Survival analysis of patients with Sjögren's syndrome in Turkey: a tertiary hospital-based study

Is high IgG level associated with disease activity and organ damage in patients with Sjögren's syndrome? A 3-year follow-up cohort study

Hypergammaglobulinemia is prevalent in primary Sjögren's syndrome (pSS) and is considered a marker of disease activity. However, limited data exist regarding its association with disease activity and organ damage. We enrolled patients with pSS from the Chinese Rheumatism Data Centre and categorized them into four groups based on the IgG levels over a 3-year follow-up: consistently high, consistently intermediate, consistently normal, and intermittent. Disease activity and organ damage at the end of the third year were compared across these groups. A total of 351 patients were included in this study, all females with a median age of 45 (IQR 35-53) years. The median baseline IgG was 17.2 (IQR 13.4-21.4) g/L. About 40% of the patients with elevated baseline IgG levels remained in the consistently high or intermediate IgG group. Compared to patients with consistently normal IgG levels, those with consistently high IgG levels had higher median SSDDI scores (2 vs. 1, p = 0.014), higher median ESSPRI scores (2.5 vs. 1.7, p = 0.005), more extra-glandular organ manifestations (IRR 2.34, 95%CI 1.48-3.7, p = < 0.001), and more extra-glandular organ damage (IRR 2.06, 95%CI 1.03-4.12, p = 0.040) at the third-year follow-up. No significant differences in extra-glandular involvement were found between the consistently intermediate IgG group and the consistently normal IgG group. The consistently high IgG level, but not the consistently intermediate level, was associated with a greater number of extra-glandular manifestations and increased extra-glandular organ damage.

Evaluation of the Incidence of Malignancy in Sjögren's Syndrome: A Single-Center Study From Turkey

OBJECTIVE

Sjögren's syndrome (SS) is known to be associated with an elevated cancer incidence. This study aimed to ascertain SS patients' cancer incidence rates and risk variables at a single center in Turkey.

METHODS

The clinical data of SS patients were analyzed retrospectively. Cancer incidences for the overall population were obtained. The standardized incidence rates (SIRs) of hematological and solid cancers were calculated in comparison with the overall population.

RESULTS

The study included 303 SS patients, of whom 27 (8.9%) were diagnosed with cancer. Twenty-one solid (6.9%) and six (2%) hematologic cancers were identified. The SIR for all cancers was 2.25 (95% confidence interval (CI) 1.513-3.228). The SIR for hematologic cancers was 7.22 (95% CI 2.93-5.04), while the SIR for non-Hodgkin lymphoma (NHL), the most prevalent malignancy, was 11.76 (95% CI 3.73-28.38). The most prevalent malignancies were papillary thyroid and breast cancers, with a SIR of 3.04 (95% CI 1.937-4.58) for solid cancers. The SIR for both papillary thyroid and breast cancers was 8.43 (95% CI 3.689-16.68) and 1.85 (95% CI 0.687-4.105), respectively. A higher risk has also been linked to the presence of lymphopenia.

CONCLUSION

SS patients exhibit an increased risk of both solid and hematologic malignancies compared to the total population. This study reveals an increased risk of NHL and thyroid cancer in the Turkish population.

British Society for Rheumatology guideline on management of adult and juvenile onset Sjögren disease

Sjögren disease (SD) is a chronic, autoimmune disease of unknown aetiology with significant impact on quality of life. Although dryness (sicca) of the eyes and mouth are the classically described features, dryness of other mucosal surfaces and systemic manifestations are common. The key management aim should be to empower the individual to manage their condition-conserving, replacing and stimulating secretions; and preventing damage and suppressing systemic disease activity. This guideline builds on and widens the recommendations developed for the first guideline published in 2017. We have included advice on the management of children and adolescents where appropriate to provide a comprehensive guideline for UK-based rheumatology teams.

