologic Studies

Adjusting for Selection Effects in Epidemiologic Studies

Assessing Competition Policy: Methodologies, Gaps and Agenda for Future Research

Research by academics and competition agencies on evaluating competition policy has grown rapidly during the last two decades. This paper surveys the literature in order to (i) assess the fitness for purpose of the main quantitative methodologies employed, and (ii) identify the main undeveloped areas and unanswered questions for future research. It suggests that policy evaluation is necessarily an imprecise science and that all existing methodologies have strengths and limitations. The areas where the need is most pressing for further work include: understanding why Article 102 cases are only infrequently evaluated; the need to bring conscious discussion of the counterfactual firmly into the foreground; a wider definition of policy to include success in deterrence and detection. At the heart of the discussion is the impact of selection bias on most aspects of evaluation. These topics are the focus of ongoing work in the CCP.

Selection bias in a population survey with registry linkage: potential effect on socioeconomic gradient in cardiovascular risk

Non-participation in population studies is likely to be a source of bias in many types of epidemiologic studies, including those describing social disparities in health. The objective of this paper is to present a non-attendance analysis evaluating the possible impact of selection bias, when investigating the association between education level and cardiovascular risk factors. Data from the INTERGENE research programme including 3,610 randomly selected individuals aged 25-74 (1,908 women and 1,702 men), in West Sweden were used. Only 42% of the invited population participated. Non-attendance analyses were done by comparing data from official registries (Statistics Sweden) covering the entire invited study population. This analysis revealed that participants were more likely to be women, have university education, high income, be married and of Nordic origin compared to non-participants. Among participants, all health behaviours studied were significantly related to education. Physical activity, alcohol use and breakfast consumption were higher in the more educated group, while there were more smokers in the less educated group. Central obesity, obesity and hypertension were also significantly associated with lower education level. Weaker associations were observed for blood lipids, diabetes, high plasma glucose level and perceived stress. The socio-demographic differences between participants and non-participants indicated by the register analysis imply potential biases in epidemiological research. For instance, the positive association between education level and frequent alcohol consumption, may, in part be explained by participation bias. For other risk factors studied, an underestimation of the importance of low socioeconomic status may be more likely.

Workplace productivity, employment issues, and resource utilization in patients with bipolar I disorder

Objective: To collect workplace productivity and healthcare utilization data from subjects with bipolar I disorder and compare the results with those from normative subjects.Methods: A cross sectional survey was administered to patients and recruiting physicians. Data collected included employment status, Endicott Workplace Productivity Scale (EWPS) results, healthcare resource utilization, and quality-of-life.Results: In comparison with normative subjects, bipolar I subjects reported lower levels of work productivity (measured by the EWPS). Bipolar I subjects also reported more frequent outpatient visits and more prescribed pharmaceuticals. Bipolar I subjects were more likely to miss work, have worked reduced hours due to medical or mental health issues, receive disability payments, been involved in a crime, be uninsured or covered by Medicare, or have been fired or laid off. The study groups were age- and gender-matched to reduce the impact of selection bias associated with a non-randomized study design. Other potential limitations affecting the results of the study include recall bias and possibly an impact of different data collection methods (e.g. Internet versus telephone).Conclusions: Bipolar I disorder is associated with a negative effect on work productivity and resource utilization and is an appropriate disease management target for employers and healthcare decision makers.

Impact of Selection Bias on the Utilization of Adjuvant Therapy for Pancreas Adenocarcinoma

