Folate analytical methodology

Folate in Health and Disease, Second Edition

Volumn , Issue , 2009, Pages 517-574

  Pfeiffer, Christine M ^a   Fazili, Zia ^a   Zhang, Mindy ^a  

^a CENTERS FOR DISEASE CONTROL AND PREVENTION   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 78650900026     PISSN: None     EISSN: None     Source Type: Book    
DOI: None     Document Type: Chapter

References (169)

1. Gregory JF. Folacin—Chromatographic and radiometric assays. In: Augustin J, Klein BP, Becker D, Venugopal PB, eds., Methods of Vitamin Assays, 4th ed. New York: John Wiley & Sons, 1985:473-96.
2. Gregory JF. Chemical and nutritional aspects of folate research: Analytical procedures, methods of folate synthesis, stability, and bioavailability of dietary folates. Adv Food Nutr Res 1989; 33;1-101.
3. Quinlivan EP, Hanson AD, Gregory JF. The analysis of folate and its metabolic precursors in biological samples. Anal Biochem 2006; 348:163-84.
4. Nelson BC. The expanding role of mass spectrometry in folate research. Curr Anal Chem 2007; 3:219-31.
5. Selhub J. Determination of tissue folate composition by affinity chromatography followed by high-pressure ion pair liquid chromatography. Anal Biochem 1989; 182:84-93.
6. Bagley PJ, Selhub J. Analysis of folates using combined affinity and ion-pair chromatography. Methods Enzymol 1997; 281:16-25.
7. Pfeiffer CM, Gregory JF. Preparation of stable-isotopically labeled folates for in vivo investigation of folate absorption and metabolism. Methods Enzymol 1997; 281:106-16.
8. Freisleben A, Schieberle P, Rychlik M. Synthesis of labeled vitamers of folic acid to be used as internal standards in stable isotope dilution assays. J Agric Food Chem 2002; 50:4760-68.
9. Pfeiffer CM, Fazili Z, McCoy L, Zhang M, Gunter EW. Determination of folate vitamers in human serum by stable-isotope-dilution tandem mass spectrometry and comparison with radioassay and microbiologic assay. Clin Chem 2004; 50:423-32.
10. Gregory JF, Sartain DB, Bay BPF. Fluorometric determination of folacin in biological materials using high performance liquid chromatography. J Nutr 1984; 114;341-53.
11. Bagley PJ, Selhub J. Analysis of folate form distribution by affinity followed by reversed-phase chromatography with electrochemical detection. Clin Chem 2000; 46:404-11.
12. Bagley PJ, Selhub J. A common mutation in the methylenetetrahydrofolate reductase gene is associated with an accumulation of formylated tetrahydrofolates in red blood cells. Proc Natl Acad Sci USA 1998; 95:13217-20.
13. Friso S, Choi S-W, Girelli D, Mason JB, Dolnikowski GG, Bagley PJ, Olivieri O, et al. A common mutation in the 5,10-methylene-tetrahydrofolate reductase gene affects genomic DNA methylation through an interaction with folate status. Proc Natl Acad Sci USA 2002; 99:5606-11.
14. Smith DE, Kok RM, Teerlink T, Jakobs C, Smulders YM. Quantitative determination of erythrocyte folate vitamer distribution by liquid chromatography-tandem mass spectrometry. Clin Chem Lab Med 2006; 44:450-59.
15. Smulders YM, Smith DEC, Kok RK, Teerlink T, Gellekink H, Vaes WHJ, Stehouwer CD, Jakobs C. Red blood cell folate vitamer distribution in healthy subjects is determined by the methylenetetrahydrofolate reductase C677T polymorphism and by the total folate status. J Nutr Biochem 2007; 18:693-99.
16. Fazili Z, Pfeiffer CM, Zhang M, Jain RB, Koontz D. Influence of 5,10-methylene-tetrahydrofolate reductase polymorphism on whole-blood folate concentrations measured by LC-MS/MS, microbiologic assay, and Bio-Rad radioassay. Clin Chem 2008; 54:197-201.
17. Huang Y, Khartulyari S, Morales ME, Stanislawska-Sachadyn A, Von Feldt JM, Whitehead AS, Blair IA. Quantification of key red blood cell folates from subjects with defined MTHFR 677C→T genotypes using stable isotope dilution liquid chromatogra-phy/mass spectrometry. Rapid Comm Mass Spectrom 2008; 22:2403-12.
