Primary Sjögren's syndrome (pSS) is an autoimmune disease characterised by infiltration of lymphocyte (LYMP) into the salivary and lacrimal glands, leading to tissue damage and glandular dysfunction. In addition, as pSS is a clinically heterogeneous disease, various extraglandular manifestations cannot be ignored (Fox, 2005). Lung involvement is common in pSS, with a reported incidence of about 9–75% in these patients. The prevalence of pSS-associated interstitial lung disease (ILD) (pSS-ILD) is 3%–11%, and pSS is therefore associated with a high risk of secondary pulmonary hypertension and ventilatory disorders (Luppi et al., 2020, Sambataro et al., 2020). ILD increases the 5-year mortality rate by 16.0%, and the 10-year overall mortality rate of pSS-ILD patients is four times that of pSS patients without ILD (Luppi et al., 2020). Therefore, it is important to identify patients at high risk of pSS-ILD as early as possible. Although high-resolution computed tomography (HRCT), as the gold standard, can detect ILD early, the guidelines do not recommend inclusion of this procedure in routine examinations to minimise radiation exposure. This is especially important for younger patients and those in whom disease progression must be monitored over time. Therefore, a simple, easy-to-use, low-cost, and less harmful method for identification is urgently required for clinical practice.

There is increasing interest in the roles of haematological markers in the evaluation of the activity of autoimmune diseases, such as pSS (Hu et al., 2014), systemic lupus erythematosus (SLE) (Qin et al., 2016), and ulcerative colitis (Lin et al., 2022), as well as in cancer and infectious diseases (Inoue et al., 2015). Clinical blood test parameters, including white blood cell (WBC), neutrophil (NEUT), LYMP, and platelet (PLT) counts, as well as haemoglobin (HB) levels, are known to be crucial markers of inflammatory responses (Ahsen et al., 2013). Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level are two traditional serological markers that are known to increase within hours of onset of inflammation and infection, but their sensitivity and specificity are unsatisfactory (Shaikh et al., 2020). Moreover, as inflammation is closely related to malnutrition, albumin (ALB) levels can reflect host systemic inflammatory processes (Wu et al., 2020). The ALB level was suggested to be a sensitive and specific biomarker for severity and a prognostic factor for mortality in burn patients (Chen et al., 2023). Several integrated systemic inflammatory indicators, including the CRP/ALB ratio (CAR), CRP/LYMP ratio (CLR), NEUT/ALB ratio (NAR), NEUT/LYMP ratio (NLR), PLT/ALB ratio (PAR), or PLT/LYMP ratio (PLR), have also been introduced as diagnostic or prognosis markers for rheumatic diseases (Gasparyan et al., 2019). NLR was reported to be a risk factor in pSS-ILD patients, and ILD was shown to significantly increase mortality risk in patients with pSS (Hu et al., 2014). In addition, several studies suggested that PLR, and NLR can be used as markers for diagnosing and monitoring of rheumatoid arthritis (RA) (Chen et al., 2019). Additionally, elevated serum tumour marker (TM) levels were shown to be associated with the onset and progression of autoimmune disease-associated ILD, and their diagnostic utility has been investigated (Bao et al., 2021, Shi et al., 2020). In addition, these non-invasive indicators can be used to check whether the potential risk of ILD in patients with rheumatic. Therefore, we speculated that integration of these indices may be helpful in screening for pSS-ILD. Nevertheless, few integrated models capable of effectively differentiating between pSS patients with and without ILD have been reported to date. Therefore, an integrated model combining multiple markers for the diagnosis of pSS-ILD is required.

Over the past decade, there has been a great deal of interest in the clinical use of nomograms, which can simplify the traditional formulae of prediction models to estimate the probability of a single endpoint event (Alivernini et al., 2021). Therefore, nomograms have significant potential for monitoring disease progression and prognosis. This study was performed to investigate and evaluate a nomogram for predicting ILD in patients with pSS.