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Lead-Time Bias

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77241. Lead time of prostate cancer detected in population based screening for prostate cancer in Japan. (PubMed)

Lead time of prostate cancer detected in population based screening for prostate cancer in Japan. We clarified that lead time bias in screen detected prostate cancer is important for evaluating the outcome of any individual screening system.Between 1992 and 2001, 195 and 958 prostate cancer cases with clinical T1c/T2N0M0 and T3N0M0 disease were enrolled in the current study as screen detected and outpatient clinic detected prostate cancer, respectively. Log10 prostate specific antigen velocity (...) was calculated using log10 prostate specific antigen at diagnosis and at the most recent screening before cancer detection. Lead time in screen detected cancer was then estimated as the year when log10 prostate specific antigen in screen detected cancer would increase to the levels of log10 prostate specific antigen in outpatient clinic detected prostate cancer.Median log10 prostate specific antigen was 0.87 and 1.08 ng/ml for clinical T1c/T2N0M0 disease, and 1.14 and 1.53 ng/ml for T3N0M0 disease in screen

2007 Journal of Urology

77242. Health-related lost productive time (LPT): recall interval and bias in LPT estimates. (PubMed)

Health-related lost productive time (LPT): recall interval and bias in LPT estimates. We examined the effect of interview characteristics (ie, recall interval, interview version) on estimates of health-related lost productive work time (LPT). Three versions of a telephone interview were administered using 7-day and 4-week recall periods. In a population-based survey, 7674 workers randomly were assigned to one of six interviews at contact; 615 participants received a follow-up interview. We

2004 Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine

77243. Survival bias associated with time-to-treatment initiation in drug effectiveness evaluation: a comparison of methods. (PubMed)

Survival bias associated with time-to-treatment initiation in drug effectiveness evaluation: a comparison of methods. The authors compared five methods of studying survival bias associated with time-to-treatment initiation in a drug effectiveness study using medical administrative databases (1996-2002) from Quebec, Canada. The first two methods illustrated how survival bias could be introduced. Three additional methods were considered to control for this bias. Methods were compared (...) the null (10% relative risk reduction). Method 3 controlled for survival bias by following patients from the end of the 90-day time window; however, it suffered a major loss of statistical efficiency and precision. Method 4 matched prescription time distribution between users and nonusers at cohort entry. Method 5 used a time-dependent variable for treatment initiation. Methods 4 and 5 better controlled for survival bias and yielded similar results, suggesting a 20% risk reduction of recurrent

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2005 American Journal of Epidemiology

77244. Effectiveness of inhaled corticosteroids in chronic obstructive pulmonary disease: immortal time bias in observational studies. (PubMed)

Effectiveness of inhaled corticosteroids in chronic obstructive pulmonary disease: immortal time bias in observational studies. Recent large-scale cohort studies that reported an important reduction in mortality and chronic obstructive pulmonary disease (COPD) morbidity with inhaled corticosteroids may be biased. We used a population-based cohort of Saskatchewan residents 55 years of age or over, first hospitalized for COPD during 1990 to 1997, to study this potential bias. These 979 subjects (...) were followed for a year from discharge until their first readmission for COPD or death (389 subjects). Inhaled corticosteroid exposure was measured as any dispensing within 90 days after discharge. Cox's proportional hazards model was used to compare the time-fixed analysis employed in the recent studies with the alternative time-dependent analysis. The time-fixed adjusted rate ratio was 0.69 (95% CI: 0.55-0.86) for inhaled corticosteroid use within 90 days, whereas the time-dependent rate ratio

2003 American Journal of Respiratory and Critical Care Medicine

77245. Inhaled corticosteroids in chronic obstructive pulmonary disease: results from two observational designs free of immortal time bias. (PubMed)

Inhaled corticosteroids in chronic obstructive pulmonary disease: results from two observational designs free of immortal time bias. Recent cohort studies in chronic obstructive pulmonary disease (COPD) have questioned the validity of previously reported associations between inhaled corticosteroids (ICS) and reductions in mortality and rehospitalization in observational studies. Using time-dependent versions of statistical survival models, these studies have suggested immortal time bias (...) as responsible for the proposed beneficial association.We explored the extent of this bias in a study of patients with COPD monitored for a year from COPD discharge with two designs free of any immortal time bias in the General Practice Research Database in the United Kingdom.In Design 1, we used only patients whose treatment status was defined on the same day of discharge to obtain a matched cohort based on propensity scores, which were derived from the patient-level baseline characteristics. In Design 2

