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Introduction of non-linearity by data transformation in method comparison and commutability studies
-
Dietmar Stöckl
Veröffentlicht/Copyright:
31. Oktober 2008
Abstract
Background: Logarithmic transformation is recommended in method comparison or commutability studies when the standard deviation of the measurement results is heteroscedastic. We show that in the case of a considerable constant difference in the relationship between the x- and y-data, logarithmic transformation introduces non-linearity.
Methods: We used a simulated bivariate dataset [n=50; no systematic differences between the x- and y-data; x-data without error and y-data with concentration-dependent random, normally distributed error (CV=7%)], from which we generated two new sets of data: one by i) multiplying the y-data by 1.1, and the second by ii) adding a constant value of 15 to the y-data.
Results: The runs test (p<0.001) confirms that logarithmic transformation of the second dataset introduces non-linearity. Consequently, applying a linear regression model to the transformed data would result in erroneous decisions about commutability and in erroneously high estimates of the limits of agreement in method comparison studies.
Conclusions: We recommend applying a linearity test after logarithmic transformation of bivariate data and, if necessary, to calculate the prediction intervals of a non-linear regression function.
Clin Chem Lab Med 2008;46:1784–5.
Received: 2008-6-27
Accepted: 2008-8-12
Published Online: 2008-10-31
Published in Print: 2008-12-01
©2008 by Walter de Gruyter Berlin New York
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Schlagwörter für diesen Artikel
heteroscedastic;
logarithmic (ln) transformation;
standard deviation
Artikel in diesem Heft
- Editors' and Publisher's Note
- CCLM Award for the most cited paper recently published
- Reviews
- Cystatin C: current position and future prospects
- Some heterogeneity factors affecting the B-type natriuretic peptides outcome: a meta-analysis
- Genetics and Molecular Diagnostics
- Effect of cyclin D1 (CCND1) polymorphism on gastric premalignant condition
- Identification of two de novo mutations in Chinese patients with X-linked adrenoleukodystrophy
- CYP21A2 gene mutation analysis in Moroccan patients with classic form of 21-hydroxylase deficiency: high regional prevalence of p.Q318X mutation and identification of a novel p.L353R mutation
- Apolipoprotein A5 gene −1131T/C polymorphism is associated with the risk of metabolic syndrome in ethnic Chinese in Taiwan
- Association of GSTM1 and GSTT1 gene polymorphisms with coronary artery disease in relation to tobacco smoking
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