18. Gregory JF, Engelhardt R, Bhandari SN, Sartain DB, Gustafson SK. Adequacy of extraction techniques for determination of folate in foods and other biological materials. J Food Comp Anal 1990; 3:134-44.
19. Wilson SD, Horne DW. High-performance liquid chromatographic determination of the distribution of naturally occurring folic acid derivatives. In: Chytil F, McCormick DB, eds., Methods in Enzymology. San Diego, CA: Academic Press, 1986:269-73.
20. Lankelma J, Van der Kleijn E. Determination of 6-methyltetrahydrofolic acid in plasma and spinal fluid by high-performance liquid chromatography, using on-column concentration and electrochemical detection. J Chromatogr 1980; 182:35-45.
21. Holt DL, Wehling RL, Zeece MG. Determination of native folates in milk and other dairy products by high-performance liquid chromatography. J Chromatogr 1988; 49:271-79.
22. Leeming RJ, Pollock A, Barley C. A critical assessment of methods for measuring folate in human serum and red blood cells. In: Cortios H-C, Ghisla S, Blau U, eds., Chemistry and Biology of Pteridines. Berlin: Walter de Gruyter & Co., 1990:188-91.
23. Kelly P, McPartlin J, Scott J. A combined high-performance liquid chromatographic-microbiological assay for serum folic acid. Anal Biochem 1996; 238:179-83.
24. Sweeney MR, McPartlin J, Weir DG, Scott JM. Measurements of sub-nanomolar concentrations of unmetabolized folic acid in serum. J Chromatogr B 2003; 788:187-91.
25. Nelson BC, Pfeiffer CM, Margolis SA, Nelson CP. Solid-phase extraction-electrospray ionization mass spectrometry for quantification of folate in human plasma or serum. Anal Biochem 2004; 325:41-51.
26. Kohashi M, Inoue K. Microdetermination of folate monoglutamates in serum by liquid chromatography with electrochemical detection. J Chromatogr 1986; 382:303-07.
27. Hahn A, Flaig KH, Rehner G. Optimized high-performance liquid chromatographic procedure for the separation and determination of the main folacins and some derivatives. J Chromatogr 1991; 545:91-100.
28. Schleyer E, Reinhardt J, Unterhalt M, Hiddemann W. Highly sensitive coupled-column high-performance liquid chromatographic method for the separation and quantitation of the diastereomers of leucovorin and 5-methyltetrahydrofolate in serum and urine. J Chromatogr B 1995; 669:319-30.
29. Garbis SD, Melse-Boonstra A, West CE, van Breemen RB. Determination of folates in human plasma using hydrophilic interaction chromatography-tandem mass spectrometry. Anal Chem 2001; 73:5358-64.
30. Day BP, Gregory JF. Determination of folacin derivatives in selected foods by high performance liquid chromatography. JAgric Food Chem 1981; 29:374-77.
31. Gounelle J-C, Ladjimi H, Prognon P. A rapid and specific extraction procedure for folates determination in rat liver and analysis by high-performance liquid chromatography with fluorometric detection. Anal Biochem 1989; 176:406-11.
32. Bird OD, Robbins M, Vandenbelt JM, Pfiffner JJ. Observations on vitamin Bc conjugase from hog kidney. J Biol Chem 1946; 163:649-59.
33. Lakshmaiah N, Ramasastri BV. Folic acid conjugase from plasma. I. Partial purification and properties. Int J Vitam Nutr Res 1975; 45:183-93.
34. Mims V, Laskowski M. Studies on vitamin Bc conjugase from chicken pancreas. J Biol Chem 1945; 160:493-503.
35. Horne DW, Krumdieck CL, Wagner C. Properties of folic acid y-glutamyl hydrolase (conjugase) in rat bile and plasma. J Nutr 1981; 111:442-49.
36. Engelhardt R, Gregory JF. Adequacy of enzymatic deconjugation in quantification of folate in foods. J Agric Food Chem 1990; 38:154-58.
37. Hyun TH, Tamura T. Trienzyme extraction in combination with microbiologic assay in food folate analysis: An updated review. Exp Biol Med 2005; 230:444-54.
38. Tamura T. Determination of food folate. Nutr Biochem 1998; 9:285-93.
39. Rebello T. Trace enrichment of biological folates on solid-phase adsorption cartridges and analysis by high-pressure liquid chromatography. Anal Biochem 1987; 166:55-64.
