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Results for “Effect Modifier, Epidemiologic”

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PubMed1993

Effects of adjacent surfaces of different shapes on regurgitant jet sizes: an in vitro study using color Doppler imaging and laser-illuminated dye visualization.

OBJECTIVES: The present study was designed to estimate the influence of different-shaped adjacent surfaces on regurgitant jets as assessed by color Doppler imaging and laser-illuminated dye optical visualization. BACKGROUND: Because color Doppler techniques provide real-time two-dimensional imaging of flow, the evaluation of valvular regurgitation by analysis of variance-encoded regurgitant jets by this method has been widely used in clinical studies. However, recent studies have demonstrated that color Doppler jet sizes are affected not only by several hemodynamic factors and instrument settings but also by the interaction between jets and adjacent wall surfaces. In clinical conditions, jets may interact with adjacent walls of variable shapes that might have different effects on the jet size. METHODS: An in vitro model was constructed consisting of a rigid, optically clear receiving chamber that had no outlet resistance and had a pulsatile pump ejecting through 1.5, 2.3 and 3.1 mm2 inflow orifices into the chamber. The surfaces were flat or smoothly and equally curved, convex and concave aluminum positioned at 0, 2 and 4 mm from and to the side of the inflow orifices. The pump was run with stroke volumes from 0.5 to 3.0 ml and with a pulse frequency of 70 beats/min. The echocardiographic and laser beams were aimed at the inflow orifice imaging jets perpendicular to the surfaces (vertical view) through the central plane of the jet flows. Maximal jet areas were measured by both color Doppler techniques and laser-illuminated dye visualization. RESULTS: Color Doppler study showed fair correlation between the jet areas and the stroke volumes (r = 0.83 to 0.99), but the jet sizes under different surface conditions were variable. All the surface jet areas at a jet-surface distance of 0 and 2 mm were smaller than free jet areas at the same stroke volume for both flat and convex surfaces (p < 0.001). Flow constraint by the concave surface resulted in the smallest jet areas (p < 0.001). The color Doppler jet areas on the curved surfaces were significantly smaller than the laser-illuminated dye visualization jet areas (p < 0.01 to 0.0001). However, at intermediate jet-surface distances (4 mm and sometimes 2 mm with higher velocity flows), jet interaction with the flat and especially with the convex surface resulted in larger jets. This effect was most pronounced on dye fluorescence studies because flow around these jets consisted mainly of low velocity vortical events with only partial surface adherence and these low velocity swirling flows were not well imaged by color Doppler technique. CONCLUSIONS: Our study suggests that the different-shaped adjacent surfaces with different degrees of flow alterations resulted in variable decreases in jet size and that color Doppler imaging could not encode and image the angled and low velocity swirling events well when jets flowed along the curved surfaces. These effects need to be taken into account when interpreting color Doppler images.

Analysis of Variance↗

PubMed1990

Sensitivity of effect variables in rheumatoid arthritis: a meta-analysis of 130 placebo controlled NSAID trials.

In a meta-analysis of placebo controlled NSAID trials, the sensitivity of the effect variables was calculated as the correlation coefficient and as the difference between drug and placebo, divided by the placebo group standard deviation. The patient's global evaluation was the most sensitive variable overall. Pain was more sensitive than Ritchie's index. Several variables may be omitted from clinical trials, especially if two active drugs are being compared. For example, the best maximum estimate for the difference in ESR between NSAIDs and placebo was 1.0 mm/hr (95% confidence interval -1.5 to 3.4 mm/hr), and for joint size 0.44% (-1.0 to 1.9%), corresponding to a quarter of a millimeter for each of the 10 joints usually measured. It is suggested to record only the patient's global evaluation, pain, and morning stiffness.

Anthropometry↗

PubMed1992

Cholesterol and coronary artery disease: age as an effect modifier.

