Using Median Regression to Obtain Adjusted Estimates of Central Tendency for Skewed Laboratory and Epidemiologic Data
Open Access
- 1 January 2009
- journal article
- Published by Oxford University Press (OUP) in Clinical Chemistry
- Vol. 55 (1), 165-169
- https://doi.org/10.1373/clinchem.2008.106260
Abstract
Background: Laboratory studies often involve analyses of highly skewed data for which means are not an adequate measure of central tendency because they are sensitive to outliers. Attempts to transform skewed data to symmetry are not always successful, and medians are better measures of central tendency for such skewed distributions. When medians are compared across groups, confounding can be an issue, so there is a need for adjusted medians. Methods: We illustrate the use of quantile regression to obtain adjusted medians. The method is illustrated by use of skewed nutrient data obtained from black and white men attending a prostate cancer screening. For 3 nutrients, saturated fats, caffeine, and vitamin K, we obtained medians adjusted by age, body mass index, and calories for men in each race group. Results: Quantile regression, linear regression, and log-normal regression produced substantially different adjusted estimates of central tendency for saturated fats, caffeine, and vitamin K. Conclusions: Our method was useful for analysis of skewed and other nonnormally distributed continuous outcome data and for calculation of adjusted medians.Keywords
Funding Information
- NIH (AI 60373, CA 74015, CA 069222, MH 054693)
- American Medical Association
- Pfizer
This publication has 8 references indexed in Scilit:
- Reference ranges of serum IGF-1 and IGFBP-3 levels in a general adult population: Results of the Study of Health in Pomerania (SHIP)Growth Hormone & IGF Research, 2008
- How many sentinel lymph nodes are enough during sentinel lymph node dissection for breast cancer?Cancer, 2008
- Quantile regression provides a fuller analysis of speed dataAccident Analysis & Prevention, 2008
- Estimating Age in Maori, Pacific Island, and European Children from New ZealandJournal of Forensic Sciences, 2008
- Prior antiplatelet use and infarct volume in ischemic strokeJournal of the Neurological Sciences, 2008
- Predicting photochemical pollution in an industrial areaEnvironmental Monitoring and Assessment, 2007
- Approximate Median Regression via the Box-Cox TransformationThe American Statistician, 2007
- Racial and anthropometric differences in plasma levels of insulin-like growth factor I and insulin-like growth factor binding protein-3Urology, 2005