Diagnostic accuracy of salivary gland ultrasound in Sjogren's syndrome: A systematic review and meta-analysis

Background: To systematically review the diagnostic accuracy of salivary gland ultrasound in primary Sjogren's syndrome (pSS). Methods: PubMed, Embase, CINAHL, Cochrane Central and Scopus and ClinicalTrials.gov were searched to identify diagnostic or validation studies in patients with pSS meeting the diagnostic criteria. A diagnostic test meta-analysis was performed using a bivariate model to calculate the pooled sensitivity, specificity, positive/negative likelihood ratios, and the diagnostic odds ratio. Meta-regression analyses were done for several pSS covariates. Results: Sixty-five studies met our criteria for the qualitative review. Fifty-four studies with a total of 6087 patients were included in the meta-analysis. Pooled sensitivity for salivary gland ultrasound was 80% [95% confidence interval (CI): 77-83%; I-2 = 78%], and specificity was 90% (95% CI: 87-92%; I-2 = 76%). The pooled positive and negative likelihood ratios were 8 (95% CI: 6.4-10) and 0.22 (95% CI: 0.19-0.25), respectively. The corresponding pooled diagnostic odds ratio (DOR) was 37 (95% CI: 28-48). Separate meta-regression models resulted in similar diagnostic estimates: (a) adjusted for mean age: sensitivity 81% (95% CI:77-84%; I-2 = 99%) and specificity 90% (95% CI: 87-93%; I-2 = 99%); (b) adjusted for mean disease duration, sensitivity 79% (95% CI:72-84%; I-2 = 99%), and specificity 90% (89-94%; I-2 = 99%). The diagnostic estimates were robust to sensitivity analyses by quality criteria, pSS diagnostic criteria and ultrasound scoring systems. Conclusion: Salivary gland ultrasound is a valuable modality for the diagnosis of Sjogren's syndrome. It is plausible that salivary gland ultrasound can be used as an important criterion for the diagnosis of pSS.