At present, tools for evaluating the impact of treatments in neuromuscular disoders are mainly limited to strength measurement. Although this parameter is important, it is not sufficient to evaluate patients’ quality of life since it is not sufficiently comprehensive to evaluate a person’s activity as a whole: walking, sitting down, running, eating, going to bed, sleeping etc. This is why JY Hogrel and his team* have devised a tool designed to measure the general activity of patients in their homes in order to reach parameters applicable to their daily life, and finally to be able to quantify any improvement during a particular therapy.


In what context was the development of this tool considered necessary ?
First we have realised that we had almost no instrument to measure the daily activity of patients in the case of systemic treatment. During the first gene or cell therapy trials only one muscle was injected and all calculations (in terms of molecular biology and genetics – and for functional parameter measurements, the strength of the function in which the muscle participated) were based on what took place in this muscle. For more systemic therapies we will need comprehensive parameters. In any case, this is already the case with pharmacological therapies. For example, at present we are preparing a therapeutic trial with PTC Therapeutics where the StepWatch Activity Monitor will be used to record the number of steps that the patient performs in one day, a parameter in direct relation to that person’s quality of life. It is an interesting indicator, but establishing a real quantification of home activity requires the collection of more complex data.

What type of data and for what reason ?
This data is necessary for attaining three objectives. The first is to obtain a general indicator of daily energy produced by the patient through his physical activities, the idea being that – behind the parameters that can be measured by captors – physical energy can be deduced and quantified.
The second objective is to describe the patient’s physical activity: how long is he/she seated, lying down or standing in a day, how long walking, running, sleeping etc.
Finally, the third objective – assuming the person can walk – is to analyse the quality of their gait. In other words, determine the so-called stationary phases of gait and to measure a certain number of parameters (regularity, symmetry, propulsive power…). From this we will be able to identify a certain number of gait cycles that can be analysed to establish whether the person is walking better or less well, or whether the quality of gait has been improved by treatment.

You mentioned energy produced by patients. How can this be measured ?
It can be measured indirectly using accelerometers – captors which measure accelerations in space. We can count the energy used by a person from the acceleration measured (especially by using the principles of dynamics, well-known to physicists).

Why do you insist that these measurements be carried out at patients’ homes ?
It’s necessary to develop a product specific to the therapeutic benefit of neuromuscular patients. Therefore, the more the product is tested in a home environment, the more we can see the impact of the therapy on peoples’ daily life, which is not really the case when they come to the laboratory. In hospital, the measurements taken are – on the one hand – very sporadic and on the other, outside the patient’s natural environment, which can be disturbing.
Using the device we are developing, patient activity can be measured over several days by using an apparatus designed to be as non-intrusive as possible. It can be worn at the belt, for example and should be so small, light and autonomous that the patient will forget it is there. We must succeed in making recordings over a sufficiently long period so that the measurements are representative of the person’s usual daily activity and can be resumed over time. Let’s look at the PTC Therapeutics trial again: bearing in mind that the patients are allowed to take off the device for only 20 minutes per day (for washing) we must be able to record 7 days of activity every six weeks. It is easy to see why the system should not inconvenience the patient.

 

Could you outline the stages of development of this tool ?
There are three stages. To begin with, we wrote a set of functional specifications describing everything the device should do. Second – and we’re at this stage now – we have sent these specifications to companies capable of developing this type of product or which have already developed comparable products, such as those for the elderly. (However, although such devices exist, their algorithms will have to be adapted to patients whose gait profiles are very different to those of the elderly. The gait is not rhythmic but balanced, absorbed, with little acceleration, and this makes the lines recording it very flat and unrecognised by the original algorithms). Finally, when these companies submit a tool, it must be validated on our patients and subjected to tests in order to evaluate the quality of gait measurement and see if the algorithms are adapted to our particular context.

Can other uses for this tool be imagined ?
We can imagine using this tool for the follow-up of the natural history of diseases and potentially to refine care management (physiotherapy, balneotherapy, stretching exercises etc) but also in terms of appliances (ortheses etc) or operations (arthrodeses etc) in order to measure the impact on daily life. These treatments can improve the muscle function of a patient, but we want to see what happens on his autonomy. In other words, we want to be able to distinguish between a “functional” improvement and an “autonomy” improvement. We can also imagine applying this kind of measurements in other populations of subjects (such as elderly people for instance).

* JY Hogrel is director of the Laboratory of Neuromuscular Physiology and Evaluation at the Institute of Myology.