Ultrasound Composite Scores for the Assessment of Inflammatory and Structural Pathologies in Psoriatic Arthritis (PsASon-Score)

Anja Ficjan; Rusmir Husic; Judith Gretler; Angelika Lackner; Winfried B Graninger; Marwin Gutierrez; Christina Duftner; Josef Hermann; Christian Dejaco


Arthritis Res Ther. 2014;16(476) 

In This Article


Clinical Findings at Baseline and Follow-up Visits

Patients' characteristics are summarized in Table 1. At baseline, 40 patients (48.2%) were in remission as judged by the evaluating physician and 28 patients (33.7%) fulfilled the MDA criteria. Of the 83 patients 13 (15.7%) did not complete 6-month follow up. At follow up, 41 patients (58.6%) had stable disease activity according to physician's evaluation (25 (35.7%) were inactive and 16 (22.9%) were active at both time points), 21 (30.0%) changed from active disease to remission and 3 (4.3%) from remission to active disease. Applying the MDA criteria, 15 of those (27.3%) being active at baseline reached MDA at follow up, 7 (25.0%) with MDA at baseline did not fulfill these criteria at the second visit, and 48 patients (68.6%) had stable disease (that is, were active (n =32) or had MDA (n =16) at both visits).

Synovial Recesses and Entheses Selected for the Ultrasound Composite Scores

Additional file 2 http://arthritis-research.com/content/16/5/476/additional details the results of selection process for the ultrasound composite scores. We made a few manual selections to improve the feasibility of the scores: (1) we included the second H-PIP instead of the first H-PIP for the PsASon22 because H-PIP2 better fitted into the construct of MCP2, MCP3, H-PIP3, H-DIP2 and H-DIP3 (that was already gathered). Also, H-PIP1 emerged from the selection process because of a high prevalence of osteophytes; however, the sensitivity of H-PIP2 for the detection of osteophytes was only slightly lower than that of H-PIP1; (2) we omitted the insertion of the Achilles tendon from both the PsASon22 and the PsASon13 scores because this site was mainly relevant for the detection of enthesophytes; and (3) we omitted the distal insertion of the triceps into the olecranon from PsASon13 because this site was mainly relevant for the detection of enthesophytes. The combination of the insertion of the common extensor tendon at the lateral epicondyle and the patellar tendon insertion into the tibial anterior tuberosity already revealed a very high sensitivity to identify patients with enthesophytes.

Table 2 summarizes the proportion of ultrasound abnormalities exclusively detected by dorsal or palmar/plantar scans of H-PIPs, H-DIPs, MTPs, F-PIPs, F-DIPs and wrists as well as by medial/lateral or suprapatellar assessments of knees. We observed that ≥20% of structural and inflammatory pathologies at the H-PIP and H-DIP level were identified by palmar or dorsal scans only. At the knees, suprapatellar, medial/lateral scans are required not to miss patients with PD-signals. At the wrists and MTPs, palmar/plantar scans appeared to be less relevant given that only a minority of patients revealed ultrasound abnormalities at these sites. At F-PIPs and F-DIPs, the proportion of erosions detected by plantar scans was >20%; however, we decided to omit plantar scans from the composite scores due to the low absolute number of erosions at these sites.

The final composite scores are depicted in Figure 1 and detailed in Table 3. The bilateral score (PsASon22) includes 22 joints (6 MCPs, 4 H-PIPs, 2 MTPs, 4 H-DIPs, 2 F-DIPs, 4 large joints) and 4 entheses, whereas the unilateral score (PsASon13) compromises 13 joints (2 MCPs, 3 H-PIPs, 1 F-PIP, 2 MTPs, 1 H-DIP and 2 F-DIPs, 2 large joints) and 2 entheses.

Figure 1.

Joints and entheses included in ultrasound composite scores. Illustration depicts joints (circles) and entheses (arrows) included in the 68-joint/14-entheses score, and the bilateral 22-joint/4-entheses (PsASon22) and the unilateral 13-joint/2-entheses composite scores (PsASon13). For the unilateral score the dominant site is investigated (for example, the right site as shown in the figure). Solid circles indicate that both, palmar and dorsal sites (suprapatellar, medial and lateral scans for the knee) are assessed, whereas striped circles mark sites investigated by dorsal scans only.

