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

ABSTRACT

OBJECTIVES: To explore the performance of laboratory items alone in systemic lupus erythematosus (SLE) classification. METHODS: 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. 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. CONCLUSION: 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.