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.<h4>Results</h4>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). Here, CD4 is linked to lung cancer.