Calcium balance is abnormal in adults with chronic kidney disease (CKD) and is associated with the development of vascular calcification. It is currently not routine to screen for vascular calcification in CKD patients. In this cross-sectional study, we investigate whether the ratio of naturally occurring calcium (Ca) isotopes, 44Ca and 42Ca, in serum could be used as a noninvasive marker of vascular calcification in CKD. We recruited 78 participants from a tertiary hospital renal center: 28 controls, 9 subjects with mild-moderate CKD, 22 undertaking dialysis and 19 who received a kidney transplant. For each participant, systolic blood pressure, ankle brachial index, pulse wave velocity, and estimated glomerular filtration rate were measured, along with serum markers. Calcium concentrations and isotope ratios were measured in urine and serum. While we found no significant association between urine Ca isotope composition (noted δ44/42Ca) between the different groups, δ44/42Ca values in serum were significantly different between healthy controls, subjects with mild-moderate CKD and those undertaking dialysis (P < 0.01). Receiver operative characteristic curve analysis shows that the diagnostic utility of serum δ44/42Ca for detecting medial artery calcification is very good (AUC = 0.818, sensitivity 81.8% and specificity 77.3%, P < 0.01), and performs better than existing biomarkers. Although our results will need to be verified in prospective studies across different institutions, serum δ44/42Ca has the potential to be used as an early screening test for vascular calcification.

中文翻译：

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钙同位素作为慢性肾病血管钙化的生物标志物。

成人慢性肾脏病 (CKD) 的钙平衡异常，并且与血管钙化的发展有关。目前在 CKD 患者中筛查血管钙化并不常规。在这项横断面研究中，我们调查了血清中天然存在的钙 (Ca) 同位素 44Ca 和 42Ca 的比率是否可以用作 CKD 血管钙化的非侵入性标志物。我们从一家三级医院肾脏中心招募了 78 名参与者：28 名对照者、9 名轻中度 CKD 受试者、22 名进行透析的受试者和 19 名接受肾移植的受试者。对于每个参与者，测量收缩压、踝肱指数、脉搏波速度和估计的肾小球滤过率，以及血清标志物。在尿液和血清中测量钙浓度和同位素比率。虽然我们发现不同组之间的尿 Ca 同位素组成（记为 δ44/42Ca）之间没有显着关联，但血清中的 δ44/42Ca 值在健康对照、轻中度 CKD 受试者和进行透析的受试者之间存在显着差异（P < 0.01） . 受试者工作特征曲线分析表明，血清δ44/42Ca检测内侧动脉钙化的诊断效用非常好（AUC=0.818，敏感性81.8%，特异性77.3%，P<0.01），优于现有生物标志物。尽管我们的结果需要在不同机构的前瞻性研究中得到验证，但血清 δ44/42Ca 有可能用作血管钙化的早期筛查试验。