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Background: Hypercalcemia is highly prevalent in kidney transplant recipients with hyperparathyroidism. However, its long-term impact on graft function is uncertain., Methods: We conducted a prospective cohort study investigating adverse graft outcomes associated with persistent hypercalcemia (free calcium > 5.2 mg/dL in ≥ 80% of measures) and inappropriately elevated intact parathyroid hormone (> 30 pg/mL) in kidney transplant recipients. Asymptomatic mild hypercalcemia was monitored unless complications developed., Results: We included 385 kidney transplant recipients. During a 4-year (range 1-9) median follow-up time, 62% of kidney transplant recipients presented persistent hypercalcemia. Compared to kidney transplant recipients without hypercalcemia, there were no significant differences in graft dysfunction (10% vs. 12%, p = 0.61), symptomatic urolithiasis (5% vs. 3%, p = 0.43), biopsy-proven calcium deposits (6% vs. 5%, p = 1.0), fractures (6% vs. 4%, p = 0.64), and a composite outcome of urolithiasis, calcium deposits, fractures, and parathyroidectomy indication (16% vs. 13%, p = 0.55). In a subset of 76 kidney transplant recipients, subjects with persistent hypercalcemia had higher urinary calcium (median 84 [43-170] vs. 38 [24-64] mg/day, p = 0.03) and intact fibroblast growth factor 23 (median 36 [24-54] vs. 27 [19-40] pg/mL, p = 0.04), and lower 25-hydroxyvitamin D levels (11.3 ± 1.2 vs. 16.3 ± 1.4 ng/mL, p < 0.001). In multivariate analysis, pretransplant intact parathyroid hormone < 300 pg/mL was associated with a reduced risk of post-transplant hypercalcemia (OR 0.51, 95% CI 0.32-0.80)., Conclusions: Long-term persistent mild hypercalcemia (tertiary hyperparathyroidism) was frequent in kidney transplant recipients in our series. This condition presented with lower phosphate and 25-hydroxyvitamin D, and higher urinary calcium and intact fibroblast growth factor 23 levels compared to kidney transplant recipients without hypercalcemia, resembling a mild form of primary hyperparathyroidism. Despite these metabolic derangements, the risk of adverse graft outcomes was low., (© 2023. The Author(s) under exclusive licence to Italian Society of Nephrology.)

Purpose: Free calcium is the gold standard for diagnosis of calcium disorders, although calcium assessment is routinely performed by albumin-adjusted calcium. Our objective was to develop a novel-specific correction equation for free calcium employing serum total calcium and other analytes., Methods: Retrospective single-center cohort study. A new equation for free calcium assessment was formulated from data of hospitalized patients (n = 3481, measurements = 7157) and tested in a validation cohort (n = 3218, measurements = 6911). All measurements were performed simultaneously from the same blood draw., Results: Total CO 2 and phosphate, in addition to albumin, were the principal factors associated to calcium misdiagnosis. A novel laboratory-specific prediction equation was developed: free calcium (mmol/L) = 0.541 + (total calcium [mmol/L] *0.441) - (serum albumin [g/L] *0.0067) - (serum phosphate [mmol/L] *0.0425) - (CO 2 [mmol/L] *0.003). This new equation substantially improved adjusted R 2 to 0.67 (95% CI 0.78-0.82, p < 0.001; Kendall's c-tau: 0.28, p < 0.001). Bland-Altman plots of estimated free calcium and free calcium showed a mean difference of - 0.0006 mmol/L (LOA + 0.126 to - 0.124). In validation cohort, the AUC-ROC curves for hypercalcemia and hypocalcemia diagnosis deploying the new equation were 0.88 (95% CI 0.86-0.89, p < 0.001) and 0.98 (95% CI 0.97-99, p < 0.001), respectively, which were superior to historical formulas for calcium. In univariate models, eGFR was associated with Ca-status misdiagnosis, yet this association disappeared when analysis was adjusted to phosphate and CO 2 ., Conclusions: The novel equation proposed for prediction of free calcium could be useful when free calcium is not available. The conventional formulas misclassify many patients, in particular when phosphate or bicarbonate disturbances are present., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Calcium intake has a role on the development of peak bone mass, and has a mild impact on the maintenance of bone mass during adulthood and the reduction of bone loss rate in postmenopausal women and the elderly in both genders. Calcium dietary intake should be privileged over supplementation. Dairy products are the main calcium dietary sources. Prospective studies have not clearly demonstrated an effect on the prevention of fractures, because of the practical difficulties of a long follow-up in order to get to solid conclusions; however the physiological rationale is that an adequate calcium intake and 25(OH) vitamin D levels exceeding 20 ng/ml is beneficial for bone health and may decrease to certain extent the risk of fractures.

Purpose: Free calcium is the gold standard for diagnosis of calcium disorders, although calcium assessment is routinely performed by albumin-adjusted calcium. Our objective was to develop a novel-specific correction equation for free calcium employing serum total calcium and other analytes. Methods: Retrospective single-center cohort study. A new equation for free calcium assessment was formulated from data of hospitalized patients (n = 3481, measurements = 7157) and tested in a validation cohort (n = 3218, measurements = 6911). All measurements were performed simultaneously from the same blood draw. Results: Total CO2 and phosphate, in addition to albumin, were the principal factors associated to calcium misdiagnosis. A novel laboratory-specific prediction equation was developed: free calcium (mmol/L) = 0.541 + (total calcium [mmol/L] *0.441) – (serum albumin [g/L] *0.0067) – (serum phosphate [mmol/L] *0.0425) – (CO2 [mmol/L] *0.003). This new equation substantially improved adjusted R2 to 0.67 (95% CI 0.78–0.82, p < 0.001; Kendall's c-tau: 0.28, p < 0.001). Bland–Altman plots of estimated free calcium and free calcium showed a mean difference of − 0.0006 mmol/L (LOA + 0.126 to − 0.124). In validation cohort, the AUC–ROC curves for hypercalcemia and hypocalcemia diagnosis deploying the new equation were 0.88 (95% CI 0.86–0.89, p < 0.001) and 0.98 (95% CI 0.97–99, p < 0.001), respectively, which were superior to historical formulas for calcium. In univariate models, eGFR was associated with Ca-status misdiagnosis, yet this association disappeared when analysis was adjusted to phosphate and CO2. Conclusions: The novel equation proposed for prediction of free calcium could be useful when free calcium is not available. The conventional formulas misclassify many patients, in particular when phosphate or bicarbonate disturbances are present. [ABSTRACT FROM AUTHOR]