Evidence for a substantial genetic influence on biochemical liver functiontests: Results from a population-based Danish twin study

Background: Biochemical liver function tests are widely used in the clinic and are some of the most frequently used tests in screening for diseases in older age groups. The aim of the present study was to estimate the relativ e importance of genetic and environmental factors to variations in these te sts among the elderly. Methods: We conducted a survey among Danish twins, 73-102 years of age, ide ntified in the population-based Danish Twin Registry. Among the 2749 indivi duals in the study population, an interview was conducted with 79%. From th ese, a blood sample was collected from 290 same-sex twin pairs, total of 58 0 subjects, within a 6-month period and analyzed for alanine aminotransfera se (ALT), lactate dehydrogenase (LDH), gamma -glutamyltransferase (GGT), bi lirubin, and albumin. The interview included questions about alcohol consum ption and body mass index (BMI; self-calculated height and weight), Heritab ility (proportion of the population variance attributable to genetic variat ion) was estimated using structural-equation analyses before and after corr ection for alcohol consumption and BMI. Results: Structural-equation analyses revealed a substantial heritability ( 35-61%) for the four biochemical liver function tests: ALT, GGT, LDH, and b ilirubin. The remaining variation could lie attributed to individuals' nonf amilial environments. Adjustment for alcohol consumption and BMI had no inf luence on the heritability for ALT, GGT, LDH, and bilirubin. For albumin, t wo models fit equally well before adjustment for alcohol and BMI: a model i ncluding additive genetic and nonshared environmental factors (AE), and a m odel including shared and nonshared environmental factors (CE). After adjus tment, the model including shared and nonshared environment was clearly the best fitting model. Conclusions: For bdth males and females, the effect of genetic factors on t he biochemical liver function tests ALT, GGT, LDH, and bilirubin is substan tial and accounts for one-third to two-thirds of the:variation among indivi duals 73-102 years of age. The heritability is equal for males and females and does not change notably after controlling for alcohol consumption and B MI. For albumin, no major impact of genetic factors was found independent o f BMI and alcohol consumption. An understanding of the genetic mechanisms u nderlying biochemical liver function tests among the very old may be of val ue in the interpretation of these tests in this age group. (C) 2001 America n Association for Clinical Chemistry.