This study is attempting to follow up the original cohort of patients who took part in the short- and mid-term study which may mean reduced patient numbers due to some inevitable patient deaths. Kaplan-Meier analysis will control for this. In terms of patient numbers, effort will be made to recruit as many patients as possible as this will increase the validity of the results. This could be a problem not only related to deaths of some of the patients but also the timeframe for completion of the project or a refusal of the patient to take part. Many of the patients are elderly and may not want to accept the invitation to come to the hospital. However, good follow-up rates were achieved in the mid-term study (around 80%) and familiarity with the team should aid recruitment as the same patients will be contacted.
In order to maintain validity and reliability of the study as part of a follow on, the methodology adopted for this project will be similar to that of the short-term study in terms of the way in which the information is gathered and the classification of the results. This will mean that if a comparison between the two is to be made, similar information is available and scientifically comparable. There should not be any significant intra and/or inter observer/operator variability with the results (different users technical ability with ultrasound) as collaboration between those responsible for collection of all the data and performing all diagnostic tests will be done to avoid any potential problems with validity. For this reason, assessments will be performed by the principal investigator under the guidance and supervision of the main research nurse responsible for data collection on the previous project. Results of this study will be analysed, evaluated and disseminated as a continuation of the previous short/mid-term study.
A possible limitation may be that patient recollection of their experience of any ulcer recurrences may be unreliable. This is an unavoidable problem but effort will be made to get the most accurate account as possible from the participants.
There is a possibility for bias of the long-term follow up results as it is more likely that patients who are having problems with their treatment results will accept the offer of additional follow-up rather than those patients who are fine. However, as all patients will be asked if they would like to participate via telephone if unwilling to come to the hospital for assessment, this should not affect research question 1.
