血糖濃度在生化自動分析儀Toshiba C16000轉滯污染的干擾研究

Carryover Interference of Blood Sugar Assay in the Chemical Analyzer Toshiba C16000

現代臨床實驗室的生化自動分析儀，包含檢體探針或是試劑探針的污染，容易產生不同程度的轉滯污染（carryover）。檢體轉滯污染是由前一支檢體帶入影響下一支檢體，因此會產生檢驗數異常容易查覺。然而試劑轉滯污染常只會發生某些特定的分析流程，較難被發現。我們在健診病人檢驗套餐中，發現飯前血糖濃度發生異常偏高（Glucose-AC＞100mg/dL）之比例由12.2％上升32.1％，但當重新單獨檢驗血糖濃度後，發現兩者檢測值之差異很大。為了解前後兩個數據差異的原因，我們設計不同檢驗項目套餐，並逐一排除可能性後，確認血糖濃度的檢測受到鹼性磷酸酶（Alkaline phosphatase，ALP）及丙麩胺醯轉移酶（Gamma-glutamyl transpeptidase，GGT）檢試劑的影響，偽性上升分別為15.9％及9.6％。經過設定儀器試劑探針的清洗步驟後，試劑引起的轉滯污染就消失。因此主要原因是由於ALP或GGT試劑中的成分在340nm有高的吸收值，進而干擾血糖濃度測定。因此醫檢師應該警覺全自動生化分析儀發生試劑轉滯污染的可能性，並小心謹慎解決問題。

In modern clinical laboratory, chemical random-access analyzers that employ dedicated probes, might have various degree of carryover, either in the sample probes or reagent probes. Sample carryover involving analytes from one sample being carried to the subsequent samples, can often be detected due to the abnormal testing results. In contrast, reagent carryover that occurs only in certain specific testing procedure, is more difficult to detect. Our laboratory had once noted that the ratio of abnormal results with elevated fasting blood sugar (>100 mg/dL) in the routine chemical profile analysis among the samples from health-check patients increased from 12.2 % to 32.1 %. However, the glucose levels might become normal if the test rechecked separately. On evaluation for reagent carryover by designing various different testing profiles, we found a significant increase of 15.9% and 9.6% in glucose levels if the glucose testing was concomitantly analyzed with alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGT), respectively. The carryover disappeared when an additional reagent probe washing was applied before the glucose testing. The insidious nature of reagent carryover is caused by the high photometric absorption at 340 nm produced by reagents used in ALP and GGT testing would interfere the glucose detection. In conclusion, the laboratorians should be alert and aware of the potential of reagent carryover in random access chemical analyzers, and should be mindful of appropriate troubleshooting techniques.