Identifying clinical course patterns in SMS data using cluster analysis

This was a secondary analysis of longitudinal SMS data collected in two randomised controlled trials conducted simultaneously from a single clinical population (n？=？322). Fortnightly SMS data collected over a year on ‘days of problematic low back pain’ and on ‘days of sick leave’ were analysed using Two-Step (probabilistic) Cluster Analysis.Clinical course patterns were identified that were clinically interpretable and different from those of the whole group. Similar patterns were obtained when the number of SMS time points was reduced to monthly. The advantages and disadvantages of this method were contrasted to that of first transforming SMS data by spline analysis.This study showed that clinical course patterns can be identified by cluster analysis using all SMS time points as cluster variables. This method is simple, intuitive and does not require a high level of statistical skill. However, there are alternative ways of managing SMS data and many different methods of cluster analysis. More research is needed, especially head-to-head studies, to identify which technique is best to use under what circumstances.Much clinical research is focused on the outcomes achieved by patients and usually such outcomes are collected at standardised time points over a follow-up period. For example in back pain research, it is routine practice to measure pain and activity limitation at time periods such as 3, 6 and 12 months after the initial contact with the patient.Recently, there has been interest in using the short message service (SMS) or text messaging, on cell phones to provide a more detailed assessment of a patient’s clinical course [1,2]. An example is using weekly SMS messages sent from an automated service to each patient’s cell phone requesting they reply with the number of days of bothersome pain experienced over the previous week. The technology for using this method is becoming common, inexpensive and widely used in some research settings.Although SMS provides les