Reviewer's report
Title:A second generation cervico-vaginal lavage device shows similar
performance as its preceding version with respect to DNA yield and HPV DNA
results
Version: 1Date:22 January 2013
Reviewer: Freija Verdoodt
Reviewer's report:
Major Compulsory Revisions:
1. The Method section lacks necessary information and detail. As a minimum, the
following points should be addressed:
1.1 In the Background section the authors refer to the Method section for a
description of the sampling devices, however, this is lacking. The authors should
give a detailed description of the 2nd generation device (user instructions, lavage
volume, transport medium, …) and clearly state differences with the 1st
generation device. Additionaly, it would be informative to include user instructions
for both generation devices (as supplementary files).
1.2 The self-sampled material is tested in two different laboratories. The reader
should be informed on possible inter-laboratory heterogeneity. Furthermore, in
Figure 2, the authors could specify the percentages of samples that were tested
in one or the other laboratorium.
1.3 Cell yield is estimated using Nanodrop. The authors should describe the
method in detail or cite published work that does.
2. Although it is mentioned that 5 samples were excluded from the analysis
because of insufficient material, results of quality control are not given. Were all
other samples of sufficient quality, and positive for human DNA? Either way,
these results should be mentioned in the Results section, and it should be made
clear what is meant by ‘insufficient material’.
3. The DNA concentration of hrHPV positive samples was comparable between
both devices, even though the second device has a smaller lavage volume. This
indicates that in total, the second generation samples contain less cellular
material. The authors could mention this and discuss its implication.
4. Statistics: The authors used a matched analysis on a posterior matching
principle, yielding an exclusion of tested samples. It might be more straight
forward to include all samples and to control for confounding factors (age, place,
lab, for instance) using an appropriate regression.
Minor Essential Revisions:
5. Abstract:
5.1. The effectiveness to recruit non-attendees, is not linked with the DNA yield
or the choice of hrHPV test. The authors should rephrase this paragraph.
5.2. To avoid misinterpretation, it is recommended to use ‘type’ merely when
referring to ‘HPV-type’ and not for the ‘type of hrHPV-test’ (which could be
replaced by, for instance, ‘choice of hrHPV-test)
5.3. Given the small difference between the response rates, “…slightly but not
significantly higher response rates” should be replaced by “similar response
rates”.
6. Background: the authors could mention and discuss screening with HPV vs.
cytology, and refer to relevant literature (e.g. Arbyn et al., Vaccine 2012).
7. It is not necessary to refer to a “T-test” as a “Two-sample T-test” (pleonasm).
8. “Quality control was performed on those samples that had a visual small pellet,
and on a random sample of 5% of the samples.” How many samples were
tested? It would be interesting to know the % of samples from the 2nd and 1st
generation device, among these samples with a visual small pellet.
9. Occasionaly, the authors use ‘HPV positive samples’ or ‘HPV positivity’
instead of ‘hrHPV positive samples’ and ‘hrHPV positivity’. (e.g. p9/al3/line1;
p10/al3/line3). This should be corrected.
10. Figures and Tables:
10.1. TABLE 2: the title should mention that “hrHPV”-positive samples are
assessed.
10.2. Table 1 & 3: The column with hrHPV negative results, and the last row
(Total) are redundant. They can be omitted.
10.3: A legend should be added to the tables, stating the test that was used and
the p-value.
11. Spelling errors:
- p4/al3/line7: ‘a’ in stead of ‘an’
- p4/al3/line3): ‘see Methods section’
- p10/line1: ‘these samples still seem appropriate’
Discretionary Revisions:
12. It would be interesting to include the costs that are linked to the 1st and 2nd
generation screeners as a discussion point. Can the authors make a comparison
(e.g. production costs, mailing costs, …) and include this aspect in the
conclusion?
Level of interest: An article of limited interest
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests