Association of conjunctival and corneal calcification with vascular calcification in dialysis patients

Conjunctival and corneal calcification (CCC) is a well-known and easily detectable extraskeletal calcification, but its association with vascular calcification was not investigated previously. The aim of this study is to investigate the relationship of CCC with vascular calcification and bone metabolism parameters in dialysis patients.

We evaluated 63 patients (30 men, 33 women; mean age, 43.5 +/- 13.4 years) who were on dialysis therapy for more than 6 months. Forty-four patients were on peritoneal dialysis and 19 patients were on hemodialysis therapy. The same observer evaluated the presence of CCC by using a slit-lamp microscope, and a total CCC score was recorded for each patient. Fifty-two age- and sex-matched healthy controls also were evaluated by using the same method. Biochemical data were collected from patient files. Bone mineral density (BMD) of the lumbar spine and femoral neck was measured, and the presence of vascular calcification was assessed by using x-ray examinations of the pelvis and hands.

Mean CCC score in patients was significantly higher than that in controls (6.2 +/- 5.1 versus 1.3 +/- 1.8; P = 0.001). CCC score correlated significantly with duration of renal replacement therapy ( r s = 0.392; P = 0.002), serum phosphorus level ( r s = 0.259; P = 0.042), and calcium x phosphorus product ( r s = 0.337; P = 0.007). However, we did not find a significant correlation with calcium, parathyroid hormone, alkaline phosphatase, albumin, or C-reactive protein level or BMD. The frequency of vascular calcification was significantly greater in patients with a high CCC score (CCC score > or = 10) compared with a low CCC score (< or =3; 56.3% versus 5.6%; P = 0.002).

Evaluation of CCC score is an easy, fast, and noninvasive method. It seems that CCC score can be used as an additional tool to assess the status of extraskeletal calcification in dialysis patients.