Dealing with missing standard deviation and mean values in meta-analysis of continuous outcomes: a systematic review.

BACKGROUND: Rigorous, informative meta-analyses rely on availability of appropriate summary statistics or individual participant data. For continuous outcomes, especially those with naturally skewed distributions, summary information on the mean or variability often goes unreported. While full reporting of original trial data is the ideal, we sought to identify methods for handling unreported mean or variability summary statistics in meta-analysis. METHODS: We undertook two systematic literature reviews to identify methodological approaches used to deal with missing mean or variability summary statistics. Five electronic databases were searched, in addition to the Cochrane Colloquium abstract books and the Cochrane Statistics Methods Group mailing list archive. We also conducted cited reference searching and emailed topic experts to identify recent methodological developments. Details recorded included the description of the method, the information required to implement the method, any underlying assumptions and whether the method could be readily applied in standard statistical software. We provided a summary description of the methods identified, illustrating selected methods in example meta-analysis scenarios. RESULTS: For missing standard deviations (SDs), following screening of 503 articles, fifteen methods were identified in addition to those reported in a previous review. These included Bayesian hierarchical modelling at the meta-analysis level; summary statistic level imputation based on observed SD values from other trials in the meta-analysis; a practical approximation based on the range; and algebraic estimation of the SD based on other summary statistics. Following screening of 1124 articles for methods estimating the mean, one approximate Bayesian computation approach and three papers based on alternative summary statistics were identified. Illustrative meta-analyses showed that when replacing a missing SD the approximation using the range minimised loss of precision and generally performed better than omitting trials. When estimating missing means, a formula using the median, lower quartile and upper quartile performed best in preserving the precision of the meta-analysis findings, although in some scenarios, omitting trials gave superior results. CONCLUSIONS: Methods based on summary statistics (minimum, maximum, lower quartile, upper quartile, median) reported in the literature facilitate more comprehensive inclusion of randomised controlled trials with missing mean or variability summary statistics within meta-analyses.

Inter-arm blood pressure difference and mortality: a cohort study in an asymptomatic primary care population at elevated cardiovascular risk.

BACKGROUND: Differences in blood pressure between arms are associated with increased cardiovascular mortality in cohorts with established vascular disease or substantially elevated cardiovascular risk. AIM: To explore the association of inter-arm difference (IAD) with mortality in a community-dwelling cohort that is free of cardiovascular disease. DESIGN AND SETTING: Cohort analysis of a randomised controlled trial in central Scotland, from April 1998 to October 2008. METHOD: Volunteers from Lanarkshire, Glasgow, and Edinburgh, free of pre-existing vascular disease and with an ankle-brachial index ≤0.95, had systolic blood pressure measured in both arms at recruitment. Inter-arm blood pressure differences were calculated and examined for cross-sectional associations and differences in prospective survival. Outcome measures were cardiovascular events and all-cause mortality during mean follow-up of 8.2 years. RESULTS: Based on a single pair of measurements, 60% of 3350 participants had a systolic IAD ≥5 mmHg and 38% ≥10 mmHg. An IAD ≥5 mmHg was associated with increased cardiovascular mortality (adjusted hazard ratio [HR] 1.91, 95% confidence interval [CI] = 1.19 to 3.07) and all-cause mortality (adjusted HR 1.44, 95% CI = 1.15 to 1.79). Within the subgroup of 764 participants who had hypertension, IADs of ≥5 mmHg or ≥10 mmHg were associated with both cardiovascular mortality (adjusted HR 2.63, 95% CI = 0.97 to 7.02, and adjusted HR 2.96, 95% CI = 1.27 to 6.88, respectively) and all-cause mortality (adjusted HR 1.67, 95% CI = 1.05 to 2.66, and adjusted HR 1.63, 95% CI = 1.06 to 2.50, respectively). IADs ≥15 mmHg were not associated with survival differences in this population. CONCLUSION: Systolic IADs in blood pressure are associated with increased risk of cardiovascular events, including mortality, in a large cohort of people free of pre-existing vascular disease.

Oxygen saturation targets in infants with bronchiolitis (BIDS): a double-blind, randomised, equivalence trial.