Additional file 3 http://arthritis-research.com/content/16/5/476/additional details the possible ranges of ultrasound composite scores and their components.

Sensitivity of the Ultrasound Composite Scores for the Detection of Ultrasound Pathologies

As detailed in Table 4, the bilateral composite score yielded sensitivity >80% for most lesions and sites using the 68-joints/14-entheses ultrasound score as the reference, whereas the unilateral score was less efficient revealing >80% sensitivity for GSS at small/large joints, GSE and osteophytes/enthesophytes only.

Both composite scores were more sensitive for the detection of PsA characteristic pathologies at small and large joints than at DIPs. Both composite scores were more efficient to identify osteophytes/enthesophytes than erosions, and among inflammatory lesions, GS-changes were more commonly detected than PD-signals.

Convergent Construct Validity of Ultrasound Composite Scores

Table 5 and Table 6 depict the association of inflammatory and structural components of the bilateral and unilateral composite scores, and the 68-joint/14-entheses score with clinical parameters of inflammation and disability (convergent construct validity). We observed weak to moderate correlations of the GSS/GSE, PD-j/e, and the GUIS scores with clinical composite scores, global assessments of pain/disease activity and acute phase reactants (Table 5). Importantly, the ultrasound composite scores yielded similar associations with clinical measures of disease activity to the 68-joint/14-entheses score (except for the component PD-teno that weakly correlated with clinical composite scores only when the sonographic 68-joint/14-entheses score was applied). Joint/enthesal erosions but not osteophytes correlated with HAQ, particularly in patients judged to be in remission in whom the activity related (that is, reversible) component of disability is assumed to be low (Table 6).[20]

Further subanalyses indicated that GSS and PD-j scores were associated with the number of SJ, the PD-j score with the number of TJ, and the GSE with the MASEI + epi (see Additional file 4 http://arthritis-research.com/content/16/5/476/additional).

Sensitivity to Change in Ultrasound Composite Scores

As detailed in Figure 2 and Additional file 5 http://arthritis-research.com/content/16/5/476/additional we observed that patients changing from a clinical status of active disease to remission/MDA yielded greater reductions in the GUIS of the bilateral, the unilateral or the 68-joint/14-entheses scores compared to patients with unchanged clinical activity. The effect size (Cohen's d statistic) for the GUIS was low to moderate ranging from 0.40 (PsASon13) to 0.75 (68-joint/14-entheses score). SRM of patients changing from active disease to remission or MDA ranged from −1.04 to −0.09 (as compared to −0.53 to −0.04 in the entire cohort).

Figure 2.

Sensitivity to change of ultrasound composite scores. Change (Δscore 6-month visit – score baseline) of global ultrasound inflammatory subscores (global ultrasound inflammation score (GUI-score)) in patients without a change in clinical disease activity (that is, active or remission at both baseline and follow-up visits) (no change DA) and patients who were active at baseline and achieved remission according to the evaluating physician (A), active-remission) or minimal disease activity (B) (active-MDA) at 6 months follow-up. Whiskers box plots show the median and 50% of cases within the boxes and all data excluding mavericks between the end points of the whiskers. Differences were tested by the Mann-Whitney U-test.

In subanalyses, we observed that the GSS/GSE was the most sensitive GUIS item to change (for details including effect size and SRM see Additional file 5 http://arthritis-research.com/content/16/5/476/additional). We also found weak to moderate correlations between ΔGUIS scores and ΔPASDAS, ΔDAPSA, ΔPtpain, ΔPGA and ΔEGA as depicted in Additional file 6 http://arthritis-research.com/content/16/5/476/additional.

Feasibility and Inter-rater Reliability

The median time to complete the bilateral and unilateral scores was 19 minutes (range 16 to 26) and 10 (9 to 13) minutes, respectively. Inter-rater reliability of components from bilateral and unilateral composite scores was moderate to good: ICCs for the GUIS were 0.84 and 0.54, respectively. ICCs of the GUIS components ranged from 0.42 (GS-teno) to 0.96 (PD-j) for the bilateral composite score and from 0.36 (GS-teno) to 0.71 (PD-j) for the unilateral score. The ICC for erosions was 0.75 and 0.64, respectively; and for the osteophyte/enthesophyte subscore, it was 0.92 and 0.41, respectively, for the bilateral and unilateral composite scores.