I am looking at patient data with clinical scores for each that run from zero to 6 (integers, where zero is best and scoring 6 on symptoms is worst). There are follow up scores on each patient (at varying time intervals) - even the number of follow-ups is unequal among patients. The average number of follow-ups is around 4 ranging from 2 through 13. Each follow-up has a timestamp.
I wish to look at trends in the follow-up - whether the scores improve/worsen or stay stable to group the patients for further analysis.
Is there any specific metric that can capture in essence, the trend of ordinal scores?
Another issue is that the range of scores is 0-6 while the range of time is in months to years. The wide range in time is causing an issue in using measures like slope or r^2