Cystatin C deficiency is associated with the progression of small abdominal aortic aneurysms

Abstract

Abstract Background The cysteine protease inhibitor cystatin C may play a role in the development and progression of abdominal aortic aneurysms (AAAs). Methods From a mass screening trial of men aged 65–73 years, 151 small AAAs were followed for a mean of 2·9 years. Of these patients, 142 had serum samples taken to determine the levels of cystatin C, creatinine and C-reactive protein (CRP). Results Serum cystatin C concentration correlated negatively with AAA size (r = − 0·22 (95 per cent confidence interval (c.i.) −0·59 to −0·02)) and annual expansion rate (r = − 0·24 (95 per cent c.i. −0·75 to −0·05)), persisting after adjustment for renal function, smoking, diastolic blood pressure, CRP, age and AAA size. Creatinine clearance and CRP did not correlate with size or expansion rate. Thirty-one AAAs had expanded to over 50 mm, when operation was recommended. The serum level of cystatin C was a significant predictor of this occurrence, with a sensitivity and specificity of 61 and 57 per cent respectively. However, initial AAA size had the optimal sensitivity and specificity (both 81 per cent) in this regard. Conclusion Deficiency of cystatin C was associated with increased aneurysm size and expansion rate, possibly due to lack of inhibition of cysteine proteases.