Improved outcomes have been associated with the use of adjuvant therapy after resection of pancreas adenocarcinoma. However, the frequency with which patients receive adjuvant therapy and the factors impacting its use remain largely undefined. We hypothesized that nonutilization of adjuvant therapy was primarily associated with patient comorbidity and onset of postoperative complications. A prospectively maintained database was reviewed to identify patients who underwent potentially curative resection of histologically confirmed pancreas adenocarcinoma at our institution from January 1996 to May 2007. Clinicopathological data and postoperative treatment history were collected to identify variables associated with receipt of adjuvant therapy. Of 119 patients, 33% did not receive adjuvant therapy. The frequency with which patients underwent adjuvant therapy did not change over time. On multivariate analysis, patient age 70 years or greater, major postoperative complications, distal pancreatectomy, absence of nodal metastases, and absence of perineural invasion were associated with decreased utilization of adjuvant therapy. One-third of patients in this contemporary dataset of patients did not go on to receive adjuvant therapy. The likelihood of receiving adjuvant treatment is negatively impacted by the course of postoperative recovery. Moreover, the fact that adjuvant therapy was undertaken less often for older patients and patients with favorable pathological features highlights the selection bias impacting the decision to pursue postoperative therapy for this disease. This selective utilization of postoperative therapy for patients with adverse oncological characteristics is likely to bias any retrospective analysis attempting to measure the efficacy of adjuvant treatment for pancreas adenocarcinoma.

COX‐2 inhibitors: complex association with lower risk of hospitalization for gastrointestinal events compared to traditional NSAIDs plus proton pump inhibitors

To compare hospitalization rates for serious upper and lower gastrointestinal (GI) events between chronic and acute users of a traditional non-steroidal anti-inflammatory drugs (tNSAID) + proton pump inhibitor (PPI) and users of a COX-2 selective inhibitor (Coxib). The PHARMO Record Linkage System, including linked drug-dispensing and hospital records of approximately 3 million individuals in the Netherlands was used. We selected new Coxib or tNSAID users (01/01/2000-31/12/2004) with > or =1 year history before the first NSAID dispensing and > or =1 year follow-up ending at the first hospitalization for GI event (the outcome), last dispensing, or end of the study period. Chronic users were patients who used any NSAIDs for > or =60 days during the first year (n = 58 770); others were acute users (n = 538 420). Multivariate analysis was performed by Poisson regression adjusted for gender, age, and duration of follow-up, tNSAID and Coxib dose, NSAID/PPI adherence, use of other gastroprotective agents, anticoagulants, acetaminophen, corticosteroids, and cardiovascular disease. The cohort included 23 999 new tNSAIDs + PPI users and 25 977 new Coxib users, with main characteristics: mean +/- SD age 58.1 +/- 15.5 vs. 56.7 +/- 17.5; female 55.3% vs. 62.2%; duration of treatment (days): 137 +/- 217 vs. 138 +/- 179, respectively. Among acute users, adjusted hazard ratios (95% Confidence Interval) were 0.21 (0.14-0.32) for upper and 0.26 (0.16-0.42) for lower GI events, for Coxib versus tNSAIDs + PPI users. Among chronic users, these were 0.35 (0.22-0.55) for upper GI and 0.43 (0.25-0.75) for lower GI events. Coxib users had significantly lower rates of GI events. Further research should elucidate the possible impact of selection bias.

Impact of the National History Day in Ohio Program on Students' Performances

This pilot study aimed at developing and validating an evaluation model to assess the impact of participation in the National History Day in Ohio program (NHD-OH) on students academic achievement and intellectual growth by using as key indicators: A) High-stakes tests, i.e., Ohio Graduation Tests (OGT) in Social Studies, Reading and Writing; B) Appreciation of history, and C) Development of critical thinking. Using a quasi-experimental study design, twenty-four tenth-graders participating in NHD-OH and twenty-four matched controls were used in the analysis to reduce the impact of selection bias. As a result of this study it was found that students participating in NHD-OH received statistically significant higher scores on the Social Studies OGT, Reading and Writing; and furthermore, demonstrated a deeper appreciation of history and a better ability to explore and integrate new perspectives.