An elevation of serum cholesterol has been one of the more frequently cited risk factors for coronary heart disease, found in both case-control and cohort studies. As a result, this country has undertaken massive screening of adults older than 20 years of age in an attempt to identify those persons with cholesterol levels greater than 200 mg/dl, and follow up with an active approach for intervention. The suggested cutpoints for borderline (200-240 mg/dl), and definite (> or = 240 mg/dl) hypercholesterolemia have been applied to all age groups despite suggestions of a diminution of risk conferred by cholesterol in the elderly. This study of 2544 white men undergoing coronary angiography shows that for all men, aged 25-84 years, plasma cholesterol levels were associated with an increase in coronary artery occlusion (rs = 0.15, p < 0.01). However, when stratified by age, this association held only for the younger men, the association diminishing to near zero in the oldest age group. The negative interaction between cholesterol levels and age in predicting coronary artery disease proved highly significant (p < 0.001) in multivariable linear regression analysis, suggesting that cholesterol levels are much less predictive of coronary artery disease in the elderly as compared to the young. These results point to the need for a more finely tuned set of criteria for the evaluation of hypercholesterolemia, one that takes into account the age of the screenee.

Adult↗

PubMed1993

Change in self-reported functioning in older persons entering a residential care facility.

We evaluated the responsiveness of measures of function in admissions to a long-term care facility. Between baseline and follow-up assessment, one-fifth or more of the subjects either worsened or improved in most aspects of reported function. We compared two measures of self-reported function (COOP charts and a short-form survey). Convergent validity was observed for changes in pain, social health, and mental health (r = 0.39-0.74), but not for physical functioning. Although the short-form physical function measure discriminated worsening on several performance-based external criteria of physical functioning (area under ROC curves up to 0.82), the COOP and other measures of physical functioning were less likely to do so. All physical function measures were less responsive for detecting improvement. Clinicians and investigators intending to monitor change in function must consider the responsiveness of their measures.

Activities of Daily Living↗

PubMed1993

Interviewer versus self-administered questionnaires in developing a disease-specific, health-related quality of life instrument for asthma.

We wished to determine the extent to which respondents provided the same answers to a health-related quality of life (HRQL) questionnaire in self- and interviewer-administered forms. One hundred and fifty patients with asthma who were symptomatic or required treatment at least once a week, and had airway hyperresponsiveness to methacholine aerosol (PC20 < 8.0 mg/ml) participated. Patients completed a 152-item HRQL questionnaire in both interviewer and self-administered forms, separated by a 2-week interval, the order determined by random allocation. The percentage of items endorsed by the self-administered approach was significantly higher than that of the interviewer-administered approach overall (46.9 vs 35.8%) (p < 0.0001). The difference was consistent across all six domains; the absolute difference in the proportion of items endorsed varied from 8.9 to 12.3%. The intraclass correlations for the proportion of subjects endorsing an item was 0.84. Self- and interviewer-administered questionnaires yield very similar results in discriminating between subjects, but the self-administered version shows systematically greater HRQL impairment.

Adult↗

PubMed1996

The evaluation of changes in functional health status in patients with abdominal complaints.

Measuring functional status changes in various patient subgroups is important in stratifying risk, assessing disease severity, and predicting and defining clinically relevant outcomes. Data from a multi-centered study of 980 primary care patients presenting with nonspecific abdominal complaints were studied to demonstrate the importance of such an assessment procedure. Patients were prospectively followed for 6 months. Five diagnostic categories based on illness duration and seriousness were derived from the clinical course of these patients. The functional status of each patient was determined at baseline, 1 month, and 6 months using the Sickness Impact Profile (SIP). Intraclass correlation coefficients accounted for two aspects of the reliability of the SIP regarding the measurement of change over time: differences between patients which are stable over time (reproducibility) and different effects of treatment between subsets (responsiveness). A priori formulated expectations about the degree of health status change in patient subgroups were evaluated with the help of effect-size calculations. Patient impairment only partially depended on the final diagnosis and was also influenced by the presence of co-morbidity, psycho-social determinants, and other complaints. The health status change in the patient subgroups agreed with a priori formulated expectations. Standardized effect-size calculations revealed that the degree of change over time in SIP scores was in accordance with these expectations. We conclude: (a) the SIP appeared to be a reliable clinimetric instrument in detecting change over time resulting from different clinical courses, (b) clinical studies that use clinimetric instruments to assess the effects of clinical interventions must adequately control for the influence of baseline "functional status" as well as traditional demographic features such as gender and age, and (c) evaluating a priori formulated clinical expectations concerning functional change with statistics such as intraclass correlation and effect sizes can lead to a clearer understanding of the clinical relevance of statistically significant changes.

Abdominal Pain↗

PubMed2006

Sleep quantity and quality as a predictor of injuries in a rural population.

