Musculoskeletal inflammation in SLE not reliably identified with existing clinical instruments
medwireNews: Existing classification systems for musculoskeletal (MSK) symptoms in people with systemic lupus erythematosus (SLE) fail to identify inflammation in a large proportion of those with synovitis, suggest findings reported in Rheumatology.
“We demonstrate that more than a quarter of SLE patients with inflammatory MSK symptoms have proven synovitis, which is associated with worse serological and clinical assessments, but not detected by validated disease activity instruments,” write Edward Vital (University of Leeds, UK) and colleagues.
Among 88 participants with SLE and inflammatory MSK symptoms, 27% had subclinical inflammation on ultrasound (US) scan, but not clinically swollen joints. And among these individuals, subclinical synovitis was associated with serological evidence of disease activity, including a significantly higher IgG titer.
The British Isles Lupus Assessment Group (BILAG) index and the SLE Disease Activity Index (SLEDAI), which are commonly used to measure disease activity in patients with SLE, identified clinical inflammation in only 34 (38%) of 88 symptomatic patients, according to BILAG A/B criteria and in 28 (32%) using SLEDAI-MSK 4 criteria.
The other patients in the study were classified as not having clinical synovitis when examined using these indices and would “therefore not meet levels of BILAG and SLEDAI criteria usually required for entry into clinical trials or to start biologic therapy,” say the researchers.
By comparison, 60 (68%) symptomatic patients were found to have inflammation on ultrasound (gray scale ≥2 and/or Power Doppler ≥1 or tenosynovitis), compared with just 4 (17%) of 23 asymptomatic patients enrolled in the study. And although the BILAG and SLEDAI instruments had high specificity of 89% each, they both had low sensitivity for US-confirmed synovitis, at 56% and 44%, respectively.
Current EULAR recommendations indicate that the best long-term outcomes among SLE patients are achieved by treating to a target of low disease activity using validated instruments such as BILAG and SLEDAI, while minimizing glucocorticoid exposure, say the researchers.
However, they note: “Our results show the limitation of directing treatment according to these tools in MSK SLE and their likely consequences,” including failure to escalate therapy despite definite synovitis in those with ongoing inflammatory symptoms who nevertheless fail to meet SLEDAI MSK or BILAG A/B criteria.
Vital and colleagues conclude that “our results demonstrate the limitations of current classification of active MSK SLE based on joint swelling, BILAG and SLEDAI and that a new classification of proven MSK inflammation may allow improvement in outcomes of immunosuppressive therapy.”
By Catherine Booth
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