Circulating KL-6 level at baseline is a predictive indicator for the occurrence of interstitial pneumonia during interferon treatment for chronic hepatitis C.

Interstitial pneumonia (IP) is a serious adverse event of interferon alpha (IFNalpha) treatment for chronic hepatitis C (CH-C). Among 558 CH-C patients who received IFNalpha treatment with or without ribavirin between January 1992 and June 2002, six patients (1.1%) developed IP, including one patient who developed IP in 1993 and again in 2002. Among the seven cases who contracted IP, at the onset of IP, seven (100%), five (71%), and two cases (29%) had elevated serum levels of KL-6, surfactant protein A (SP-A), and surfactant protein D (SP-D), respectively. Prior to starting IFN treatment (baseline), the serum SP-A and SP-D levels were within the normal range in all seven cases, but the serum KL-6 level was elevated in five of the seven cases, contrasting with that in three of 48 age-adjusted CH-C patients who did not develop IP during IFN treatment (71 vs. 6%; P=0.0003). Furthermore, the circulating KL-6 level at baseline was significantly higher among the seven cases than among the controls (543+/-105 vs. 304+/-98 U/ml, P=0.0001). These results indicate that measurement of the circulating KL-6 level in CH-C patients before IFN treatment may be useful for predicting the occurrence of IP during IFN treatment.