2005 American Journal of Respiratory and Critical Care Medicine

77246. Inhaled steroids and mortality in COPD: bias from unaccounted immortal time. (PubMed)

Inhaled steroids and mortality in COPD: bias from unaccounted immortal time. A recent observational study, which suggested that inhaled corticosteroids (ICS) with or without long-acting bronchodilators are effective at reducing all-cause mortality in chronic obstructive pulmonary disease (COPD) patients, may be subject to immortal time bias. This bias was assessed using a population-based cohort of 3,524 newly treated COPD patients from Saskatchewan, Canada, observed from 1990-1999. Regular (...) users of bronchodilators or ICS were followed for 3 yrs, during which time 860 deaths occurred. Cox's proportional hazards model was used to compare the hierarchical intention-to-treat approach employed in the recent study, a technique subject to bias from two sources of immortal time, with the conventional intention-to-treat approach and the according-to-treatment approach. The adjusted rate ratio of death using the hierarchical intention-to-treat approach was 0.66 (95%) confidence interval (CI

2004 European Respiratory Journal

77247. Bias in Estimates of Quantitative-Trait–Locus Effect in Genome Scans: Demonstration of the Phenomenon and a Method-of-Moments Procedure for Reducing Bias (PubMed)

is the selection process. Generally, QTL effects are reported only at locations where statistically significant results are obtained. This conditional reporting can lead to a marked upward bias. In this article, we demonstrate this bias and show that its magnitude can be large. We then present a simple method-of-moments (MOM)-based procedure to obtain more-accurate estimates, and we demonstrate its validity via Monte Carlo simulation. Finally, limitations of the MOM approach are noted, and we discuss some (...) Bias in Estimates of Quantitative-Trait–Locus Effect in Genome Scans: Demonstration of the Phenomenon and a Method-of-Moments Procedure for Reducing Bias An attractive feature of variance-components methods (including the Haseman-Elston tests) for the detection of quantitative-trait loci (QTL) is that these methods provide estimates of the QTL effect. However, estimates that are obtained by commonly used methods can be biased for several reasons. Perhaps the largest source of bias

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2002 American Journal of Human Genetics

77248. Intermediate-Term Results of Laparoscopic Repair of Giant Paraesophageal Hernia: Lack of Follow-up Esophagogram Leads to Detection Bias (PubMed)

Intermediate-Term Results of Laparoscopic Repair of Giant Paraesophageal Hernia: Lack of Follow-up Esophagogram Leads to Detection Bias This retrospective study was performed to review the intermediate-term results of the laparoscopic repair of giant paraesophageal hernia (PEH) in the unit.This retrospective 8-year case series involved 42 patients. The clinical records were retrieved, reviewed individually, and data were collected regarding symptoms, investigation, operative details, and follow

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2007 JSLS : Journal of the Society of Laparoendoscopic Surgeons

77249. Timing payments to subjects of mail surveys: cost-effectiveness and bias. (PubMed)

Timing payments to subjects of mail surveys: cost-effectiveness and bias. Although mailed surveys are an important component of epidemiological research, results from mailed surveys are often suspect because of poor response rates and the potential for nonresponse bias. Previous work has demonstrated that paying subjects to complete questionnaires increases response rates, but this work has not well addressed the impact of the timing of incentives on total cost, cost effectiveness, and response (...) bias. We surveyed 400 university employees about health benefits. By random allocation, half received a check for $5 along with the mailed survey, and the other half received the promise of $5 on return of a completed survey. The response rates for both groups were about the same (64 and 59%, respectively), but prepayment was less expensive in aggregate and less expensive per response. In addition, we found that subjects with lower salaries were more likely to respond when paid in advance. We

1996 Journal of Clinical Epidemiology

77250. Detection and kinetic studies of triplex formation by oligodeoxynucleotides using real-time biomolecular interaction analysis (BIA). (PubMed)

Detection and kinetic studies of triplex formation by oligodeoxynucleotides using real-time biomolecular interaction analysis (BIA). Real-time biomolecular interaction analysis (BIA) has been applied to triplex formation between oligodeoxynucleotides. 5'-Biotinylated oligonucleotides were immobilised on the streptavidin-coated surface of a biosensor chip and subsequently hybridised to their complementary strand. Sequence-specific triplex formation was observed when a suitable third-strand

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1995 Nucleic acids research

77251. Long microsatellite alleles in Drosophila melanogaster have a downward mutation bias and short persistence times, which cause their genome-wide underrepresentation. (PubMed)

Long microsatellite alleles in Drosophila melanogaster have a downward mutation bias and short persistence times, which cause their genome-wide underrepresentation. Microsatellites are short tandemly repeated DNA sequence motifs that are highly variable in most organisms. In contrast to mammals, long microsatellites (>15 repeats) are extremely rare in the Drosophila melanogaster genome. To investigate this paucity of long microsatellites in Drosophila, we studied 19 loci with exceptionally long (...) microsatellite alleles. Inter- and intraspecific analysis showed that long microsatellite alleles arose in D. melanogaster only very recently. This lack of old alleles with many repeats indicated that long microsatellite alleles have short persistence times. The size distribution of microsatellite mutations in mutation-accumulation lines suggests that long alleles have a mutation bias toward a reduction in the number of repeat units. This bias causes the short persistence times of long microsatellite alleles