Long-term survival analysis of patients with primary Sjögren's syndrome in China: A multicenter retrospective cohort study

AIM

This study aimed to evaluate the long-term survival, causes of death, and prognostic factors in Chinese patients with primary Sjögren syndrome (pSS).

METHODS

We included patients with pSS registered in the Chinese Rheumatism Data Centre between May 2016 and December 2021, and collected baseline clinical, laboratory, and treatment data. Survival and standard mortality rates were calculated using general population mortality data. Factors related to mortality were identified using Cox proportional hazards regression.

RESULTS

Among the 8588 patients included, 274 died during a median follow-up of 4.0 years. The overall standardized mortality ratio was 1.61 (95% CI: 1.43-1.81). Overall survival rates were 98.2% at 5 years and 93.8% at 10 years. The predominant causes of death were comorbidities, including cardiovascular diseases, tumors, and infections, while the most frequent pSS-related causes of death were interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH). Male sex, older age, ILD, PAH, and high EULAR Sjögren's syndrome disease activity index (ESSDAI), thrombocytopenia, anemia, high immunoglobulin A (IgA) level, and glucocorticoid treatment independently increased the mortality risk, while using hydroxychloroquine was a protective factor.

CONCLUSION

Mortality rates have significantly increased in Chinese patients with pSS. Comorbidities, rather than pSS-related organ damage, were the main causes of death. All-cause mortality was associated with male sex, older age, ILD, PAH, high ESSDAI, thrombocytopenia, anemia, high IgA level, and glucocorticoid treatment, whereas hydroxychloroquine use might improve the long-term survival.

Epidemiology of Sjögren syndrome

Sjögren syndrome is a phenotypically varied autoimmune disorder that can occur alone in primary Sjögren syndrome or in association with other connective tissue diseases (CTDs), including rheumatoid arthritis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc). The estimation of the prevalence and incidence of Sjögren syndrome varies depending on diagnostic criteria and study design, making it difficult to estimate geographical and temporal trends. Nonetheless, disease phenotype is influenced by geographical origin, which is a risk factor for systemic activity. Whether mortality in primary Sjögren syndrome is increased compared with that of the general population is not yet known, but extra-glandular manifestations, in particular lymphomas, are clear risk factors for mortality. In CTDs associated with Sjögren syndrome, lymphoma risk seems higher than that of patients with CTD alone, and there is potentially lower disease activity in SLE with Sjögren syndrome and in SSc with Sjögren syndrome than in SLE or SSc alone.

Idiopathic inflammatory myopathies - The burden of disease: Cohort analysis focusing on damage and comorbidities

INTRODUCTION/BACKGROUND

Idiopathic Inflammatory Myopathies (IIM) continue to be a major clinical challenge worldwide. The exact aetiopathogenesis of this chronic and disabling disease remains elusive, preventing the development of novel and effective therapeutic strategies and leading to a high incidence of damage. The complexity of treating these diseases is even greater due to the numerous comorbidities that affect these patients.

METHODS

Retrospective review of the cohort of patients diagnosed with IIM and followed in a dedicated unit of a tertiary hospital between 1971 and December 2022, with particular attention to damage and comorbidities. Damage was assessed using the Myositis Damage Index. Comorbidities were recorded and analysed as a whole and also assessed using the Charlson Comorbidity Index. Health Assessment Questionnaire (HAQ) Disability Index (DI) was performed by phone call in December 2022, to all patients actively followed-up in the Unit.

RESULTS

Analysis of 149 patients with a mean follow-up of 9 years (range 0-51) revealed >90% with damage and comorbidities. Most comorbidities were a consequence of the damage and were particularly related to prolonged steroid therapy. Cardiovascular damage, which occurred either as cardiovascular risk factors or as end-organ sequelae (cardiovascular disease and chronic kidney disease), was the main cause and a major contributor to death. Depression was also high on the list of associated comorbidities. Median HAQ was 2.09 representing high negative impact in quality of life.

