NEW YORK – After instruction by a nurse, patients with psoriatic arthritis do at least as well as nurses but better than physicians in counting tender and swollen joints, according to a cross-sectional study that employed ultrasound as a gold standard.
"Patient counts of swollen joints correlated with both effusion and synovitis as detected by ultrasound, suggesting that patients can learn to monitor their own disease," reported Dr. Agnes Szentpetery of the department of rheumatology at St. Vincent’s Hospital, Dublin.
In this study, described as the first ever conducted in psoriatic arthritis to compare joint counts by patients, nurses, physicians, and ultrasound (US), 50 patients with a mean age of 50 years were enrolled. All received instruction from a nurse on how to assess and count tender and swollen joints. The major focus of the correlations was in 34 joints assessed with US, although further correlations were made between patients, nurses, and physicians for 28 (JC28) and 66 swollen and 68 tender (JC 66/68) counts.
"Joint counts [confirming active disease] were higher for patients and nurses than for physicians," reported Dr. Szentpetery, who presented these data at the joint meetings of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis and the Spondyloarthritis Research & Treatment Network (SPARTAN). Doctor and nurse counts for swollen joints, unlike patient counts, did not correlate with US evidence of effusion, although they did for synovitis.
For tender joints, there was moderate or good agreement between patient and doctor for 11 joints, doctor and nurse for 12 joints, and patient and nurse for 19 joints. (This nurse was different from the one who provided instruction on joint counts.) However, correlation between any of these observers and US evidence of tender joints was uniformly poor.
Small joints in the hand, particularly the proximal interphalangeal joint, offered the best interobserver agreement for correlations, according to Dr. Szentpetery. Although no correlations rose above good and most were moderate between any two observers, Dr. Szentpetery stressed that patients performed at levels comparable with doctors and nurses, compared with US.
"Although this was a small study, the results support patient joint counts, and we have already begun routinely instructing patients in our clinic," Dr. Szentpetery reported.
Asked for a comment, Dr. John D. Reveille, professor of rheumatology and clinical immunogenetics at the University of Texas Health Sciences Center at Houston, said that he is remaining cautious until a larger study generates more data. He said that similar efforts to instruct patients to perform joint counts in rheumatoid arthritis failed to produce acceptable rates of accuracy.
"It may be possible to enlist patients to perform accurate joint counts if they are motivated and receive appropriate education, but you may need a special population and the right education," said Dr. Reveille, who is chair of SPARTAN’s executive committee.
However, joint counts are perceived to be so time consuming that many clinics do not perform them at all, according to Dr. Szentpetery. Moreover, she suggested that the absolute number of tender or swollen joints at any moment in time may be less important than the change in joint involvement after treatment is initiated, an outcome that may be best measured by patients.
"I agree that this is a small study, and more data are needed, but our data suggest patients may have a role in joint counts, which is an attractive strategy for reducing work for the clinicians," Dr. Szentpetery said.
Dr. Szentpetery and Dr. Reveille reported no relevant financial conflicts.