title: High reproducibility of histological characterization by whole virtual slide quantification; an example using carotid plaque specimens.
abstract: OBJECTIVE
  Tissue biobanks are an important source for discovery and validation studies aiming for new proteins that are causally related with disease development. There is an increasing demand for accurate and reproducible histological characterization, especially for subsequent analysis and interpretation of data in association studies. We assessed reproducibility of one semiquantative and two quantitative methods for histological tissue characterization. We introduce a new automated method for whole digital slide quantification. Carotid atherosclerotic plaques were used to test reproducibility.
  
  
  METHODS
  50 atherosclerotic plaques that were obtained during carotid endarterectomy were analysed. For the semiquantitative analysis, 6 different plaque characteristics were scored in categories by two independent observers, and Cohen's κ was used to test intra- and interobserver reproducibility. The computer-aided method (assessed by two independent observers) and automated method were tested on CD68 (for macrophages) and α smooth muscle actin (for smooth muscle cells) stainings. Agreement for these two methods (done on a continuous scale) was assessed by intraclass correlation coefficients (ICCs).
  
  
  RESULTS
  For the semiquantitative analysis, κ values ranged from 0.55 to 0.69 for interobserver variability, and were slightly higher for intraobserver reproducibility in both observers. The computer-aided method yielded intra- and interobserver ICCs between 0.6 and 0.9. The new automated method performed most optimal regarding reproducibility, with ICCs ranging from 0.92 to 0.97.
  
  
  CONCLUSIONS
  The analysis of performance of three methods for histological slide characterization on carotid atherosclerotic plaques showed high precision and agreement in repeated measurements for the automated method for whole digital slide quantification. We suggest that this method can fulfill the need for reproducible histological quantification.
authors.affiliation: Experimental Cardiology Laboratory, University Medical Center Utrecht, Utrecht, the Netherlands; Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands; Department of Vascular Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Joyce E P
authors.initials: JE
authors.lastname: Vrijenhoek
authors.affiliation: Experimental Cardiology Laboratory, University Medical Center Utrecht, Utrecht, the Netherlands; Department of Vascular Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Bastiaan G L
authors.initials: BG
authors.lastname: Nelissen
authors.affiliation: Experimental Cardiology Laboratory, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Velema
authors.affiliation: Experimental Cardiology Laboratory, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Kristy
authors.initials: K
authors.lastname: Vons
authors.affiliation: Department of Vascular Surgery, St. Antonius Hospital Nieuwegein, Nieuwegein, the Netherlands.
authors.forename: Jean-Paul P M
authors.initials: JP
authors.lastname: de Vries
authors.affiliation: Julius Center of Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Marinus J C
authors.initials: MJ
authors.lastname: Eijkemans
authors.affiliation: Experimental Cardiology Laboratory, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Hester M
authors.initials: HM
authors.lastname: den Ruijter
authors.affiliation: Department of Vascular Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Gert Jan
authors.initials: GJ
authors.lastname: de Borst
authors.affiliation: Department of Vascular Surgery, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Frans L
authors.initials: FL
authors.lastname: Moll
authors.affiliation: Experimental Cardiology Laboratory, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Gerard
authors.initials: G
authors.lastname: Pasterkamp
mesh_terms: D000368:Aged; D002339:Carotid Arteries / Q000473:pathology*; D002340:Carotid Artery Diseases / Q000473:pathology*; D016894:Endarterectomy, Carotid; D005260:Female; D006652:Histological Techniques / Q000379:methods*; D006801:Humans; D008264:Macrophages / Q000473:pathology; D008297:Male; D015588:Observer Variation; D058226:Plaque, Atherosclerotic / Q000473:pathology*; D015203:Reproducibility of Results