40. Lucock MD, Hartley R, Smithells RW. A rapid and specific HPLC-electrochemical method for the determination of endogenous 5-methyltetrahydrofolic acid in plasma using solid phase sample preparation with internal standardization. Biomed Chromatogr 1989; 3:58-63.
41. Priest DG, Bunni MA. A comparison of HPLC and ternary complex-based assays of tissue reduced folates. Anal Lett 1992; 25:219-30.
42. Etienne MC, Speziale N, Milano G. HPLC of folinic acid diastereomers and 5-meth-yltetrahydro-folate in plasma. Clin Chem 1993; 39:82-86.
43. Belz S, Frickel C, Wolfrom C, Nau H, Henze G. High-performance liquid chromatographic determination of methotrexate, 7-hydroxymethotrexate, 5-methyl-tetrahydro-folic acid and folinic acid in serum and cerebrospinal fluid. J Chromatogr B 1994; 661:109-18.
44. Chladek J, Sispera L, Martinkova J. High-performance liquid chromatographic assay for the determination of 5-methyltetrahydrofolate in human plasma. J Chromatogr B 2000; 744:307-13.
45. Opladen T, Ramaekers VT, Heimann G, Blau N. Analysis of 5-methyltetrahydrofolate in serum of healthy children. Mol Gen Metab 2006; 87:61-65.
46. Pawlosky RJ, Flanagan VP, Pfeiffer CM. Determination of 5-methyltetrahydrofolic acid in human serum by stable-isotope dilution high-performance liquid chromatography-mass spectrometry. Anal Biochem 2001; 298:299-305.
47. Nelson BC, Satterfield MB, Sniegoski LT, Welch MJ. Simultaneous quantification of homocysteine and folate in human serum or plasma using liquid chromatography/tan-dem mass spectrometry. Anal Chem 2005; 77:3586-93.
48. Stokes P, Webb K. Analysis of some folate monoglutamates by high-performance liquid chromatography-mass spectrometry. J Chromatogr A 1999; 864:59-67.
49. Pawlosky RJ, Flanagan VP. A quantitative stable-isotope LC-MS method for the determination of folic acid in fortified foods. JAgric Food Chem 2001; 49:1282-86.
50. Wigertz K, Jagerstad M. Comparison of a HPLC and radioprotein-binding assay for the determination of folates in milk and blood samples. Food Chem 1995; 54:429-36.
51. Vahteristo LT, Ollilainen V, Koivistoinen PE, Varo P. Improvements in the analysis of reduced folate monoglutamates and folic acid in food by high-performance liquid chromatography. J Agric Food Chem 1996; 44:477-82.
52. Osseyi ES, Wehling RL, Albrecht JA. Liquid chromatographic method for determining added folic acid in fortified cereal products. J Chromatogr A 1998; 826:235-240.
53. Doherty RB, Beecher GR. A method for the analysis of natural and synthetic folate in foods. J Agric Food Chem 2003; 51:354-61.
54. Rychlik M, Freisleben A. Quantification of pantothenic acid and folates by stable isotope dilution assays. J Food Comp Anal 2002; 15:399-409.
55. Freisleben A, Schieberle P, Rychlik M. Specific and sensitive quantification of folate vitamers in foods by stable isotope dilution assays using high-performance liquid chromatography-tandem mass spectrometry. Anal Biochem 2003; 376:149-56.
56. Selhub J, Ahmad O, Rosenberg IH. Preparation and use of affinity columns with bovine milk folate-binding protein (FBP) covalently linked to Sepharose 4B. Methods Enzymol 1980; 66:686-90.
57. Nelson BC, Pfeiffer CM, Margolis SA, Nelson CP. Affinity extraction combined with stable isotope dilution LC/MS for the determination of 5-methyltetrahydrofolate in human plasma. Anal Biochem 2003; 313:117-27.
58. Lyngbye J, Hansen SI, Holm J. Kinetics of folate protein binding. Methods Enymol 1980; 66:694-709.
59. Pfeiffer CM, Rogers LM, Gregory JF. Determination of folate in cereal-grain food products using trienzyme extraction and combined affinity and reversed-phase liquid chromatography. J Agric Food Chem 1997; 45:407-13.
60. Freisleben A, Schieberle P, Rychlik M. Comparison of folate quantification in foods by high-performance liquid chromatography-fluorescence detection to that by stable isotope dilution assays using high-performance liquid chromatography-tandem mass spectrometry. Anal Biochem 2003; 315:247-55.
