1. An assessment tool for dactylitis Philip Helliwell

2. Definition of dactylitis Uniform swelling of a digit such that the soft tissues between the joints are diffusely swollen to the extent that the actual joint swelling can no longer be independently recognised. Adapted from: Rothschild BM, Pingitore C, and Eaton M. Dactylitis: implications for clinical practice. Seminars in Arthritis & Rheumatism. 1998;28:41-7

3. Dactylitis instrument based on a surrogate of volume Joint circumference measurement has a long history in rheumatology (but poor inter-rater reliability) Use contralateral digit as comparator Easily measured in both finger and toes Provides a definition for borderline cases eg 10% difference in circumference

4. Final instrument Based on finger and toe circumference Incorporates a score for tenderness based on Ritchie method –0 = no tenderness on squeezing –1 = tender –2 = tender and wince –3 = tender and withdraw

5. What if opposite digits are involved? Normative data for fingers are available from an anthropometric survey of British workers in the 1980s Normative data for toes required – data on 50 people (1,000 digits) collected for this study

6. Case 1: 1 dactylitic finger Score 28.4 Injected with steroid 1 week later score 4.6

7. Case 2: 4 dactylitic digits Both 2 nd toes involved Total score 96.1

8. Dactylitis – can we agree? Previous work Dafna Gladman has shown moderate inter-observer agreement: Kappa statistic 0.57

9. Reliability study 7 patients all with psoriatic arthritis 5 health professionals (4 physicians and 1 specialist nurse) No pre-study training given Assessed patients in turn scoring: –Presence or absence of dactylitis and tenderness score –Measured circumference of all 20 digits Repeated above after interval of 60 minutes

10. Circumferometer

11. Patient 4 in reliability study

12. Patient 1 in reliability study

13. Reliability – agreement statistics Percentage exact agreement by joint Kappa statistics for – tender and non-tender dactylitis –Between and within observers

14. Percentage exact agreement by digit Median agreement 93%

15. Inter observer agreement – first examination Inter observer agreement for presence of tender dactylitis. Kappa statistics are based on recorded tender dactylitis for 140 digits. Tender dactylitis Overall kappa 0.54

16. Inter observer agreement – first examination Inter observer agreement for presence of non- tender dactylitis. Kappa statistics are based on recorded tender dactylitis for 140 digits. Non-tender dactylitis Overall kappa 0.17

17. Kappa agreement statistics intra-rater Any tender dactylitis: 0.82 Any non-tender dactylitis: 0.58

18. Dactylitis instrument Median and inter-quartile range Intra-class correlation coefficients

19. Raw dactylitis scores by patient

20. ICC statistics 1.Inter-rater 0.90, 95% CI 0.74 – 0.98 2.Intra-rater 0.84, 95% CI 0.71 – 0.92

21. Revised instrument Variation may exist as a result of: –Differences in measuring circumference –Differences in judging degree of swelling –Differences in assessing response to squeeze

22. Difference in digital circumference for tender dactylitis by examiner Median = 11.7%

23. Revised instrument Variation may exist as a result of: –Differences in measuring circumference –Differences in judging degree of swelling –Differences in assessing response to squeeze Revised instrument records presence or absence of tenderness and uses 10% cutoff to define dactylitis

24. Revised dactylitis instrument scores

25. ICC statistics 1.Inter-rater 0.76 (0.48 – 0.94) 2.Intra-rater 0.91 (0.83 – 0.95)

26. ICC statistics 1.Inter-rater 0.76 (0.48 – 0.94) 2.Intra-rater 0.91 (0.83 – 0.95) 1.Inter-rater 0.97 (0.90 – 0.99) 2.Intra-rater 0.91 (0.83 – 0.95)

27. Dactylitis instrument - revised Limits of agreement (mean difference ± 2xsd): All raters: - 5.4 ± 37.4 (-2 ± 17) Individual raters: MEANLOA PSH-1.36.8 RDM-19.370.4 GI-3.335.4 JF1.68.4 IS-4.817.2

28. Dactylitis assessment tool Quick and easy to measure Intra- and inter-rater reliability: good by ICC individually variable by LOA Still require data on responsiveness in a clinical trial setting