Fasting urinary hydroxyproline: creatinine ratios in silicosis.

Abstract

Fasting urinary hydroxyproline: creatinine (HOP:C) ratios were measured in 74 patients with suspected (borderline) silicosis (10), simple silicosis (46) and complicated silicosis (9 silicotuberculosis, 4 massive fibrosis, and 5 combined silicotuberculosis and massive fibrosis) and in 18 healthy subjects (controls). There was no statistically significant difference in urinary HOP:C ratios between control subjects (mean 13.8, SD 3.6) and suspected silicotics (mean 18.0, SD 7.6); however, urinary HOP:C ratios were significantly higher in both simple silicosis (mean 25.0, SD 9.9, p less than 0.001) and complicated silicosis (silicotuberculosis and progressive massive fibrosis) (mean 28.6, SD 11.3; p less than 0.001). Urinary HOP:C ratios appeared to show a graduated increase to their highest levels in category 2 silicosis and thereafter remained constant or declined slightly in category 3 silicosis and massive fibrosis. The results support the suggestion that urinary hydroxyproline might be useful as an indicator of disease progression in established silicosis. However, further longitudinal studies are needed to confirm its predictive value.