Review Reports

Round 1

Reviewer 1 Report

It is always good to see new investigators conducting studies to understand MECFS. This reviewer would like to encourage the authors to use more current and relevant references throughout the manuscript: many are dated and do not contain information pertaining to what is referred to in the manuscript. There are other statements that should be supported with a reference, e.g., "In about 70% of cases, an acute viral infection ...". 

Much more detail is required in the Materials & Methods. For example, describe how the IOM criteria was applied to identify cases. The various blood assay results that are presented are hard to interpret. Of the 351 ME/CFS cases, were assay results available for all or only subsets? If only a subset, how would the effect the results. Statistics should have been used to determine differences between gender and age distributions in the patients. Authors should consider including a comparison group, e.g., MS, FM, etc. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper by Lutz et al is a retrospective data analysis of blood samples from ME/CFS patients in which several pathology tests had been obtained especially those related to immune function. The sample size was 262 and they used the laboratory reference levels of each measure as a comparative control. They conclude from their analysis that the immune system is dysfunctional in ME/CFS patients as a group and that altered immunological measures are useful as biomarkers.

Whilst I do not disagree with altered immune function in ME/CFS I have some doubts about the statistical significance of some of their findings.

For example the comparison to laboratory norm levels. My understanding is that these reference levels are based on the normal range presented in 95% of the population. That therefore suggests that in a study of x number of people a variation of less than 5% from this normal range is also expected in the normal healthy population. Many of the reported differences reported in this paper however are less than 5% and therefore I wonder if they are significant or just expected in any population? Furthermore for a change to be significant then it should be greater than the 5% perhaps around the 10% mark to be significant. Could the authors comment on how they determine statistical significance for these altered measures and which ones they consider to be statistically significant? This also relates to the suitability of their use as biomarkers.

For prevalence of EBV infection this is very common in most populations with reports around 90-95% so the 74% EBV antibodies in ME/CFS patients seems lower if anything. I think having %s of prevalence in normal populations puts these things into perspective.

The number of patients displaying both humoral and immune alterations was quite low (Table 2). Do the authors think this is significant? How does this compare to immune disorders? Same with Table 3.

Overall I think some more statistical analysis would assist in determining which measures are significant, it would also be useful to have some discussion on how these levels of altered measures compare to some immune and autoimmune disorders.

In terms of using altered immune measures of biomarkers I am not sure this study supports this and when compared to other studies the ranges of alterations is significantly different between studies for example in this study the authors detected a 5.7% reduction in IgG3, another group 9% and another group 64%. Can the authors comment on this wide range of observations in different cohorts and how this could be overcome if wanting to look at these measures as biomarkers? Additionally which measures are they suggesting would be useful as biomarkers?

Minor comments:

In Table 1 I think in the parameter column that female and male should be swapped in order to match the figures in the next column

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I am happy with the amendments made by the authors.

Author Response

Thank you very much for your positive review.