title: The association between content of the elements S, Cl, K, Fe, Cu, Zn and Br in normal and cirrhotic liver tissue from Danes and Greenlandic Inuit examined by dual hierarchical clustering analysis.
abstract: METHODS
  Meta-analysis of previous studies evaluating associations between content of elements sulphur (S), chlorine (Cl), potassium (K), iron (Fe), copper (Cu), zinc (Zn) and bromine (Br) in normal and cirrhotic autopsy liver tissue samples.
  
  
  METHODS
  Normal liver samples from 45 Greenlandic Inuit, median age 60 years and from 71 Danes, median age 61 years. Cirrhotic liver samples from 27 Danes, median age 71 years. Element content was measured using X-ray fluorescence spectrometry.
  
  
  METHODS
  Dual hierarchical clustering analysis, creating a dual dendrogram, one clustering element contents according to calculated similarities, one clustering elements according to correlation coefficients between the element contents, both using Euclidian distance and Ward Procedure.
  
  
  RESULTS
  One dendrogram separated subjects in 7 clusters showing no differences in ethnicity, gender or age. The analysis discriminated between elements in normal and cirrhotic livers. The other dendrogram clustered elements in four clusters: sulphur and chlorine; copper and bromine; potassium and zinc; iron. There were significant correlations between the elements in normal liver samples: S was associated with Cl, K, Br and Zn; Cl with S and Br; K with S, Br and Zn; Cu with Br. Zn with S and K. Br with S, Cl, K and Cu. Fe did not show significant associations with any other element.
  
  
  CONCLUSIONS
  In contrast to simple statistical methods, which analyses content of elements separately one by one, dual hierarchical clustering analysis incorporates all elements at the same time and can be used to examine the linkage and interplay between multiple elements in tissue samples.
authors.affiliation: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, DK-1871 Frederiksberg C, Denmark. Electronic address: jla@life.ku.dk.
authors.forename: Jens
authors.initials: J
authors.lastname: Laursen
authors.affiliation: Department of Rheumatology, Rigshospitalet, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark. Electronic address: nils.mil@dadlnet.dk.
authors.forename: Nils
authors.initials: N
authors.lastname: Milman
authors.affiliation: Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark. Electronic address: pind@chem.au.dk.
authors.forename: Niels
authors.initials: N
authors.lastname: Pind
authors.affiliation: Medical Clinic, 3900 Nuuk, Greenland. Electronic address: hsp@peqqik.gl.
authors.forename: Henrik
authors.initials: H
authors.lastname: Pedersen
authors.affiliation: Medical Clinic, 3900 Nuuk, Greenland. Electronic address: gm@peqqik.gl.
authors.forename: Gert
authors.initials: G
authors.lastname: Mulvad
mesh_terms: D001966:Bromine / Q000032:analysis*; D002713:Chlorine / Q000032:analysis*; D003300:Copper / Q000032:analysis*; D006116:Greenland; D006801:Humans; D004930:Inuit; D007501:Iron / Q000032:analysis*; D008099:Liver / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000378:metabolism*; D011188:Potassium / Q000032:analysis*; D013052:Spectrometry, X-Ray Emission; D013455:Sulfur / Q000032:analysis*; D015032:Zinc / Q000032:analysis*
chemical_list: D002713:Chlorine; D013455:Sulfur; D003300:Copper; D007501:Iron; D015032:Zinc; D011188:Potassium; D001966:Bromine
keywords: Cluster analysis; Liver; Trace elements