Have you stress tested your assay?

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• 作者：Zheng Cao ; Ping Wang ; ^{pwang@houstonmethodist.org" class="auth_mail" title="E-mail the corresponding author}
• 关键词：HgbA1c ; hemoglobin A1c ; NHANES ; National health and nutritional examination survey ; NGSP ; National glycohemoglobin standardization program ; IFCC ; International federation of clinical chemistry ; DCCT ; Diabetes control and complications trial ; HPLC ; high performance liquid chromatography ; QC ; quality control ; HMH ; Houston Methodist Hospital
• 刊名：Practical Laboratory Medicine
• 出版年：2016
• 出版时间：1 August 2016
• 年：2016
• 卷：5
• 期：Complete
• 页码：21-23
• 全文大小：506 K

文摘

When a clinical assay is stressed with extraordinarily high volume of specimens over a short period of time, extra caution may be needed to avoid systematic errors and biases. Here we report our experience with a HgbA1c assay used for high volume wellness screening purpose, to illustrate the importance of stress testing during assay validation.

Design and Methods

Over 15,000 whole blood specimens were tested for HgbA1c in a period of 2 months. HgbA1c was tested by an immunoturbidimetric method on a high through-put automation line. The HgbA1c population distribution in our study was compared to that from the NHANES database. Daily distributions of HgbA1c values ≥6%, means and medians were plotted. Correlation studies were performed between the high through-put immunoturbidimetric assay and a medium through-put HPLC method.

Results

We observed a shift of HgbA1c distribution to the higher values compared to the NHANES. A bias of 15–20% was noted from further stress testing where large number of samples were batched and tested using the immunoturbidimetric assay. A 5–7% higher bias remained after implementing a cuvette washing program after each HgbA1c sample. We hypothesized this bias was caused by build-up of blood cell fragments in the cuvettes when continuous whole blood samples are run through the system. Our experience suggests stress testing needs to be incorporated early in the test validation process for high volume batched screening applications. This seemingly extra validation step may save significant troubleshooting and retesting efforts down the road.