BACKGROUND: The American Academy of Pediatrics recommends a permissive hypoxaemic target for an oxygen saturation of 90% for children with bronchiolitis, which is consistent with the WHO recommendations for targets in children with lower respiratory tract infections. No evidence exists to support this threshold. We aimed to assess whether the 90% or higher target for management of oxygen supplementation was equivalent to a normoxic 94% or higher target for infants admitted to hospital with viral bronchiolitis. METHODS: We did a parallel-group, randomised, controlled, equivalence trial of infants aged 6 weeks to 12 months of age with physician-diagnosed bronchiolitis newly admitted into eight paediatric hospital units in the UK (the Bronchiolitis of Infancy Discharge Study [BIDS]). A central computer randomly allocated (1:1) infants, in varying length blocks of four and six and without stratification, to be clipped to standard oximeters (patients treated with oxygen if pulse oxygen saturation [SpO2] <94%) or modified oximeters (displayed a measured value of 90% as 94%, therefore oxygen not given until SpO2 <90%). All parents, clinical staff, and outcome assessors were masked to allocation. The primary outcome was time to resolution of cough (prespecified equivalence limits of plus or minus 2 days) in the intention-to-treat population. This trial is registered with ISRCTN, number ISRCTN28405428. FINDINGS: Between Oct 3, and March 30, 2012, and Oct 1, and March 29, 2013, we randomly assigned 308 infants to standard oximeters and 307 infants to modified oximeters. Cough resolved by 15·0 days (median) in both groups (95% CI for difference -1 to 2) and so oxygen thresholds were equivalent. We recorded 35 serious adverse events in 32 infants in the standard care group and 25 serious adverse events in 24 infants in the modified care group. In the standard care group, eight infants transferred to a high-dependency unit, 23 were readmitted, and one had a prolonged hospital stay. In the modified care group, 12 infants were transferred to a high-dependency unit and 12 were readmitted to hospital. Recorded adverse events did not differ significantly. INTERPRETATION: Management of infants with bronchiolitis to an oxygen saturation target of 90% or higher is as safe and clinically effective as one of 94% or higher. Future research should assess the benefits and risks of different oxygen saturation targets in acute respiratory infection in older children, particularly in developing nations where resources are scarce. FUNDING: National Institute for Health Research, Health Technology Assessment programme.

Effect of a lifestyle intervention on weight change in south Asian individuals in the UK at high risk of type 2 diabetes: a family-cluster randomised controlled trial.

BACKGROUND: The susceptibility to type 2 diabetes of people of south Asian descent is established, but there is little trial-based evidence for interventions to tackle this problem. We assessed a weight control and physical activity intervention in south Asian individuals in the UK. METHODS: We did this non-blinded trial in two National Health Service (NHS) regions in Scotland (UK). Between July 1, 2007, and Oct 31, 2009, we recruited men and women of Indian and Pakistani origin, aged 35 years or older, with waist circumference 90 cm or greater in men or 80 cm or greater in women, and with impaired glucose tolerance or impaired fasting glucose determined by oral glucose tolerance test. Families were randomised (using a random number generator program, with permuted blocks of random size, stratified by location [Edinburgh or Glasgow], ethnic group [Indian or Pakistani], and number of participants in the family [one vs more than one]) to intervention or control. Participants in the same family were not randomised separately. The intervention group received 15 visits from a dietitian over 3 years and the control group received four visits in the same period. The primary outcome was weight change at 3 years. Analysis was by modified intention to treat, excluding participants who died or were lost to follow-up. We used linear regression models to provide mean differences in baseline-adjusted weight at 3 years. This trial is registered, number ISRCTN25729565. FINDINGS: Of 1319 people who were screened with an oral glucose tolerance test, 196 (15%) had impaired glucose tolerance or impaired fasting glucose and 171 entered the trial. Participants were in 156 family clusters that were randomised (78 families with 85 participants were allocated to intervention; 78 families with 86 participants were allocated to control). 167 (98%) participants in 152 families completed the trial. Mean weight loss in the intervention group was 1.13 kg (SD 4.12), compared with a mean weight gain of 0.51 kg (3.65) in the control group, an adjusted mean difference of -1.64 kg (95% CI -2.83 to -0.44). INTERPRETATION: Modest, medium-term changes in weight are achievable as a component of lifestyle-change strategies, which might control or prevent adiposity-related diseases. FUNDING: National Prevention Research Initiative, NHS Research and Development; NHS National Services Scotland; NHS Health Scotland.

Reduction of adverse effects from intravenous acetylcysteine treatment for paracetamol poisoning: a randomised controlled trial.

BACKGROUND: Paracetamol poisoning is common worldwide. It is treated with intravenous acetylcysteine, but the standard regimen is complex and associated with frequent adverse effects related to concentration, which can cause treatment interruption. We aimed to ascertain whether adverse effects could be reduced with either a shorter modified acetylcysteine schedule, antiemetic pretreatment, or both. METHODS: We undertook a double-blind, randomised factorial study at three UK hospitals, between Sept 6, 2010, and Dec 31, 2012. We randomly allocated patients with acute paracetamol overdose to either the standard intravenous acetylcysteine regimen (duration 20·25 h) or a shorter (12 h) modified protocol, with or without intravenous ondansetron pretreatment (4 mg). Masking was achieved by infusion of 5% dextrose (during acetylcysteine delivery) or saline (for antiemetic pretreatment). Randomisation was done via the internet and included a minimisation procedure by prognostic factors. The primary outcome was absence of vomiting, retching, or need for rescue antiemetic treatment at 2 h. Prespecified secondary outcomes included a greater than 50% increase in alanine aminotransferase activity over the admission value. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov (identifier NCT01050270). FINDINGS: Of 222 patients who underwent randomisation, 217 were assessable 2 h after the start of acetylcysteine treatment. Vomiting, retching, or need for rescue antiemetic treatment at 2 h was reported in 39 of 108 patients assigned to the shorter modified protocol compared with 71 of 109 allocated to the standard acetylcysteine regimen (adjusted odds ratio 0·26, 97·5% CI 0·13-0·52; p<0·0001), and in 45 of 109 patients who received ondansetron compared with 65 of 108 allocated placebo (0·41, 0·20-0·80; p=0·003). Severe anaphylactoid reactions were recorded in five patients assigned to the shorter modified acetylcysteine regimen versus 31 who were allocated to the standard protocol (adjusted common odds ratio 0·23, 97·5% CI 0·12-0·43; p<0·0001). The proportion of patients with a 50% increase in alanine aminotransferase activity did not differ between the standard (9/110) and shorter modified (13/112) regimens (adjusted odds ratio 0·60, 97·5% CI 0·20-1·83); however, the proportion was higher with ondansetron (16/111) than with placebo (6/111; 3·30, 1·01-10·72; p=0·024). INTERPRETATION: In patients with paracetamol poisoning, a 12 h modified acetylcysteine regimen resulted in less vomiting, fewer anaphylactoid reactions, and reduced need for treatment interruption. This study was not powered to detect non-inferiority of the shorter protocol versus the standard approach; therefore, further research is needed to confirm the efficacy of the 12 h modified acetylcysteine regimen. FUNDING: Chief Scientist Office of the Scottish Government.

Advancing care for traumatic brain injury: findings from the IMPACT studies and perspectives on future research.

Research in traumatic brain injury (TBI) is challenging for several reasons; in particular, the heterogeneity between patients regarding causes, pathophysiology, treatment, and outcome. Advances in basic science have failed to translate into successful clinical treatments, and the evidence underpinning guideline recommendations is weak. Because clinical research has been hampered by non-standardised data collection, restricted multidisciplinary collaboration, and the lack of sensitivity of classification and efficacy analyses, multidisciplinary collaborations are now being fostered. Approaches to deal with heterogeneity have been developed by the IMPACT study group. These approaches can increase statistical power in clinical trials by up to 50% and are also relevant to other heterogeneous neurological diseases, such as stroke and subarachnoid haemorrhage. Rather than trying to limit heterogeneity, we might also be able to exploit it by analysing differences in treatment and outcome between countries and centres in comparative effectiveness research. This approach has great potential to advance care in patients with TBI.

Smoking, hypercholesterolaemia and hypertension as risk factors for cognitive impairment in older adults.

BACKGROUND: the prevalence of all types of cognitive impairment, including dementia, is increasing but knowledge of aetiological factors is still evolving. OBJECTIVE: this study aimed to evaluate the association between cardiovascular risk factors and cognitive function in older persons. DESIGN, SETTING AND SUBJECTS: a population-based cohort design involving 2,312 men and women (aged 50-75) enrolled in the University of Edinburgh Aspirin for Asymptomatic Atherosclerosis trial. METHODS: cognitive tests included the Mill Hill Vocabulary Scale, auditory verbal learning test (AVLT), digit symbol test, verbal fluency test (VFT), Raven's Progressive Matrices and the trail making test. A 'g' score (measure of general intelligence) was computed for each subject. Regression analysis was used to evaluate the association between relevant variables. RESULTS: higher diastolic BP was negatively associated with AVLT (ß = -0.153, P < 0.01), and with an estimated decline on AVLT (ß = -0.125, P < 0.01). Smoking was negatively associated with all the cognitive variables except VFT. The total cholesterol level was not associated with cognitive function or estimated decline. CONCLUSIONS: smoking and elevated blood pressure may be risk factors for cognitive decline, and thus potential targets for preventive and therapeutic interventions.

Prediction of outcome after moderate and severe traumatic brain injury: external validation of the International Mission on Prognosis and Analysis of Clinical Trials (IMPACT) and Corticoid Randomisation After Significant Head injury (CRASH) prognostic models.

OBJECTIVE: The International Mission on Prognosis and Analysis of Clinical Trials and Corticoid Randomisation After Significant Head injury prognostic models predict outcome after traumatic brain injury but have not been compared in large datasets. The objective of this is study is to validate externally and compare the International Mission on Prognosis and Analysis of Clinical Trials and Corticoid Randomisation after Significant Head injury prognostic models for prediction of outcome after moderate or severe traumatic brain injury. DESIGN: External validation study. PATIENTS: We considered five new datasets with a total of 9,036 patients, comprising three randomized trials and two observational series, containing prospectively collected individual traumatic brain injury patient data. MEASUREMENTS AND MAIN RESULTS: Outcomes were mortality and unfavorable outcome, based on the Glasgow Outcome Score at 6 months after injury. To assess performance, we studied the discrimination of the models (by area under the receiver operating characteristic curves), and calibration (by comparison of the mean observed to predicted outcomes and calibration slopes). The highest discrimination was found in the Trauma Audit and Research Network trauma registry (area under the receiver operating characteristic curves between 0.83 and 0.87), and the lowest discrimination in the Pharmos trial (area under the receiver operating characteristic curves between 0.65 and 0.71). Although differences in predictor effects between development and validation populations were found (calibration slopes varying between 0.58 and 1.53), the differences in discrimination were largely explained by differences in case mix in the validation studies. Calibration was good, the fraction of observed outcomes generally agreed well with the mean predicted outcome. No meaningful differences were noted in performance between the International Mission on Prognosis and Analysis of Clinical Trials and Corticoid Randomisation After Significant Head injury models. More complex models discriminated slightly better than simpler variants. CONCLUSIONS: Since both the International Mission on Prognosis and Analysis of Clinical Trials and the Corticoid Randomisation After Significant Head injury prognostic models show good generalizability to more recent data, they are valid instruments to quantify prognosis in traumatic brain injury.

Pain in patients attending a specialist cancer service: prevalence and association with emotional distress.

CONTEXT: We know little about how many outpatients of a modern cancer center suffer from clinically significant unrelieved pain and the characteristics of these patients to guide better care. OBJECTIVES: To determine the prevalence of clinically significant pain (CSP) in the outpatients of a regional cancer center and the association with distress and other variables. METHODS: A secondary analysis of cross-sectional, self-reported and clinical data from 2768 patients reattending selected clinics of a regional National Health Service cancer center in the U.K. Pain was measured using the pain severity scale of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, emotional distress was measured by the Hospital Anxiety and Depression Scale, and demographic and clinical data were taken from medical records. RESULTS: Fifty-four percent (95% confidence interval [CI] 52-56) of patients reported pain at least "a little" in the previous week and 18% (95% CI 17-20) at least "quite a bit" (CSP). The strongest independent associations of CSP were active disease (odds ratio [OR] 1.95, 95% CI 1.5-2.5) and emotional distress (OR 4.8, 95% CI 4-6). CONCLUSION: CSP is surprisingly common in outpatients of specialist cancer services, and it is strongly and independently associated with emotional distress. Better symptom management should consider pain and distress together.

Does the extended Glasgow Outcome Scale add value to the conventional Glasgow Outcome Scale?