This study aimed to assess the association of sleep disturbance and injuries in a rural population of Iowa. Study participants were 1345 adults who were enrolled in the KCRHS. Sleep problems were assessed based on self-reports at the beginning of the study. Injury information was collected by telephone interviews an average of every 6 months from August 1999 to June 2004. Sleeping for less than 7.5 hours increased the risk for injuries by 61% (rate ratio, 1.61; 95% confidence interval, 1.21-2.15) compared with sleeping for 7.5 to 8.5 hours (reference). Snoring frequency/severity and daytime fatigue/sleepiness were not significant in predicting the risk for injuries. Alcohol consumption of 1 to 2 or more drinks per day increased the risk for injuries among those who had sleep problems. Having adequate hours of sleep is important in preventing injuries. Avoiding alcohol consumption would be especially helpful in reducing injuries among people with sleep disturbance.

Adolescent↗

PubMed2004

Magnesium prophylaxis for arrhythmias after cardiac surgery: a meta-analysis of randomized controlled trials.

BACKGROUND: Magnesium supplementation may reduce the incidence of arrhythmias, which often occur after cardiac surgery; however, recent findings of the effectiveness of magnesium prophylaxis have yielded discrepant results. METHODS: We searched electronic databases for randomized controlled trials of magnesium for the prevention of arrhythmias after cardiac surgery. The primary outcomes comprised the incidence of supraventricular and ventricular arrhythmias, and the secondary outcomes comprised serum magnesium concentration, length of hospital stay, myocardial infarction, and mortality. Effect sizes were estimated using a random-effects model. RESULTS: Seventeen trials (n=2069 patients) met the inclusion criteria. Pooled serum magnesium concentration at 24 hours after surgery in the treatment group was significantly higher than that in the control group (weighted mean difference=0.45 mmol/L [1.1 mg/dL]; 95% confidence interval [CI]: 0.30 to 0.59 mmol/L [0.7 to 1.4 mg/dL]; P <0.001). Magnesium supplementation reduced the risk of supraventricular arrhythmias (relative risk [RR]=0.77; 95% CI: 0.63 to 0.93; P=0.002) and ventricular arrhythmias (RR = 0.52; 95% CI: 0.31 to 0.87; P <0.0001), but had no effect on the length of hospital stay (weighted mean difference=-0.28 days; 95% CI: -0.70 to 1.27 days; P=0.48), the incidence of perioperative myocardial infarction (RR=1.03; 95% CI: 0.52 to 2.05; P = 0.99), or mortality (RR=0.97; 95% CI: 0.43 to 2.20; P=0.94). CONCLUSION: Administration of prophylactic magnesium reduced the risk of supraventricular arrhythmias after cardiac surgery by 23% (atrial fibrillation by 29%) and of ventricular arrhythmias by 48%. Supplementation had no notable benefit with respect to length of hospitalization, incidence of myocardial infarction, or mortality.

Arrhythmias, Cardiac↗

PubMed2004

Synergism between smoking and vital exhaustion in the risk of ischemic stroke: evidence from the ARIC study.

PURPOSE: To examine the synergism between vital exhaustion and cigarette smoking in producing ischemic stroke. Vital exhaustion (VE), a state characterized by unusual fatigue, irritability, and feelings of demoralization, is measured by the Maastricht questionnaire (MQ), a 21-item inventory of symptoms. METHODS: The Atherosclerosis Risk in Communities (ARIC) Study is an ongoing cohort study, initiated in 1987. The MQ was administered at the second follow-up visit (1990-1992), and participants were subsequently followed for an average of 6.27 years. Four US communities (Minneapolis, Minnesota; Washington County, Maryland; Forsyth County, North Carolina; and Jackson, Mississippi). 13,066 participants aged 48 to 67 years at baseline (Visit 2) with no history of stroke. Validated hospitalized ischemic stroke. RESULTS: During the follow-up period, there were 202 incident ischemic strokes. After multivariate adjustment, current smoking, and high VE were independent risk factors for incident stroke: (smoking vs. non-smoking HR=1.76, p < 0.01; high VE vs. low VE HR=1.94, p < 0.01). For persons with both VE and smoking vs. persons with neither, HR=2.71 (p < 0.001). The proportion of stroke disease burden due to VE and smoking that could be attributed to their interaction was 81 to 93 percent. CONCLUSIONS: The combination of cigarette smoking and VE is synergistic in the production of stroke.

Aged↗

PubMed2005

Lifetime alcohol intake and breast cancer risk.