61. Gregory JF, Toth JP. Chemical synthesis of deuterated folate monoglutamates and in vivo assessment of urinary excretion of deuterated folates in man. Anal Biochem 1988; 170:94-104.
62. Chapman SK, Greene BC, Streiff RR. A study of serum folate by high-performance ionexchange and ion-pair partition chromatography. J Chromatogr 1978; 145:302-06.
63. Giulidori P, Galli-Kienle M, Stramentinoli G. Liquid-chromatographic monitoring of 5-methyltetrahydrofolate in plasma. Clin Chem 1981; 27:2041-43.
64. Hyland K, Surtees R. Measurement of 5-methyltetrahydrofolate in cerebrospinal fluid using HPLC with coulometric electrochemical detection. Pteridines 1992; 3:149-50.
65. Birmingham BK, Greene DS. Analysis of folinic acid in human serum using highperformance liquid chromatography with amperometric detection. J Pharm Sci 1983; 72:1306-09.
66. 13C-labeled and unlabeled) in human plasma and urine by combined liquid chromatography mass spectrometry. Anal Biochem 2002; 305:206-13.
67. Kok RM, Smith DE, Dainty JR, van den Akker JT, Finglas PM, Smulders YM, Jakobs C, de Meer K. 5-Methyltetrahydrofolic acid and folic acid measured in plasma with liquid chromatography tandem mass spectrometery: Applications to folate absorption and metabolism. Anal Biochem 2004; 326:129-38.
68. Nelson BC, Dalluge JJ, Margolis SA. Preliminary application of liquid chromatography-electrospray-ionization mass spectrometry to the detection of 5-methyltetrahydrofolic acid monoglutamate in human plasma. J Chromatogr B 2001; 765:141-50.
69. Satterfield MB, Sniegoski LT, Sharpless KE, Welch MJ, Hornikova A, Zhang N-F, Pfeiffer CM, Fazili Z, Zhang M, Nelson BC. Development of a new standard reference material: SRM 1955 (homocysteine and folate in human serum). Anal Bioanal Chem 2006; 385:612-22.
70. Luo W, Li H, Zhang Y, Ang CY. Rapid method for the determination of total 5-meth-yl-tetrahydrofolate in blood by liquid chromatography with fluorescence detection. J Chromatogr B 2002; 766:331-37.
71. Fazili Z, Pfeiffer CM, Zhang M, Jain R. Erythrocyte folate extraction and quantitative determination by liquid chromatography-tandem mass spectrometry: Comparison of results with microbiologic assay. Clin Chem 2005; 51:2318-25.
72. Hoppner K, Lampi B. Reversed phase high pressure liquid chromatography of folates in human whole blood. Nutr Rep Int 1983; 27:911-19.
73. Lucock MD, Daskalakis I, Schorah CJ, Levene MI, Hartley R. Analysis and biochemistry of blood folate. Biochem Mol Med 1996; 58:93-112.
74. Pfeiffer CM, Gregory JF III. Enzymatic deconjugation of erythrocyte polyglutamyl folates during preparation for folate assay: Investigation with reversed-phase liquid chromatography. Clin Chem 1996; 42:1847-54.
75. Wright AJA, Finglas PM, Southon S. Erythrocyte folate analysis: A cause for concern? Clin Chem 1998; 44:1886-91.
76. Wright AJA, Finglas PM, Southon S. Erythrocyte folate analysis: Saponin added during lysis of whole blood can increase apparent folate concentrations depending on hemo-lysate pH. Clin Chem 2000; 46:1978-86.
77. O’Broin S, Kelleher B. Optimization of erythrocyte folate extraction. Clin Chem 2001; 47:2181-82.
78. Fazili Z, Pfeiffer CM. Measurement of folates in serum and conventionally prepared whole blood lysates: Application of an automated 96-well plate isotope-dilution tandem mass spectrometry method. Clin Chem 2004; 50:2378-81.
79. Davis SR, Quinlivan EP, Shelnutt KP, Maneval DR, Ghandour H, Capdevila A, Coats BS, et al. The methylene-tetrahydrofolate reductase 677C→T polymorphism and dietary folate restriction affect plasma one-carbon metabolites and red blood cell folate concentrations and distribution in women. JNutr 2005; 135:1040-44.
80. White DR, Lee HS, Krüger RE. Reversed-phase HPLC/EC determination of folate in citrus juice by direct injection with column switching. J Agric Food Chem 1991; 39:714-17.
