Parallel groups

We may therefore consider a double star system, each having a configuration for each phase of 4 x 8 units, that is, four units in series group to make up the required phase voltage and eight in parallel group to make up the required kVAr (Figure 25.6). 

Youle M, Oslo M (2007) A double-blind, parallel-group, placebo-controUed, multicentre study of acetyl L-carnitine in the symptomatic treatment of antiretroviral toxic neuropathy in patients with HIV-1 infection. HIV Med 8(4) 241-250... 

Parallel group studies are not particularly useful for IVIVC development, as by definition, subjects receive only one treatment and so there would be no reference for each subject for individual deconvolution. This becomes less problematic as the variability of the drug declines. Thus, it may be acceptable for a low variability drug to use a mean reference profile for deconvolution of the mean profile for each ER treatment. 

Official Title Effect of EGb 761 on the Ratio of the Isoforms of the Protein Precursor of Beta Amyloid Platelets on Patients With Mild to Moderate Alzheimer s Disease. A Phase II, Randomized, Double-Blind Trial, on Parallel Groups Versus Placebo Primary Outcome Measures Effect of EGb 761 on the ratio of the isoform of the protein precursor of beta amyloid platelets Secondary Outcome Measures Efficacy of EGb 761 on the cognitive functions and safety of EGb 761 at a dosage of 240 mg per day Total Enrollment 40 Study Start July 2005... 

Randomized Parallel Group Fixed Dose Subjects are divided into several groups, such as placebo, 10 mg, 20 mg, and 40 mg. Subjects continue with this regimen for the duration of the trial. 

Randomized Parallel Group Optional Titration Subjects are divided into placebo and active groups. Active groups all start with the same dose, say, 10mg. Depending on response and safety assessment, dose can be increased to 20mg and then 40mg for selected subjects. 

CAPRIE was a 19,185-patient, 304-center, international, randomized, double-blind, parallel-group trial comparing Plavix (75mg daily) with aspirin (325mg daily). The outcome was to compare the first occurrence of new ischemic stroke, new myocardial infarction, or other vascular death. The following are tabulated results ... 

Bousquet, J, Tosserard, B., and Medley, H.V., Double-blind parallel group study to compare the long term clinical efficacy and safety of two different methods of administering inhaled fluticasone propionate in chronic severe asthmatic patients, Eur. Resp. J., 8 427S (1995). 

Johnson JR, Bumell-Nugent M, Lossignol D, Ganae-Motan ED, Potts R, Fallon MT. (2010) Multicenter, double-blind, randomized, placebo-controlled, parallel-group study of the efficacy, safety, and tolerability of THC CBD extract and THC extract in patients with intractable can correlated pain. J Pain Symptom Manage 39 167-179. 

Biederman J, Krishnan S, Zhang Y, McGough JJ, Findling RL. (2007) Efficacy and tolerability of lisdexamfetamine dimesylate (NRP-104) in children with attention-deficit/hyperactivity disorder A Phase 111, multicenter, randomized, double-blind, forced-dose, parallel-group study. Clin Ther 29 450 63. 

Subjects are randomised to receive either A or P throughout the study, that is, parallel groups. 

The advantages of a parallel-group design can be summarised as follows ... 

Choosing the most appropriate design (for example using a cross-over design rather than a parallel group design where this is appropriate)... 

The simplest trial design of course is the parallel group design assigning patients to receive either treatment A or treatment B. While this is a valid and effective design... 

In Section 3.3.3 we introduced the general structure for a significance test with the comparison of two means in a parallel group trial. This resulted in a procedure which goes under the general heading of the two-sample (or unpaired) t-test. This test was developed for continuous data, although it is applicable more widely and, in particular, is frequently used for score and count data. 

The previous sections have dealt with the t-tests, methods applicable to continuous data. We will now consider tests for binary data, where the outcome at the subject level is a simple dichotomy success/failure. In a between-patient, parallel group trial our goal here is to compare two proportions or rates. 

Consider the data presented in table 4.4 relating to the binary outcome died/survival in a parallel group trial. 

To explain in a little more detail, consider a parallel group trial in which we are comparing two treatment means using the unpaired t-test. The null hypothesis Hg p.1 = p.2 that the treatment means are equal is either true or not true God knows, we don t We mere mortals have to make do with data and on the basis of data we will see either a significant p-value (p < 0.05) or a non-significant p-value (p = NS ). The various possibilities are contained in Table 8.1. 

In a parallel group, placebo-controlled trial in acute stroke the primary endpoint is success on the Barthel index at month 3. Previous data suggests that the success rate on placebo will be 35 per cent and it is required to detect an improvement in the active treatment group to 50 per cent. How many patients are needed for 90 per cent power ... 

Which statistical test was to be used for the comparison of the treatment groups in terms of the primary endpoint do you think This is a comparison between two independent groups in a parallel group trial and the primary endpoint is continuous so the sample size calculation will undoubtedly have been based on the two-sample t-test (although this is not specified). 

---