Wittbrodt Matthew T, Espinoza Sofia, Millard-Stafford Mindy L
Clin Chem Lab Med. 2015 Sep 1;53(10):1613-9. doi: 10.1515/cclm-2014-1006.
Plasma osmolality (POsm) is a gold standard to assess hydration status but requires venipuncture. POsm obtained by lancing a digit, a source of capillary puncture blood (CAP), has not been validated. This study compared POsm from CAP versus venous blood (VEN) and validated its sensitivity to detect dehydration.
Healthy young adults (Study A: n=20 men, 22 women; Study B: n=23 men, 23 women) participated. In Study A, CAP and VEN were compared under controlled euhydration meeting dietary reference intakes for water (3.7 L men, 2.7 L women). In Study B, CAP was assessed for sensitivity to detect dehydration with receiver operating characteristic analysis over two 24 h periods: euhydration for 24 h followed by water restriction over 24 h. POsm was measured using freezing point depression.
For all subjects, CAP POsm (283.0±3.9 mOsm/kg) was not significantly different (p=0.07) from VEN (284.2±3.5) during euhydration and met analytical goals for individuality and heterogeneity. When outliers (n=3) were eliminated, mean difference was -1.6 (±3.2) lower (p<0.01) with CAP. Fluid restriction increased (p<0.001) CAP POsm (284.0±4.4 to 292.8±5.2 mOsm/kg), achieving excellent accuracy (0.92) and sensitivity (89.1%) to predict mild dehydration (2% body mass loss).
POsm via CAP exhibited similar coefficients of variation and analytical goals compared to VEN combined with excellent accuracy and sensitivity to detect dehydration. Although CAP values were approximately 2 mOsm/kg lower than VEN, CAP appears an adequate substitute for tracking changes in non-clinical settings.
血浆渗透压（POsm）是评估水合状态的金标准，但需要静脉穿刺。通过刺破手指获取的POsm（一种毛细血管穿刺血[CAP]来源）尚未得到验证。本研究比较了CAP与静脉血（VEN）的POsm，并验证了其检测脱水的敏感性。
健康年轻成年人（研究A：20名男性，22名女性；研究B：23名男性，23名女性）参与研究。在研究A中，在符合水的膳食参考摄入量（男性3.7升，女性2.7升）的受控正常水合状态下比较CAP和VEN。在研究B中，通过在两个24小时期间进行的受试者工作特征分析评估CAP检测脱水的敏感性：24小时正常水合状态，随后24小时限水。使用冰点降低法测量POsm。
对于所有受试者，在正常水合状态下，CAP的POsm（283.0±3.9毫摩尔/千克）与VEN（差异无统计学意义（p = 0.07），为284.2±3.5），且满足个体性和异质性的分析目标。去除异常值（n = 3）后，CAP的平均差异低1.6（±3.2）（p < 0.01）。限水使CAP的POsm升高（p < 0.001）（从284.0±4.4升高至292.8±5.2毫摩尔/千克），对预测轻度脱水（体重减轻2%）具有出色的准确性（0.92）和敏感性（89.1%）。
与VEN相比，通过CAP获得的POsm表现出相似的变异系数和分析目标，同时在检测脱水方面具有出色的准确性和敏感性。尽管CAP值比VEN低约2毫摩尔/千克，但在非临床环境中，CAP似乎是追踪变化的合适替代方法。
