Summary

A study of 959 black and white women shows that the normal range for 24-h urine calcium excretion in white women is 30–300 mg and 10–285 mg in black women. Clinical laboratories use a normal range for 24-h urine calcium excretion of 100–300 mg; there is a need for them to update their age- and race-specific ranges.

Introduction

Recommendations for a normal range for 24-h urine calcium vary from a low of 50 mg to a high of 400 mg; most “laboratory normal ranges” based on older literature are incorrect. The objective of this analysis is to define a normal range for young women age 25–45 years and older women age 55–90 years, white and black, for 24-h urine calcium and calcium/creatinine ratio, and to examine the relationship between 24-h urine calcium, calcium absorption, and vitamin D metabolites.

Methods

Data from 3 studies was collected on 959 normal black and white women, ages 25–87 years, for 24-h urine calcium, creatinine, calcium intake, serum 25-hydroxyvitamin D (25OHD),1,25 dihydroxyvitamin D (1,25(OH)₂D), and calcium absorption. Urine calcium and creatinine were measured on an auto-analyzer. Calcium absorption was measured by a single isotope method. Serum 25OHD and 1,25(OH)₂D were measured by competitive protein binding assay or radioimmunoassay. Because 24-h urine calcium did not fit a normal distribution, non-parametric methods were used to determine the 95% reference interval (RI) and 90% non-parametric confidence intervals (CI) calculated for groups.

Results

The 95% reference intervals for 24-h urine calcium for women were as follows: black older 7–225 mg, black younger 8–285 mg; white older 37–275 mg, and white younger 23–287 mg. In older white women, 24-h urine calcium was significantly correlated with serum 1,25(OH)₂ D, r = 0.23, p < 0.001, calcium intake r = 0.12, p = 0.001, and calcium absorption r = 0.18, p = 0.003, but not serum 25OHD r = 0.07, p = 0.06.

Conclusions

The normal reference interval for 24-h urine calcium for black women is lower than white women. Twenty-four-hour urine calcium was correlated with serum 1,25(OH)₂ D calcium intake and calcium absorption, but not serum 25OHD. This range will be useful clinically for defining hypercalciuria and for following patients on vitamin D and calcium treatment.

中文翻译：

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正常女性 24 小时尿钙、钙/肌酐比值以及与钙吸收和血清维生素 D 代谢物的相关性的参考范围。

概括

一项针对 959 名黑人和白人女性的研究表明，白人女性 24 小时尿钙排泄的正常范围为 30-300 毫克，黑人女性为 10-285 毫克。临床实验室使用 24 小时尿钙排泄 100-300 mg 的正常范围；他们需要更新他们的年龄和种族特定范围。

介绍

建议的 24 小时尿钙正常范围从 50 毫克到 400 毫克不等；大多数基于旧文献的“实验室正常范围”都是不正确的。该分析的目的是为 25-45 岁的年轻女性和 55-90 岁的老年女性（白人和黑人）确定 24 小时尿钙和钙/肌酐比值的正常范围，并检查两者之间的关系。 24 小时尿钙、钙吸收和维生素 D 代谢物。

方法

3 项研究的数据收集了 959 名 25-87 岁的正常黑人和白人女性的 24 小时尿钙、肌酐、钙摄入量、血清 25-羟基维生素 D (25OHD)、1,25 二羟基维生素 D (1,25 (OH) ₂ D) 和钙吸收。在自动分析仪上测量尿钙和肌酐。钙吸收通过单一同位素方法测量。血清 25OHD 和 1,25(OH) ₂ D 通过竞争性蛋白结合测定法或放射免疫测定法测量。由于 24 小时尿钙不符合正态分布，因此使用非参数方法确定为组计算的 95% 参考区间 (RI) 和 90% 非参数置信区间 (CI)。

结果

女性 24 小时尿钙的 95% 参考区间如下：老年黑人 7-225 mg，年轻黑人 8-285 mg；老年白人 37-275 毫克，年轻白人 23-287 毫克。在老年白人女性中，24 小时尿钙与血清 1,25(OH) ₂ D 显着相关，r = 0.23，p < 0.001，钙摄入量r = 0.12，p = 0.001，钙吸收r = 0.18，p = 0.003，但不是血清 25OHD r = 0.07，p = 0.06。

结论

黑人女性 24 小时尿钙的正常参考区间低于白人女性。24 小时尿钙与血清 1,25(OH) ₂ D 钙摄入量和钙吸收相关，但与血清 25OHD 无关。该范围将在临床上用于定义高钙尿症和跟踪患者接受维生素 D 和钙治疗。