title: Brief communication: clinical implications of short-term variability in liver function test results.
abstract: BACKGROUND
  Clinicians sometimes order liver tests as part of a screening examination or general work-up. Current guidelines do not recommend routine retesting of abnormal results in asymptomatic patients.
  
  
  OBJECTIVE
  To characterize the magnitude of intraindividual variability of liver test results and determine the proportion of adults with persistently elevated levels after 1 positive test.
  
  
  METHODS
  Reliability study.
  
  
  METHODS
  The NHANES (National Health and Nutrition Examination Survey) III First and Second Examinations (1988 to 1994).
  
  
  METHODS
  1864 men and women age 18 years or older living in the United States.
  
  
  METHODS
  Repeated measurements (mean, 17.5 days apart) of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase, gamma-glutamyltransferase, and bilirubin.
  
  
  RESULTS
  Using NHANES III cutoffs for normal levels, 38% of adults with initially elevated bilirubin levels had normal levels at the second examination. These proportions were 36%, 31%, 17%, and 12% for AST, ALT, alkaline phosphatase, and gamma-glutamyltranferase, respectively. More than 95% of initially normal results remained normal. The results did not differ by alcohol consumption; hepatitis A, B, or C serologic status; recent infection; body mass index; or sociodemographic characteristics. Intraindividual variability was significantly higher for bilirubin (coefficient of variation, 23.4%) and ALT (coefficient of variation, 20.4%) than for AST (coefficient of variation, 13.9%), gamma-glutamyltransferase (coefficient of variation, 13.8%), and alkaline phosphatase (coefficient of variation, 6.7%).
  
  
  CONCLUSIONS
  Only 2 measurements were available. Complete liver disease history was lacking.
  
  
  CONCLUSIONS
  If retested, more than 30% of adults with elevated AST, ALT, or bilirubin levels would be reclassified as normal. Clinicians should be aware of the high intraindividual variability in common liver tests, and practice guidelines should explicitly recommend retesting of asymptomatic individuals with abnormal liver test results.
authors.affiliation: Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205-2223, USA. mlazo@jhsph.edu
authors.forename: Mariana
authors.initials: M
authors.lastname: Lazo
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Selvin
authors.forename: Jeanne M
authors.initials: JM
authors.lastname: Clark
mesh_terms: D000293:Adolescent; D000328:Adult; D000410:Alanine Transaminase / Q000097:blood; D000469:Alkaline Phosphatase / Q000097:blood; D001219:Aspartate Aminotransferases / Q000097:blood; D001663:Bilirubin / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008107:Liver Diseases / Q000175:diagnosis; D008111:Liver Function Tests / Q000592:standards*; D008297:Male; D015203:Reproducibility of Results; D005723:gamma-Glutamyltransferase / Q000097:blood
chemical_list: D005723:gamma-Glutamyltransferase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D000469:Alkaline Phosphatase; D001663:Bilirubin