Did you know that Single Case Experimental Designs, (personalised clinical studies), typically associated with testing pharmaceuticals, have broader application and can be used to test medical devices too? Single-case designs can also make sense of the large amounts of digital data produced by medical devices such as sleep monitoring devices and heart rate sensors. In this blog, we explore how Single Case Designs can be used to test medical devices and analyse data collected from them.
What is considered a medical device?
The Therapeutic Goods Administration (TGA) defines a medical device as a device used for humans intended to diagnose, prevent, monitor, treat or alleviate a disease or injury, or modify or monitor anatomy or physiological functions of the body, generally through a physical, mechanical or chemical action. Examples include neurostimulators, hearing aids and actigraphs.
Assessing the efficacy and safety of medical devices
When the efficacy and safety of a medical device need to be assessed, the usual approach is to conduct a randomised controlled trial. However, there can be issues associated with using standard clinical trial methodology for medical device evaluation. These include: placebo comparisons are difficult for many medical devices, blinding may be unethical or impossible, and control groups are difficult to implement. Some medical devices are indicated for a very small target population, so it is very difficult to recruit a large enough sample of patients to evaluate them in a standard clinical trial.
Single Case Experimental Designs
Single-Case Experimental Designs (SCEDs) are experimental designs that test the effect of a treatment or intervention using a small number of patients (typically one to three), using repeated measurements, sequential (± randomised) introduction of the treatment, and method-specific data analysis. They are ideal for catering to heterogeneous patient profiles and for overcoming methodological biases associated with standard clinical trials.
SCEDs are also well suited for testing medical devices that cannot or should not be withdrawn/removed from the patient. In a multiple baseline SCED, the outcome is measured across multiple individuals (or clinical contexts), starting with baseline (phase A), then proceeding with the treatment (phase B). Return to baseline is not necessary to demonstrate treatment effect. Instead, the device can be monitored in another person or clinical context, depending on the type of treatment. If this design is conducted across multiple people, the start of treatment is randomly staggered so that participants start the treatment at different times. The figure below shows a multiple baseline SCED design where the treatment (dotted vertical line) is implemented at different times across three different participants to determine the effect on an outcome.
Simulated data from a multiple baseline SCED design across three different participants
Pooled SCEDs, where data from multiple individual SCEDs are aggregated, are useful for assessing the efficacy of medical devices such as assistive devices, orthotics (Maguire et al., 2020) and external prostheses (Widehammar et al., 2022), hearing aids and other types of medical devices intended to compensate for deficiencies. They are also well suited to neurological medical devices such as neurostimulators (Tavakoli et al., 2023 and Frost et al., 2017). Based on certain study parameters, sample sizes can also be calculated for pooled SCEDs.
Single Case Observational Designs
Single Case Designs are not only used for testing treatments and interventions. The data collected over time using a medical device such as an actigraph or sleep tracker (e.g., the Oura ring shown below), can be analysed using a Single Case Observational Design (SCOD), also known as N-of-1 Observational Studies (N1OS). SCODs involve repeated measurement of an outcome (e.g., sleep parameters or pain) in an individual over time, without any intervention, to draw conclusions about naturally occurring patterns and outcome predictors for an individual patient. This information can provide insight into potential intervention strategies that could be effective for that particular individual.
A sleep tracking medical device, the Oura ring
Medical devices can closely monitor patients, gathering detailed data on device performance, tolerability, and quality of life impact. SCDs can make sense of this large amount of data, allowing fine-tuning of device settings and configurations to match each patient's unique physiology and preferences. By generating robust data on device efficacy and safety, SCDs can pave the way for evidence-based practice, regulatory decisions, and clinical guidelines. In fact, both individual and pooled SCEDs are included in regulatory guidelines for the clinical development of medical devices published by the Haute Autorité de Santé (French National Authority for Health), the consultative body that provides independent scientific advice to the French public authorities (Haute Autorite de Sante, 2021).
N-of-1 Hub has experience working with medical device companies to test their products. N-of-1 Hub is a consulting company that specialises in designing, conducting and analysing personalised clinical studies using single-case designs. N-of-1 Hub provides consulting and collaborative services to companies, clinicians, researchers, and healthcare consumers who wish to conduct personalised clinical studies using single-case designs. N-of-1 Hub also offers data management and analysis services and customised workshops and courses.
For further information about N-of-1 Hub, and to discuss your study needs, please contact us
References
Frost K, Carey J, Broback T et al. N-of-1 Trial in Person with Pontine Stroke Receiving Repetitive Transcranial Magnetic Stimulation to Improve Hand Function. J Neuroimaging Psychiatry Neurol. 2017;2(2):36-42.
Haute Autorite de Sante (2021) Methodology for the clinical development of medical devices.https://www.has-sante.fr/upload/docs/application/pdf/2021-09/guide_methodology_for_the_clinical_development_of_md.pdf
Maguire C, Sieben J, Lutz N et al. Replacing canes with an elasticated orthotic-garment in chronic stroke patients - The influence on gait and balance. A series of N-of-1 trials. J Bodyw Mov Ther. 2020 Oct;24(4):203-214.
Tavakoli S, Poorjavad M, Taheri N et al. Neuromuscular Electrical Stimulation in Conjunction with Conventional Swallowing Therapy in the Treatment of Dysphagia Caused by Multiple Sclerosis: A Single-Case Experimental Design. Folia Phoniatr Logop 2023;75(5):350-362.
Widehammar C, Hiyoshi A, Holmqvist K et al. Effect of multi-grip myoelectric prosthetic hands on daily activities, pain-related disability and prosthesis use compared with single-grip myoelectric prostheses: A single-case study. J Rehabil Med. 2022 Jan 3:54:jrm00245.