4.2.1 When is a foot ulcer not a foot ulcer? – The validation of prevalence data (76)

Jill Firth, Research Fellow, School of Healthcare, University of Leeds, Leeds, United Kingdom Co authors: Claire Hale, Philip Helliwell, Jackie Hill & Andrea Nelson J.Firth@leeds.ac.uk

Abstract:

Aim:

The aim of this study was to establish the prevalence of foot ulceration in patients with rheumatoid arthritis (RA). Many prevalence studies of lower limb ulceration have relied upon reporting by health professionals, but this approach neglects patients who are self caring and may lead to an under-estimation of prevalence. This presentation will outline the methodological approach to the validation of self reported prevalence data and the related findings.

Methods:

A postal survey of all the patients with RA on a diagnostic register in an acute trust (n=1130) was undertaken in May, 2005. Respondents reporting open or healed ulceration were asked to indicate the anatomical site on a diagram of the lower limb (Thurtle & Cawley, 1983). Sites of ulcers marked above the ankle were verified with case notes and reclassified as leg ulcers, equating to false positives. Additional false positives among respondents were identified through clinical examination, case note review and contact with health professionals. A random sample of respondents who denied ulceration were also examined (n=70) to assess the false negative rate.

Results:

Based upon self report, the point prevalence (open ulceration at the time of the study) was 3.96% and the overall prevalence (open and healed) 12.34%. The false positive rate without using the diagrammatic questionnaire data to exclude leg ulceration was high at 21.21%, but fell to 10.76% with the location data used. Interestingly the false negative rate was also noteworthy at 11.76%. After the validation phase, the final estimate of point prevalence was 3.39% and the overall prevalence 9.73%.

Conclusions:

Reliance solely on self report would have led to a relative over estimation of point prevalence by 17% and overall prevalence by 27%. Self reported prevalence data may be validated using a variety of strategies and this enhances the accuracy of prevalence estimates.

Biography:

Jill Firth qualified as a Registered General Nurse in 1989 and latterly worked as a Rheumatology Nurse Specialist for Bradford Teaching Hospitals NHS Trust for a period of eight years. In 2004 she was awarded the Smith & Nephew Foundation Doctoral Nursing Scholarship to look at the prevalence and predictors of foot ulceration in patients with rheumatoid arthritis. This enabled her to undertake a full-time PhD at the University of Leeds, which is close to completion. Jill was recently awarded the Smith & Nephew Foundation Post Doctoral Research Fellowship and will continue research relating to foot ulceration in rheumatoid arthritis.