Academic journal article Scandinavian Journal of Work, Environment & Health

Evaluation of Occupational Health Interventions Using a Randomized Controlled Trial: Challenges and Alternative Research Designs

Academic journal article Scandinavian Journal of Work, Environment & Health

Evaluation of Occupational Health Interventions Using a Randomized Controlled Trial: Challenges and Alternative Research Designs

Article excerpt

The randomized controlled trial (RCT) is considered the gold standard in evaluative medical research as causal inferences about the therapy under study can be drawn. The first RCT was reported in a 1948 issue of the British Medical Journal (BMJ) and involved the experimental treatment of pulmonary tuberculosis (1). In this trial, a particular group of English tuberculosis patients from different care facilities, comparable in the symptoms of the disease and age were included. The included patients were assigned to either a combined medicine and bed-rest therapy, or bed-rest therapy alone, based on a statistical series of random sampled numbers. Neither the patients nor the doctors involved knew the condition the patient was assigned to, later to be named a "double blind" procedure. Therapy progress was reported on forms particularly designed for this trial. Due to this design, the researchers were able to demonstrate the added value of the combined treatment over the bed-rest treatment, but only in the first three months after onset of the disease. Thereafter a deterioration emerged, probably due to resistance to the medicine under study. Many researchers have followed this example ever since. The beauty of the randomization procedure is that chance (probably) ensures that known and unknown prognostic factors are balanced over the treatment conditions and thus do not interfere with the treatment-outcome relationship. Therefore, conclusive statements about the effectiveness of the therapy can be made.

In occupational health research, a typical RCT aims, for instance, to reduce productivity loss at work (ie, a primary outcome) for a randomly chosen group of employees with medically verified upper-extremity disorder (ie, specific characteristics) via an ergonomic assessment at the worksite and a physician contacting each employee's supervisor to discuss potential accommodations at work (ie, a multicomponent intervention). The effectiveness of the intervention is evaluated by the change in primary outcome from pre- to post-test in the intervention group relative to the change in this outcome in the reference group that did not receive the intervention (2). However, occupational health researchers are increasingly addressing questions regarding the outcomes of complex interventions. A complex intervention can consist of (i) multiple components, (ii) multiple providers and thus multiple levels, (iii) multiple locations, and/or (iv) multiple (varying) outcomes. The components, providers, locations and outcomes are interdependent and therefore the intervention can be difficult to standardize or administer uniformly (3-5). Furthermore, the context is often complex and thus nearly impossible to control entirely (6). Conducting an RCT on a complex intervention within an occupational health context is thus not always the most feasible option (7, 8).

The British Medical Research Council (MRC) recently published an updated guide that underlines the need for innovative evaluation methods (9). Although the MRC considers individual randomization in trials as the most robust design to prevent allocation bias, it is more and more acknowledged that common evaluation methods are not always practical or ethical for complex interventions (9). The RCT sometimes even offers too little information to draw meaningful conclusions for science or practice. More specifically, an RCT allows conclusions on the effectiveness of the intervention for a selected sample of individuals. Researchers have argued that because of complexity in the intervention and context, the required conditions that are needed for an efficacy trial will never occur (10). Even if an efficacy trial has been performed with success, then it still is "highly unlikely that interventions that do well in efficacy studies will do well in effectiveness studies, or in real-world applications" [(10) p1262].

In order to further develop the evidence base in occupational health there is a clear need for alternatives to the RCT. …

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