PCDHGA12 methylation biomarker in bronchial washing specimens as an adjunctive diagnostic tool to bronchoscopy in lung cancer

The use of bronchoscopy is central to the diagnosis of lung cancer. However, the sensitivity of bronchoscopy is low. In addition, bronchial washing cytology, which is a routine adjunctive test, does not significantly improve the performance of bronchoscopy owing to its low sensitivity. To enhance the diagnostic performance of bronchoscopy, the protocadherin GA12 (PCDHGA12) methylation biomarker in bronchial washings was introduced as a novel adjunctive diagnostic test. A total of 98 patients who underwent bronchoscopy owing to suspicion of lung cancer were analyzed. Cytological examination and PCDHGA12 methylation biomarker testing of the bronchial washing fluid were performed. The performance of the tests was analyzed. The final diagnosis in 60 patients was lung cancer and in 38 patients was benign disease. The PCDHGA12 methylation biomarker had a sensitivity of 75.0%, a specificity of 78.9% and a positive predictive value (PPV) of 84.9%, whereas cytological assessment had a sensitivity of 45.0%, a specificity of 92.1% and a PPV of 90%. Patients with positive PCDHGA12 methylation test had an odds ratio for lung cancer of 11.25 (confidence interval, 4.25-29.8) compared with negative subjects. The combination of the two tests exhibited an increased sensitivity (83.3%), a specificity of 71.1% and a PPV of 82.0%. Furthermore, considering the non-diagnostic bronchoscopy group alone, the test demonstrated a sensitivity of 61.9% and a specificity of 78.9%. The results of the present study demonstrated that PCDHGA12 methylation, as a lung cancer biomarker in bronchial washings, may be a used as an adjunctive test to bronchoscopy.