Yongquan Lai1, Guodong Zhang1, Zhiwei Zhou1, Neil Inhaber2, Jonathan A Bernstein3, Priya S Chockalingam1, Jiang Wu4. 1. Clinical Biomarker Innovation and Development, Takeda Pharmaceuticals International Co., 125 Binney Street, Cambridge, MA, USA. 2. Global Medical Affairs, Takeda Pharmaceuticals International Co., 300 Shire Way, Lexington, MA, USA. 3. Department of Internal Medicine, Division of Immunology, University of Cincinnati College of Medicine, Bernstein Allergy Group and Bernstein Clinical Research Center, Cincinnati, OH, USA. 4. Clinical Biomarker Innovation and Development, Takeda Pharmaceuticals International Co., 125 Binney Street, Cambridge, MA, USA. Electronic address: jiang.wu1@takeda.com.
Abstract
BACKGROUND: Hereditary angioedema (HAE) is a rare genetic disease caused by deficiency or dysfunction of C1 esterase inhibitor (C1-INH). Timely and accurate diagnosis is an ongoing challenge. Measurement of plasma C1-INH activity is currently the critical standard test. We describe a novel and highly robust point-of-care assay to quantify C1-INH activity in dried blood spot (DBS). METHODS: C1-INH was extracted from 3 mm punches of DBS samples and incubated with excess amount of C1 esterase (C1s). The mixture was subsequentially incubated with C1s substrate, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitation of the enzyme reaction product. RESULTS: The assay was validated within a quantification range from 100 to 1500 mU/mL. The intra-day precision and accuracy ranged from 4.0% to 11.6% and -11.1% to -2.1%, and the inter-day precision and accuracy were 8.1-13.1% and -10.3% to 0.9%, respectively. Normal C1-INH activity (n = 103) ranged from 311 to 1090 mU/mL, whereas 23 out of 24 HAE patients exhibited C1-INH activity lower than 100 mU/mL. CONCLUSION: DBS specimen collection for measurement of functional C1-INH activity in a physician's office is straightforward and not limited by logistic considerations and therefore, appropriate for the diagnosis of HAE in high throughput diagnostic laboratories.
BACKGROUND:Hereditary angioedema (HAE) is a rare genetic disease caused by deficiency or dysfunction of C1 esterase inhibitor (C1-INH). Timely and accurate diagnosis is an ongoing challenge. Measurement of plasma C1-INH activity is currently the critical standard test. We describe a novel and highly robust point-of-care assay to quantify C1-INH activity in dried blood spot (DBS). METHODS:C1-INH was extracted from 3 mm punches of DBS samples and incubated with excess amount of C1 esterase (C1s). The mixture was subsequentially incubated with C1s substrate, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitation of the enzyme reaction product. RESULTS: The assay was validated within a quantification range from 100 to 1500 mU/mL. The intra-day precision and accuracy ranged from 4.0% to 11.6% and -11.1% to -2.1%, and the inter-day precision and accuracy were 8.1-13.1% and -10.3% to 0.9%, respectively. Normal C1-INH activity (n = 103) ranged from 311 to 1090 mU/mL, whereas 23 out of 24 HAE patients exhibited C1-INH activity lower than 100 mU/mL. CONCLUSION: DBS specimen collection for measurement of functional C1-INH activity in a physician's office is straightforward and not limited by logistic considerations and therefore, appropriate for the diagnosis of HAE in high throughput diagnostic laboratories.
Authors: Linsheng Liu; Xurui Jin; Yangfeng Wu; Mei Yang; Tao Xu; Xianglian Li; Jianhong Ren; Lijing L Yan Journal: Front Cardiovasc Med Date: 2020-10-09