If you’ve ever tried navigating the world of clinical trials for Amyotrophic Lateral Sclerosis (ALS) you’ve probably noticed that any study you come across is grouped into one of two types: observational or interventional. But what’s the difference between these two broad categories of studies?

The key distinction between observational and interventional studies lies in how the researchers interact with the study’s participants. In an interventional study, the researchers are trying to change something about the subjects – things like having them take an experimental drug or therapy, use a medical device, or asking them to modify their behavior in some way. These changes are referred to as “interventions.”

In an observational study the researchers do not intervene in the course of the subject’s condition – they observe the subjects to gather data and learn more about their disease. The subjects may receive other medical interventions as part of their normal medical care, but they are not prescribed anything by the researchers.

More often, when people talk about “clinical trials,” they are referring to interventional studies. These studies help determine if a particular intervention is safe and improves the subjects’ condition. Interventional studies often have precisely defined inclusion and exclusion criteria –requirements that subjects must meet in order to participate. This is to increase the likelihood that the trial will provide easily interpretable data as to whether the treatment is safe and/or beneficial. In some cases, the inclusion and exclusion criteria are designed to test whether the intervention is effective and safe in a specific predefined subset of the patient population. Interventional studies also often involve a control group that receives a placebo, or a benign treatment that mimics the intervention being investigated, such as a sugar pill. This placebo helps researchers confirm that any changes they observe are a direct result of the interventional treatment. In trials with an open-label extension, all participants are able to receive the treatment after the trial has ended, including those who were initially in the placebo group.

While interventional studies tend to receive a lot of attention, observational studies are also extremely important, especially for a disease as complex and poorly understood as ALS. Similar to an interventional study, observational studies often have carefully designed inclusion and exclusion criteria. Participants in an observational study might be asked to fill out surveys, attend regular appointments with physicians, or provide biological samples to help researchers learn about their condition.

The data gained from observational studies can be invaluable in informing the drug discovery process that identifies promising candidates to be tested in trials. Observational studies of the genetics of ALS patients have led to the discovery of the genes behind some forms of familiar ALS, like SOD1 and C9orf72. Observational biomarker studies have led to the discovery of important benchmarks for diagnosing ALS, tracking disease progression, and determining if treatments are having positive effects.

The ALS Therapy Development Institute’s (ALS TDI) Precision Medicine Program (PMP) is an example of an observational study that seeks to find answers to questions like these, and help us learn more about ALS. The PMP is a telehealth program that people living with ALS can participate in from anywhere in the world without leaving their homes. Through the PMP, researchers at ALS TDI partner with people with ALS to gather data on movement, lifestyle, medical history, genetics, biomarkers, voice recordings, and patient cell biology. In addition to helping inform our research at ALS TDI, participants can access their own data through an online portal. This data enables participants to understand their disease progression and may even help them to know if an intervention is impacting their progression.

Both observational and interventional studies are essential pieces of the puzzle in the search for effective treatments for ALS. To learn more about currently available clinical trials and studies, visit our clinical trials database. For more information and to sign up for the Precision Medicine Program, click here.