Parallel trials

NOTE The author has, on behalf of engineering personnel, occasionally conducted properly controlled, parallel trials of magnetic devices in hardworking industrial cooling systems. All trials were less than successful. 

The carryover effect is only one type of issue that may complicate the interpretation of results from a cross-over study. A more complete description of the potential pitfalls in the analysis of cross-over studies is beyond the scope of this chapter. The reader should simply be aware that, although cross-over studies may be less expensive to conduct than parallel trials initially, they also carry a higher risk of producing results that are fficult or impossible to interpret, thus requiring that the study be repeated to obtain clear results. 

Finally, trials can follow parallel or crossover study designs. In a parallel trial, patients are assigned to a therapy that they remain on, and they are compared with patients in alternate therapy groups. In a crossover trial, patients switch or change therapy assignments during the course of the trial. 

During the trial, the patient crosses over from one treatment to the other. See also clinical trial parallel trial. 

As is known, the degree of freedom is equal to the difference between the number of trials (taken into account when calculating regression coefficients) and the number of coefficients that are calculated from outcomes of those trials independently of one another. We should remember that replicated (parallel) trials may not be considered independent because they give one degree of freedom [36]. Based on the above, to calculate fLF we may use the formula ... 

S.V. Vorhees, Behavioral effects of prenatal methylmercury in rats A parallel trial to the Collaborative Behavioral Teratology Study, Neurobeh. Toxicol. Teratol., 7(6) (1985) 717-725. 

If one or more parallel trials are available for the data from Table 5.13, then for the pleasure of statistical calculation, we can compute new values for the given coefficients and consequently we can investigate their statistical behaviour. A real residual variance can then be established. Unfortunately, we do not have the repeated data for our problem of gaseous permeation through a porous membrane. It is known that the matrix has the values djj = 1/N, dj = 0, j k... 

N gives the total number of experiments in the plan. When we use a complete second order plan, it is not necessary to have parallel trials to calculate the reproducibility variance, because it is estimated through the experiments carried out at the centre of the experimental plan. The model adequacy also has to be examined with the next procedure ... 

Ondo WG, Tintner R, Voung KD, Lai D, Ringholz G (2005) Doubleblind, placebo-con Rolled, irrrforced dtr adon parallel trial of que-dapirre for dopaminergic-irrduced hallucinadons in Parkinson s disease. Mov Disord 20(8) 958-963. 

Pugh ND, Sissons GRJ, Ruttley MST, Berg BCJ, Nossen JO, Eide H. lodixanol in femoral arteriography (phase III) a comparative double-parallel trial between lodixanol and iopromide. Appl Radiol 2002 31(Suppl) 81-6. 

A PHASE 2 DOUBLE-BLIND PARALLEL TRIAL OF DOSE TOLERANCE, SAFETY, AND EFFICACY COMPARING DRUG A TO PLACEBO IN CONTROLLING SYMPTOMS OF MILD TO MODERATE HYPERTENSION... 

The objective is the essence of a protocol. It should state explicitly the purpose of the clinical research project. One short statement should describe the type of trial (i.e., open, double-blind, crossover) and why the trial is being conducted. In addition, a brief description of the medications to be used, the indication ) for effectiveness, and the type of subject population to be evaluated should be included. The objective should be stated succinctly, as in the following example The objective of this controlled, double-blind, parallel trial is to evaluate the efficacy and safety of medication X versus medication Y in (diagnosis of disease) as found in an outpatient (or other) population. In one simple statement, the purpose of the trial, the controls, the diagnosis of the subject population, and the setting where these subjects will be observed have been presented. Objectives should reflect the phase or type of clinical research that will be conducted. 

Figures 1, 2, and 3 outline the unit operations for the different processing trials. SO2 addition is commonly used in commercial processing of Thompson seedless grapes into concentrates. We were particularly interested in its influence on composition and quality and did parallel trials with and without addition of 70 ppm S02 ...

The nature of statistical problems in general is such that usually all observable outcomes are possible under many theories, although they are not equally likely for every theory. (For example, in a randomized two-group parallel trial with many patients, a large difference in outcome between the two groups would seem to be most unlikely if the two treatments are in fact identical, but it is never impossible.) What the frequentist does is to replace the strictly logical argument,... 

Consider a two-group parallel trial which is to be stratified by sex (that is to say, sex will be fitted as a main effect but not necessarily as an interaction). Let N be the target number of individuals to be studied in a conventional trial. Let the overall arrival rate for patients be r and let the population demographic fraction be /, and suppose that the arrival rate for women is fr and for men is (1 — f)r. Let tn be the time to recruit if there is no discrimination (tn stand for time no ), as in a conventional trial. Let tt (f) be the time to recruit if equal numbers of males and females are required for the same total... 

Study Design. This was a randomized, double-blind, controlled, parallel trial conducted at the Chicago Center for Clinical Research, Chicago, IL. The study design is illustrated in Figure 1. 

Medicines are available for patients as authorised medicines or as pharmacy preparations (unlicensed medicines). Market logic ensures that only medicines with sufficient return on investment will be marketed. However, health care logic requires pharmacists to provide their patients with necessary medicines. There are regulations that cover medicines for clinical research, marketing authorisation and import, as well as traffic between European countries (parallel imports). If medicines are not available as authorised medicines, various options such as compassionate use or parallel trial programme can be considered. The authorisation of medicines for orphan diseases is promoted by the orphan dmg regulations. The system of reimbursement will be discussed briefly due to its special situation at the interface of both public health and social insurances. 

Several options to get authorisations for named patients have been applied in the past and still are in practice in order to maintain the supply chain with the most important medicines. As long as they are classified as IMPs and thus not allowed on the market, patients may be treated in some countries, e.g. Switzerland, in a parallel trial programme or within an extended access. Procedures follow those for compassionate use and requests have to be submitted to the ethical committee as well. A parallel trial programme will always require Ethical Approval and would therefore be a Clinical trial in the UK. Single cases different from compassionate use have to be authorised but do not need an ethical committee approval. 

Ghosh, S. K., Ekpo, E. B., Shah, I. U., Girling, A. J., Jenkins, C., and Sinclair, A. J., 1994, A doubleblind placebo-controlled parallel trial of vitamin C treatment in elderly patients with hypertension. Gerontology 40 268-272. 

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