CONCLUSIONS

Although survival rates have increased in recent decades, patients with IIM carry a high burden of disease with poor quality of life, mainly caused by damage and comorbidities. While comorbidities accumulation is the major factor for poor quality of life, damage severity is the main predictor for mortality. Improved therapeutic strategies are needed to reduce the need for steroids and to introduce routine screening and management of comorbidities as an essential partner of immunosuppressive therapy, leading to comprehensive care of myositis patients and effective improvement of their quality of life.

The risk of developing non-Hodgkin lymphoma and the mortality rate in primary Sjögren's syndrome: a single-centre, retrospective cohort study

Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease that is manifested by the sensation of dry eyes and dry mouth. The higher incidence of non-Hodgkin lymphoma (NHL) among pSS has already been extensively researched. However, there are uncertanties whether the mortality risk in pSS patients and in pSS patients with NHL is increased. The purpose of this study was to describe the prevalence of NHL among pSS patients and to calculate their mortality risk. We retrospectively analysed data on 1367 patients treated in our rheumatology department under the ICD-10 code M35.0. The study finally recruited 155 patients who met the 2016 ACR/EULAR criteria for the diagnosis of pSS. Descriptive statistics was used in data analysis. We applied the indirect standardization by age to compare the incidence rate of NHL in our cohort to general population. Additionally, we compared the mortality in our study to the general population by calculating the standardized mortality ratio (SMR). The overall incidence rate of NHL was 440 per 100,000 patient-years. The SIR compared to the general population was 30.13 (95% CI 12.87-54.63). The overall mortality rate of pSS patients in our cohort was nearly identical to that of the general population (SMR = 0.98 [95% CI (0.47-1.69)]). This study confirms that there are significant differences in lymphoma prevalence, histology, and prognosis across the studied populations. Furthermore, this study found that patients with pSS have similar mortality risk as the general population, and no patient in our cohort died from NHL.

Mortality risk factors in primary Sjögren syndrome: a real-world, retrospective, cohort study

Background

What baseline predictors would be involved in mortality in people with primary Sjögren syndrome (SjS) remains uncertain. This study aimed to investigate the baseline characteristics collected at the time of diagnosis of SjS associated with mortality and to identify mortality risk factors for all-cause death and deaths related to systemic SjS activity measured by the ESSDAI score.

Methods

In this international, real-world, retrospective, cohort study, we retrospectively collected data from 27 countries on mortality and causes of death from the Big Data Sjögren Registry. Inclusion criteria consisted of fulfilling 2002/2016 SjS classification criteria, and exclusion criteria included chronic HCV/HIV infections and associated systemic autoimmune diseases. A statistical approach based on a directed acyclic graph was used, with all-cause and Sjögren-related mortality as primary endpoints. The key determinants that defined the disease phenotype at diagnosis (glandular, systemic, and immunological) were analysed as independent variables.

Findings

Between January 1st, 2014 and December 31, 2023, data from 11,372 patients with primary SjS (93.5% women, 78.4% classified as White, mean age at diagnosis of 51.1 years) included in the Registry were analysed. 876 (7.7%) deaths were recorded after a mean follow-up of 8.6 years (SD 7.12). Univariate analysis of prognostic factors for all-cause death identified eight Sjögren-related variables (ocular and oral tests, salivary biopsy, ESSDAI, ANA, anti-Ro, anti-La, and cryoglobulins). The multivariate CPH model adjusted for these variables and the epidemiological features showed that DAS-ESSDAI (high vs no high: HR = 1.68; 95% CI, 1.27-2.22) and cryoglobulins (positive vs negative: HR = 1.72; 95% CI, 1.22-2.42) were independent predictors of all-cause death. Of the 640 deaths with available information detailing the specific cause of death, 14% were due to systemic SjS. Univariate analysis of prognostic factors for Sjögren-cause death identified five Sjögren-related variables (oral tests, clinESSDAI, DAS-ESSDAI, ANA, and cryoglobulins). The multivariate competing risks CPH model adjusted for these variables and the epidemiological features showed that oral tests (abnormal vs normal results: HR = 1.38; 95% CI, 1.01-1.87), DAS-ESSDAI (high vs no high: HR = 1.55; 95% CI, 1.22-1.96) and cryoglobulins (positive vs negative: HR = 1.52; 95% CI, 1.16-2) were independent predictors of SjS-related death.

