Daria Pašalić
Department of Medical Chemistry, Biochemistry and Clinical Chemistry
Zagreb University School of Medicine
Šalata ul 2.
10 000 Zagreb, Croatia
Phone +385 (1) 4590 205; +385 (1) 4566 940
E-mail: dariapasalic [at] gmail [dot] com

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Anna Carobene.Biological variation remains relevant Biochemia Medica 2015;25(Suppl 1):S9-S10.

Standardization laboratory, Laboratory Medicine Department, San Raphael hospital, Milan, Italy


Biological variation (BV) data, if correctly defined, have many useful and important applications. The Stockholm conference assigned to BV the second rank in the hierarchy, but for practical reasons intra- and inter-individual BV data became the main tool for setting analytical quality specification. Moreover it enables the assessment of the significance of changes in serial measurements observed within a subject and it, can be used to derive an index of individuality (II) to assess the utility of conventional population-based reference intervals.

BV data, available in a database held in Westgard website(, is now widely used and referenced as an important source for clinical application.

Some limitations of this data, however, have been identified in recent published reviews and were presented during the 1st strategic conference of European Federation of Clinical Chemistry and Laboratory Medicine (EFLM). This conference, held in Milano on November 2014, entitled “Defining analytical performance specifications 15 years after the Stockholm conference” had the primary aim to investigate if the hierarchy established by the “consensus agreement” of the Stockholm Conference was still valid 15 years later or if it should be modified.

In Milano the previous hierarchy to set analytical performance specification has been simplified in three models, and the one based on components of biological variation, also if with some recognized limitations, still remains in the second place.

The theory of BV is valid, but, to be successfully applied, it needs robust experimental data. A careful evaluation of those presently available put in evidence large differences in published data, showing a great heterogeneity among them, very often not clearly justified.

Causal factors responsible for these differences may include methodological issues associated with the data production or true variability associated with the different populations studied.

With the exception of few common analytes, the current available BV values come from a limited number of scientific publications, and sometimes were obtained with an in adequate scientific design (insufficient number of subjects, of samplings per subject, measurements performed with obsolete methods, samples measured in single, insufficient statistical analysis, etc. ).

Despite the poor reliability of part of the BV information, the 1st strategic conference has confirmed the importance of a BV database, provided that it includes only studies that comply with the critical appraisal check list proposed by Bartlett et al. to enable standardized assessment of papers on BV. A “Task and Finish Groups (TFG) on biological variation database” was been created after the strategic conference, to pursue this purpose.

The Biological variation working group of EFLM is also working to update the current available BV data through a multicenter project named “Samples collection from healthy volunteers for biological variation values update”. The project has been designed in order to guarantee the containment of the pre-analytical variables (collection, handling and sample storage) that can negatively impact on results, to harmonize the procedures concerning the population selection, to obtain results by analytical methods currently used, and to update BV database with values obtained by an adequate statistical analysis, complying with the protocol defined by Fraser and Harry.


e-mail: carobene [dot] anna [at] hsr [dot] it