The MSK components of the BILAG and SLEDAI have limited sensitivity, specificity and responsiveness. We aimed to develop a better disease activity tool for MSK lupus.
“LAMDA” was derived using data from the multicentre USEFUL study (PMID:33792659); 133 patients with inflammatory MSK pain received intramuscular depomedrone then were assessed for 66/68 SJC/TJC, BILAG-2004, SLEDAI-2K, physician MSK-VAS, inflammatory markers, patient pain and disease-activity-VAS and MSK-ultrasound. Baseline variables were modelled against US using penalized (Lasso) regression. For validation we evaluated: (i) responsiveness at week 6 in USEFUL and (ii) association with quality of life and treatment decision in an independent study (n=100).
LAMDA was a composite of SJC, patient-MSK-pain-VAS, physician-MSK-disease-activity-VAS and ESR ranging from 0 to 26.5. Response effect size was greater for the LAMDA (0.37) than the BILAG-MSK (0.31), SLEDAI-MSK (0.27) and total US score (0.33). With active US at baseline, LAMDA’s effect size was 0.42.
In the validation study LAMDA score correlated with better physical function (R = -0.49, p<0.001), pain (R = -0.44, p=0.002) and Burden to Others (R = -0.38, p=0.009). LAMDA was higher when therapy was increased (mean (95% CI) difference 12.9 (5.8, 19.9), p<0.001).
LAMDA is a continuous disease activity instrument for MSK lupus that is sensitive to imaging-synovitis without swelling, more responsive than other instruments and correlates with quality of life and treatment decision. LAMDA may improve the ability of clinicians to monitor and treat MSK lupus, and determine the efficacy of therapies in clinical trials.