[Value of CD4+/CD8+ Ratio Combined with nCD64 Index in Bronchoalveolar Lavage Fluid for Differential Diagnosis of Lung Cancer and Non-lung Cancer Diseases].

Abstract

Background: Distinguishing lung cancer from pulmonary infection and interstitial lung disease (ILD) remains challenging. This study aimed to evaluate the diagnostic value of T lymphocyte subsets and neutrophil CD64 (nCD64) index in bronchoalveolar lavage fluid (BALF), alone and in combination, to address this challenge.

Methods: BALF was collected between October 2021 and October 2022 from 70 patients admitted to West China Hospital, Sichuan University. Based on final diagnosis, the patients were divided into the lung cancer group (21 cases, including 14 with pure lung cancer and 7 with lung cancer and infection) and the non‑lung cancer group (49 cases, including 39 with pulmonary infection and 10 with ILD). Flow cytometry was used to detect T lymphocyte subsets and CD64 expression in BALF, and the CD4+/CD8+ ratio and nCD64 index were calculated. Receiver operating characteristic (ROC) curves were used to evaluate the performance of both indicators in differentiating lung cancer from pulmonary infection and from ILD, and the area under the curve (AUC) and 95% confidence interval (CI) were calculated. The diagnostic efficacy of combining the CD4+/CD8+ ratio and nCD64 index for differentiating lung cancer from pulmonary infection was further analyzed. Firth's logistic regression was performed to adjust for age and to assess the independent differential diagnosis value of the two indicators between lung cancer and pulmonary infection.

Results: Compared with the non-lung cancer group, the lung cancer group showed significantly lower CD4+ T cell proportion, CD4+/CD8+ ratio, and nCD64 index (all P<0.05). Further analysis revealed that the lung cancer group also had significantly lower values of the above indicators compared with the pulmonary infection group (P<0.05), but no significant differences were observed compared with the ILD group (P>0.05). ROC curve analysis showed that the CD4+/CD8+ ratio had an AUC of 0.712 (95%CI: 0.575‑0.849, P=0.008) for differentiating lung cancer from pulmonary infection, with a sensitivity of 56.76% and a specificity of 85.00%; the nCD64 index had an AUC of 0.677 (95%CI: 0.539‑0.814, P=0.026), with a sensitivity of 44.74% and a specificity of 95.24%. When the two indicators were combined, the parallel test increased the sensitivity to 78.38%, while the serial test achieved 100.00% specificity and positive predictive value. After adjusting for age, Firth's logistic regression demonstrated that both the CD4+/CD8+ ratio and nCD64 index retained independent differential diagnosis value for differentiating lung cancer from pulmonary infection (both P<0.05).

Conclusions: The combined detection of the CD4+/CD8+ ratio and nCD64 index in BALF improves the diagnostic efficacy for differentiating lung cancer from pulmonary infection.