title: The marker of cobalamin deficiency, plasma methylmalonic acid, correlates to plasma creatinine.
abstract: OBJECTIVE
  To examine the relationship between the two diagnostic tests, plasma methylmalonic acid and plasma cobalamins, and their association with plasma creatinine, age and sex.
  
  
  METHODS
  Cross-sectional study of simultaneous laboratory measurements.
  
  
  METHODS
  County of Aarhus, Denmark.
  
  
  METHODS
  Records on 1689 patients who had their first plasma methylmalonic acid measurement during 1995 and 1996, and who had a simultaneous measurement of plasma cobalamins. Plasma creatinine values measured within a week of measurements of plasma methylmalonic acid and plasma cobalamins were available for 1255 of the patients.
  
  
  METHODS
  Predictors of variation in plasma methylmalonic acid; plasma cobalamins, plasma creatinine, age and sex.
  
  
  RESULTS
  Plasma methylmalonic acid was positively correlated with plasma creatinine, even for plasma creatinine within the normal range. These associations remained in a multiple regression analysis. For plasma cobalamins below 200 pmol L-1, there was a strong negative correlation between plasma methylmalonic acid and plasma cobalamins, whilst the association was weak for higher plasma cobalamin levels. Plasma methylmalonic acid increased and plasma cobalamins decreased with age.
  
  
  CONCLUSIONS
  The strong correlation between plasma methylmalonic acid and plasma creatinine suggests that plasma creatinine - also within the normal range - must be taken into consideration when interpreting plasma methylmalonic acid.
authors.affiliation: Department of Haematology, AAS, Aarhus University Hospital, Aarhus, Denmark. Anne_Mette.Hvas@aas.auh.dk
authors.forename: A M
authors.initials: AM
authors.lastname: Hvas
authors.forename: S
authors.initials: S
authors.lastname: Juul
authors.forename: L U
authors.initials: LU
authors.lastname: Gerdes
authors.forename: E
authors.initials: E
authors.lastname: Nexø
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008764:Methylmalonic Acid / Q000097:blood*; D008875:Middle Aged; D012016:Reference Values; D012737:Sex Factors; D014806:Vitamin B 12 Deficiency / Q000097:blood / Q000175:diagnosis*
chemical_list: D015415:Biomarkers; D008764:Methylmalonic Acid; D003404:Creatinine