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PubMed2000

Comparison of balanced and random allocation in clinical trials: a simulation study.

BACKGROUND: Before analysing the results of a randomised controlled clinical trial in which 200 children were balanced over five prognostic factors, we wanted to know the efficiency of balanced allocation compared to simple randomisation as well as the efficiency of adjusted as compared to unadjusted statistical analysis in small and large sample sizes. METHODS: A simulation study with 1000 replications of each assignment was performed for both relatively large trials (n = 100) and for small trials (n = 20). Four options for the design and analysis were studied: (1) simple randomisation with simple univariate analysis, (2) simple randomisation with multivariate modelling, (3) balanced allocation with simple univariate analysis and (4) balanced allocation with multivariate modelling. In addition, we also considered the effect of an unmeasured covariable, which was either uncorrelated or correlated with another covariate. RESULTS/CONCLUSION: The simulations show that a combination of balanced allocation and multivariate analysis as compared to simple randomisation and multivariate analysis leads to more valid and precise treatment effects as well as to smaller confidence intervals, especially in small trials (n = 20). Multivariate analysis with all known prognostic factors produces on average smaller Type I errors and Type II errors in balanced allocation compared to simple randomisation. If an unmeasured covariate is strongly correlated with another covariate the treatment effect is estimated more precisely as compared to an unmeasured covariate that is not correlate or less strongly correlated.

Confidence Intervals↗
PubMed2004

Statistical comparison of random allocation methods in cancer clinical trials.

The selection of a trial design is an important issue in the planning of clinical trials. One of the most important considerations in trial design is the method of treatment allocation and appropriate analysis plan corresponding to the design. In this article, we conducted computer simulations using the actual data from 2158 rectal cancer patients enrolled in the surgery-alone group from seven randomized controlled trials in Japan to compare the performance of allocation methods, simple randomization, stratified randomization and minimization in relatively small-scale trials (total number of two groups are 50, 100, 150 or 200 patients). The degree of imbalance in prognostic factors between groups was evaluated by changing the allocation probability of minimization from 1.00 to 0.70 by 0.05. The simulation demonstrated that minimization provides the best performance to ensure balance in the number of patients between groups and prognostic factors. Moreover, to achieve the 1 percentile for the p-value of chi-square test around 0.50 with respect to balance in prognostic factors, the allocation probability of minimization was required to be set to 0.95 for 50, 0.80 for 100, 0.75 for 150 and 0.70 for 200 patients. When the sample size was larger, sufficient balance could be achieved even if reducing allocation probability. The simulation using actual data demonstrated that unadjusted tests for the allocation factors resulted in conservative type I errors when dynamic allocation, such as minimization, was used. In contrast, adjusted tests for allocation factors as covariates improved type I errors closer to the nominal significance level and they provided slightly higher power. In conclusion, both the statistical and clinical validity of minimization was demonstrated in our study.

Aged↗
PubMed1989

Covariate imbalance and random allocation in clinical trials.

A model is developed to estimate the effect of covariate imbalance on the size of a test of treatment efficacy in randomized clinical trials comparing two treatments when dispersion parameters are known. It is concluded that tests of homogeneity on the covariates should not be performed, that covariate imbalance is just as much a problem for large studies as for small ones in terms of effect on size, and that the effect of correlation between covariates and measures of efficacy is more complex than has previously been suggested. The best way to adjust for covariate imbalance is by an analysis of covariance.

Analysis of Variance↗
PubMed2003

The Home Office and random allocation experiments.

By examining the history of the random experiment in the Home Office in the United Kingdom, this article demonstrates that research is not an altogether rational process and that fashion, personality, and politics are at least as important as science and evidence when setting research and policy programs and determining methodologies. The article also shows that even in 1970, the research world was a village and that issues and fashions on one side of it could determine the outcome of decisions on the other side, even though they had no direct relevance. On a more optimistic note, the article shows how the fashions go in cycles so that if you could not get the research funded in the last cycle, just wait 20 years for the cycle to come around and try again.

History, 20th Century↗
PubMed2004

Prevalence of lipoatrophy and mitochondrial DNA content of blood and subcutaneous fat in HIV-1-infected patients randomly allocated to zidovudine- or stavudine-based therapy.

INTRODUCTION: Mitochondrial toxicity resulting from mitochondrial DNA (mtDNA) depletion is suggested to be involved in the pathogenesis of lipodystrophy. METHODS: We cross-sectionally assessed lipodystrophy both clinically and radiographically in patients who, 4 years before, had been enrolled in a randomized comparative trial of stavudine- or zidovudine-based therapy. mtDNA content was measured in peripheral blood mononuclear cells (PBMCs) and subcutaneous adipose tissue from the thigh and back. RESULTS: Twenty-eight of the 45 patients enrolled in the original trial were included. Despite comparable exposure to stavudine or zidovudine (51 and 50 months, respectively), lipoatrophy prevalence by intent-to-treat analysis was significantly greater in stavudine recipients (82 vs 9%, P=0.0001). Likewise, those allocated to stavudine had significantly less peripheral fat. In an analysis restricted to patients who had remained on randomly allocated nucleoside reverse transcriptase inhibitors (NRTIs), mtDNA in PBMCs decreased after the start of treatment in both groups (P<0.0001) (-73% for stavudine and -67% for zidovudine, P=0.11), resulting in significantly lower levels in patients with lipoatrophy (P=0.007). The mtDNA content in subcutaneous adipose tissue from the thigh, but not from the back, was significantly lower in patients allocated to stavudine compared to zidovudine (P=0.01). mtDNA in adipose tissue from either location did not differ significantly between those with or without lipoatrophy. DISCUSSION: This study objectively confirms that regimens containing stavudine are associated with a greater risk of lipoatrophy than those containing zidovudine. mtDNA in PBMCs markedly declined with both treatments and was lowest in patients with lipoatrophy. The lack of difference in mtDNA in adipose tissue from patients with as opposed to without lipoatrophy may have been masked by a relative preponderance of stromal and vascular tissue in the subcutaneous tissue samples from these patients, combined with compensatory mitochondrial proliferation in remaining adipocytes. However, our findings may also suggest that the different risk of lipoatrophy observed between NRTIs cannot solely be explained by differences in mtDNA depletion directly at the level of peripheral adipose tissue.

Adipose Tissue↗
PubMed1988

Dialyzer re-use--a multiple crossover study with random allocation to order of treatment.

A multiple crossover research study was used to evaluate the effect of dialyzer re-use on fever, blood leaks, serum urea and creatinine values and symptoms. Each of 6 crossover periods consisted of 4 weeks on either single-use or re-use, 1 week washout, 4 weeks on the alternative treatment and 1 week washout. The re-use consisted of 6 uses of each dialyzer and the washout weeks consisted of 3 single-use sessions. Analysis of paired observations within rather than between patients showed no effects of time (i.e. among crossover periods 1 through 6) or number of re-uses (i.e. among uses 1 through 6). There was no significant difference for temperature change during dialysis, blood leak rate, or the serum urea and creatinine values before the first dialysis of each washout period. There were no differences for symptoms of pruritus, cramps, nausea, headache, chest pain, backache or fatigue. There were no clinical advantages or disadvantages associated with dialyzer re-use.

Cellulose↗
PubMed1998

Intention-to-treat analysis of 200 patients with rheumatoid arthritis 12 years after random allocation to either sulfasalazine or penicillamine.

OBJECTIVE: To assess existing disease modifying antirheumatic drugs (DMARD) using a strategy aiming for sustained suppression of inflammation. METHODS: We conducted intention-to-treat analysis of open randomized study [sulfasalazine (SASP) or penicillamine (PEN)], followup 12 years, conducted at specialist rheumatology clinics in Glasgow, Scotland. Subjects were 200 patients with rheumatoid arthritis (RA) with established disease. In this "true to life" approach, comorbidity was not an exclusion criterion unless it prejudiced assessment of drug toxicity. The main outcome measure was the Health Assessment Questionnaire (HAQ) functional score. RESULTS: Over 12 year followup 95 (47.5%) patients died; this was the commonest reason for study groups being unfulfilled. There was one drug related death (methotrexate). Patients who were socially disadvantaged were more likely to die prematurely. HAQ did not deteriorate significantly in those who continued taking their original DMARD, or in the SASP intention-to-treat group over 12 years. Sustained suppression of disease activity was possible in the entire group available for followup at 12 years. Most toxicity occurred early and no unexpected side effects were observed. CONCLUSION: High premature mortality in RA was confirmed and an association between mortality and deprivation was demonstrated. Sustained reduction in acute phase response was possible using sequential single DMARD. This study provides useful baseline and longterm information against which to evaluate combination therapy or new agents.

Adult↗
PubMed1992

Infection pattern in children with vesicoureteral reflux randomly allocated to operation or long-term antibacterial prophylaxis. The International Reflux Study in Children.

A total of 306 children with grade III to IV vesicoureteral reflux (international classification) and a history of documented urinary tract infection was randomized into medical (155 patients) or surgical (151 patients) treatment arms in the European portion of the International Reflux Study in Children. Children treated medically were maintained on prophylactic antibacterials as long as the reflux persisted, while those treated surgically were covered prophylactically until followup studies at 6 months postoperatively demonstrated the reflux to be corrected. Standard definitions for bacteriuria were used, and the distinction was made clinically among acute pyelonephritis, cystitis and asymptomatic bacteriuria, supported in many instances by additional laboratory testing. Urine was cultured after 3 months and whenever suspicious symptoms occurred. Urinary tract infections developed during the first 5-year followup period in 59 patients (38%) in the medical group and in 59 (39%) in the surgical group but the incidence of pyelonephritis was higher in the medical group (21%) than in the surgical group (10%) (p < 0.01). Pyelonephritis often followed catheterization or cystoscopy but asymptomatic bacteriuria was uncommon after these procedures in either group. Recurrent infections were related to age, sex and treatment center. They were common in boys and girls entering under 1 year of age but were less common in girls and rare in boys entering after 1 year of age. Recurrences were lowest among the Finnish children and highest in the German and Belgian children.

Anti-Bacterial Agents↗
PubMed2006

Metacognitive therapy versus exposure and response prevention for pediatric obsessive-compulsive disorder. A case series with randomized allocation.

BACKGROUND: Exposure with ritual prevention (ERP) is the psychotherapeutic treatment of choice for pediatric obsessive-compulsive disorder (OCD). In the present study, a new treatment rationale - metacognitive therapy (MCT) for children - was developed and evaluated. METHODS: Ten children and adolescents with OCD were randomly assigned to either MCT or ERP therapy condition. Patients were assessed before and after treatment and at the 3-month and 2-year follow-up by means of symptom severity interviews. Depressive symptoms were also assessed. Manualized treatment involved up to 20 sessions on a weekly basis. RESULTS: We found clinically and statistically significant improvements in symptom severity after treatment. At the 3-month and 2-year follow-up, the attained improvements during treatment were retained. CONCLUSIONS: Despite some methodological limitations, results showed that MCT proved to be a promising psychotherapeutic alternative to the well-established ERP in the treatment of pediatric OCD. Further investigations into the efficacy of MCT are necessary to answer questions as to the working mechanisms underlying therapy for OCD.

Adolescent↗
PubMed1997

Follow-up study of patients randomly allocated ramipril or placebo for heart failure after acute myocardial infarction: AIRE Extension (AIREX) Study. Acute Infarction Ramipril Efficacy.

BACKGROUND: In the Acute Infarction Ramipril Efficacy (AIRE) Study, the effect of angiotensin-converting-enzyme (ACE) inhibition on the survival of patients with clinical heart failure after acute myocardial infarction (AMI), was assessed. At an average follow-up time of 15 months after randomisation, all-cause mortality was reduced from 22.6% (placebo group) to 16.9% (ramipril group) representing an absolute mortality reduction of 5.7% and a relative risk reduction of 27% (95% CI 11-40%; p = 0.002). Our aim in this study was to assess the long-term (3 years after the AIRE Study closed) magnitude, duration, and reliability of the survival benefits observed after treatment with ramipril (target dose 5 mg twice a day) when compared with placebo. METHODS: We investigated the mortality status of all 603 patients recruited from the 30 UK centres involved in the AIRE Study. Through government records we were able to confirm the death or survival of all 603 patients exactly 3 years after the close of the AIRE Study. Follow-up was for a minimum of 42 months and a mean of 59 months. The average duration of treatment with masked trial medication was 13.4 months for placebo and 12.4 months for ramipril. FINDINGS: By 0000 h March 1, 1996, death from all causes had occurred in 117 (38.9%) of 301 patients randomly assigned placebo and 83 (27.5%) of 302 patients randomly assigned ramipril, representing a relative risk reduction of 36% (95% CI 15-52%; p = 0.002) and an absolute reduction in mortality of 11.4% (114 additional 5-year survivors per 1000 patients treated for an average of 12.4 months). INTERPRETATION: Our data provide robust evidence that administration of ramipril to patients with clinically defined heart failure after AMI results in a survival benefit that is not only large in magnitude, but also sustained over many years.

Aged↗
PubMed1995

United Kingdom Prospective Diabetes Study (UKPDS). 13: Relative efficacy of randomly allocated diet, sulphonylurea, insulin, or metformin in patients with newly diagnosed non-insulin dependent diabetes followed for three years.

OBJECTIVE: To assess the relative efficacy of treatments for non-insulin dependent diabetes over three years from diagnosis. DESIGN: Multicentre, randomised, controlled trial allocating patients to treatment with diet alone or additional chlorpropamide, glibenclamide, insulin, or metformin (if obese) to achieve fasting plasma glucose concentrations < or = 6 mmol/l. SETTING: Outpatient diabetic clinics in 15 British hospitals. SUBJECTS: 2520 subjects who, after a three month dietary run in period, had fasting plasma glucose concentrations of 6.1-14.9 mmol/l but no hyperglycaemic symptoms. MAIN OUTCOME MEASURES: Fasting plasma glucose, glycated haemoglobin, and fasting plasma insulin concentrations; body weight; compliance; and hypoglycaemia. RESULTS: Median fasting plasma glucose concentrations were significantly lower at three years in patients allocated to chlorpropamide, glibenclamide, or insulin rather than diet alone (7.0, 7.6, 7.4, and 9.0 mmol/l respectively; P < 0.001) with lower mean glycated haemoglobin values (6.8%, 6.9%, 7.0%, and 7.6%, respectively; P < 0.001). Mean body weight increased significantly with chlorpropamide, glibenclamide, and insulin but not diet (by 3.5, 4.8, 4.8, and 1.7 kg; P < 0.001). A similar pattern was seen for mean fasting plasma insulin concentration (by 0.9, 1.2, 2.4, and -0.1 mU/l; P < 0.001). In obese subjects metformin was as effective as the other drugs with no change in mean body weight and significant reduction in mean fasting plasma insulin concentration (-2.5 mU/l; P < 0.001). More hypoglycaemic episodes occurred with sulphonylurea or insulin than with diet or metformin. CONCLUSION: The drugs had similar glucose lowering efficacy, although most patients remained hyperglycaemic. Long term follow up is required to determine the risk-benefit ratio of the glycaemic improvement, side effects, changes in body weight, and plasma insulin concentration.

Adult↗