Daily life activity routine discovery in hemiparetic rehabilitation patients using topic models.

BACKGROUND: Monitoring natural behavior and activity routines of hemiparetic rehabilitation patients across the day can provide valuable progress information for therapists and patients and contribute to an optimized rehabilitation process. In particular, continuous patient monitoring could add type, frequency and duration of daily life activity routines and hence complement standard clinical scores that are assessed for particular tasks only. Machine learning methods have been applied to infer activity routines from sensor data. However, supervised methods require activity annotations to build recognition models and thus require extensive patient supervision. Discovery methods, including topic models could provide patient routine information and deal with variability in activity and movement performance across patients. Topic models have been used to discover characteristic activity routine patterns of healthy individuals using activity primitives recognized from supervised sensor data. Yet, the applicability of topic models for hemiparetic rehabilitation patients and techniques to derive activity primitives without supervision needs to be addressed. OBJECTIVES: We investigate, 1) whether a topic model-based activity routine discovery framework can infer activity routines of rehabilitation patients from wearable motion sensor data. 2) We compare the performance of our topic model-based activity routine discovery using rule-based and clustering-based activity vocabulary. METHODS: We analyze the activity routine discovery in a dataset recorded with 11 hemiparetic rehabilitation patients during up to ten full recording days per individual in an ambulatory daycare rehabilitation center using wearable motion sensors attached to both wrists and the non-affected thigh. We introduce and compare rule-based and clustering-based activity vocabulary to process statistical and frequency acceleration features to activity words. Activity words were used for activity routine pattern discovery using topic models based on Latent Dirichlet Allocation. Discovered activity routine patterns were then mapped to six categorized activity routines. RESULTS: Using the rule-based approach, activity routines could be discovered with an average accuracy of 76% across all patients. The rule-based approach outperformed clustering by 10% and showed less confusions for predicted activity routines. CONCLUSION: Topic models are suitable to discover daily life activity routines in hemiparetic rehabilitation patients without trained classifiers and activity annotations. Activity routines show characteristic patterns regarding activity primitives including body and extremity postures and movement. A patient-independent rule set can be derived. Including expert knowledge supports successful activity routine discovery over completely data-driven clustering.

[Possible aggravation of a Henoch Schoenlein purpura by isotretinoin]. / Mögliche Aggravation einer Purpura Schönlein-Henoch durch Isotretinoin.

We report on a 16 year old patient with a hemorrhagic bullous form of a Henoch-Schönlein purpura. The cause for the event could not be determined, but the patient recovered without complications. Since he had begun a therapy with isotretinoin due to an acne inversa 3 weeks before, a possible association between the event and the treatment could not be excluded, and the case was reported to Swissmedic. In the comment, we discuss the pharmacology of isotretinoin, drug-induced vasculitis, and its pathomechanisms. As a general reminder, the criteria for the causality assessment of adverse drug reactions as well as the reporting system of adverse drug reactions in Switzerland are discussed.