title: C-methacetin breath test reproducibility study reveals persistent CYP1A2 stimulation on repeat examinations.
abstract: OBJECTIVE
  To find the most reproducible quantitative parameter of a standard (13)C-methacetin breath test ((13)C-MBT).
  
  
  METHODS
  Twenty healthy volunteers (10 female, 10 male) underwent the (13)C-MBT after intake of 75 mg (13)C-methacetin p.o. on three occasions. Short- and medium-term reproducibility was assessed with paired examinations taken at an interval of 2 and 18 d (medians), respectively.
  
  
  RESULTS
  The reproducibility of the 1-h cumulative (13)C recovery (AUC(0-60)), characterized by a coefficient of variation of 10%, appeared to be considerably better than the reproducibility of the maximum momentary (13)C recovery or the time of reaching it. Remarkably, as opposed to the short gap between consecutive examinations, the capacity of the liver to handle (13)C-methacetin increased slightly but statistically significantly when a repeat dose was administered after two to three weeks. Regarding the AUC(0-60), the magnitude of this fixed bias amounted to 7.5%. Neither the time gap between the repeat examinations nor the gender of the subjects affected the (13)C-MBT reproducibility.
  
  
  CONCLUSIONS
  (13)C-MBT is most reproducibly quantified by the cumulative (13)C recovery, but the exactitude thereof may be modestly affected by persistent stimulation of CYP1A2 on repeat examinations.
authors.affiliation: Department of Basic Biomedical Science, School of Pharmacy, Medical University of Silesia, PL-41-205 Sosnowiec, Poland. akj@sum.edu.pl
authors.forename: Anna
authors.initials: A
authors.lastname: Kasicka-Jonderko
authors.forename: Anna
authors.initials: A
authors.lastname: Nita
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Jonderko
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kamińska
authors.forename: Barbara
authors.initials: B
authors.lastname: Błońska-Fajfrowska
mesh_terms: D000081:Acetamides / Q000378:metabolism*; D000328:Adult; D019540:Area Under Curve; D001944:Breath Tests / Q000379:methods*; D002247:Carbon Isotopes / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D000081:Acetamides; D002247:Carbon Isotopes; C035495:methacetin; D019388:Cytochrome P-450 CYP1A2