The Glasgow Outcome Scale (GOS) is firmly established as the primary outcome measure for use in Phase III trials of interventions in traumatic brain injury (TBI). However, the GOS has been criticized for its lack of sensitivity to detect small but clinically relevant changes in outcome. The Glasgow Outcome Scale-Extended (GOSE) potentially addresses this criticism, and in this study we estimate the efficiency gain associated with using the GOSE in place of the GOS in ordinal analysis of 6-month outcome. The study uses both simulation and the reanalysis of existing data from two completed TBI studies, one an observational cohort study and the other a randomized controlled trial. As expected, the results show that using an ordinal technique to analyze the GOS gives a substantial gain in efficiency relative to the conventional analysis, which collapses the GOS onto a binary scale (favorable versus unfavorable outcome). We also found that using the GOSE gave a modest but consistent increase in efficiency relative to the GOS in both studies, corresponding to a reduction in the required sample size of the order of 3-5%. We recommend that the GOSE be used in place of the GOS as the primary outcome measure in trials of TBI, with an appropriate ordinal approach being taken to the statistical analysis.

Thoughts of death and suicide reported by cancer patients who endorsed the "suicidal thoughts" item of the PHQ-9 during routine screening for depression.

BACKGROUND: Patients with serious medical illnesses, such as cancer, are at increased risk of suicide but are also often facing death. The Patient Health Questionnaire-9 (PHQ-9) is widely used to screen patients for depression. It includes an item that asks about thoughts of death and hurting yourself (Item-9). OBJECTIVE: To describe the nature of thoughts of death and suicide reported in clinical interviews carried out to further assess suicidal ideation of cancer outpatients who had endorsed the "suicidal thoughts item" (Item-9) of the PHQ-9 during routine depression screening. METHOD: Secondary analysis of anonymized service data (with ethical approval) derived from the routine clinical administration of self-report questionnaires and telephone interviews to outpatients attending a Cancer Centre in the UK. RESULTS: Complete data were available on 330/463 (71%) of patients who had endorsed Item-9. In a subsequent structured telephone interview, approximately one-third of these patients denied any thoughts that they would be better off dead, another third acknowledged having thoughts that they would be better off dead, but not of suicide, and the remaining third reported clear thoughts of committing suicide. CONCLUSION: Only one-third of cancer outpatients who endorse the "suicidal thoughts item" of the PHQ-9 report suicidal thoughts at a subsequent interview. Services planning to set up depression screening with the PHQ-9 need to carefully consider the relative benefits and burden to their service and patients of including Item-9 and interviewing all those who endorse it.

Large between-center differences in outcome after moderate and severe traumatic brain injury in the international mission on prognosis and clinical trial design in traumatic brain injury (IMPACT) study.

BACKGROUND: Differences between centers in patient outcome after traumatic brain injury are of importance for multicenter studies and have seldom been studied. OBJECTIVE: To quantify the differences in centers enrolling patients in randomized clinical trials (RCTs) and surveys. METHODS: We analyzed individual patient data from 9578 patients with moderate and severe traumatic brain injury enrolled in 10 RCTs and 3 observational studies. We used random-effects logistic regression models to estimate the between-center differences in unfavorable outcome (dead, vegetative state, or severe disability measured with the Glasgow Outcome Scale) at 6 months adjusted for differences in patient characteristics. We calculated the difference in odds of unfavorable outcome between the centers at the higher end vs those at the lower end of the outcome distribution. We analyzed the total database, Europe and the United States separately, and 4 larger RCTs. RESULTS: The 9578 patients were enrolled at 265 centers, and 4629 (48%) had an unfavorable outcome. After adjustment for patient characteristics, there was a 3.3-fold difference in the odds of unfavorable outcome between the centers at the lower end of the outcome distribution (2.5th percentile) vs those at the higher end of the outcome distribution (97.5th percentile; P<.001). In the 4 larger RCTs, the differences between centers were similar. However, differences were smaller between centers in the United States (2.4-fold) than between centers in Europe (3.8-fold). CONCLUSION: Outcome after traumatic brain injury differs substantially between centers, particularly in Europe. Further research is needed to study explanations for these differences to suggest where quality of care might be improved.

Screening for major depression in cancer outpatients: the diagnostic accuracy of the 9-item patient health questionnaire.