81. Wilson SD, Horne DW. High-performance liquid chromatographic determination of the distribution of naturally occurring folic acid derivatives in rat liver. Anal Biochem 1984; 142:529-35.
82. Konings EJM. A validated liquid chromatographic method for determining folates in vegetables, milk powder, liver, and flour. J AOAC Int 1999; 82:119-27.
83. Ndaw S, Bergaentzle M, Aoude-Werner D, Lahely S, Hasselmann C. Determination of folates in foods by high-performance liquid chromatography with fluorescence detection after precolumn conversion to 5-methyltetrahydrofolates. J Chromatogr A 2001; 928:77-90.
84. Zhang G-F, Storozhenko S, Van Der Straeten D, Lambert WE. Investigation of the extraction behavior of the main monoglutamate folates from spinach by liquid chromatography-electrospray ionization tandem mass spectrometry. J Chromatogr A 2005; 1078:59-66.
85. Poo-Prieto R, Haytowitz DB, Holden JM, Rogers G, Choumenkovitch SF. Use of the affinity/HPLC method for quantitative estimation of folic acid in enriched cereal-grain products. J Nutr 2006; 136:3079-83.
86. Varela-Moreiras G, Seyoum E, Selhub J. Combined affinity and ion pair liquid chromatographies for the analysis of folate distribution in tissues. J Nutr Biochem 1991; 2:44-53.
87. Vahteristo L, Ollilainen V, Varo P. HPLC determination of folate in liver and liver products. J Food Sci 1996; 61:524-26.
88. Vahteristo LT, Ollilainen V, Varo P. Liquid chromatographic determination of folate monoglutamates in fish, meat, eggs, and dairy products consumed in Finland. J AOAC Intl 1997; 80:373-78.
89. Ruggeri S, Vahteristo LT, Aguzzi A, Finglas P, Carnovale E. Determination of folate vitamers in food and in Italian reference diet by high-performance liquid chromatography. J Chromatogr A 1999; 855:237-45.
90. Belz S, Nau H. Determination of folate patterns in mouse plasma, erythrocytes, and embryos by HPLC coupled with a microbiological assay. Anal Biochem 1998; 265:157-66.
91. Rychlik M. Simultaneous analysis of folic acid and pantothenic acid in foods enriched with vitamins by stable isotope dilution assays. Anal Chim Acta 2003; 495:133-41.
92. Nelson BC, Sharpless KE, Sander LC. Quantitative determination of folic acid in mul-tivitamin/multielement tablets using liquid chromatography/tandem mass spectrometry. J Chromatogr A 2006; 1135:203-11.
93. Ueland PM, Midttun Ø, Winderberg A, Svardal A, Skalevik R, Hustad S. Quantitative profiling of folate and one-carbon metabolism in large-scale epidemiological studies by mass spectrometry. Clin Chem Lab Med 2007; 45:1737-45.
94. Phillips KM, Ruggio DM, Ashraf-Khorassani M, Haytowitz DB. Difference in folate content of green and red sweet peppers (Capsicum annuum) determined by liquid chromatography-mass spectrometry. J Agric Food Chem 2006; 54:9998-10002.
95. Hannisdal R, Ueland PM, Svardal A. Liquid chromatography—tandem mass spectrometry analysis of folate and folate catabolites in human serum. Clin Chem 2009; 55:1147-54.
96. Thomas PM, Flanagan VP, Pawlosky RJ. Determination of 5-methyltetrahydrofolic acid and folic acid in citrus juices using stable isotope dilution-mass spectrometry. J Agric Food Chem 2003; 51:1293-96.
97. Pawlosky RJ, Flanagan VP, Doherty RF. A mass spectrometric validated highperformance liquid chromatography procedure for the determination of folates in foods. J Agric Food Chem 2003; 51:3726-30.
98. Santosh-Kumar CR, Deutsch JC, Hassell KL, Kolhouse NM, Kolhouse JF. Quantitation of red blood cell folates by stable isotope dilution gas chromatography-mass spectrometry utilizing a folate internal standard. Anal Biochem 1995; 225:1-9.
99. Dueker SR, Lin Y, Jones AD, Mercer R, Fabbro E, Miller JW, Green R, Clifford AJ. Determination of blood folate using acid extraction and internally standardized gas chromatography-mass spectrometry detection. Anal Biochem 2000; 283:266-75.
100. Lin Y, Dueker SR, Jones AD, Clifford AJ. A parallel processing solid phase extraction protocol for the determination of whole blood folate. Anal Biochem 2002; 301:14-20.
