Alberta Precision Laboratories and Department of Pathology and Laboratory Medicine, University of Calgary, Calgary, Canada.
Clin Chem Lab Med. 2022 Apr 20;60(6):851-858. doi: 10.1515/cclm-2021-1279. Print 2022 May 25.
We compare measurement uncertainty (MU) calculations to real patient result variation observed by physicians using as our model anion gap (AGAP) sequentially measured on two different instrument types. An approach for discretely quantifying the pre-analytical contributions and validating AGAP MU estimates for interpretation of patient results is proposed.
AGAP was calculated from sodium, chloride, and bicarbonate reported from chemistry or blood gas analyzers which employ different methodologies and specimen types. AGAP MU was calculated using a top-down approach both assuming no correlation between measurands and alternatively, including consideration of measurand correlation. MU-derived reference change values (RCV) were calculated between chemistry and blood gas analyzers results. Observational paired AGAP data (n=39,626 subjects) was obtained from retrospectively analyzed specimens from five urban tertiary care hospitals in Calgary, Alberta, Canada.
The MU derived AGAP RCV for paired specimen data by the two platforms was 5.2-6.1 mmol/L assuming no correlation and 2.6-3.1 mmol/L assuming correlation. From the paired chemistry and blood gas data, total observed variation on a reported AGAP has a 95% confidence interval of ±6.0 mmol/L. When the MU-derived RCV assuming correlation is directly compared against the observed distribution of patient results, we obtained a pre-analytical variation contribution of 2.9-3.5 mmol/L to the AGAP observed variation. In contrast, assuming no correlation leads to a negligible pre-analytical contribution (<1.0 mmol/L).
MU estimates assuming no correlation are more representative of the total variation seen in real patient data. We present a pragmatic approach for validating an MU calculation to inform clinical decisions and determine the pre-analytical contribution to MU in this system.
我们比较了使用两种不同仪器类型连续测量的阴离子间隙（AGAP）来比较测量不确定度（MU）计算值与医生观察到的真实患者结果变化。提出了一种离散量化分析前贡献并验证 AGAP MU 估计值以解释患者结果的方法。
AGAP 是根据化学或血气分析仪报告的钠、氯和碳酸氢盐计算得出的，这些分析仪采用不同的方法和标本类型。AGAP MU 是使用自上而下的方法计算的，假设测量值之间没有相关性，或者同时考虑测量值之间的相关性。计算了化学和血气分析仪结果之间 MU 衍生的参考变化值（RCV）。从加拿大阿尔伯塔省卡尔加里的五家城市三级护理医院回顾性分析的标本中获得了 39626 名患者的配对 AGAP 数据。
假设无相关性，两种平台的配对标本数据得出的 MU 衍生 AGAP RCV 为 5.2-6.1mmol/L，假设相关性为 2.6-3.1mmol/L。从配对的化学和血气数据中，报告的 AGAP 总观测变异有 95%的置信区间为±6.0mmol/L。当直接将假设相关的 MU 衍生 RCV 与患者结果的观测分布进行比较时，我们发现 AGAP 观测到的变异中有 2.9-3.5mmol/L 的分析前变异贡献。相比之下，假设无相关性导致分析前贡献可忽略不计（<1.0mmol/L）。
假设无相关性的 MU 估计值更能代表真实患者数据中看到的总变异。我们提出了一种实用的方法来验证 MU 计算值，以告知临床决策并确定该系统中 MU 的分析前贡献。
