Methodology article

The limits of log-ratios

Vasily Sharov¹ , Ka Yin Kwong¹ , Bryan Frank¹ , Emily Chen¹ , Jeremy Hasseman¹ , Renee Gaspard¹ , Yan Yu¹ , Ivana Yang¹ and John Quackenbush^1,2,3

¹  The Institute for Genomic Research, Rockville, MD, USA

²  Department of Biochemistry, The George Washington University School of Medicine, Washington, DC, USA

³  Department of Biostatistics, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, MD, USA

author email corresponding author email

BMC Biotechnology 2004, 4:3doi:10.1186/1472-6750-4-3

Published:	8 March 2004

Abstract

Background

DNA microarray assays typically compare two biological samples and present the results of those comparisons gene-by-gene as the logarithm base two of the ratio of the measured expression levels for the two samples.

Results

Because of the fixed dynamic range of fluorescence and other detection systems, there is a limit to the range of comparisons that can be made using any array technology, and this must be taken into account when interpreting the results of any such analysis.

Conclusions

The dynamic range of microarray data collection systems results in limits in the comparative analyses that can be derived from such measurements and suggests that optimal results can be obtained by making measurements that avoid the boundaries of that dynamic range.