Chyle test is not a valuable laboratory index in identifying chylothorax after pulmonary resection and lymph node...

Chyle test is widely used to identify chylothorax after pulmonary resection and lymph node dissection for primary non-small cell lung cancer (NSCLC). Low accuracy of chyle test in identifying chylothorax is rarely reported. This observational study was designed to identify the diagnostic value of chyle test.

From September 2016 to March 2017, 185 consecutive patients either suspected or histologically documented lung cancer were screened for this observational study. Except exclusion, 108 patients were eligible for further analysis. Daily chest-tube output as well as the postoperative day of chest tube removal was documented. Chyle test was analyzed with 108 cases, and the results were blinded to the thoracic surgeons. Chest tube was timely removed regardless of the results of chyle test. A high-output pleural effusion and an associated change in quality of the pleural fluid, from serous to milky yellowish after normal diet, led to the diagnosis of chylothorax. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of chyle test in identifying chylothorax were calculated.

Of 108 patients, 4 (3.7%) were observed with chylothorax after pulmonary resection and lymph node dissection for primary NSCLC. Postoperative chylothorax was conservatively managed in three patients and chest tubes were removed 12 days (from 10 to 16) after surgery. Failed in conservative treatment, one patient underwent thoracic duct ligation performed by video-assisted thoracic surgery. For patients without chylothorax, the median day of chest tube removal was postoperative day 4. Among the 108 patients, 75.9% (82/108) was found with a positive chyle test result, of which 95.1% (78/82) was false positive in identifying chylothorax. The sensitivity and specificity of chyle test in identifying chylothorax were 100% and 25%, respectively. The positive predictive value, negative predictive value, and accuracy of chyle test for chylothorax diagnosis were 4.9%, 100%, and 27.8%, respectively.

It was suggested that the specificity and accuracy of chyle test in identifying chylothorax were relatively low. Chyle test is not a good laboratory index in identifying chylothorax. With highly positive result, chyle test should not preclude the removal of chest tube in patients after pulmonary resection and lymph node dissection for primary NSCLC.