Small Animal Department, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
Department of Morphology, Imaging, Orthopedics, Rehabilitation, and Nutrition, Ghent University, Ghent, Belgium.
J Vet Intern Med. 2023 Sep-Oct;37(5):1794-1805. doi: 10.1111/jvim.16811. Epub 2023 Aug 11.
Stability of serum symmetric dimethylarginine (sSDMA) during short- and long-term storage has not been assessed for the immunoassay of the Point-of-Care IDEXX Catalyst DX (POC) analyzer and the Enzyme Multiplied Immunoassay Technique of IDEXX commercial laboratory (CL). Also, the agreement between both analyzers is questioned.
To determine (a) the effect of storage time and temperature on sSDMA measured by POC and CL; (b) the agreement between sSDMA measured by POC and CL; and (c) the imprecision of the POC.
Serum of cats (n = 17) and dogs (n = 18) with a range of SDMA concentrations (6 to >100 μg/dL).
Based on an equivalence trial with predefined equivalence range (-3.0 to +3.0 μg/dL) and using T0 as baseline, stability was evaluated after 24 hours at 22°C and 4°C (POC); after 7 days at 4°C (POC and CL) and after 10 and 24 months at -24°C and -80°C (CL). Bland-Altman plots enabled method comparison. Imprecision of the POC was assessed by duplicate sSDMA measurements at T0.
The POC analyzer produced equivalent sSDMA measurements if samples were stored for 24 hours at 4°C (95% confidence interval [CI]: -2.5-2.0 μg/dL), but not when stored for 24 hours at room temperature (RT; 95% CI: -4.1 to 0.5 μg/dL) or after 7 days at 4°C (95% CI: -3.6-1.0 μg/dL). The CL analyzer was less affected by preanalytical variation with clinically similar results obtained when samples were stored for 7 days at 4°C (95% CI: -2.2 to 2.4 μg/dL) and for at least 24 months at -24°C (95% CI: -1.7 to 2.9 μg/dL) and -80°C (95% CI: -1.5 to 3 μg/dL). A relevant mean difference of -2.3 μg/dL between both analyzers was found. Duplicate POC measurements were equivalent (95% CI: -2.6 to 2.0 μg/dL).
Delayed analysis may significantly change sSDMA depending on storage and measurement conditions. Interchangeable use of assays should be done with caution because analytical variation could be interpreted as clinically relevant change.
尚未评估即时检验 IDEXX Catalyst DX（POC）分析仪和 IDEXX 商业实验室（CL）的酶联免疫吸附测定法的血清对称二甲基精氨酸（sSDMA）在短期和长期储存过程中的稳定性。此外，还质疑了这两种分析仪之间的一致性。
确定（a）储存时间和温度对 POC 和 CL 测量的 sSDMA 的影响；（b）POC 和 CL 测量的 sSDMA 的一致性；（c）POC 的不精密度。
具有一系列 SDMA 浓度（6 至> 100μg/dL）的猫（n=17）和狗（n=18）的血清。
基于具有预定义等效范围（-3.0 至+3.0μg/dL）的等效试验，并以 T0 作为基线，在 22°C 和 4°C（POC）下储存 24 小时后，在 4°C（POC 和 CL）下储存 7 天后，以及在-24°C 和-80°C（CL）下储存 10 和 24 个月后，评估稳定性。Bland-Altman 图可用于方法比较。通过在 T0 时重复测量 sSDMA 来评估 POC 的不精密度。
如果样品在 4°C 下储存 24 小时（95%置信区间[CI]：-2.5-2.0μg/dL），则 POC 分析仪可产生等效的 sSDMA 测量值，但如果在室温（RT；95%CI：-4.1 至 0.5μg/dL）下储存 24 小时或在 4°C 下储存 7 天后（95%CI：-3.6-1.0μg/dL）则不行。CL 分析仪受分析前变异的影响较小，当样品在 4°C 下储存 7 天（95%CI：-2.2 至 2.4μg/dL）和在-24°C 下储存至少 24 个月（95%CI：-1.7 至 2.9μg/dL）时，获得了临床相似的结果）和-80°C（95%CI：-1.5 至 3μg/dL）。发现两个分析仪之间存在相关的平均差异 2.3μg/dL。POC 的重复测量值是等效的（95%CI：-2.6 至 2.0μg/dL）。
延迟分析可能会根据储存和测量条件显著改变 sSDMA。由于分析变异可能被解释为临床相关的变化，因此应谨慎使用分析物的互换使用。
