Within-person biological variation estimates from the European Biological Variation Study (EuBIVAS) for serum potassium and creatinine used to obtain personalized reference intervals

Biological variation estimates of Alzheimer's disease plasma biomarkers in healthy individuals

“…33,36 Here, all II values were below 0.6, except for p-tau181 and Aβ42/Aβ40, which had slightly higher values, indicating marked individuality for these analytes. 33,36,72 This study has limitations. Although well powered in individuallevel serial sampling, the number of participants was relatively small, possibly affecting CV G more than CV I estimates.…”

“…The RCV was calculated at a 95% bidirectional alpha (z = 1.65) as RCV = 100*(exp[± z x √2 x σ]–1), where σ = √ln(σ 2 CVi + σ 2 CVi ), with σ 2 CVi = ln(CVi 2 + 1) and σ 2 CVa = ln(CVa 2 + 1). The II was calculated as the ratio of CV I and CV G for each biomarker, indicating whether population‐based reference intervals can be useful for evaluating results 33,36 . We also calculated the number of samples needed to be collected to estimate an individual's homeostatic point (NHSP) with a “D” absolute percentage proximity to the individual's true value with the equation n = (z x √[CV I 2 + CV A 2 ]/D) 2 , in which z = 1.96, corresponding to a 95% alpha.…”

“…the analytical performance specifications (APS) that clinical-grade assays should meet; 34,35 and the index of individuality (II), which evaluates the utility of population based reference intervals. 33,36 European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group on Biological Variation. 37,38 The EuBIVAS is a highly powered multi-center study that included weekly blood sampling over 10 weeks from presumably healthy volunteers from five European countries and that has delivered high-quality BV estimates for many measurands widely used in diverse medical areas.…”

“…These parameters, alongside known assay‐dependent analytical variation (CV A ), can provide highly clinically useful information for biomarker implementation. These include the reference change value (RCV), 32,33 which enumerates the change needed between consecutive measurements to exceed biological and analytical variation; the analytical performance specifications (APS) that clinical‐grade assays should meet; 34,35 and the index of individuality (II), which evaluates the utility of population based reference intervals 33,36 . Thus, high‐quality BV data are needed in this rapidly developing area of AD diagnostics, in which specific biomarkers and assays are being considered for clinical implementation and therapeutic trial use.…”

Biological variation and reference change value of the estimated glomerular filtration rate in humans: A systematic review and meta-analysis

“…For laboratory parameters with a high index of individuality (II), defined as II = CV I /CV G , and especially for an II >1.4, the use of RIs is considered suitable. For laboratory parameters with a low II, i.e., when CV I is lower compared to CV G , the individual itself, rather than the reference population, is considered to be the best point of reference for the assessment of serial change ( 35 ). With an II of 0.3 ( 12 ), the latter also applies to the eGFR.…”