Interpretation

The key mortality risk factors at the time of SjS diagnosis were positive cryoglobulins and a high systemic activity scored using the ESSDAI, conferring a 2-times increased risk of all-cause and SjS-related death. ESSDAI measurement and cryoglobulin testing should be considered mandatory when an individual is diagnosed with SjS.

Funding

Novartis.

Screening biomarkers for Sjogren's Syndrome by computer analysis and evaluating the expression correlations with the levels of immune cells

Background

Sjögren's syndrome (SS) is a systemic autoimmune disease that affects about 0.04-0.1% of the general population. SS diagnosis depends on symptoms, clinical signs, autoimmune serology, and even invasive histopathological examination. This study explored biomarkers for SS diagnosis.

Methods

We downloaded three datasets of SS patients' and healthy pepole's whole blood (GSE51092, GSE66795, and GSE140161) from the Gene Expression Omnibus (GEO) database. We used machine learning algorithm to mine possible diagnostic biomarkers for SS patients. Additionally, we assessed the biomarkers' diagnostic value using the receiver operating characteristic (ROC) curve. Moreover, we confirmed the expression of the biomarkers through the reverse transcription quantitative polymerase chain reaction (RT-qPCR) using our own Chinese cohort. Eventually, the proportions of 22 immune cells in SS patients were calculated by CIBERSORT, and connections between the expression of the biomarkers and immune cell ratios were studied.

Results

We obtained 43 DEGs that were mainly involved in immune-related pathways. Next, 11 candidate biomarkers were selected and validated by the validation cohort data set. Besides, the area under curves (AUC) of XAF1, STAT1, IFI27, HES4, TTC21A, and OTOF in the discovery and validation datasets were 0.903 and 0.877, respectively. Subsequently, eight genes, including HES4, IFI27, LY6E, OTOF, STAT1, TTC21A, XAF1, and ZCCHC2, were selected as prospective biomarkers and verified by RT-qPCR. Finally, we revealed the most relevant immune cells with the expression of HES4, IFI27, LY6E, OTOF, TTC21A, XAF1, and ZCCHC2.

Conclusion

In this paper, we identified seven key biomarkers that have potential value for diagnosing Chinese SS patients.

Primary-Sjögren's-Syndrome-Related Interstitial Lung Disease: A Clinical Review Discussing Current Controversies

Lung involvement, especially interstitial lung disease, is a potentially severe extra-glandular manifestation of Primary Sjogren's Syndrome (pSS-ILD). ILD can manifest either as a late complication of pSS or anticipate sicca symptoms, likely reflecting two different patho-physiological entities. Presence of lung involvement in pSS subjects can remain subclinical for a long time; therefore, patients should be actively screened, and lung ultrasound is currently being investigated as a potential low cost, radiation-free, easily repeatable screening tool for detection of ILD. In contrast, rheumatologic evaluation, serology testing, and minor salivary gland biopsy are crucial for the recognition of pSS in apparently idiopathic ILD patients. Whether the HRCT pattern influences prognosis and treatment response in pSS-ILD is not clear; a UIP pattern associated with a worse prognosis in some studies, but not in others. Many aspects of pSS-ILD, including its actual prevalence, association with specific clinical-serological characteristics, and prognosis, are still debated by the current literature, likely due to poor phenotypic stratification of patients in clinical studies. In the present review, we critically discuss these and other clinically relevant "hot topics" in pSS-ILD. More specifically, after a focused discussion, we compiled a list of questions regarding pSS-ILD that, in our opinion, are not easily answered by the available literature. We subsequently tried to formulate adequate answers on the basis of an extensive literature search and our clinical experience. At the same, we highlighted different issues that require further investigation.

