Characteristics of bone mineral metabolism in patients with stage 3-5 chronic kidney disease not on dialysis: results of the OSERCE study

OSERCE is a multi-centre and cross-sectional study with the aim of analysing the biochemical, clinical, and management characteristics of bone mineral metabolism alterations and the level of compliance with K/DOQI guideline recommendations in patients with chronic kidney disease (CKD) not on dialysis. The study included a total of 634 patients from 32 different Spanish nephrology units, all with CKD, estimated glomerular filtration rates <60ml/min/1.73m(2), and not on dialysis (K/DOQI stage: 33% stage 3, 46% stage 4, and 21% stage 5). In 409 of these patients, laboratory parameters were also measured in a centralised laboratory, including creatinine, calcium, phosphorous, intact parathyroid hormone (PTH), 25-OH-vitamin D, and 1,25-OH2-Vitamin D levels. The rates of non-compliance with the K/DOQI objectives for calcium, phosphorous, intact PTH, and calcium x phosphate product among these patients were 45%, 22%, 70%, and 4%, respectively. Of the 70% of patients with intact PTH levels outside of the target range established by the K/DOQI guidelines, 55.5% had values above the upper limit and 14.5% had values below the lower limit. Of the 45% of patients with calcium levels outside of the target range, 40% had values above the upper limit and 5% had values below the lower limit. Of the 22% of patients with phosphorous levels outside of the target range, 19% had values above the upper limit, and 3% had values below the lower limit. Finally, 4% of patients also had values for the calcium x phosphate product that were outside of the recommended range. Only 1.8% of patients complied with all four K/DOQI objectives. The values detected in centralised laboratory analyses were not significantly different from those measured in the laboratories at each institution. In addition, 81.5% of patients had a deficiency of calcidiol (25-OH-D-3) (<30ng/ml); of these, 35% had moderate-severe deficiency (<15ng/ml) and 47% had mild deficiency (15-30ng/ml). Calcitriol (1,25-OH2-D-3) levels were deficient in 64.7% of patients. Whereas the calcidiol deficiency was not correlated with the CKD stage, calcitriol deficiencies were more pronounced at more advanced stages of CKD. The results of the OSERCE study confirm the difficulty in reaching the target values recommended by the K/DOQI guidelines in patients with CKD not on dialysis, in particular in the form of poor control of secondary hyperparathyroidism and vitamin D deficiency. With this in mind, we must review strategies for treating bone mineral metabolism alterations in these patients, and perhaps revise the target parameters set by current guidelines.