BACKGROUND: Systematic screening for depression has been recommended for patients who have medical conditions like cancer. The 9-item Patient Health Questionnaire (PHQ-9) is becoming widely used, but its diagnostic accuracy has not yet been tested in a cancer patient population. In this article, the authors report on the performance of the PHQ-9 as a screening instrument for major depressive disorder (MDD) in patients with cancer. METHODS: Data obtained from a depression screening service for patients who were attending clinics of a Regional Cancer Centre in Edinburgh, United Kingdom were used. Patients had completed both the PHQ-9 and a 2-stage procedure to identify cases of MDD. Performance of the PHQ-9 in identifying cases of MDD was determined using receiver operating characteristic (ROC) analysis. RESULTS: Data were available on 4264 patients. When scored as a continuous measure, the PHQ-9 performed well with an area under the ROC curve of 0.94 (95% confidence interval [CI], 0.93-0.95). A cutoff score of ≥ 8 provided a sensitivity of 93% (95% CI, 89%-95%), a specificity of 81% (95% CI, 80%-82%), a positive predictive value (PPV) of 25%, and a negative predictive value (NPV) of 99% and could be considered optimum in a screening context. The PHQ-9 did not perform as well when it was scored using an algorithm with a sensitivity of 56% (95% CI, 55%-57%), a specificity of 96% (95% CI, 95%-97%), a PPV of 52%, and an NPV of 97%. CONCLUSIONS: The PHQ-9 scored as a continuous measure with a cutoff score of ≥ 8 performed well in identifying MDD in cancer patients and should be considered as a screening instrument in this population.

Measuring improvement in depression in cancer patients: a 50% drop on the self-rated SCL-20 compared with a diagnostic interview.

OBJECTIVE: To determine the validity of a 50% drop in the 20-item Symptom Checklist Depression Scale (SCL-20) score against the "gold standard" of no longer meeting criteria for major depression as assessed using a diagnostic interview in an outpatient cancer population and also to examine the validity of other potential cut-offs (i.e., percentage drops). MATERIALS AND METHODS: Secondary analysis of data from a randomized trial which compared collaborative care with usual care for cancer patients with major depression. A total of 194 trial participants who had both SCL-20 scores and depression diagnoses on the Structured Clinical Interview for DSM-IV at both baseline and at 12-week outcome formed the analyzed sample. RESULTS: A 50% reduction in the SCL-20 score from baseline to 12 weeks correctly identified the patients who no longer met criteria for major depression in 153 (78.9%) of 194 (95% CI 73.1% to 84.6%) cases. Most of those misclassified had not achieved a 50% reduction in SCL-20 score despite no longer meeting criteria for major depression. Examination of the performance of percentage drops other than 50% on the SCL-20 using a receiver operating characteristics (ROC) curve and histogram of misclassification suggested that the 50% drop was best if both a low overall misclassification rate and the minimizing of false positives of improvement were required. CONCLUSIONS: A 50% reduction in the SCL-20 score performs well as a conservative measure of change in depression status in cancer patients.

Aspirin for prevention of cardiovascular events in a general population screened for a low ankle brachial index: a randomized controlled trial.

CONTEXT: A low ankle brachial index (ABI) indicates atherosclerosis and an increased risk of cardiovascular and cerebrovascular events. Screening for a low ABI can identify an asymptomatic higher risk group potentially amenable to preventive treatments. OBJECTIVE: To determine the effectiveness of aspirin in preventing events in people with a low ABI identified on screening the general population. DESIGN, SETTING, AND PARTICIPANTS: The Aspirin for Asymptomatic Atherosclerosis trial was an intention-to-treat double-blind randomized controlled trial conducted from April 1998 to October 2008, involving 28,980 men and women aged 50 to 75 years living in central Scotland, free of clinical cardiovascular disease, recruited from a community health registry, and had an ABI screening test. Of those, 3350 with a low ABI (< or = 0.95) were entered into the trial, which was powered to detect a 25% proportional risk reduction in events. INTERVENTIONS: Once daily 100 mg aspirin (enteric coated) or placebo. MAIN OUTCOME MEASURES: The primary end point was a composite of initial fatal or nonfatal coronary event or stroke or revascularization. Two secondary end points were (1) all initial vascular events defined as a composite of a primary end point event or angina, intermittent claudication, or transient ischemic attack; and (2) all-cause mortality. RESULTS: After a mean (SD) follow-up of 8.2 (1.6) years, 357 participants had a primary end point event (13.5 per 1000 person-years, 95% confidence interval [CI], 12.2-15.0). No statistically significant difference was found between groups (13.7 events per 1000 person-years in the aspirin group vs 13.3 in the placebo group; hazard ratio [HR], 1.03; 95% CI, 0.84-1.27). A vascular event comprising the secondary end point occurred in 578 participants (22.8 per 1000 person-years; 95% CI, 21.0-24.8) and no statistically significant difference between groups (22.8 events per 1000 person-years in the aspirin group vs 22.9 in the placebo group; HR, 1.00; 95% CI, 0.85-1.17). There was no significant difference in all-cause mortality between groups (176 vs 186 deaths, respectively; HR, 0.95; 95% CI, 0.77-1.16). An initial event of major hemorrhage requiring admission to hospital occurred in 34 participants (2.5 per 1000 person-years) in the aspirin group and 20 (1.5 per 1000 person-years) in the placebo group (HR, 1.71; 95% CI, 0.99-2.97). CONCLUSION: Among participants without clinical cardiovascular disease, identified with a low ABI based on screening a general population, the administration of aspirin compared with placebo did not result in a significant reduction in vascular events. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN66587262.

IMPACT recommendations for improving the design and analysis of clinical trials in moderate to severe traumatic brain injury.

Clinical trials in traumatic brain injury (TBI) pose complex methodological challenges, largely related to the heterogeneity of the population. The International Mission on Prognosis and Clinical Trial Design in TBI study group has explored approaches for dealing with this heterogeneity with the aim to optimize clinical trials in TBI. Extensive prognostic analyses and simulation studies were conducted on individual patient data from eight trials and three observational studies. Here, we integrate the results of these studies into the International Mission on Prognosis and Clinical Trial Design in TBI recommendations for design and analysis of trials in TBI: Details of the major baseline prognostic characteristics should be provided in every report on a TBI study; in trials they should be differentiated per treatment group. We also advocate the reporting of the baseline prognostic risk as determined by validated prognostic models. Inclusion criteria should be as broad as is compatible with the current understanding of the mechanisms of action of the intervention being evaluated. This will maximize recruitment rates and enhance the generalizability of the results. The statistical analysis should incorporate prespecified covariate adjustment to mitigate the effects of the heterogeneity. The statistical analysis should use an ordinal approach, based on either sliding dichotomy or proportional odds methodology. Broad inclusion criteria, prespecified covariate adjustment, and an ordinal analysis will promote an efficient trial, yielding gains in statistical efficiency of more than 40%. This corresponds to being able to detect a 7% treatment effect with the same number of patients needed to demonstrate a 10% difference with an unadjusted analysis based on the dichotomized Glasgow outcome scale.

A simulation study evaluating approaches to the analysis of ordinal outcome data in randomized controlled trials in traumatic brain injury: results from the IMPACT Project.

BACKGROUND: Clinical trials in traumatic brain injury have a disappointing track record, with a long history of 'negative' Phase III trials. One contributor to this lack of success is almost certainly the low efficiency of the conventional approach to the analysis, which discards information by dichotomizing an ordinal outcome scale. PURPOSE: Our goal was to evaluate the potential efficiency gains, which can be achieved by using techniques, which extract additional information from ordinal outcome data - the proportional odds model and the sliding dichotomy. In addition, we evaluated the additional efficiency gains, which can be achieved through covariate adjustment. METHODS: The study was based on simulations, which were built around a database of patient-level data extracted from eight Phase III trials and three observational studies in traumatic brain injury. Two different putative treatment effects were explored, one which followed the proportional odds model, and the other which assumed that the effect of the intervention was to reduce the risk of death without changing the distribution of outcomes within survivors. The results are expressed as efficiency gains, reported as the percentage reduction in sample size that can be used with the ordinal analyses without loss of statistical power relative to the conventional binary analysis. RESULTS: The simulation results show substantial efficiency gains. Use of the sliding dichotomy allows sample sizes to be reduced by up to 40% without loss of statistical power. The proportional odds model gives modest additional gains over and above the gains achieved by use of the sliding dichotomy. LIMITATIONS: As with any simulation study, it is difficult to know how far the findings may be extrapolated beyond the actual situations that were modeled. CONCLUSIONS: Both ordinal techniques offer substantial efficiency gains relative to the conventional binary analysis. The choice between the two techniques involves subtle value judgments. In the situations examined, the proportional odds model gave efficiency gains over and above the sliding dichotomy, but arguably, the sliding dichotomy is more intuitive and clinically appealing.

Association between raised inflammatory markers and cognitive decline in elderly people with type 2 diabetes: the Edinburgh Type 2 Diabetes Study.

