Estudo clínico da associação entre calcificação de córnea e conjuntiva e marcadores do metabolismo mineral e ósseo em pacientes com doença renal crônica dialítica

Abstract

Introduction: Chronic Kidney Disease (CKD) affects a large percentage of patients worldwide. Renal replacement therapy keeps patients with CKD alive. Mineral and bone disease is a common complication of CKD (CKD-BMD) and includes changes in serum concentrations of phosphorus, parathyroid hormone (PTH), calcium (Ca), and vitamin D, in addition to vascular and soft tissue calcifications. Corneal and conjunctival calcification (CCC) is poorly studied in this population despite the eyes being the main site of metastatic calcification in patients with CKD. It is not known whether CCC correlates with coronary artery calcification and CKD-MBD biomarkers. Methods: this was a prospective observational study that included patients on dialysis for at least 3 months. Clinical, demographic, and biochemical factors (Ca, phosphorus, PTH, alkaline phosphatase, and vitamin D) were analyzed. CCC was evaluated by slit-lamp ophthalmologic examination and optical coherence tomography (OCT) by the same observer. Coronary calcium scores (Agatston) were assessed by tomography. Results: We included 34 patients [48.0 ± 15.2 years, 61.8% women, on hemodialysis for 5.7 (2.7- 9.3) years, 79.4% with hyperparathyroidism]. Laboratory tests were: PTH 731(336-1366) pg/ml, vitamin D 33.2 ± 13.7 ng/ml, alkaline phosphatase 148 (94-400) UI/L, ionized Ca 4.91 ± 0 .42 mg/dl, total Ca 9.3 ± 1.0 mg/ml, and phosphorus 5.3 ± 1.9 mg/ml. In the slit lamp ophthalmological examination, we obtained a median of CCC scores were 5 (1-12) and 9 (3-14.5), obtained from slit lamp and OCT, respectively. The scores obtained by the slit lamp tended to underestimate those obtained by the OCT, although they had a good correlation with each other. Hyperphosphatemia was more frequent in patients with moderate/severe CCC than in those with CCC mild. Hyperphosphatemia remained an independent risk factor for moderate/severe CCC [relative risk 5.33 (95% CI 1.02-27.76), p=0.047], even after adjusting for age and presence of diabetes. We found no correlation between coronary calcium scores and CCC obtained either by slit lamp or by OCT. Conclusion: CCC is frequent in patients with CKD on dialysis and does not correlate with coronary calcium scores. Hyperphosphatemia appears to independently contribute to CCC.