Figure 4

Representative examples of SELDI spectra from quality control samples. Examples of spectra illustrate differences between highly consistent spectra and low quality spectra. The spectra in blue are examples of the highly consistent spectra, which include the majority of the 144 quality control samples. All spectra have very similar peak patterns as could be expected for the biological replicates of quality control samples. This indicates that the experiments were conducted consistently and that the spectra are of high quality. In contrast, the spectra in red are the low quality spectra detected by the correlation matrix and that need to be discarded prior to data analysis. All of the low quality spectra are different from the high quality spectra in terms of the peak patterns. Furthermore, unique peak patterns do not exist among the low quality spectra.