Research methods
A randomized controlled trial (RCT) refers to a type of experiment in which researchers randomly group eligible human research participants or other units of research (such as clinics, schools, playfields) into categories to either receive or not receive a single or multiple interventions under comparison (Solomon et al. 2009, p.5). The primary objective of undertaking an RCT is testing whether the intervention works compared to a control condition with or without an intervention.
Relevance of a pilot study
A pilot study is often the first step towards undertaking an RCT intervention. The pilot study offers the investigators a unique chance to identity and prepare for challenges of assessing an intervention (Domanski & Mckinlay 2009, p.12). Eventually, it augments the scientific rigour and value of the main study. A pilot study in an RCT is therefore undertaken for three main objectives: (i) evaluating both the feasibility and acceptability of the specific intervention under investigation; (ii) evaluating the feasibility and acceptability of the research design and procedures; and (iii) aiding the determination of sizes of effect to adopt in calculation of sample size (Solomon et al. 2009, p.45).
Importance of a sample size calculation
Given that an RCT is conducted to obtain the highest level of evidence in comparing a new intervention to the existing gold standard, an appropriate sample size needs to be investigated so as to reliably determine the difference between the specific groups. The number of subjects in the study need to be right but neither more nor less than actually required. If few participants are sampled, it would not be possible to identify significant differences between the interventions. Similarly, sampling more patients than necessary would increase the cost of the RCT, time as well as effort for the investigators besides being unethical. An appropriate number of subject for RCT is therefore significant for a number of reasons: (i) to facilitate reliable determination of differences; (ii) meet ethical obligations; and (iii) for appropriate use of resources (Solomon et al. 2009, p.59). The sample size in a clinical trial need to be right so as to reliably provide answers to the primary goal or outcome of the trial. Estimating the number of subjects for a trial based on secondary objectives of the study often require sampling larger numbers of participants.
Importance of randomization
Randomization or the random allocation of subjects to be assigned one or alternative interventions under the study is the key distinguishing aspect of RCT study. Randomization is done after evaluation of eligibility and recruitment but prior to the intervention to be investigated commences. The goal of randomization in a trial is to make sure any observe differences between groups is purely as a result of differences in the treatment alone as opposed to the impacts of confounding (both known and unknown) or bias (Domanski & Mckinlay 2009, p.46). As such, it serves to ensure that the groups have similarities in all considerations except for the intervention being investigated. Random allocation therefore strives to ensure that all study subjects have equal chance of allocation to the control group or treatment, and that the probability of being assigned an intervention is same regardless of the stage at which the subject entered the study. Proper randomization in RCT has therefore three main advantages: (i) elimination of bias in treatment; (ii) facilitation of binding/masking of identity of treatments from researchers, subjects, and evaluators; (iii) permitting the adoption of probability theory to indicate the likelihood difference in results between treatment groups is just a matter of chance; and (iv) giving validity to statistical tests using probability theory (Domanski & Mckinlay 2009, p.61).
Methods for reducing bias performance bias and detection bias
Performance bias
The main appeal of RCT in health care is its ability to reduce selection bias. Performance bias refers to the tendency of subjects to modify their behavior or responses to questions because they are aware of the trial and their treatment allocation. Many medical trials use binding to minimize performance bias because a subject who is unaware of his/her allocation status is rendered unable to act basing on that knowledge (Solomon et al. 2009, p.78). Eliminating performance bias calls for an intervention to be fixed in nature together with a uniform action.
Detection bias
Detection bias often occurs when the methods for evaluating outcome fail to be uniform either between a test and comparator group or within a study. It is facilitated by unbinded assessors and participants as well as unreliable surrogate endpoints. Detection bias can be reduced through binding of both assessors and participants during evaluation of outcomes with subjective or intermittent features e.g. pain. Assessor bindings stops the investigator, either knowingly or unknowingly, from misinterpreting a participant’s sate, generating a more/less favorable reaction or manipulating data (Domanski & Mckinlay 2009, p.75). The participant is preventing from giving a better result because they trust or hope a treatment will work or for the sake of pleasing the investigator.
Choice of outcome measures
The choice of outcome measures in RCT study is crucial because it affects the generalizability of the results. This is especially because their use often considerably impact the face validity of the study’s results. Pragmatic outcome measures are directed at measuring the effectiveness of an intervention in real life conditions as well as if it works in ways that matter to the subject (Domanski & Mckinlay 2009, p.78). Choosing rating scales may not reflect the clinical reality in addition to the likelihood of difference between rating scale response on the one hand and a pragmatic clinical endpoint e.g. discharge from hospital.
Reference:
SOLOMON, P. L., CAVANAUGH, M. M., & DRAINE, J. (2009). Randomized controlled trials design and implementation for community-based psychosocial interventions. New York, Oxford University Press.
DOMANSKI, M. J., & MCKINLAY, S. (2009). Successful randomized trials: a handbook for the 21st century. Philadelphia, Lippincott Williams & Wilkins.