Effects of Advanced Course-taking on Math and Science Achievement: Addressing Selection Bias Using Propensity Scores

Does taking advanced courses improve scores on basic achievement tests? This question is difficult to answer because there are many systematic differences between students who choose to take advanced courses and those who don’t. This paper uses cutting-edge propensity score methods to control for the selection bias that exists when studying the effects of advanced course-taking on a basic achievement test in math and science. In particular, the differential achievement between advanced course-taking and non-advanced course-taking students in a basic math and science proficiency test in high school is estimated, controlling for several background variables and using data from the Third International Mathematics and Science Study (TIMSS). Because propensity score methods adjust for selection bias on observed background variables, but not on unobserved background variables, we also consider the potential impact of selection bias due to unobserved measures (hidden bias) through a sensitivity analysis. Our analysis found that advanced course-taking is consistently associated with higher achievement. Sensitivity analysis suggests that this can be the result of hidden bias due to extreme differences in unobserved background variables, but cannot be explained if the differences in unobserved background variables are only moderate.

Birthplace and survival among Asian women diagnosed with breast cancer in cancer registry data: the impact of selection bias

Birthplace and survival among Asian women diagnosed with breast cancer in cancer registry data: the impact of selection bias

Birthplace and survival among Asian women diagnosed with breast cancer in cancer registry data: the impact of selection bias

Birthplace and survival among Asian women diagnosed with breast cancer in cancer registry data: the impact of selection bias

Acute Pulmonary Embolism: Impact of Selection Bias in Prospective Diagnostic Studies

We evaluated selection bias in a prospective study of 1,162 consecutive patients with suspected pulmonary embolism. Of these, 983 were eligible, and 627 could actually be included. During two months extensive data were collected on all non-included patients. Finally, our patient characteristics were compared with those of the PIOPED study (1990) and the study of Hull et al. (1994). Compared with included patients, the non-included patients had more often non-diagnostic V/Q scans (50% vs. 36%, p <0.01) and were more often already hospitalized (31% vs. 22%, P = 0.04). The subgroup of patients not included due to refusal or inability to give informed consent (IC) was older (mean age 61 vs. 53 years, P <0.01), more often suffered from malignancies (26% vs. 11%, P <0.01) and frequently had non-diagnostic V/Q scans (57%) as compared to included patients. In our study, 54% of all patients screened was eventually included versus 27% in the PIOPED study. In the PIOPED study patients who had contra-indications for pulmonary angiography were excluded, while in the study of Hull et al. those with inadequate cardiorespiratory reserve were excluded. In studies on new diagnostic technologies, patient selection bias does occur. The potential for such a selection bias should be taken into account when diagnostic strategies are devised to improve their generalizability and acceptability.

Differential expansion rates of small abdominal aortic aneurysms between the apolipoprotein E genotypes

Abstract Background Carriers of the E4 allele for the gene encoding apolipoprotein E (apoE) have an increased risk of atherosclerosis. The distribution of apoE genotypes among men with a small abdominal aortic aneurysm (AAA) was compared with that among healthy men, and any differences between the genotypes in aneurysm expansion measured over 2–4·5 years were examined. Methods The patients originate from a population ultrasonographic screening programme with about 4800 participating 65–73-year-old men in a defined geographical region. Of 191 patients diagnosed, 57 of 77 who have been followed for 2 years or more were genotyped. Aneurysm expansion rates were determined from linear regression of diameter versus time of examination. The influence of apoE genotype on expansion rate was analysed using analysis of variance, with initial aneurysm size and smoking status as covariates. Results The E4E4 genotype was not seen among patients with an AAA, whereas three patients had the rare E2E4 genotype. These patients had higher expansion rates than patients with the common genotype E3E3 (P = 0·009), whereas patients with the genotype E3E4 had lower rates (P = 0·034) (see Table over). Conclusion The findings suggest that the common polymorphism of the apoE gene influences the prognosis in patients with a small AAA. As regards the E3E4 genotype, the findings are unexpected, when compared with the known influence of E4 on the risk of atherosclerosis. This may partly explain the familial tendency of AAA, and inconsistent finding of coexisting atherosclerosis in patients with AAA. However, an impact of selection bias, due to differential survival or referral to surgery of patients with AAA, cannot be excluded.

Translating Quantitative Methods for Qualitative Researchers: The Case of Selection Bias

Translating Quantitative Methods for Qualitative Researchers: The Case of Selection Bias