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2000 Genetics

77252. Bias inherent in retrospective waiting-time studies: experience from a vascular surgery waiting list (PubMed)

Bias inherent in retrospective waiting-time studies: experience from a vascular surgery waiting list 10906915 2000 08 01 2018 11 13 0820-3946 162 13 2000 Jun 27 CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne CMAJ Bias inherent in retrospective waiting-time studies: experience from a vascular surgery waiting list. 1821-2 Sobolev B B Brown P P Zelt D D Shortt S S eng Journal Article Research Support, Non-U.S. Gov't Canada CMAJ 9711805 0820-3946 AIM IM (...) CMAJ. 2001 Jan 9;164(1):14 11202659 CMAJ. 2001 Jan 9;164(1):14 11202660 Bias Humans Ontario Outcome Assessment (Health Care) Prospective Studies Research Design Retrospective Studies Time Factors Vascular Surgical Procedures Waiting Lists 2000 7 25 11 0 2000 8 6 11 0 2000 7 25 11 0 ppublish 10906915 PMC1231370 Nat Cell Biol. 2000 Mar;2(3):156-62 10707086 Br Med J (Clin Res Ed). 1987 Nov 7;295(6607):1197-8 3120941 Stat Med. 1993 May 15;12(9):867-79 8327803 J Clin Oncol. 1997 Mar;15(3):1261-71

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2000 CMAJ: Canadian Medical Association Journal

77253. Lack of concealment may lead to selection bias in cluster randomized trials of palliative care. (PubMed)

Lack of concealment may lead to selection bias in cluster randomized trials of palliative care. Comprehensive palliative care programs are often implemented on a community level, and to evaluate such interventions, randomization by cluster (community) may be the only feasible method. In trials randomizing individual subjects, the importance of proper concealment has been stressed. In cluster randomized trials, however, concealment of individual patient allocation is often impossible (...) . The following risk of selection bias has been given little attention. In the present study, comparing palliative care to conventional care, community health care districts were defined as clusters and randomized. The patients' treatment assignment was determined by the allocation of the cluster in which they resided, and hence predictable by their address. A biased selection based on practical considerations related to patients' diagnoses and hospital departments was suspected. To explore this, cancer

2002 Palliative medicine

77254. Histopathologic extent of cervical intraepithelial neoplasia 3 lesions in the atypical squamous cells of undetermined significance low-grade squamous intraepithelial lesion triage study: implications for subject safety and lead-time bias. (PubMed)

Histopathologic extent of cervical intraepithelial neoplasia 3 lesions in the atypical squamous cells of undetermined significance low-grade squamous intraepithelial lesion triage study: implications for subject safety and lead-time bias. Cervical intraepithelial neoplasia 3 (CIN3) is the precursor of mostsquamous carcinomas and serves as a surrogate end point. However, small CIN3 lesions are rarely associated with concurrent invasion. We hypothesized that aggressive follow-up for cytology (...) of atypical squamous cells of undetermined significance (ASCUS) or low-grade squamous intraepithelial lesion (LSIL) leads predominantly to detection of smaller CIN3 lesions than those usually associated with cancer. We assessed this hypothesis in a masked histopathologic review of 330 CIN3 lesions in the ASCUS LSILTriage Study, focusing on ASCUS referrals. ASCUS referrals underwent randomized management [colposcopy for repeat cytology of high-grade squamous intraepithelial lesion (HSIL), colposcopy

2003 Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology

77255. Time-dependent bias was common in survival analyses published in leading clinical journals. (PubMed)

Time-dependent bias was common in survival analyses published in leading clinical journals. In survival analysis, "baseline immeasurable" time-dependent factors cannot be recorded at baseline, and change value after patient observation starts. Time-dependent bias can occur if such variables are not analyzed appropriately. This study sought to determine the prevalence of such time-dependent bias in highly-cited medical journals.We searched Medline databases to identify all observational studies (...) that used a survival analysis in American Journal of Medicine, Annals of Internal Medicine, Archives of Internal Medicine, British Medical Journal, Chest, Circulation, Journal of the American Medical Association, Lancet, and New England Journal of Medicine between 1998 and 2002. Studies with "baseline immeasurable" time-dependent factors were susceptible to time-dependent bias if a time-dependent covariate analysis was not used.Of 682 eligible studies, 127 (18.6%, 95% CI 15.8-21.8%) contained

2004 Journal of Clinical Epidemiology

77256. Evaluation of the Houston biochemical relapse definition in men treated with prolonged neoadjuvant and adjuvant androgen ablation and assessment of follow-up lead-time bias. (PubMed)

Evaluation of the Houston biochemical relapse definition in men treated with prolonged neoadjuvant and adjuvant androgen ablation and assessment of follow-up lead-time bias. To validate the Houston prostate-specific antigen relapse definition in a mature cohort of men treated with external beam radiotherapy (EBRT) and adjuvant androgen ablation (AA) and men treated with EBRT monotherapy, and to compare these results with the American Society for Therapeutic Radiology and Oncology (ASTRO

2003 Biology and Physics

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