Sjögren's syndrome

Sjögren’s syndrome (SjS) is an autoimmune disease characterized by the triad of sicca symptoms, fatigue and pain. This diagnosis is usually made in women at the average age of 60 years. Diagnosis is made when sicca symptoms persist for more than three months, after the exclusion of possible differential diagnoses, and using the ACR/EULAR 2016 classification criteria for SjS. Many organs can be affected in the course of this disease. Xerosis cutis and pruritus are the most common skin manifestations, followed by leukocytoclastic vasculitis and subacute cutaneous lupus erythematosus. In addition, SjS patients often have myoarthralgia and neuropsychiatric symptoms. In the long term, attention must be paid to the increased risk of cardiovascular disease and lymphoma. Due to the multiorgan involvement in SjS patients, interdisciplinary care is required.

Interstitial lung disease in Primary Sjögren's syndrome

Background

Interstitial lung disease (ILD) may cause life-threatening complications of primary Sjogren’s syndrome (pSS), and has a poor prognosis in terms of survival and quality of life. To date, few studies have investigated the risk factors for ILD detected by high-resolution computed tomography (HRCT) in pSS patients with or without respiratory symptoms.

Methods

Data of 333 patients with newly diagnosed pSS were retrospectively analysed. Interstitial lung disease involvement was defined as typical abnormalities on HRCT and/or pulmonary function tests. Multivariate regression model was used to evaluate the association between interstitial lung disease and pSS characteristics.

Results

Sixty-six patients (19.82%) were diagnosed with pSS-ILD. Ground glass opacities (87.88%) and septal/sub pleural lines (81.82%) were most frequent. Based on pulmonary high-resolution computed tomography, patients were divided into nonspecific (n = 42), usual (n = 20), lymphocytic interstitial pneumonia (n = 3) and cryptogenic organising pneumonia (n = 1) groups. There was a strong association between erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP) and the HRCT-score. Pulmonary function tests revealed impaired diffusion capacity for carbon monoxide and total lung capacity, and coexistence of small airway lesions in pSS-interstitial lung disease. On logistic regression analysis, age, Raynaud’s phenomenon, lymphopenia, cough, dyspnoea and rampant dental caries were risk factors associated with pSS-interstitial lung disease.

Conclusions

Interstitial lung disease involvement in pSS is a common clinical occurrence. The clinical manifestation is nonspecific and variable; Raynaud’s phenomenon and lymphopenia may predict its onset. pSS patients with advanced age, dry cough and dyspnoea should be systematically evaluated for ILD involvement and managed according to their symptoms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-022-01868-5.

Mortality in Inflammatory Rheumatic Diseases: Lithuanian National Registry Data and Systematic Review

Despite significant improvement in survival, rheumatic diseases (RD) are associated with premature mortality rates comparable to cardiovascular and neoplastic disorders. The aim of our study was to assess mortality, causes of death, and life expectancy in an inflammatory RD retrospective cohort and compare those with the general population as well as with the results of previously published studies in a systematic literature review. Patients with the first-time diagnosis of inflammatory RD during 2012-2019 were identified and cross-checked for their vital status and the date of death. Sex- and age-standardized mortality ratios (SMR) as well as life expectancy for patients with inflammatory RDs were calculated. The results of a systematic literature review were included in meta-standardized mortality ratio calculations. 11,636 patients with newly diagnosed RD were identified. During a total of 43,064.34 person-years of follow-up, 950 death cases occurred. The prevailing causes of death for the total cohort were cardiovascular diseases and neoplasms. The age- and sex-adjusted SMR for the total cohort was calculated to be 1.32 (1.23; 1.40). Patients with rheumatoid arthritis if diagnosed at age 18-19 tend to live for 1.63 years less than the general population, patients with spondyloarthritis-for 2.7 years less, patients with connective tissue diseases-for almost nine years less than the general population. The findings of our study support the hypothesis that patients with RD have a higher risk of mortality and lower life expectancy than the general population.