PURPOSE: Moderate alcohol intake of one to two drinks per day has been consistently associated with a 30-50% increase in breast cancer. Despite the consistency in the overall association, several important questions remain, including whether the association between alcohol intake and breast cancer risk is affected by the timing of alcohol exposure, modified by other risk factors such as body mass index (BMI), menopausal status, and hormone replacement therapy (HRT), or more pronounced among hormone receptor positive tumors or invasive rather than in situ disease. METHODS: To address these questions, we conducted a large population-based study (1508 cases and 1556 controls) that collected detailed information on alcohol and other exposures throughout the lifecourse. RESULTS: Consumption of 15-30 grams/day (approximately one to two drinks) throughout life was associated with a modest 33% increase in risk (odds ratio [OR] = 1.33, 95% confidence interval (CI) = 1.01-1.74), but heavier consumption (> or = 30 grams per day) was not. Risk did not vary with alcohol type (beer, wine, or hard liquor) or by patterns of use, such as recent use, intake prior to age 20 years, or whether use began at an early age. The association with lifetime intake was limited to women with a BMI < 25 (OR = 2.13, 95% CI = 1.29-3.54). Alcohol consumption of approximately one drink per day was associated with estrogen receptor positive tumors among women with a BMI < 25, but not among women BMI > or = 25. Also, the elevated OR was observed only among women diagnosed with invasive (OR = 1.56, 95% CI = 1.11-2.18), but not in situ breast tumors. CONCLUSIONS: These data give added support that moderate alcohol consumption over the life course increases breast cancer risk, particularly among women with low BMI and those diagnosed with estrogen receptor positive tumors or with invasive rather than in situ disease. Risk is confined to moderate intake and does not vary with the timing of use, with heavier doses, or with the type of alcohol consumed.

Adolescent↗

PubMed2006

Do health behaviors moderate the effect of socioeconomic status on metabolic syndrome?

PURPOSE: The purpose of this study is to determine whether the effect of socioeconomic factors on metabolic syndrome is influenced by such covariates as health behavior and psychosocial factors. METHODS: This study used data collected from 4400 households during the 2001 Korea National Health and Nutrition Examination Survey. A stratified multistage probability sampling method was applied and the final sample included 6601 subjects older than 20 years who had completed necessary health examinations. RESULTS: The prevalence of metabolic syndrome in Koreans was 25.5% (95% confidence interval [CI], 23.8-27.2) for men and 28.7% (95% CI, 27.2-30.2) for women. Analysis of moderator effects showed that interactions between education and smoking or exercise status and between income and alcohol or smoking status were significant. The significance of the interaction terms indicates that health behavior and psychosocial factors modified the relationship between socioeconomic factors and metabolic syndrome. CONCLUSIONS: Results of this study provide evidence that such behaviors as smoking, drinking alcohol, and insufficient exercise contribute to the incidence of metabolic syndrome. Changes to higher socioeconomic status may not reduce the odds of metabolic syndrome unless behavior also is adapted.

Adult↗

PubMed2006

Methodological issues associated with group intervention research.

Interventions using a group format can be powerful treatment modalities. However, a review of nursing journals most likely to report the conduct of group research by nurses showed that less than 1% of nursing research reports used this approach and that none accounted for group-level effects in the analysis. This article discusses methodological issues inherent in group intervention research. We begin by offering examples of variables that can be incorporated into group research. We then present some challenges that researchers must address in collecting data when group formats are used. We end with recommendations for conducting group intervention research and by addressing issues associated with interpreting and reporting results.

Analysis of Variance↗

PubMed2005

Analyzing the duration of recurrent events in clinical trials: a comparison of approaches using data from the UK700 trial of psychiatric case management.

In studies of chronic disease the outcome measure may be based upon the duration of recurring illness. Our example is the UK700 trial of psychiatric case management, where the total number of days spent in hospital over a 2-year follow-up was the primary outcome. Investigations of treatment effect modifiers were undertaken using an analysis of that primary outcome, a comparison of length of hospitalizations, and also a multi-state modeling approach. The days in hospital outcome was relatively straightforward to analyze, and allowed the complete randomized treatment groups to be compared. In contrast, the comparison of length of hospitalizations included only hospitalized patients, with censored observations not being well accommodated. The multi-state model provided separate treatment effect estimates for admission and discharge, this being more informative about how any reduction in days spent in hospital is achieved. Estimation of the treatment effects through the use of proportional hazards regression allowed appropriate incorporation of censored observations. However, with the multi-state model approach treatment effect estimates are not based upon comparisons of complete randomized treatment groups, as individuals are removed from the risk set for admission whilst at risk for discharge, and vice versa. We conclude that total duration is an appropriate primary outcome for clinical trials, but that multi-state models deserve greater use as an informative secondary analysis.

