Classifying systemic lupus erythematosus using laboratory items alone: a preliminary study.

Abstract

To explore the performance of laboratory items alone in systemic lupus erythematosus (SLE) classification. Our cohort consisted of 352 and 385 (control) patients with and without SLE. This study evaluated the performance of the American College of Rheumatology (ACR)-1997, Systemic Lupus International Collaborating Clinics (SLICC)-2012, European League Against Rheumatism (EULAR)/ACR-2019, and Systemic Lupus Erythematosus Risk Probability Index (SLERPI) using laboratory items alone, including blood and urine test results. The median ratio of laboratory items/total items was 66.7%, 75.0%, 60.4%, and 77.4% in ACR-1997, SLICC-2012, EULAR/ACR-2019, and SLERPI, respectively. After including laboratory items alone, the sensitivity of ACR-1997, SLICC-2012, EULAR/ACR-2019, and SLERPI was 31.3% (95% confidence interval [CI]: 26.4%-36.4%), 79.8% (95% CI: 75.3%-83.9%), 75.9% (95% CI: 71.0%-80.2%), and 85.2% (95% CI: 81.1%-88.8%), respectively. We referenced the SLERPI and removed the additional restrictions, i.e., SLICC-2012 criteria only needs to fulfill at least four items (mSLICC-2012) and EULAR/ACR-2019 criteria needs to have ≥ 10 points (mEULAR/ACR-2019) to qualify for SLE classification. The mSLICC-2012 and mEULAR/ACR-2019 criteria, including laboratory items alone, newly identified 13 and 25 patients, respectively. Based on laboratory items alone, the combination of mSLICC-2012, mEULAR/ACR-2019, and SLERPI identified 348 patients with an improved sensitivity of 90.6% (95% CI: 87.1%-93.5%). Patients, who were classified according to the mEULAR/ACR-2019 criteria, all met the other criteria. Incorporating laboratory items alone was clinically feasible to help identify SLE. SLERPI and SLICC-2012, using laboratory items alone, were more worthwhile to promote in the clinic compared with EULAR/ACR-2019. Key Points • Laboratory items play a crucial role in the SLE classification criteria, and incorporating laboratory items alone was clinically feasible to help in the identification of SLE. • The SLERPI and SLICC-2012, using laboratory items alone, were more worthwhile to promote in the clinic compared with EULAR/ACR-2019, and the combination of the two could further improve the sensitivity. • The relative simplicity of evaluating laboratory indices may help nonrheumatologists and inexperienced rheumatologists to identify SLE more quickly, thereby reducing the risk of delayed diagnosis in patients.