Merits and demerits of various biomarkers of chronic lung diseases with special reference to club cell protein 16 (CC-16) and early detection of chronic silicosis

Abstract

Silicosis is a widely prevalent occupational lung disease with high morbidity and premature mortality. It is caused by continuous or intermittent exposure to respirable crystalline silica (RCS) dust while working in relevant work places. Conventionally silicosis is detected by the chest radiography and/or high resolution computerized tomography (HRCT) scan supported by evidence of impaired lung function test through spirometry. Secondary prevention of silicosis may be a possible strategy for reduction of silicosis associated morbidity and mortality provided there is a suitable biomarker available to predict it at its early stages among the silica dust exposed workers. This article has attempted to review the merits and demerits of various possible biomarkers such as silicon, respirable crystalline silica, TNF alpha, IL-6, IL-8, CC-16 etc. Of them, CC-16 has the distinct advantages over other markers. CC-16 is mostly secreted from the club cells of terminal bronchioles of lung and is easily diffusible in to the peripheral circulation. It is inversely correlated with the extent of silicotic lung damage. Recently Indian Council of Medical Research – National Institute of Occupational Health (ICMR-NIOH) through their research work has conclusively evidenced that CC-16 may be used as a proxy marker and screening tool for early detection of chronic silicosis by periodic screening among silica dust exposed workers. Further work towards CC-16 marker may be useful for control of chronic silicosis. This will also facilitate elimination of tuberculosis.