Case Management↗

PubMed2006

Continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries after the study period: was this the Hawthorne effect?

BACKGROUND: The incidence of birth trauma and birth asphyxia related to instrumental deliveries in our obstetric unit was high (2.8%) in 1998-1999. A study was performed in 2000 to identify the risk factors. Unexpectedly, the incidence (0.6%) was reduced significantly during the study period. We attributed this phenomenon to the famous Hawthorne effect (tendency to improve performance because of awareness of being studied). OBJECTIVES: The objectives were to study whether there is a continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries in the post-study period (2001-2003) and to investigate the presence of underlying confounding factors apart from the Hawthorne effect. METHOD: To compare the hospital obstetric statistics among the pre-study period (1998-1999), the study period (2000) and the post-study period (2001-2003), in particular the incidence of birth trauma and birth asphyxia related to instrumental deliveries, the instrumental delivery rate, the overall Caesarean section rate, the Caesarean section rate for no progress of labour, the incidence of failed instrumental delivery, the incidence of attempted instrumental delivery in the operating theatre, and incidence of direct second-stage Caesarean sections. RESULTS: The incidence of birth trauma and birth asphyxia related to instrumental deliveries (0.6%) during the study period (2000) was significantly lower than that (2.8%) during the pre-study period (1998-1999; RR 0.27, 95% CI 0.11-0.70). This phenomenon continued into the post-study period (2001-2003) when the incidence of 1.0% was similarly lower than that in the pre-study period (RR 0.35, 95% CI 0.20-0.64). The instrumental delivery rate decreased further in the post-study period (13.5%) compared with those in the study (16.6%) and pre-study (19.5%) periods (RR 0.81, 95% CI 0.75-0.89 and RR 0.69, 95% CI 0.65-0.74, respectively). There was a marked increase in the direct second-stage Caesarean section rate in the post-study period (7.1%) compared to those in the study (0.4%) and pre-study (0.7%) periods (RR 15.9, 95% CI 5.05-49.73 and RR 9.77, 95% CI 5.28-18.08, respectively). CONCLUSION: A change in obstetric practice was identified that may explain the continued reduction in the incidence of birth trauma and birth asphyxia related to instrumental deliveries in the post-study period.

Asphyxia Neonatorum↗

PubMed2006

Improving compliance with postpolypectomy surveillance guidelines: an interventional study using a continuous quality improvement initiative.

BACKGROUND: Despite guidelines, physicians tend to perform postpolypectomy surveillance colonoscopies too frequently. OBJECTIVE: The objective of the study was to determine the baseline compliance rate with postpolypectomy guidelines in our unit and to determine the influence of a continuous quality improvement (CQI) intervention on improving the compliance rate and on decreasing the potential additional costs because of the scheduling of postpolypectomy surveillance colonoscopies earlier than indicated. DESIGN: This was a single-arm, pretest-posttest design. SETTING: This study took place at a tertiary care, academic medical center. PATIENTS: The medical records of all patients who underwent colonoscopy with polypectomy in our unit retrospectively during 6 months preceding (baseline period) and prospectively for 6 months after an intervention (postintervention period) were reviewed for patient demographics, colonoscopy findings, and scheduling of repeat colonoscopies. INTERVENTION: We used 3 components: (1) distribution of a wallet-size card with a summary of postpolypectomy guidelines to all endoscopists, (2) placement of guideline charts near computers used for typing endoscopy reports, and (3) distribution and reinforcement of the guidelines in a monthly continuous quality improvement meeting. MAIN OUTCOME MEASURES: The main outcome measures were compliance rates, mean times to repeat colonoscopy, and additional costs from surveillance colonoscopies being scheduled earlier than indicated were compared between the two periods. RESULTS: There were 278 patients in the baseline period and 242 in the postintervention period, with similar patient and polyp characteristics. After the intervention, the compliance rate with guidelines improved from 57.2% to 81% (p < 0.001). The mean time to a repeat colonoscopy increased from 4.5 to 5.2 years (p = 0.003) (i.e., a 14% reduction in the number of postpolypectomy surveillance colonoscopies performed per year). This would result in a reduction of a total of 73 surveillance colonoscopies per year in our unit, with a projected cost savings of 171,331 dollars per year (cost of a colonoscopy assumed at 2347 dollars). LIMITATIONS: The limitation of the study was possible enhanced performance secondary to being observed (Hawthorne effect). Because more than 1 intervention was used, we do not know which one is more effective. CONCLUSIONS: Relatively simple and easy-to-implement quality improvement initiatives can significantly enhance compliance with postpolypectomy guidelines and result in cost savings because of a reduction in the number of postpolypectomy surveillance colonoscopies being scheduled earlier than recommended guidelines.

