Background Primary Sjögren’s syndrome (pSS) is a systemic auto-immune disease, characterised by abnormalities of B cell homeostasis. Several studies demonstrated that the repartition of blood B cell subsets is altered during pSS.
Objectives The aim of this prospective study was to determine the diagnostic value of blood B-cell subset profiling for pSS.
Methods This cross-sectional study was conducted in a monocentric cohort of patients with suspected pSS prospectively included between November 2006 and April 2011. Clinical examination, basic biology, immunological tests and minor labial salivary gland biopsy were performed systematically. For blood B-cell subset profiling, the ratio (Bm2+Bm2’)/(eBm5+Bm5) was determined using flow cytometry. The gold standard for the analysis was a clinical diagnosis of pSS performed by a group of experts, blinded to the results of B-cell profiling.
Results 170 patients have been included in the study. 72 patients had pSS, of whom 58 (80.6%) fulfilled AECG criteria. No differences were found between the 2 groups concerning age, disease duration, and sex ratio. All items of AECG criteria were significantly associated with the diagnosis of pSS except xerostomy. The mean (Bm2+Bm2’)/(eBm5+Bm5) ratio was significantly higher in the pSS group than in the non-pSS group (7.2±7.0 vs. 3.2±2.4, P<0.001). By ROC curve analysis ≥5 was the best cut-off, with 51.4% sensitivity, 82.7% specificity, 68.5% positive predictive value, and 67.9% negative predictive value (figure). High values of this ratio strongly suggested pSS diagnosis. Thus, a cut-off of 6.5 increased Sp to 92.9% and PPV to 80.6% and a cut-off of 9 provided 98% Sp and 90.5% PPV (with 40.3% and 26.4% Se, respectively). Among the 17 non-pSS patients who had a ratio ≥5, 8 had idiopathic sicca, 5 had secondary SS, and 4 had drug-induced sicca.
Conclusions Blood B cell profiling using flow cytometry is a simple test that displays good diagnostic properties for pSS. Its inclusion into diagnostic criteria should be evaluated.
Disclosure of Interest None Declared