101. Lin Y, Dueker SR, Clifford AJ. Human whole blood folate analysis using a selected ion monitoring gas chromatography with mass selective detection protocol. Anal Biochem 2003; 312:255-57.
102. Owens JE, Holstege DM, Clifford AJ. Quantitation of total folate in whole blood using LC-MS/MS. J Agric Food Chem 2005; 53:7390-94.
103. Owens JE, Holstege DM, Clifford AJ. High-throughput method for the quantitation of total folate in whole blood using LC-MS/MS. J Agric Food Chem 2007; 55:3292-97.
104. Hannisdal R, Svardal A, Ueland PM. Measurement of folate in fresh and archival serum samples asp-aminobenzoylglutamate equivalents. Clin Chem 2008; 54:665-72.
105. DaCosta M, Rothenberg SP. Identification of an immunoreactive folate in serum extracts by radioimmunoassay. Br J Haematol 1971; 21:121.
106. Hendel J. Radioimmunoassay for pteroylglutamic acid. Clin Chem 1981; 27:701.
107. Wilson DH, Williams G, Herrmann R, Wiesner D, Brookhart P. Issues in immunoassay standardization: The ARCHITECT folate model for intermethod harmonization. Clin Chem 2005; 51:684-87.
108. Shane B, Tamura T, Stokstad ELR. Folate assay: A comparison of radioassay and microbiological methods. Clin Chim Acta 1980; 100:13-19.
109. Givas JK, Gutcho S. pH dependence of the binding of folates to milk binder in radioassay of folates. Clin Chem 1975; 21:427.
110. Waxman S, Schreiber C. Determination of folate by use of radioactive folate and binding proteins. In: McCormick DB, Wright LD, eds., Methods in Enzymology, vol. 66. New York: Academic Press, 1980:468-83.
111. Blackmore S, Pfeiffer C, Hamilton MS, Lee A. Recoveries of folate species from serum pools sent to participants of the UK NEQAS Haematinics Scheme in February and March 2004. Clin Chim Acta 2005; 355:S459.
112. Billen J. Zaman Z, Claeys G, Blanckaert N. Limited dynamic range of a new assay for serum folate. Clin Chem 1999; 45:581-82.
113. Lindemans J, Van Kapel J, Abels J. Evaluation of a radioassay for serum folate and the effects of ascorbate and methotrexate. Clin Chim Acta 1975; 65:15-20.
114. Carmel R. Effects of antineoplastic drugs on Lactobacillus casei and radioisotopic assays from serum folate. Am J Clin Pathol 1978; 69:137-39.
115. Herbert V. Aseptic addition method for Lactobacillus casei assay of folate activity in human serum. J Clin Pathol 1966; 19:12-16.
116. Davis RE, Nicol DJ, Kelly A. An automated method for the measurement of folate activity. J Clin Pathol 1970; 23:47-53.
117. Scott JM, Ghanta V, Herbert V. Trouble-free microbiologie serum and red cell folate assays. Am J Med Technol 1974; 40:125-34.
118. Grossowicz N, Waxman S, Schreiber C. Cryoprotected Lactobacillus casei: An approach to standardization of microbiological assay of folic acid in serum. Clin Chem 1981; 27:745-47.
119. Newman EM, Tsai JF. Microbiological analysis of 5-formyletrahydrofolic acid and other folates using an automatic 96-well plate reader. Anal Biochem 1986; 154:509-15.
120. Horne DW, Patterson D. Lactobacillus casei microbiological assay of folic acid derivatives in 96-well microtiter plates. Clin Chem 1988; 34:2357-59.
121. Horne DW. Microbiological assay of folates in 96-well microtitre plates. Methods Enzymol 1997; 281:38-43.
122. O’Broin S, Kelleher B. Microbiological assay on microtitre plates of folate in serum and red cells. J Clin Pathol 1992; 45:344-47.
123. Molloy AM, Scott JM. Microbiological assay for serum, plasma, and red cell folate using cryopreserved, microtitre plate method. Methods Enzymol 1997; 281:43-53.
124. O’Broin SD, Kelleher BP, Davoren A, Gunter EW. Field-study screening of blood folate concentrations: Specimen stability and finger-stick sampling. Am J Clin Nutr 1997; 66:1398-405.
125. O’Broin SD, Gunter EW. Screening of folate status with use of dried blood spots on filter paper. Am J Clin Nutr 1999; 70:359-67.
