BACKGROUND: Newborn screening (NBS) for inborn errors of propionate, methionine, and cobalamin metabolism relies on finding abnormal concentrations of methionine and propionylcarnitine. These analytes are not specific for these conditions and lead to frequent false-positive results. More specific markers are total homocysteine (tHCY), methylmalonic acid (MMA), and methylcitric acid (MCA), but these markers are not detected by current NBS methods. To improve this situation, we developed a method for the detection of tHCY, MMA, and MCA in dried blood spots (DBSs) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). METHODS: The analytes were extracted from a single 4.8-mm DBS punch with acetonitrile:water:formic acid (59:41:0.42) containing dithiothreitol and isotopically labeled standards (d(3)-MMA, d(3)-MCA, d(8)-homocystine). The extract was dried and treated with 3 N HCl in n-butanol to form butylesters. After evaporation of the butanol, the residue was reconstituted and centrifuged and the supernatant was subjected to LC-MS/MS analysis. Algorithms were developed to apply this method as an efficient and effective second-tier assay on samples with abnormal results by primary screening. RESULTS: The 99th percentiles determined from the analysis of 200 control DBSs for MMA, MCA, and HCY were 1.5, 0.5, and 9.8 μmol/L, respectively. Since 2005, prospective application of this second-tier analysis to 2.3% of all NBS samples led to the identification of 13 affected infants. CONCLUSIONS: Application of this assay reduced the false-positive rate and improved the positive predictive value of NBS for conditions associated with abnormal propionylcarnitine and methionine concentrations.
BACKGROUND: Newborn screening (NBS) for inborn errors of propionate, methionine, and cobalamin metabolism relies on finding abnormal concentrations of methionine and propionylcarnitine. These analytes are not specific for these conditions and lead to frequent false-positive results. More specific markers are total homocysteine (tHCY), methylmalonic acid (MMA), and methylcitric acid (MCA), but these markers are not detected by current NBS methods. To improve this situation, we developed a method for the detection of tHCY, MMA, and MCA in dried blood spots (DBSs) by liquid chromatography-tandem mass spectrometry (LC-MS/MS). METHODS: The analytes were extracted from a single 4.8-mm DBS punch with acetonitrile:water:formic acid (59:41:0.42) containing dithiothreitol and isotopically labeled standards (d(3)-MMA, d(3)-MCA, d(8)-homocystine). The extract was dried and treated with 3 N HCl in n-butanol to form butylesters. After evaporation of the butanol, the residue was reconstituted and centrifuged and the supernatant was subjected to LC-MS/MS analysis. Algorithms were developed to apply this method as an efficient and effective second-tier assay on samples with abnormal results by primary screening. RESULTS: The 99th percentiles determined from the analysis of 200 control DBSs for MMA, MCA, and HCY were 1.5, 0.5, and 9.8 μmol/L, respectively. Since 2005, prospective application of this second-tier analysis to 2.3% of all NBS samples led to the identification of 13 affected infants. CONCLUSIONS: Application of this assay reduced the false-positive rate and improved the positive predictive value of NBS for conditions associated with abnormal propionylcarnitine and methionine concentrations.
Authors: Gwendolyn Gramer; Junmin Fang-Hoffmann; Patrik Feyh; Glynis Klinke; Peter Monostori; Jürgen G Okun; Georg F Hoffmann Journal: World J Pediatr Date: 2018-06-15 Impact factor: 2.764
Authors: Jürgen G Okun; Hongying Gan-Schreier; Tawfeq Ben-Omran; Kathrin V Schmidt; Junmin Fang-Hoffmann; Gwendolyn Gramer; Ghassan Abdoh; Noora Shahbeck; Hilal Al Rifai; Abdul Latif Al Khal; Gisela Haege; Chuan-Chi Chiang; David C Kasper; Bridget Wilcken; Peter Burgard; Georg F Hoffmann Journal: JIMD Rep Date: 2016-06-21
Authors: Gerarda Cappuccio; Paldeep S Atwal; Taraka R Donti; Kiki Ugarte; Nadia Merchant; William J Craigen; V Reid Sutton; Sarah H Elsea Journal: JIMD Rep Date: 2016-11-30
Authors: Lynn B Bailey; Patrick J Stover; Helene McNulty; Michael F Fenech; Jesse F Gregory; James L Mills; Christine M Pfeiffer; Zia Fazili; Mindy Zhang; Per M Ueland; Anne M Molloy; Marie A Caudill; Barry Shane; Robert J Berry; Regan L Bailey; Dorothy B Hausman; Ramkripa Raghavan; Daniel J Raiten Journal: J Nutr Date: 2015-06-03 Impact factor: 4.798