To demonstrate that digital biomarkers collected by a smartphone application can distinguish healthy controls (HC) from subjects with radiologically isolated syndrome (RIS).

RIS is defined by the incidental finding of MRI lesions suggestive of multiple sclerosis in subjects  with a normal neurological examination. Some studies suggested that the use of wearables could unveil infra-clinical differences between RIS subjects and HC.

We created a mobile app called MS Screen Test (MSST) that contains:

• Finger tapping speed test
• Level test: the subject is asked to tilt the phone to move a ball inside a target, then maintain it inside the target for 10 seconds
• Low contrast vision (LCV) test: letters with varying contrast randomly appearing on the screen. The subject has to tap on the screen each time a letter is seen. 
• Cognition test: letters or digits randomly appear on the screen. The subject has to tap on the screen only if a letter is seen. 

A cohort of HC and RIS subjects were evaluated to compare performances on MSST.

60 HC and 16 RIS subjects were prospectively included (F/M 3.15, mean age 41.6 yrs)

Compared to HC, RIS subjects had a lower tapping speed on both dominant (5.6 Hz vs 6.5 Hz, p=0.001) and non dominant hand (5.1 Hz vs 5.6 Hz, p=0.04), fewer detected letters on the LCV test (10 vs 13, p=0.001) and a higher latency of response on the cognitive test (731 ms vs 599 ms, p<0.0001).

On the level test, the time during which the ball was maintained is the target was shorter for RIS subjects (3 sec vs 4.9 sec, p=0.05).

Our study confirms that digital biomarkers collected by a smartphone can unveil differences between HC and subjects at a presymptomatic stage of MS.