目的：TCO2檢驗結果為臨床醫師作為診斷慢性代謝性酸中毒之依據之一。目前國內 TCO2分析包括生化分析儀測定、外送至代檢機構執行，以及因成本考量不開放臨床申請。 本研究主要探討TCO2以血液氣體分析儀執行的可行性，評估血液氣體分析儀與生化分析儀 之間的相關性及結果差異，提供臨床醫師診斷慢性代謝性酸中毒之依據。 材料與方法：以隨機方法收集2017年5月份的Blood gas檢體102件、生化檢體101件及健 康檢查者生化檢體20件，共計223件血液檢體。使用Olympus AU 680生化自動分析儀測定 TCO2及 Siemens Rapidlab 1265血液氣體分析儀的ctCO2 計算值，分別分析血漿及血清之 CO2濃度。以20位健康者之血清做為生物參考值驗證。以SPSS 22.0版統計軟體進行相關性 及差異性分析，以p<0.05具統計之差異。 結果：不論以血漿或血清分析TCO2，血液氣體分析儀分析都大於生化自動分析儀之結 果(r＝0.99)。以生化自動分析儀TCO2之生物參考值區分 <21 mmol/L、21-31 mmol/L、>31 mmol/L，分別統計其差異性，血漿平均值分別為 1.1 mmol/L、1.1mmol/L、1.3 mmol/L，血 清平均值分別為 0.5 mmol/L、1.5 mmol/L、1.9 mmol/L。血液氣體分析儀分析大於生化自動 分析儀分析值平均大於1 mmol/L (r＝0.99，p<0.05)。生物參考值驗證，20支健康者TCO2都 落在參考值內。 結論：因國內TCO2 檢驗，除檢驗室自行以生化儀器分析外，部分檢驗室外送代檢機 構分析，主要因TCO2 檢驗的檢體收集與處理有特別之限制與要求，影響結果差異太大， 因此不建議TCO2 檢驗委外代檢。本研究結果證實，檢驗室以血液氣體分析儀分析血清檢 體，可做為TCO2 檢驗的替代方法，以血液氣體分析儀分析ctCO2的結果減1 mmol/L，可做 為TCO2的分析結果，並可套用生化分析儀生物參考值，提供臨床醫師診斷慢性代謝性酸中 毒之依據。

Objective: TCO2 (Total CO2) is an analyte that is widely used to diagnose the chronic metabolic acidosis of patients; however, there are various approaches to measure TCO2, which is not only analyzed by biochemistry analyzers, but transported to reference laboratories for analysis. Moreover, laboratory department in certain hospitals in Taiwan takes into account of a large cost, so they have no choice but to cancel TCO2 tests. The aim of this study was to assess the feasibility of blood gas analyzer for alternative method to TCO2 test and evaluate the correlation and difference of results of TCO2 concentration between blood gas analyzer and biochemistry analyzer. Methods and material: A randomized sampling approach was used that 223 blood samples were collected, including blood gases (n=102), biochemical specimens drawn from patients (n=101) and from healthy adults (n=20) in May 2017. The Siemens Rapidlab 1265 blood gas analyzer was used for calculated total CO2 (ctCO2), while the Olympus AU680 was utilized for measured TCO2. The validity of reference interval was tested by 20 serum samples from healthy adults. Statistical analysis, including correlation and difference of values, was performed using SPSS 22.0 version. P values <0.05 were considered significant. Results: The Rapidlap 1265 blood gas analyzer had a higher TCO2 concentration than the Olympus AU680 biochemistry analyzer showed in plasma or serum (r=0.99). In addition, we used 3 groups of TCO2 reference interval—<21 mmol/L, 21-31 mmol/L, and >31 mmol/L for comparing individual mean difference of values, in which results of plasma were 1.1 mmol/l, 1.1 mmol/L, and 1.3 mmol/L, and that of serum were 0.5 mmol/L, 1.5 mmol/L, and 1.9 mmol/L. We noted that mean TCO2 concentration was more than 1 mmol/L with ctCO2 higher for the Rapidlab 1265 than TCO2 for the Olympus AU680 (r=0.99, p<0.05). For the validity of reference interval, all of results of 20 serum samples were within interval. Conclusion: Approaches for measurement of TCO2 concentration in Taiwan are analyzed by biochemistry analyzers or transported to reference laboratories. With the strict requirements to collect and process specimens of TCO2 testing, transported to reference laboratories for analysis is not recommended. It is because transportation from long distance to reference laboratories affect a large difference for TCO2 testing. This study has evidenced that blood gas analyzer can be an alternative method for TCO2 testing. Also, substracting 1 mmol/L from the values of ctCO2 of blood gas analyzers and being applied with laboratory interval of biochemistry analyzers offer clinical physicians a quick data for diagnosing chronic metabolic acidosis of patients.