126. Keagy PM. Microbiological and animal assays. In: Augustin J, Klein BP, Becker D, Venugopal PB, eds., Methods of Vitamin Assays, 4th ed. New York: John Wiley & Sons, 1985:445-71.
127. Tamura T. Microbiological assay of folates. In: Picciano MF, Stokstad ELR, Gregory JF III, eds., Folic Acid Metabolism in Health and Disease. New York: Wiley-Liss, 1990:121-37.
128. Bogner AL, Shane B. Bacterial folylpoly(y-glutamate) synthase-dihydrofolate synthase. Methods Enzymol 1986; 122:349-59.
129. Tamura T, Shin YS, Williams MA, Stokstad ELR. Lactobacillus casei response to pteroylpolyglutamates. Anal Biochem 1972; 49:517-21.
130. Phillips DR, Wright AJA. Studies on the response of Lactobacillus casei to different folate monoglutamates. Br J Nutr 1982; 47:183-89.
131. Phillips DR, Wright AJA. Studies on the response of Lactobacillus casei to folate vitamin in foods. Br J Nutr 1983; 49:181-86.
132. Wright AJA, Phillips DR. The threshold growth response of Lactobacillus casei to 5-methyl-tetrahydrofolic acid: Implications for folate assays. Br J Nutr 1985; 53:569-73.
133. Beard MEJ, Allen DM. Effect of antimicrobial agents on the Lactobacillus casei folate assay. Am J Clin Pathol 1967; 48:401-04.
134. Cole AJL, Bate J, Gyde OHB. Rifampicin and folate and vitamin B12 assays. BMJ 1973; 2:53.
135. Mehta BM, Hutchison DJ. A microbiologic disc assay for 5-methyltetrahydrofolate in the presence of methotrexate. Cancer ChemotherRep 1977; 61:1657-63.
136. Kelleher BP, O’Broin SD. High serum folate and the calculation of red cell folate. Clin Lab Haematol 1995;17:204-5.
137. Philpott N, Kelleher BP, Smith OP, O’Broin SD. High serum folates and the simplification of red cell folate analysis. Clin Lab Haematol 2001; 23:15-20.
138. O’Broin S, Gunter E. Dried-serum spot assay for folate. Clin Chem 2002; 48:1128-30.
139. DeVries JW, Keagy PM, Hudson CA, Rader JI. AACC collaborative study of a method for determining total folate in cereal products—Microbiological assay using trienzyme extraction (AACC method 86-47). Cereal Foods World 2001; 46:216-19.
140. Tietz NW, ed. Clinical Guide to Laboratory Tests, 3rd ed. Philadelphia: WB Saunders, 1995.
141. Young DS. Effects of Drugs on Clinical Laboratory Tests, 4th ed. Washington, DC: AACC Press, 1995.
142. Young DS. Effects of Preanalytical Variables on Clinical Laboratory Tests, 2nd ed. Washington, DC: AACC Press, 1997.
143. O’Broin JD, Temperly IJ, Scott JM. Erythrocyte, plasma, and serum folate: Specimen stability before microbiological assay. Clin Chem 1980; 26:522-24.
144. Tamura T, Freebert LE, Cornwell PE. Inhibition of EDTA of growth of Lactobacillus casei in the folate microbiological assay and its reversal by added manganese or iron. Clin Chem 1990; 36:1993.
145. van Eijsden M, van der Wal MF, Hornstra G, Bonsel GJ. Can whole blood samples be stored over 24 hours without compromising stability of c-reactive protein, retinol, ferritin, folic acid, and fatty acids in epidemiologic research? Clin Chem 2005; 51:230-32.
146. Drammeh BS, Schleicher RL, Pfeiffer CM, Jain RB, Zhang M, Nguyen PH. Effects of delayed sample processing and freezing on serum concentrations of selected nutritional indicators. Clin Chem 2008; 54:1883-91.
147. Kubasik NP, Graham M, Sine HE. Storage and stability of folate and vitamin B-12 in plasma and blood samples. Clin Chim Acta 1979; 95:147-49.
148. Komaromy-Hiller G, Nuttall KL, Ashwood ER. Effect of storage on serum vitamin B12 and folate stability. Ann Clin Lab Sci 1997; 27:249-53.
149. Lawrence JM, Umekubo MA, Chiu V, Petitti DB. Split sample analysis of serum folate levels after 18 days in frozen storage. Clin Lab 2000; 46:483-86.
