The Value of LDH Level of BAL Fluid in Differentiating Benign from Malignant Solitary Pulmonary Nodules

Background: Serum lactate dehydrogenase (LDH) concentra-tion is an indicator for tissue injury. It may be secreted locally in many conditions. For the first time, this study was per-formed to investigate the value of LDH level in bronchoalveo-lar lavage fluid (BALF) in differentiation of benign from ma-lignant single pulmonary nodules (SPNs) and to assess its re-lationship with serum LDH levels. Methods: This study was a prospective case-control clinical study. It included 59 patients with a SPN and 21 non-smoker healthy adult volunteers as controls. They underwent broncho-scopy with BAL, Transbronchial needle aspiration (TBNA), and transbronchial biopsy (TBB). Both total serum and BAL LDH levels were measured. Results: The range of the BAL LDH levels in the control group was 4.60-26 mIU/ml, in patients with benign nodule was 6 – 83 mIU/ml, and in those with malignant nodule was 33-147 mIU/ml. Overall, the mean BALF LDH level was significantly higher in patients with a malignant pulmonary nodule (85.92 ± 28.31) as compared with that of either patients with a benign nodule (19.08 ± 18.35) (p<0.0001) or control group (12.16 ± 6.18) (p<0.0001). No significant difference between the abso-lute value of BAL LDH level in patients with benign pulmonary nodule and the control subjects was found (p=0.23). There was no correlation between BALF LDH and serum LDH level in patients with SPNs (p=0.595). Conclusion: BALF LDH levels are increased in patients with malignant SPN, but had no significant rise in benign solitary pulmonary nodules. This factor is useful in differentiating be-nign from malignant SPNs. A low BAL fluid LDH level in a patient with SPN who does not have a tissue diagnosis may be deemed acceptable for observation and follow up. This may save patients the need for operative procedures