A nomogram based on ultrasound scoring system for differentiating between immunoglobulin G4-related sialadenitis and primary Sjögren syndrome

Abstract

Objectives: Accurate distinguishing between immunoglobulin G4-related sialadenitis (IgG4-RS) and primary Sjögren syndrome (pSS) is crucial due to their different treatment approaches. This study aimed to construct and validate a nomogram based on the ultrasound (US) scoring system for the differentiation of IgG4-RS and pSS.

Methods: A total of 193 patients with a clinical diagnosis of IgG4-RS or pSS treated at our institution were enrolled in the training cohort (n = 135; IgG4-RS = 28, pSS = 107) and the validation cohort (n = 58; IgG4-RS = 15, pSS = 43). The least absolute shrinkage and selection operator regression algorithm was utilized to screen the most optimal clinical features and US scoring parameters. A model for the differential diagnosis of IgG4-RS or pSS was built using logistic regression and visualized as a nomogram. The performance levels of the nomogram model were evaluated and validated in both the training and validation cohorts.

Results: The nomogram incorporating clinical features and US scoring parameters showed better predictive value in differentiating IgG4-RS from pSS, with the area under the curves of 0.947 and 0.958 for the training cohort and the validation cohort, respectively. Decision curve analysis demonstrated that the nomogram was clinically useful.

Conclusions: A nomogram based on the US scoring system showed favourable predictive efficacy in differentiating IgG4-RS from pSS. It has the potential to aid in clinical decision-making.

Keywords: immunoglobulin G4-related sialadenitis; nomogram; primary Sjögren syndrome; salivary gland; ultrasound scoring system.

Figure 1.

Flowchart illustrating the patient selection process. Abbreviations: IgG4-RS = immunoglobulin G4-related sialadenitis; pSS = primary Sjögren's syndrome; US = ultrasound.

Figure 2.

Selection of clinical features and US scoring parameters via the LASSO regression algorithm. (A) Tuning parameter (λ) selection in LASSO model used tenfold cross-validation via 1-standard error criterion. The optimal values of the LASSO tuning parameter (λ) are indicated by the dotted vertical lines (the right one), and a value λ of 0.089 with log (λ) = −2.414 was chosen. (B) LASSO coefficient profiles of the 13 clinical and US parameters. A coefficient profile plot was generated versus the selected log (λ) value using tenfold cross-validation. Five clinical and US parameters with nonzero coefficients were finally selected. Abbreviations: LASSO = least absolute shrinkage and selection operator; US = ultrasound.

Figure 3.

Developed nomogram and ROC curves, calibration curves and DCA for the nomogram. (A) Sex, dry mouth, SMG enlargement, PGUS scores, and SMGUS scores were used for building the nomogram model. (B) ROC curves of the nomogram in the training and validation cohorts. Calibration curves for the nomogram model in the training (C) and validation (D) cohorts. The curves indicate the goodness of fit for the nomogram. The 45° straight line represents a perfect match between the actual (y-axis) and nomogram-predicted (x-axis) probabilities. A closer distance between 2 curves indicates higher accuracy. (E) DCA for the nomogram model in the training and validation cohorts. The DCA indicates that across the majority of the range of reasonable threshold probabilities in both cohorts, using the model to distinguish IgG4-RS from pSS was more beneficial than the “treat-all-patients as IgG4-RS” scheme or the “treat-all-patients as pSS” scheme. Abbreviations: DCA = decision curve analysis; IgG4-RS = immunoglobulin G4-related sialadenitis; PGUS = parotid gland ultrasound; pSS = primary Sjögren’s syndrome; ROC = receiver operating characteristic; SMG = submandibular gland; SMGUS = submandibular gland ultrasound.

Figure 4.

A 32-year-old male with IgG4-RS presented with dry mouth and SMG enlargement. (A and B) The US images of bilateral parotid gland showing PGUS scores were determined to be 4 points. The detailed scores were as follows: parenchymal echogenicity comparable to thyroid were both rated 0 point, mild inhomogeneity were both rated 1 point, absence of hypoechogenic areas were both rated 0 point, a few hyperechoic foci were both rated 1 point, and well-defined borders were both rated 0 point. (C and D) The US images of bilateral SMG showing SMGUS scores were determined to be 18 points. The detailed scores were as follows: parenchymal echogenicity decreased compared to thyroid were both rated 1 point, grossly inhomogeneity were both rated 3 points, numerous hypoechogenic areas were both rated 3 points, present of hyperechoic foci were both rated 1 point, and partly defined borders were both rated 1 points. (E) According to the nomogram, the prediction probability of pSS is less than 10.00%. Abbreviations: IgG4-RS = immunoglobulin G4-related sialadenitis ; PGUS = parotid gland ultrasound; pSS = primary Sjögren’s syndrome; SMG = submandibular gland; SMGUS = submandibular gland ultrasound; US = ultrasound.

Figure 5.

A 49-year-old woman with pSS presented with dry mouth and without SMG enlargement. (A and B) The US images of bilateral parotid gland showing PGUS scores were determined to be 22 points. The detailed scores were as follows: parenchymal echogenicity decreased compared to thyroid were both rated 1 point, grossly inhomogeneity were both rated 3 points, numerous hypoechogenic areas were both rated 3 points, numerous hyperechogenic reflections were both rated 3 points, and partly defined borders were both rated 1 points. (C and D) The US images of bilateral SMG showing SMGUS scores were determined to be 18 points. The detailed scores were as follows: parenchymal echogenicity decreased compared to thyroid were both rated 1 point, grossly inhomogeneity were both rated 3 points, numerous hypoechogenic areas were both rated 3 points, present of hyperechoic foci were both rated 1 point, and partly defined borders were both rated 1 points. (E) According to the nomogram, the prediction probability of pSS is greater than 90.00%. Abbreviations: PGUS = parotid gland ultrasound; pSS = primary Sjögren’s syndrome; SMG = submandibular gland; SMGUS = submandibular gland ultrasound; US = ultrasound.