Colonoscopy↗

PubMed2005

Assessment of patient functional status after surgery.

BACKGROUND: Improvement in day-to-day functioning is a valued outcome of surgical intervention. A new functional status assessment instrument, the Activities Assessment Scale (AAS), was designed for a randomized clinical trial evaluating laparoscopic versus open hernia repair procedures. STUDY DESIGN: The study data set included 2,164 patients at baseline and 1,562 patients at 3-month followup. Only male patients were enrolled in the trial. The psychometric characteristics of the AAS were examined in statistical analyses of cross-sectional and longitudinal data from the trial. Correlational analyses, factor analyses, and t-tests were used to evaluate scale performance. RESULTS: We found that the AAS was a reliable measure (Cronbach's Coefficient Alpha =0.85) in the patient population studied. Factor analyses identified three subscales (sedentary activities; ambulatory activities; work and exercise activities). Construct validity was demonstrated by a correlation of 0.65 between the AAS and the physical functioning (PF) dimension of the SF-36 (p < 0.001); comparisons between clinical subgroups further confirmed its validity (p < 0.001). Patients reporting improvement on the physical functioning dimension after surgery showed an effect size of 1.20 for preoperative-postoperative change in their AAS scores. CONCLUSIONS: The AAS has been demonstrated to be a reliable, valid, and clinically responsive instrument that can be used to evaluate patient functioning after hernia surgery. It is easy to administer and requires less than 5 minutes of patient time to complete. This measurement system may prove useful in assessing surgical outcomes in both research and office practice settings.

Activities of Daily Living↗

PubMed2006

Direct observations of nursing home care quality: Does care change when observed?

OBJECTIVES: Recent research demonstrates that care recorded by nursing home (NH) staff is often inaccurate. Direct observations of care may therefore be of critical importance in assessing and improving care in this setting. Unfortunately, despite their apparent use in several types of quality assurance activities, there is little written information about the reliability or accuracy of observational procedures in NHs. This paper provides information about one important measurement issue (reactivity) that is often cited as a limitation of observational procedures in measuring usual care practices accurately. DESIGN: Descriptive. SETTING: Seven nursing homes. PARTICIPANTS: Staff and residents. MEASUREMENTS: Direct observational time in bed; repositioning and feeding assistance. RESULTS: Observational measures of care quality were stable over multiple observation periods and consistently detected quality problems even on the first and last days of observation. CONCLUSION: Direct observations of care provided to residents do not appear to change provider behavior.

Attitude of Health Personnel↗

PubMed2004

Larger effect sizes were associated with higher quality ratings in complementary and alternative medicine randomized controlled trials.

OBJECTIVE: To determine if the quality of complementary and alternative medicine (CAM) placebo controlled randomized controlled trials (RCTs) is related to the effect sizes they produce when the type of interventions and outcome variables are controlled. STUDY DESIGN AND SETTING: A sample of 25 CAM meta-analyses was identified from MEDLINE and hand searches containing published effect sizes for at least three efficacy trials employing placebo control groups. From these 25 reviews, 26 pairs of trials were selected: the one reporting the largest effect size and the matching trial reporting the smallest effect size. Quality and publication characteristics were then abstracted from each trial. RESULTS: Unlike the preponderance of past evidence examining the relationship between quality and effect size, the present study found that trials possessing the largest effect sizes within a meta-analysis were also associated with higher quality ratings than their counterparts possessing the lowest effect sizes (P=.019). CONCLUSIONS: Possible theoretical reasons for this unexpected positive relationship include (a) sampling error, (b) reduced within group variation, (c) fraudulent reporting, and (d) the restriction of the analyses to placebo controlled trial.

Complementary Therapies↗