Ten-year survival analysis of patients with primary Sjögren's syndrome in China: a national prospective cohort study

Aims

To investigate the long-term survival of patients with primary Sjögren's syndrome (pSS) in China.

Methods

Patients with pSS who fulfilled the 2002 American-European Consensus Group classification criteria were prospectively enrolled from 2004 to 2011. Their baseline clinical, laboratory, and therapeutic data were collected. The primary endpoint was all-cause death by January 2018. The standard mortality ratio (SMR) was calculated by comparing with age-matched and sex-matched mortality data of the general population. Kaplan-Meier curves were obtained by time-to-event analysis. Univariate and multivariate Cox hazards regression analyses were performed to identify risk factors for mortality.

Results

A total of 1054 patients were enrolled and 834 patients were followed up for a median of 94.8 months, with 48 confirmed deaths. The total SMR was 3.63 [95% confidence interval (CI) 2.60-4.66]. The 3-, 5-, and 10-year survival rates were 98.4%, 97.5%, and 92.9%, respectively. Infection, malignancy, and respiratory failure were the top three causes of mortality. We identified male sex [hazard ratio (HR) = 3.00, 95% CI 1.23-7.31], age at diagnosis ⩾50 years of age (HR = 7.69, 95% CI 3.01-19.62), thrombocytopenia (HR = 1.93, 95% CI 1.01-3.72), and interstitial lung disease (HR = 5.96, 95% CI 2.24-15.82) as the independent prognostic factors of death.

Conclusions

The mortality rates of Chinese patients with pSS are higher than those of the general population. Male patients of elder age at diagnosis complicated with thrombocytopenia and interstitial lung disease might be suggestive for poorer survival and require closer follow up.

The management of Sjögren's syndrome: British Society for Rheumatology guideline scope

The guideline will be developed using the methods and processes outlined in Creating Clinical Guidelines: Our Protocol [1]. This development process to produce guidance, advice and recommendations for practice has National Institute for Health and Care Excellence (NICE) accreditation.

Mortality in patients with primary Sjögren's syndrome: A systematic review and meta-analysis

OBJECTIVE

It remains debated whether patients with primary Sjögren's syndrome (pSS) are at greater risk of mortality. We aimed to determine the magnitude of all-cause mortality risk in patients with pSS compared with the general population through a systematic review and meta-analysis.

METHODS

We searched Pubmed, EMBASE and Cochrane Library for studies published from inception to October 2020. STATA meta-analysis software was used to calculate the pooled risk estimates for mortality (standardized mortality ratio, SMR).

RESULTS

Our search identified 2796 articles, of which 14 studies with 14584 patients were eventually included for the analysis. A total of 902 deaths were observed. Overall, we found a 1.46-fold increased risk of death in pSS patients when compared with the general population (meta-SMR: 1.46, 95% CI 1.10-1.93). Subgroup analyses showed that mortality risks were higher in European countries (meta-SMR: 1.55, 95% CI 1.04-2.33), in retrospective studies (meta-SMR: 1.50, 95% CI 1.09-2.05), in studies based on referral cohorts (meta-SMR: 1.55, 95% CI 1.04-2.30), in studies that enrolled patients >500 (meta-SMR: 1.70, 95% CI 1.11-2.61), and in studies with follow-up time longer than 8 years (meta-SMR: 1.55, 95% CI 0.87-2.77). Significantly greater mortality risk was found in patients with older age, male gender, vasculitis, interstitial lung disease, low complements, positive anti-La/SSB and cryoglobulinemia.

