title: An enzymatic method for 5-fluorocytosine.
abstract: We developed an enzymatic method for determination of 5-fluorocytosine in serum, using creatine iminohydrolase (EC 3.5.4.21), the Cobas-Bio analyzer, and an extant ammonia method. Analytical recovery (y) of drug added to serum (x) was good, with y = 0.97x-0.7, Sy.x = 3.6, r = 0.997 (n = 65) over the range 6.25 to 150 mg/L. Comparison with an HPLC method (x) showed good agreement: y = 0.98x + 1.34, Sy.x = 3.7 (n = 37), as analyzed with the Deming debiased regression. Precision was good, CVs being less than 3% for within-run and less than 6% for between-run controls. Ammonia, amphotericin B, glucose, urea, and hemolysis do not interfere, but bilirubin shows analyte-dependent interference and lipemia interferes when triglycerides exceed 5 g/L. This assay is accurate, inexpensive, and easy to perform. It can be easily adapted for routine or emergency use.
authors.affiliation: Department of Clinical Pathology, NIAID, Bethesda, MD 20892.
authors.forename: C M
authors.initials: CM
authors.lastname: Huang
authors.forename: M H
authors.initials: MH
authors.lastname: Kroll
authors.forename: M
authors.initials: M
authors.lastname: Ruddel
authors.forename: R G
authors.initials: RG
authors.lastname: Washburn
authors.forename: J E
authors.initials: JE
authors.lastname: Bennett
mesh_terms: D000619:Aminohydrolases; D002851:Chromatography, High Pressure Liquid; D005437:Flucytosine / Q000097:blood*; D006801:Humans; D011786:Quality Control; D013223:Statistics as Topic
chemical_list: D005437:Flucytosine; D000619:Aminohydrolases; C023157:creatinine deiminase