Terms and symbols used in studies on biological variation: the need for harmonization.

There is an increasing interest among professionals in laboratory medicine to achieve global harmonization , and that needs to go beyond the analytical phase and must include all steps within the total testing process, as well as terminology and units (1). The generation and application of data on biological variation (BV) have been studied for many years (2, 3). Unfortunately , the range of terms and variety of symbols used to define the components of BV has become ever larger with the increasing body of literature. This issue has been given little attention to date. We aimed to (a) assess the degree of heterogeneity in terms and symbols used to define the components of BV in the 13 highest ranked clinical chemistry journals in the Web of Science category Medical Laboratory Technology within the 2012 Thomson Reuters Journal Citation Reports and (b) propose terms and symbols to be used in the future. Journals included were Clin-A MEDLINE search using " biological variation " as a keyword, over a 5-year period from Jan. 1, 2009, to Dec. 31, 2013, identified 241 articles. Only 125 (51.9%) were related to BV, and only 62 (49.6%) contained terms and symbols for components of BV. We identified 68 terms and 25 symbols for the component of BV applicable to individuals and 47 terms and 18 symbols for the component applicable to groups of individuals. Most common terms and symbols are listed in Table 1. Clearly, there is marked hetero-geneity in the usage of terms and symbols in the literature. The terms " within-subject BV " and " between-subject BV " were most commonly used, as recommended many years ago by Fraser and Harris (4). Our results indicate that the terms " subject, " " individual, " and " person " are interchangeably used as the term for the component of BV applicable to individuals. However, some authors and even some journals use the terms " within-person " and " within-subject " to distinguish between the standard deviations or coefficients of variation for a single individual and for the pooled value from studies on a number of individuals, respectively. This difference has not been acknowledged uniformly in the literature. Table 1. Terms and symbols most commonly used to define the component of BV applicable to individuals and groups.