In the present study, a nomogram was developed to predict MPE among patients with PE. The nomogram incorporated four variables, including sCEA, pCEA, pLDH, and sNSE. The nomogram showed good discriminatory ability, calibration, and clinical usefulness. MPE is a common complication associated with a wide variety of neoplasms, including lung, breast, lymphoma, ovarian, and gastric cancers. Jung (9) reported that MPE is a serious complication of advanced tumors, with relatively high morbidity and mortality rates. Early differentiation of benign from malignant conditions is crucial for selecting the appropriate treatment, for example, surgery can be an effective treatment option for malignant lung cancer that has not invaded the pleura, leading to significant improvements in survival time. Additionally, patients with BPE, such as TPE and parapneumonic effusions can be clinically cured if treated in time.
Traditionally, differential diagnosis can be made based on certain specific findings, such as pleural biopsy, diagnostic thoracentesis, and PE cytology. (10) Unfortunately, these methods have limitations, such as invasiveness and limited diagnostic efficacy. (11) In this study, the sensitivity of cytology was 56.7%, and this result was also unsatisfactory. Earlier studies focused on specific factors associated with MPE, such as single-cell analysis of diverse immunophenotypes,(12)they performed single-cell RNA sequencing on 62,382 cells from MPE patients induced by non-small-cell lung cancer to describe the composition, lineage, and functional states of infiltrating immune cells in MPE, or the landscape map of human MPE immune cells ,(13)which described the interplay in MPE among different Th cells, as well as Th cells and lung cancer cells or mesothelial cells. However, these studies mentioned above were not available in the public clinical setting although they might have high diagnostic value, for the new markers were inaccessible.
In clinical practice, relying on a single parameter to distinguish between two conditions has limited effectiveness due to low sensitivity or specificity. Instead, combining several markers to construct a mathematical model can significantly improve diagnostic accuracy. Previous studies have developed several models for predicting MPE, and it was pointed out by the authors that these models could improve the diagnosis of MPE. For example, Chen et al. (14) revealed that the combination of FTIR near-infrared spectroscopy (NIRS) and machine learning is an innovative, rapid, and convenient method for clinical PE classification. Wang et al. (15, 16) reported a classification model to identify BPE and MPE using a CT volume and its 3D PE mask as inputs based on artificial intelligence. However, these models mentioned above may have disadvantages of high cost, the need for additional examinations, and trained personnel. We established a 4-marker predictive model by multivariate regression analysis in the development set. The 4-markers involved in our model were easily obtained, and more importantly, the total cost of the indexes involved in the scoring model was acceptable. The diagnostic performance was evaluated as very good in the same set through the use of bootstrap resampling. To the best of our knowledge, there have been few studies aimed at developing a simple and user-friendly predictive model based on common clinical parameters for identifying MPE.
The clinical diagnostic efficiency of sCEA, pCEA, pLDH, and sNSE in the diagnosis of MPE was reportedly satisfactory. (17, 18, 19, 20, 21) A large body of work on the function of tumor markers showed that these contributed to the identification of MPE.(22)However, sSCC levels were filtered out by LASSO regression analysis, which is considered superior to select predictors by univariate analysis. (23) The difference between our study and previous studies may be attributed to the different causes of MPE. SCC is a relatively specific tumor marker for squamous cell carcinoma of the lung. The results showed that the percentage of squamous cell carcinoma of the lung (7.83%) in our study was lower than that in previous studies (100.00%). (22) Regarding “sCEA” and “pCEA”, it has been reported that CEA was especially associated with adenocarcinoma of the lung, (24, 25) and pCEA was an effective indicator for identifying lung cancer-associated MPE among various tumor biomarkers. (26) In general, CEA is a broad-spectrum tumor marker that can indicate the presence of various tumors. It is a useful tumor marker for evaluating the effectiveness of treatment, disease progression, monitoring, and prognosis estimation of colorectal cancer, breast cancer, and lung cancer. However, its specificity and sensitivity are not strong, and its role in the early detection of tumors is not significant. Regarding the “pLDH” and “sNSE”, it has been reported that LDH levels were positively correlated with lymphoma-associated MPE, and providing a sensitivity of 76.00% and a specificity of 81.00% to differentiate lymphoma-associated MPE and TPE. (27) For “sNSE”, it has been reported that sNSE levels are positively associated with small-cell lung carcinoma (SCLC), with a sensitivity of 60.78% and a specificity of 81.11% for the diagnosis of SCLC. SCLC is characterized by a high proliferation rate, early metastases, and an exceptionally poor prognosis. (28) These four predictors are readily available clinically, and the nomogram demonstrated good discriminatory ability and calibration, with the DCA evaluation showing its clinical utility. As pleural biopsy is an invasive procedure that patients may find difficult to undergo, and the sensitivity of cytology examination after diagnostic thoracentesis is low, and multiple inspections are required, this cost-free nomogram may be useful in screening MPE in these patients with PE.
This study has several limitations. Firstly, it is important to note some markers that could potentially aid in malignant diagnosis, such as adenosine deaminase (ADA), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), were not evaluated in this study due to the limited availability of patients who underwent these tests. Nevertheless, previous studies have shown that ADA and CRP showed no significant difference between PE and MPE.[27] this is a single-center, retrospective study with a limited number of patients. As a result, the prevalence of PE observed in this study may not accurately reflect the prevalence of PE in the wider Chinese population. To validate this predictive model, further studies with larger sample sizes from multiple centers are required. It is important to note that if these predictive models are used in a different population, they should be reassessed.
Our study has successfully developed a predictive model consisting of four markers that is both user-friendly and reliable for classifying PE into subtypes, specifically malignant or benign. This breakthrough provides a valuable tool for medical professionals to accurately diagnose and treat patients with PE. The proposed mathematical model has the potential to serve as a valuable supplementary diagnostic tool in differentiating MPE from BPE in clinical settings.