Intensive Care Unit, Centre Hospitalier du Dr. Schaffner de Lens, Lens cedex, France,
Intensive Care Med. 2012 Dec;38(12):2026-31. doi: 10.1007/s00134-012-2679-9. Epub 2012 Aug 25.
To examine the repeatability of Stewart's parameters and anion gap in a cohort of critically ill patients and to determine the smallest detectable changes in individual patients.
A total of 161 patients were included prospectively. They underwent two subsequent blood samplings within 10 min of each other and samples were analyzed using the same central laboratory analyzer. Measured and calculated parameters from the two samples were compared. The repeatability was expressed as the smallest detectable difference (SDD), coefficient of variation (CV) and intraclass correlation coefficient (ICC).
The mean differences ± SD (mEq/L) for the repeated measurements were 0.1 ± 0.76, 0.12 ± 0.68, -0.02 ± 1.02, and -0.08 ± 1.05 for the apparent strong ion difference (SID(app)), effective strong ion difference (SID(eff)), strong ion gap (SIG), and albumin-corrected anion gap (AG(corr)), respectively. The SDDs (mEq/L) for SID(app), SID(eff), SIG, and AG(corr), were ±1.49, ±1.33, ±2, and ±2.06, respectively. The CVs (%) for these variables were 1.4, 1.45, 13.3, and 4.15, respectively. The ICCs for all these variables were high, largely above 0.75.
The repeatability of all these calculated variables was good. In repeated measurements, a change in value of these parameters exceeding 1.96√2 CV (%), the least significant change (LSC) or the SDD should be regarded as significant. Use of SDD is preferable to CV and LSC (%) because of its independence from the levels of variables and its expression in absolute units. Expressed as SDD, a SIG change value, e.g., of at least ±2 mEq/L should be significant.
在一组危重症患者中检查斯图尔特（Stewart）参数和阴离子间隙的可重复性，并确定个体患者的最小可检测变化。
共前瞻性纳入 161 例患者。他们在彼此相隔 10 分钟内进行了两次后续血液采样，并且使用相同的中心实验室分析仪分析样本。比较两次采样的测量值和计算值。可重复性用最小可检测差值（SDD）、变异系数（CV）和组内相关系数（ICC）表示。
两次重复测量的平均差值（mEq/L）分别为 0.1±0.76、0.12±0.68、-0.02±1.02 和-0.08±1.05，用于表观强离子差（SID(app)）、有效强离子差（SID(eff)）、强离子间隙（SIG）和白蛋白校正阴离子间隙（AG(corr)）。SID(app)、SID(eff)、SIG 和 AG(corr)的 SDD（mEq/L）分别为±1.49、±1.33、±2 和±2.06。这些变量的 CV（%）分别为 1.4、1.45、13.3 和 4.15。所有这些变量的 ICC 均较高，大部分大于 0.75。
所有这些计算变量的可重复性都很好。在重复测量中，这些参数的变化值超过 1.96√2 CV（%）、最小有意义变化（LSC）或 SDD 应被视为显著变化。由于其独立于变量的水平并且以绝对单位表示，因此使用 SDD 比 CV 和 LSC（%）更可取。以 SDD 表示，SIG 变化值至少为±2 mEq/L 应具有统计学意义。