CONCLUSION

The existing data indicated ∼50% increase of mortality among patients with pSS compared with the general population. More attention should be paid to those patients with poor prognostic factors.

Extraglandular ocular involvement and morbidity and mortality in primary Sjögren's Syndrome

Purpose

To report the significance of extraglandular ocular involvement and long-term systemic morbidity and mortality in primary Sjögren’s Syndrome (SS).

Methods

This retrospective, longitudinal cohort study included consecutive patients with primary SS evaluated at a tertiary referral center. An electronic chart review was performed and all available data were extracted from clinic visits between October 1999 and March 2019. The primary outcome measures included occurrence of extraglandular ocular manifestations of SS, serological markers, prevalence of malignancy, and incidence of death.

Results

One hundred and twenty-six SS patients with minimum 3 years of follow-up (median 9.6, range 3.0–15.9 years, total of 1,235 patient-years) were included. Of those, 10 patients with inflammatory keratolysis or scleritis had 2.3 times greater likelihood of death compared to the rest of the cohort (OR = 2.3, 95% confidence interval [CI] 0.5 to 4.0, p = 0.01) due to SS related complications. The lifetime prevalence of any malignancy in the entire cohort was 15.5%. The most common hematologic malignancy was non-Hodgkin’s lymphoma (4.8%) and the most common solid malignancy was breast cancer (6.0%). Men SS patients were more likely to have a history of or concurrent malignancy compared to women (30.0% versus 13.7%, p = 0.16) and double the mortality (OR = 2.1, 95% CI 0.09 to 1.4, p = 0.04), independent of malignancy.

Conclusions

SS patients with serious ocular manifestations, particularly men, may be at greater risk for mortality due to SS complications. The eye seems to be the barometer of systemic disease activity.

Clinical and serological characteristics of seronegative primary Sjögren's syndrome: a comparative study

OBJECTIVES

This study compared the clinical and serological characteristics of seronegative and seropositive primary Sjögren syndrome (pSS) and examined whether current classification criteria for pSS cover seronegative pSS.

METHODS

The study group comprised 375 patients (341 women and 34 men) diagnosed with pSS. A clinical diagnosis by an expert rheumatologist was considered the "gold standard" for the diagnosis of pSS. The clinical and serological characteristics of the patients were retrospectively collected from hospital medical files.

RESULTS

Fifty-eight of the 375 pSS patients (15.5%) were seronegative for ANA, RF, anti-Ro, and anti-La autoantibodies. Seronegative pSS was diagnosed based on lymphocytic infiltrations in lip biopsy samples. There were no statistically significant differences in terms of patient age, age at diagnosis, sex distribution, clinical features, and laboratory findings between seronegative and seropositive pSS. The frequency of hypergammaglobulinemia was higher in seropositive pSS. The 2016 ACR/ULAR criteria best covered most seronegative pSS cases (84.5%). For seronegative pSS, the agreement between the 2002 AECG, 2012 ACR, and 2016 ACR/EULAR criteria was relatively low.

CONCLUSIONS

The clinical features of seronegative pSS (i.e., a lack of four autoantibodies in serum) were similar to those of seropositive pSS. The current classification criteria for pSS should not be used in the diagnosis of seronegative pSS, as the agreement between the different sets of criteria was low, and some patients fell outside the classification. Further clinical and laboratory studies are needed to identify the features that distinguish seronegative pSS. Key Points • Approximately 15% of the pSS patients were seronegative for ANA, RF, anti-Ro, and anti-La autoantibodies. • Seronegative pSS was diagnosed based on lymphocytic infiltrations in lip biopsy samples. • The clinical features of seronegative pSS were similar to those of seropositive pSS. • The current classification criteria for pSS should not be used in the diagnosis of seronegative patients, as the agreement between the different sets of criteria was low, and some patients fell outside the classification.