Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands 6009, Australia.
J Clin Endocrinol Metab. 2012 Sep;97(9):3138-45. doi: 10.1210/jc.2012-1429. Epub 2012 Jun 28.
Serum total calcium (tCa) is routinely measured for diagnosing calcium disorders but may not reflect levels of biologically active ionized calcium (iCa) in disease or detect all cases of primary hyperparathyroidism.
We investigated the utility of measuring iCa and tCa for diagnosing primary hyperparathyroidism.
This was an observational, retrospective, cross-sectional study.
We studied a biochemistry cohort of consecutive ambulatory outpatients with suspected bone or calcium metabolism disorders referred for calcium metabolism biochemistry panels and a surgical cohort of consecutive tertiary hospital patients whose parathyroid specimens were submitted to a single center, and consecutive parathyroidectomy patients of a single surgeon with specimens submitted to a different center.
In 5490 biochemistry cohort patients, discordance between iCa and tCa in classifying calcium status occurred in 12.6% of cases overall but was worse in hypercalcemic (whether defined by tCa and/or iCa) cases (49%) and hypocalcemic cases (92%). Reliance on tCa alone would miss 45% with ionized hypercalcemia. In 315 biochemistry cohort cases with PTH-dependent hypercalcemia, 130 (41%) had isolated ionized hypercalcemia at diagnosis. In 143 patients with histologically proven parathyroid disease, 24% had isolated ionized hypercalcemia at diagnosis. These patients were younger (P = 0.022) with milder ionized hypercalcemia and better renal function (both P ≤ 0.001) than patients presenting with concurrently elevated iCa and tCa.
In abnormal calcium states, tCa frequently disagrees with iCa in classifying calcium status. Histologically proven parathyroid disease can present with isolated ionized hypercalcemia. Measurement of iCa is required to accurately assess calcium status and improve diagnostic accuracy.
血清总钙（tCa）通常用于诊断钙代谢紊乱，但可能无法反映疾病中生物活性离子钙（iCa）的水平，也无法检测到所有原发性甲状旁腺功能亢进症病例。
我们研究了测量 iCa 和 tCa 对诊断原发性甲状旁腺功能亢进症的作用。
这是一项观察性、回顾性、横断面研究。
我们研究了一个生物化学队列，包括连续的疑似骨或钙代谢紊乱的门诊患者，这些患者接受了钙代谢生化检测；还研究了一个连续的三级医院患者的手术队列，这些患者的甲状旁腺标本被送到一个中心；以及一个连续的、由一位外科医生进行手术的患者的甲状旁腺标本被送到不同中心的患者。
在 5490 名生物化学队列患者中，iCa 和 tCa 在分类钙状态方面的不一致在总体上发生在 12.6%的病例中，但在高钙血症（无论是通过 tCa 和/或 iCa 定义）病例（49%）和低钙血症病例（92%）中更为严重。仅依赖 tCa 会导致 45%的离子性高钙血症漏诊。在 315 名生物化学队列中有甲状旁腺素依赖性高钙血症的患者中，有 130 例（41%）在诊断时存在单纯离子性高钙血症。在 143 例经组织学证实的甲状旁腺疾病患者中，有 24%的患者在诊断时存在单纯离子性高钙血症。这些患者更年轻（P = 0.022），离子性高钙血症较轻，肾功能较好（均 P ≤ 0.001），与同时存在 iCa 和 tCa 升高的患者相比。
在异常钙状态下，tCa 在分类钙状态方面经常与 iCa 不一致。经组织学证实的甲状旁腺疾病可表现为单纯离子性高钙血症。需要测量 iCa 以准确评估钙状态并提高诊断准确性。
