Conducting correlation analysis: important limitations and pitfalls

Clinical Kidney Journal, vol. 14, pp. 2332–2337

Abstract

The correlation coefficient is a statistical measure often used in studies to show an association between variables or to look at the agreement between two methods. In this paper, we will discuss not only the basics of the correlation coefficient, such as its assumptions and how it is interpreted, but also important limitations when using the correlation coefficient, such as its assumption of a linear association and its sensitivity to the range of observations. We will also discuss why the coefficient is invalid when used to assess agreement of two methods aiming to measure a certain value, and discuss better alternatives, such as the intraclass coefficient and Bland-Altman's limits of agreement. The concepts discussed in this paper are supported with examples from literature in the field of nephrology.

Authors 7

1. Roemer J. Janse corresponding Aachen Department of Clinical Epidemiology

   Leiden University Medical Center

   Affiliation as printed

   Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands

2. Tiny Hoekstra

   Amsterdam University Medical Centers · Amsterdam Cardiovascular Sciences · Vrije Universiteit Amsterdam

   Affiliation as printed

   Department of Nephrology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands

3. Kitty J. Jager

   Amsterdam University Medical Centers · University of Amsterdam

   Affiliation as printed

   ERA-EDTA Registry, Department of Medical Informatics, Amsterdam Public Health Research Institute, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands

4. Carmine Zoccali

   National Research Council

   Affiliation as printed

   CNR-IFC, Center of Clinical Physiology, Clinical Epidemiology of Renal Diseases and Hypertension, Reggio Calabria, Italy

5. Giovanni Luigi Tripepi

   National Research Council

   Affiliation as printed

   CNR-IFC, Center of Clinical Physiology, Clinical Epidemiology of Renal Diseases and Hypertension, Reggio Calabria, Italy

6. Friedo Wilhelm Dekker Aachen Department of Clinical Epidemiology

   Leiden University Medical Center

   Affiliation as printed

   Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands

7. Merel van Diepen Aachen Department of Clinical Epidemiology

   Leiden University Medical Center

   Affiliation as printed

   Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands