Random allocation

Kiuchi T, Ohashi Y, Konishi M, Bandai Y, Kosuge T, Kakizoe T. A world wide web-based user interface for a data management system for use in multi-institutional clinical trials—development and experimental operation of an automated subjects registration and random allocation system. Controlled Clin Trials 1996 17 6 476-93. 

Random allocation of animals to treatment groups is a prerequisite of good experimental design. If not carried out, one can never be sure whether treatment-... 

Blocked randomisation If using blocked randomisation, we ensure balance between treatments within a block of patients. Suppose for example, we again wish to randomise the two treatments A and B to 12 patients in blocks of size four. Then within each block of four patients, treatments are randomly allocated to patients to ensure that two patients receive both A and B. For example ... 

There are two major types of weaknesses associated with meta-analysis. Bias and heterogeneity. When planning a clinical trial every effort is made to minimise the impact of bias on the results. For example, clinicians and patients are kept unaware of the treatment being used for each individual patient, so-called double-blind studies and patients are randomly allocated to a treatment. However, in meta-analysis there... 

The mated females are randomly allocated to treatment groups using a stratified procedure to ensure approximate equal mean body weights in all groups. 

Blackburn et al. (1981) studied 49 patients with mild to moderately severe depressions in a psychiatric outpatient department and 39 patients from a general practice in Edinburgh, i.e. a total of 88 patients, of whom 64 (14 men, 50 women) completed the study. The patients were selected on the basis of the Research Diagnostic Criteria (Spitzer et al., 1978) as well as various rating and selfrating scales one-third of the patients each received one of the following, randomly allocated treatments for a maximum of 20 weeks ... 

Fluoride is a potent stimulator of trabecular bone formation. Sodium monofluorophosphate was given to 48 patients with osteoporosis due to glucocorticoids (more than 10 mg of prednisone equivalents/day). Patients were randomly allocated to 1 g of calcium carbonate (control) or 200 mg of sodium monofluorophosphate plus 1 g of... 

In 814 patients randomly allocated to fish oils for 18 weeks for the reduction of re-stenosis after percutaneous transluminal coronary angioplasty, gastrointestinal adverse effects, most commonly bloating and burping, were reported in 37% of patients taking fish oils, versus 31% of those taking placebo (13). 

However, in 18 healthy men randomly allocated to N-3 polyunsaturated fatty acids 10 g/day or placebo for 14 days, the addition of a single intravenous dose of acetylsalicylic acid 100 mg did not alter the small effect of polyunsaturated fatty acids on platelet aggregation (17). 

An equal number of randomly allocated replicate samples should be taken. 

As an example of a more complex case, we might want to compare various methods of encouraging diabetic patients to attend their next routine clinic appointment. During their May visit to the clinic, all patients will be issued with an appointment card that details when they should attend in June, but then various additional measures may be taken. Patients are randomly allocated to 4 groups ... 

The planned experimental approach would be to take a group of volunteers, randomly allocate them to smoke or not smoke, leave them to indulge/not indulge... 

Intramuscular ziprasidone has recently been compared with intramuscular haloperidol in the treatment of acute psychosis for a very short period (83). Patients were randomly allocated to intramuscular ziprasidone for up to 3... 

Lorazepam shares with other benzodiazepines the ability to impair explicit memory, but has a distinct further effect on implicit memory as well (10). However, it impairs memory more than its chemically and kinetically similar analogue, oxazepam (11). The effects of lorazepam 2.5 mg and diazepam 0.3 mg/kg on explicit and implicit memory tasks have been examined in 24 men and 24 women randomly allocated to lorazepam, diazepam, or placebo (10). An implicit word-stem completion task and explicit memory tasks of immediate and delayed word recall and word recognition were administered 90 minutes after drug administration. Both diazepam and lorazepam significantly impaired performance on explicit memory measures. Only lorazepam significantly impaired performance on the implicit memory task. 

In a randomized, placebo-controlled, double-blind study of the relative efficacies of patient-controlled analgesia (PCA) regimens (63), 60 patients undergoing elective total hip or knee replacement were randomly allocated to receive epidural diamorphine 2.5 mg followed by a PCA bolus 1 mg with a 20-minute lockout (group 1), subcutaneous diamorphine 2.5 mg followed by a PCA bolus 1 mg with a 10-minute lockout (group 2), or epidural diamorphine 2.5 mg in 4 ml of 0.125% bupivacaine followed by a PCA bolus of 1 mg diamorphine in 4 ml... 

It is important that the method of randomization is actually random. Treatment allocation according to day of the week, date of birth, date of admission or by alternate cases, is not random. The investigator will often know what treatment the patient will get if they enter the trial and so these methods are open to bias. Randomization must be based on tables of random numbers or computer-generated random allocation. It is also important that randomization is secure. Central telephone randomization is preferable to other methods, such as sealed envelopes containing the treatment allocation. 

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