On 2013 Jul 30, Allison Stelling commented:

I am confused by one of the author's statements at the end of the paper (page 8):

"Infrared dyes and Raman spectroscopy have emerged as leading optical technologies, providing excellent selectivity in many different cases of solid tumors (27–30). However, they provide only limited biological or chemical information, and in vivo data suggest that it lacks the sensitivity and specificity of REIMS (31)."

I am familiar with both vibrational spectroscopic and mass spectroscopic methods for the analysis of tissues. If anything, vibrational (Raman and IR) spectra yield more information than mass spectra; as the techniques are a direct and non-invasive measure of chemical bonds. Mass spectra- as the name implies- give only molecular weight information, and do so in a manner that destroys the sample and permits no further analysis. My recent paper (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3604012/) demonstrates that infrared spectroscopy in particular is quite suitable for intraoperative measurements, is likely more cost-effective and is a goodly bit smaller than the mass spectrometer used in this work.

It would have been interesting to see the results from an animal model for both healthy and tumor tissue, as such a model might help train the classification programs and aid in data interpretation.

That being said, this is a quite interesting paper that illuminates the power of traditional analytical chemistry methods for rapid tumor diagnostics. I am mildly skeptical of the results shown in table 2, as the authors show sensitivity and specificity levels over a sampling of, in some cases, n = 2 or even 1 patients. However, I completely understand that these measurements are difficult to orchestrate and this is interesting preliminary work.

I would have liked to see a plot of variance within individuals with the same diagnosis- the presence of low molecular weight chemical species must surely have a fair amount of variance between patients (or even within the same patient), as the expression of such species depends on individual genotypes and their interrelationships with the chemical micro/nano environment. (Basically, I'd like to be able to see on the plots which spectra came from which patients, as many spectra were acquired from individual patients. The total numbers of spectra and total number of patients are listed in tables 1 and 2, but it would be nice know in each case how many measurements were taken and have this visualized with error bars in the plots shown in figures 3, 4, and 5- or even listed in table S1.) -Dr. Stelling

On 2013 Jul 30, Allison Stelling commented:

I am confused by one of the author's statements at the end of the paper (page 8):

"Infrared dyes and Raman spectroscopy have emerged as leading optical technologies, providing excellent selectivity in many different cases of solid tumors (27–30). However, they provide only limited biological or chemical information, and in vivo data suggest that it lacks the sensitivity and specificity of REIMS (31)."

I am familiar with both vibrational spectroscopic and mass spectroscopic methods for the analysis of tissues. If anything, vibrational (Raman and IR) spectra yield more information than mass spectra; as the techniques are a direct and non-invasive measure of chemical bonds. Mass spectra- as the name implies- give only molecular weight information, and do so in a manner that destroys the sample and permits no further analysis. My recent paper (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3604012/) demonstrates that infrared spectroscopy in particular is quite suitable for intraoperative measurements, is likely more cost-effective and is a goodly bit smaller than the mass spectrometer used in this work.

It would have been interesting to see the results from an animal model for both healthy and tumor tissue, as such a model might help train the classification programs and aid in data interpretation.

That being said, this is a quite interesting paper that illuminates the power of traditional analytical chemistry methods for rapid tumor diagnostics. I am mildly skeptical of the results shown in table 2, as the authors show sensitivity and specificity levels over a sampling of, in some cases, n = 2 or even 1 patients. However, I completely understand that these measurements are difficult to orchestrate and this is interesting preliminary work.

I would have liked to see a plot of variance within individuals with the same diagnosis- the presence of low molecular weight chemical species must surely have a fair amount of variance between patients (or even within the same patient), as the expression of such species depends on individual genotypes and their interrelationships with the chemical micro/nano environment. (Basically, I'd like to be able to see on the plots which spectra came from which patients, as many spectra were acquired from individual patients. The total numbers of spectra and total number of patients are listed in tables 1 and 2, but it would be nice know in each case how many measurements were taken and have this visualized with error bars in the plots shown in figures 3, 4, and 5- or even listed in table S1.) -Dr. Stelling