Diagnostic accuracy of KL-6 as a marker of amiodarone-induced pulmonary toxicity.

The diagnostic accuracy of KL-6 as an indicator of amiodarone-induced pulmonary toxicity was studied in 14 men (mean age = 62 +/- 12, range 33-76 years) treated with amiodarone. The indications for amiodarone were sustained ventricular tachycardia in 13 patients and atrial fibrillation in 1 patient with refractory heart failure. The KL-6 cut-off level was set at 520 U/mL. Group A consisted of two patients with amiodarone-induced pulmonary toxicity, group B of five patients with other pulmonary disorders, and group C of seven patients without pulmonary disease. KL-6 levels, percent diffusing capacity for carbon monoxide (%DLCO), and other laboratory markers were compared among these three groups. KL-6 levels were significantly higher in group A than in group B and C (2550 +/- 36, 252 +/- 99, 198 +/- 82 U/mL, respectively; P < 0.0001). KL-6 levels in group B were below the cutoff value. %DLCO, C-reactive protein (CRP), and lactic dehydrogenase (LDH) were abnormal in group A. The abnormal rates of CRP and LDH in group B were 80% and 40%, respectively. Of the seven patients with pulmonary disease, three patients (43%) could not undergo %DLCO testing because of poor physical condition. In one patient with amiodarone-induced pulmonary toxicity, the KL-6 level increased from 695 to 2,100 U/mL at a time of progression of interstitial changes. KL-6 may be a useful marker of amiodarone-induced pulmonary toxicity.