150. Kelleher B, O’Broin S. Choice of materials for long-term quality control of blood folate assays. Clin Chem 1996; 42:652-54.
151. Ocké MC, Schrijver J, Obermann-de Boer GL, Ploemberg BPM, Haenen GR, Dromhout D. Stability of blood (pro)vitamins during four years of storage at -20°C: Consequences for epidemiologic research. J Clin Epidemiol 1995; 48:1077-85.
152. Dawson DW, Fish DI, Frew IDO, Roome T, Tilston I. Laboratory diagnosis of megaloblastic anaemia: Current methods assessed by external quality assurance trials. J Clin Pathol 1987; 40:393-97.
153. Brown RD, Jun R, Hughes W, Watman R, Arnold B, Kronenberg H. Red cell folate assays: Some answers to current problems with radioassay variability. Pathology 1990; 22:82-87.
154. van den Berg H, Finglas PM, Bates C. FLAIR intercomparisons on serum and red cell foalte. Int J Vit Nutr Res 1994; 64:288-93.
155. Gunter EW, Bowman BA, Caudill SP, Twite DB, Adams MJ, Sampson EJ. Results of an international round robin for serum and whole-blood folate. Clin Chem 1996; 42:1689-94.
156. Owen WE, Roberts WL. Comparison of five automated serum and whole blood folate assays. Am J Clin Pathol 2003; 120:121-26.
157. Bock JL, Endres DB, Elin RJ, Wang E, Rosenzweig B, Klee GG. Comparison of fresh frozen serum to traditional proficiency testing material in a College of American Pathologists Survey for ferritin, folate, and vitamin B12. Arch Pathol Lab Med 2005; 129:323-27.
158. Pfeiffer CM, Gunter EW, Caudill SP. Comparison of serum and whole blood folate measurements in 12 laboratories: An international study. Clin Chem 2001; 47:A62 (abstract 203).
159. Clifford AJ, Noceti EM, Block-Joy A, Block T, Block G. Erythrocyte folate and its response to folic acid supplementation is assay dependent in women. J Nutr 2005; 135:137-43.
160. Pfeiffer CM, Johnson CL, Jain RB, Yetley EA, Picciano MF, Rader JI, Fisher KD, Mulinare J, Osterloh JD. Trends in blood folate and vitamin B12 concentrations in the United States, 1988-2004. Am J Clin Nutr 2007; 86:718-27.
161. Senti FR, Pilch SM. Analysis of folate data from the Second National Health and Nutrition Examination Survey (NHANES II). J Nutr 1985; 115:1398-402.
162. Life Sciences Research Office. Assessment of Folate Methodology Used in the Third National Health and Nutrition Examination Survey (NHANES 1988-1994). Prepared for the Center for Food Safety and Applied Nutrition, Food and Drug Administration, Department of Health and Human Services. Washington, DC: US Government Printing Office, 1994.
163. Levine S. Analytical inaccuracy for folic acid with a popular commercial vitamin B12/folate kit [Letter]. Clin Chem 1993; 39:2209-10.
164. Fazili Z, Pfeiffer CM, Zhang M. Comparison of serum folate species analyzed by LC-MS/MS with total folate measured by microbiologic assay and Bio-Rad radioassay. Clin Chem 2007; 53:781-84.
165. Finglas PM, Faure U, Southgate DAT. First BCR-intercomparison on the determination of folates in food. Food Chem 1993; 46:199-213.
166. Finglas PM, Wigertz K, Vahteristo L, Witthoft C, Southon S, De Froidmont-Gortz I. Standardisation of HPLC techniques for the determination of naturally-occurring folates in food. Food Chem 1999; 64:245-55.
167. Puwastien P, Pinprapai N, Judprasong K, Tamura T. International inter-laboratory analyses of food folate. J Food Comp Anal 2005; 18:387-97.
168. Thorpe SJ, Sands D, Heath A, Blackmore S, Lee A, Hamilton M, O’Broin S, Nelson BC, Pfeiffer C. International standard for serum vitamin B12 and serum folate: International collaborative study to evaluate a batch of lyophilized serum for B12 and folate content. Clin Chem Lab Med 2007; 45:380-86.
169. Thorpe SJ, Sands D, Heath AB, Hamilton MS, Blackmore S, Barrowcliffe T. An international standard for whole blood folate: Evaluation of a lyophilized haemolysate in an international collaborative study. Clin Chem Lab Med 2004; 42:533-39.