Evaluation of osteoporosis related parameters and bone mineral density in chronic kidney disease

Aim: As the glomerular filtration rate (GFR) decreases during the course of chronic kidney disease (CKD), changes in calcium, phosphorus, parathormone and vitamin D metabolism give rise various bone diseases and mineral metabolism disorders. Mineral bone disorder occurs when gfr<60 ml/min/1.73m2. The most common bone mineral disorder is osteoporosis. The incidence of osteoporosis is increased in patients with chronic kidney disease compared to that of the general population. Our aim in this study is to determine bone mineral density with DEXA in stage 3 and 4 chronic kidney disease patients, to compare parameteres related to osteoporosis and fracture risks between the two groups. Methods: Patients aged between 18-70 years with Stage 3 and Stage 4 CKD according to the 2012 KDIGO classification, followed in the nephrology outpatient clinic of Aydın Adnan Menderes University, were included in the study. Patients with history of malignancy, bisphosphonate therapy and steroid use, oral contraceptive use and a diagnosis of rheumatoid arthritis were not included in the study. The patients were informed about the study and their consent was signed during routine outpatient clinic visit. 25 OH vitamin D, PTH, ALP, Ca, P, magnesium, albumin, TSH, fT4, glucose, uric acid, bicarbonate, hemoglobin and GFR levels were obtained from the laboratory tests of the patients. Bone densitometry test was performed in the nuclear medicine department. Bone mineral density was measured. The fracture risk of the patients was calculated with the FRAX Turkey model. Height and weight measurements were recorded. An application was made to BAP (Scientific research project) for costs. SPSS-22 program was used for statistical evaluation. P value <0.05 was considered statistically significant. Results: The mean age of the Stage 3 and Stage 4 patients included in the study were similiar and 64 years. GFR values were 49 ml/min/1.73m2 in the stage 3 CKD patients and 26 ml/min/1.73 m2 in the stage 4 CKD group. DM was found to be the most common cause of CKD in both groups. Bone mineral densities of CKD stage 3 and 4 patient groups were evaluated with DEXA, 23% of the stage 3 patient groups were found to be normal, 56.3% were osteopenic, and 20.7% were osteoporotic. In the stage 4 group, 13.8% of the patients were normal, 44.8% were osteopenic, and 41.4% were osteoporotic. The rate of osteoporosis in the stage 4 patient group was 2 times higher than in stage 3, and it was found to be statistically significantly higher (p:0.010). Laboratory parameters of the groups were compared, pth, p, uric acid levels were statistically significantly higher in stage 4 CKD patients, albumin, hemoglobin, ca and bicarbonate levels were found to be statistically significantly lower in stage 4 patients. L1-L4 vertebra T score, z score and BMD values evaluated in lumbar spinal region were found to be significantly lower in the Stage 4 patient group compared to the Stage 3 patient group. The femoral neck BMD value measured in the femur region was also significantly lower in the stage 4 patient group than in the stage 3 patient group. There was no significant difference between the FRAX fracture risk results between the stages. In the correlation analysis, a positive correlation was found with L1-L4 vertebra total t score and hemoglobin and 25 OH vitamin D levels in stage 3 CKD and stage 4 CKD patient groups. In addition, a positive correlation was found between femur total t score and BMI, hemoglobin, bicarbonate and GFR. A negative correlation was found between age and PTH level. Conclusion: Early screening, diagnosis and management of osteoporosis are important to reduce the morbidity and mortality burden in chronic kidney disease. In chronic kidney disease, the rate of osteoporosis increases as GFR decreases. According to the results of our study, the L1-L4 t score determined by DEXA is lower in stage 4 CKD patients than in stage 3 CKD patients, and the rate of osteoporotic patients is higher in stage 4. No statistically significant difference was found between Stage 3 and Stage 4 in terms of FRAX scores. Studies with large patient populations are needed regarding the use of the FRAX score in CKD patients. Key Words: Chronic kidney disease, Bone mineral disorder, Osteoporosis, DEXA