OBJECTIVE: To determine whether circulating levels of the inflammatory markers C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha are associated with cognitive ability and estimated lifetime cognitive decline in an elderly population with type 2 diabetes. RESEARCH DESIGN AND METHODS: A cross-sectional study of 1,066 men and women aged 60-75 years with type 2 diabetes and living in Lothian, Scotland (the Edinburgh Type 2 Diabetes Study), was performed. Seven cognitive tests were used to measure abilities in memory, nonverbal reasoning, information processing speed, executive function, and mental flexibility. The results were used to derive a general intelligence factor (g). A vocabulary-based test was administered as an estimate of peak prior cognitive ability. Results on the cognitive tests were assessed for statistical association with inflammatory markers measured in a venous blood sample at the time of cognitive testing. RESULTS: Higher IL-6 and TNF-alpha levels were associated with poorer age- and sex-adjusted scores on the majority of the individual cognitive tests. They were also associated with g using standardized regression coefficients -0.074 to -0.173 (P < 0.05). After adjusting for vocabulary, education level, cardiovascular dysfunction, duration of diabetes, and glycemic control, IL-6 remained associated with three of the cognitive tests and with g. CONCLUSIONS: In this representative population of people with type 2 diabetes, elevated circulating levels of inflammatory markers were associated with poorer cognitive ability. IL-6 levels were also associated with estimated lifetime cognitive decline.

Baseline characteristics and statistical power in randomized controlled trials: selection, prognostic targeting, or covariate adjustment?

OBJECTIVE: Heterogeneity of patients is a common problem in randomized controlled trials (RCTs) in various fields of clinical research. We aimed to investigate the potential benefits of different approaches for dealing with heterogeneity in a case study on traumatic brain injury (TBI). DESIGN AND SETTING: Statistical modeling studies in three surveys and six randomized controlled trials. PATIENTS: Individual patient data (n = 8033) from the IMPACT database. INTERVENTIONS: We investigated the statistical power and efficiency of randomized controlled trials (RCTs) in relation to (1) selection according to baseline characteristics, (2) prognostic targeting (i.e., excluding those with a relatively extreme prognosis), and (3) covariate-adjusted analysis. Statistical power was expressed as the required sample size for obtaining 80% power and efficiency as the relative change in study duration, reflecting both gains in power and adverse effects on recruitment. Uniform and targeted treatment effects were simulated for 6 month unfavorable outcome. RESULTS: For a uniform treatment effect, selection resulted ina sample size reduction of 33% in the surveys and 5% in the RCTs, but decreased recruitment by 65% and 41%, respectively. Hence, the relative study duration was prolonged (surveys: 95%; RCTs: 60%). Prognostic targeting resulted in sample size reductions of 28% and 17%, and increased relative study duration by 5% in surveys and 11% in the RCTs. Covariate adjustment reduced sample sizes by 30% and 16%, respectively, and did not affect recruitment. For a targeted treatment effect, the sample size reductions by selection (surveys: 47%; RCTs: 20%) and prognostic targeting (surveys: 49%; RCTs: 41%) were larger and adverse effects on recruitment smaller. CONCLUSIONS: The benefits of selection and prognostic targeting in terms of statistical power are reversed by adverse effects on recruitment. Covariate adjusted analysis in a broadly selected group of patients is advisable if a uniform treatment effect is assumed, since there is no decrease in recruitment.

Patient and general practitioner preferences for the treatment of depression in patients with cancer: how, who, and where?

OBJECTIVE: The objective of this study was to determine and compare patient and general practitioner (GP) preferences for the treatment of depression in patients with cancer. METHODS: A treatment preference questionnaire was completed by 100 patients who had been diagnosed with both cancer and major depressive disorder and by 86 GPs who had had experience of at least 1 patient with cancer and depression. Participants were asked to rank options for how depression should be treated, who should deliver the treatment, and where treatment should occur. RESULTS: The top three preferences of patients and GPs for how depression should be treated differed (P<.001). Patients preferred talking treatment alone, whereas GPs preferred a combination of drug and talking treatment. Both patients and GPs preferred treatment to be given by the GP, with older patients having a stronger preference for this. Counselors and cancer nurses were also popular preferences; mental heath professionals were unpopular. The preferred place of treatment was primary care for both patients and GPs, although many patients preferred treatment in the cancer center. CONCLUSION: Effective and acceptable services for depressed cancer patients need to take patients and GP preferences into account. A model of service that allows a choice of initial treatment modality and collaborative care between primary care and cancer center nurse would meet this requirement.