title: Within-subject biological variation in disease: collated data and clinical consequences.
abstract: Quantitative data on the components of biological variation (BV) are used for several purposes, including calculating the reference change value (RCV) required for the assessment of the significance of changes in serial results in an individual. Pathology may modify the set point in diseased patients and, more importantly, the variation around that set-point. Our aim was to collate all published BV data in situations other than health. We report the within-subject coefficient of variation (CV(I)) for 66 quantities in 34 disease states. We compared the results with the CV(I) determined in healthy individuals and examined whether the data derived in specific diseases could be useful for clinical applications. For the majority of quantities studied, CV(I) values are of the same order in disease and health: thus the use of RCV derived from healthy subjects for monitoring patients would be reasonable. However, for a small number of quantities considered to be disease specific markers, the CV(I) differed from those in health. This could mean that RCV derived from healthy CV(I) may be inappropriate for monitoring patients in certain diseases. Hence, disease-specific RCVs may be clinically useful.
authors.affiliation: Analytical Quality Commission of the Spanish Society of Clinical Biochemistry and Molecular Pathology (SEQC), Barcelona, Spain. cricos@vhebron.net
authors.forename: Carmen
authors.initials: C
authors.lastname: Ricós
authors.forename: Natalia
authors.initials: N
authors.lastname: Iglesias
authors.forename: José-Vicente
authors.initials: JV
authors.lastname: García-Lario
authors.forename: Margarita
authors.initials: M
authors.lastname: Simón
authors.forename: Fernando
authors.initials: F
authors.lastname: Cava
authors.forename: Amparo
authors.initials: A
authors.lastname: Hernández
authors.forename: Carmen
authors.initials: C
authors.lastname: Perich
authors.forename: Joanna
authors.initials: J
authors.lastname: Minchinela
authors.forename: Virtudes
authors.initials: V
authors.lastname: Alvarez
authors.forename: Maria-Vicenta
authors.initials: MV
authors.lastname: Doménech
authors.forename: Carlos-Victor
authors.initials: CV
authors.lastname: Jiménez
authors.forename: Carmen
authors.initials: C
authors.lastname: Biosca
authors.forename: Raquel
authors.initials: R
authors.lastname: Tena
mesh_terms: D000465:Algorithms; D001826:Body Fluids / Q000737:chemistry; D002624:Chemistry, Clinical / Q000592:standards* / Q000706:statistics & numerical data; D016208:Databases, Factual; D006801:Humans; D011237:Predictive Value of Tests; D011786:Quality Control; D012016:Reference Values