Magnetic resonance imaging changes of sacroiliac joints in patients with recent-onset inflammatory back pain: inter-reader reliability and prevalence of abnormalities

To study the inter-reader reliability of detecting abnormalities of sacroiliac (SI) joints in patients with recent-onset inflammatory back pain by magnetic resonance imaging (MRI), and to study the prevalence of inflammation and structural changes at various sites of the SI joints. Sixty-eight patients with inflammatory back pain (at least four of the five following criteria: symptom onset before age 40, insidious onset, morning stiffness, duration >3 months, improvement with exercise — or three out of five of these plus night pain) were included (38% male; mean age, 34.9 years [standard deviation 10.3]; 46% HLA-B27-positive; mean symptom duration, 18 months), with symptom duration <2 years. A MRI scan of the SI joints was made in the coronal plane with the following sequences: T1-weighted spin echo, short-tau inversion recovery, T2-weighted fast-spin echo with fat saturation, and T1-spin echo with fat saturation after the administration of gadolinium. Both SI joints were scored for inflammation (separately for subchondral bone and bone marrow, joint space, joint capsule, ligaments) as well as for structural changes (erosions, sclerosis, ankylosis), by two observers independently. Agreement between the two readers was analysed by concordance and discordance rates and by kappa statistics. Inflammation was present in 32 SI joints of 22 patients, most frequently located in bone marrow and/or subchondral bone (29 joints in 21 patients). Readers agreed on the presence of inflammation in 85% of the cases in the right SI joint and in 78% of the cases in the left SI joint. Structural changes on MRI were present in 11 patients. Ten of these 11 patients also showed signs of inflammation. Agreement on the presence or absence of inflammation and structural changes of SI joints by MRI was acceptable, and was sufficiently high to be useful in ascertaining inflammatory and structural changes due to sacroiliitis. About one-third of patients with recent-onset inflammatory back pain show inflammation, and about one-sixth show structural changes in at least one SI joint

The influence of peripheral arthritis on disease activity in ankylosing spondylitis patients as measured with the Bath Ankylosing Spondylitis Disease Activity Index

To assess the differences in disease activity as measured by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) between patients with and without peripheral arthritis/enthesitis. To investigate whether scores on the BASDAI change by omitting the 2 questions on peripheral disease. Disease activity was assessed on a 10-cm visual analog scale and by BASDAI. Alternative BASDAIs were constructed by omitting the peripheral joints question and/or the enthesitis question. Correlations between the alternative BASDAIs and other measures of disease activity were calculated. Generalized estimating equations (GEE) were used to assess whether having peripheral arthritis influenced BASDAI and alternative BASDAI scores, and to assess whether peripheral arthritis influenced the score of the individual questions of the BASDAI. At baseline, the BASDAI was calculated in 214 patients. In patients with peripheral arthritis (n = 56), the mean (SD) BASDAI score was 4.4 (2.3) as compared with 3.1 (1.9) (P <0.0001) in the patients without peripheral arthritis (n = 158). The relationship between arthritis and the BASDAI score appeared to be truly longitudinal (GEE regression coefficient beta = 0.64; 95% confidence interval 0.28-1.00). Peripheral arthritis was significantly longitudinally associated with all separate item scores of the BASDAI. Omitting the peripheral joints and/or enthesitis question from the BASDAI questionnaire only partially explained the difference in BASDAI score between the 2 groups. Disease activity measured by the BASDAI is higher in patients with concomitant peripheral disease compared with patients with disease restricted to the axial skeleton. The increased BASDAI score in patients with peripheral arthritis is partially explained by increased overall disease activity as well as by a disproportionate contribution of the peripheral joints question to the overall scor

Measurement of spinal mobility in ankylosing spondylitis: comparison of occiput-to-wall and tragus-to-wall distance

To investigate if the tragus-to-wall distance (TWD) is more reliable compared to the occiput-to-wall distance (OWD) as a measurement for thoracic spine extension in patients with ankylosing spondylitis (AS). Data from the OASIS cohort, an international longitudinal observational study on outcome in AS, were used. Measurements of OWD and TWD were performed at baseline and at 6, 12, 18, and 24 months. Paired data of Tx and Tx+6 months were used to perform test-retest measurements (intraclass correlations, limits of agreement, and interperiod correlation matrix). Bland and Altman plots were constructed to investigate the agreement between both observations, assuming that there was no true change between 0 and 6 months. To investigate whether a change in disease activity would have influenced the results, limits of agreement were calculated in a subgroup of patients with a stable Bath Ankylosing Spondylitis Disease Activity Index (BASDAI; defined as a maximum BASDAI change of +/- 1) between T0 and T6 and compared with the results of the whole group. Limits of agreement were also calculated for kyphosed patients only. The test-retest intraclass correlations were between 0.94 and 0.96 for OWD and between 0.93 and 0.95 for TWD. The direct measurement-remeasurement correlation calculated by extrapolation of the interperiod correlation regression line was 0.92 for OWD and 0.90 for TWD. OWD and TWD showed comparable reliability on the entire value of scores. The lower 95% limit of agreement was between -3.4 cm and -2.5 cm for OWD and between -3.4 cm and -3.1 cm for TWD. The upper limit of agreement was between 3.1 cm and 4.2 cm for OWD and between 2.9 cm and 3.9 cm for TWD. In all patients as well as in kyphosed patients only, limits of agreement were comparable between OWD and TWD. The patterns of the scatterplots according to Bland and Altman were similar for OWD and TWD. Measurement error was more pronounced in kyphosed patients compared to patients with a normal thoracic extension. However, over the entire range of kyphosis, measurement error was similar. OWD and TWD are equally reliable in assessing thoracic spine extension. Although the TWD is in general easier to perform in AS patients compared to OWD, we recommend the OWD measurement over TWD: in OWD measurement a value of zero easily distinguishes patients with normal thoracic spine extension from kyphosed patient