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1
Department of Clinical Chemistry, Rikshospitalet University Hospital of Oslo, N-0027 Oslo, Norway.
2
Department of Clinical Biochemistry, Odense University Hospital, 5000 Odense C, Denmark.
3
NOKLUS, Norwegian Centre for External Quality Assurance of Primary Care Laboratories, Division for General Practice, University of Bergen, N-5020 Bergen, Norway.
4
Department of Pathology, University of Virginia Health System, Charlottesville, VA 22908.
5
Biochemical Medicine, Tayside University Hospitals NHS Trust, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland.
6
Department of Clinical Biochemistry, Sønderborg Hospital, 6400 Sønderborg, Denmark.
aAuthor for correspondence. Fax 47-2307-1080; e-mail ari.lahti{at}rikshospitalet.no.
Background: The aim of this study was to develop new and useful criteria for partitioning reference values into subgroups applicable to gaussian distributions and to distributions that can be transformed to gaussian distributions.
Methods: The proposed criteria relate to percentages of the subgroups outside each of the reference limits of the combined distribution. Critical values suggested as partitioning criteria for these percentages were derived from analytical bias quality specifications for using common reference intervals throughout a geographic area. As alternative partitioning criteria to the actual percentages, these were transformed mathematically to critical distances between the reference limits of the subgroup distributions, to be applied to each pair of reference limits, the upper and the lower, at a time. The new criteria were tested using data on various plasma proteins collected from 
500 reference individuals, and the outcomes were compared with those given by the currently widely applied and recommended partitioning model of Harris and Boyd, the "Harris-Boyd model".
Results: We suggest 4.1% as the critical minimum percentage outside that would justify partitioning into subgroups, and 3.2% as the critical maximum percentage outside that would justify combining them. Percentages between these two values should be classified as marginal, implying that nonstatistical considerations are required to make the final decision on partitioning. The correlation between the critical percentages and the critical distances was mathematically precise in the new model, whereas this correlation is rather approximate in the Harris-Boyd model because focus on the difference between means in this model makes high precision hard to achieve. The application examples suggested that the new model is more radical than the Harris-Boyd model.
Conclusions: New percentage and distance criteria, to be used for partitioning gaussian-distributed data, have been developed. The distance criteria, applied separately to both reference limit pairs of the subgroup distributions, seemed more reliable and correlated more accurately with the critical percentages than the distance criteria of the Harris-Boyd model. As opposed to the Harris-Boyd model, the new model is easily adjustable to new critical values of the percentages, should they need to be changed in the future.
The following articles in journals at HighWire Press have cited this article:
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  O. Axler, J. Ahnstrom, and B. Dahlback An ELISA for apolipoprotein M reveals a strong correlation to total cholesterol in human plasma J. Lipid Res., August 1, 2007; 48(8): 1772 - 1780. [Abstract] [Full Text] [PDF]
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 T. L. Nielsen, C. Hagen, K. Wraae, K. Brixen, P. H. Petersen, E. Haug, R. Larsen, and M. Andersen Visceral and Subcutaneous Adipose Tissue Assessed by Magnetic Resonance Imaging in Relation to Circulating Androgens, Sex Hormone-Binding Globulin, and Luteinizing Hormone in Young Men J. Clin. Endocrinol. Metab., July 1, 2007; 92(7): 2696 - 2705. [Abstract] [Full Text] [PDF]
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 S. Hartmann, J. G. Okun, C. Schmidt, C.-D. Langhans, S. F. Garbade, P. Burgard, D. Haas, J. O. Sass, W. L. Nyhan, and G. F. Hoffmann Comprehensive Detection of Disorders of Purine and Pyrimidine Metabolism by HPLC with Electrospray Ionization Tandem Mass Spectrometry Clin. Chem., June 1, 2006; 52(6): 1127 - 1137. [Abstract] [Full Text] [PDF]
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H. Berrahmoune, J. V. Lamont, B. Herbeth, P. S. FitzGerald, and S. Visvikis-Siest Biological Determinants of and Reference Values for Plasma Interleukin-8, Monocyte Chemoattractant Protein-1, Epidermal Growth Factor, and Vascular Endothelial Growth Factor: Results from the STANISLAS Cohort Clin. Chem., March 1, 2006; 52(3): 504 - 510. [Abstract] [Full Text] [PDF]
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E. Grossi, R. Colombo, S. Cavuto, and C. Franzini The REALAB Project: A New Method for the Formulation of Reference Intervals Based on Current Data Clin. Chem., July 1, 2005; 51(7): 1232 - 1240. [Abstract] [Full Text] [PDF]
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A. Lahti, P. Hyltoft Petersen, J. C. Boyd, P. Rustad, P. Laake, and H. E. Solberg Partitioning of Nongaussian-Distributed Biochemical Reference Data into Subgroups Clin. Chem., May 1, 2004; 50(5): 891 - 900. [Abstract] [Full Text] [PDF]
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A. Lahti, P. Hyltoft Petersen, and J. C. Boyd Impact of Subgroup Prevalences on Partitioning of Gaussian-distributed Reference Values Clin. Chem., November 1, 2002; 48(11): 1987 - 1999. [Abstract] [Full Text] [PDF]
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