Reviewer's report
Title:Comparing urine samples and cervical swabs for Chlamydia testing in a
female population by means of the SDA method.
Version: 1Date:5 November 2009
Reviewer: marian Currie
Reviewer's report:
Comparing urine samples and cervical swabs for Chlamydia testing in a female
population by means of the SDA method.
Haugland Siren. 1, Thune Turid. 2, Fosse Beata. 3, Wentzel-Larsen Tore.4,
Hjelmevoll Stig Ove. 5, Myrmel Helge. 3.
Thank you for asking me to review this paper which describes a laboratory-based
study designed to determine if strand displacement amplification (SDA) coupled
with fluorescent energy transfer (ET) measurement is as effective in detecting
chlamydia DNA in urine specimens from women as it is in detecting chlamydia
DNA in cervical swabs.
The study question is well defined.
Compulsory Revisions
Background
The first 3 paragraphs of the background are not really related to the question
and could be omitted or condensed. The fourth paragraph is most relevant.
Methods
The paragraph entitled ethics should be moved to the beginning of the Methods
section.
Reword the second sentence of the last paragraph before Laboratory methods.
"A woman was considered CT positive if both FCU and the cervical swab were
positive by the SDA method (BDPT) or if one of the specimens tested positive by
the SDA method and at least one specimen was positive for the Cobas
TaqManCT or the in-house PCR."
Study population
1. Most of the paragraph headed Participants belongs in the Results
section. Exclusion criteria should stay in this paragraph.
2. I am not entirely sure what a "low threshold" drop-in policy is?
Perhaps there is/are another word(s) that could be used or the term could be
explained?
3. I would prefer to know how many patients, and the proportion of
females, who attend the clinic and test positive annually rather than the
population of Bergen.
Specimen collection
It is probably the electronic upload but organisms should be italicized.
Statistical analysis
I would like to know how many Bootstrap computations were undertaken.
Think about moving the information about the stats packages to where you
describe their uses.
Data
1. The results should commence with a description of the participants, i.e. most
of the paragraph Participants previously mentioned. I would like to know exactly
why the 15 women were excluded from the study, i.e.
proportion pregnant and proportion who had used antibiotics. I would also like to
know the proportions in the various age groups - numbers and % 2. The
information in Table 3 is partly replicated in the text. I think it would be better to
omit most of information in the Results (page 10 paragraph 3) concerning Table
3 and let it speak for itself. Either that or omit Table 3 and put the results in the
text including 95% CI. If Table 3 remains please retitle i.e. remove "shows" from
title.
3. It would be good to have the 95% CI for the PPV and NPV.
Discussion and conclusions
I think the discussion needs to address comparisons with SOLVs. These are an
"express' method which may be more acceptable to women than FCU and have
greater sensitivity and Specificity. The authors need to make their case for FCU
over SOLVs rather than just state that vaginal swabs are not validated by the
manufacturers of the two most commonly used NAATs in Norway.
Schachter J, Chernesky MA, Willis DE, Fine PM, Martin DH, Fuller D, Jordan JA,
Janda W, Hook EW 3rd. Vaginal swabs are the specimens of choice when
screening for Chlamydia trachomatis and Neisseria
gonorrhoeae: results from a multicenter evaluation of the APTIMA assays for
both infections. Sex Transm Dis. 2005 Dec;32(12):725-8.
Chlamydia trachomatis Load at Matched Anatomic Sites: Implications for
Screening Strategies Claude-Edouard C. Michel, Christopher Sonnex,
Christopher A. Carne, John A. White, Jose Paolo V. Magbanua, Elpidio Cesar B.
Nadala, Jr., and Helen H. Lee J Clin Microbiol. 2007 May; 45(5): 1395-1402.
Published online 2007 March 21. doi: 10.1128/JCM.00100-07. PMCID:
PMC1865904
| Abstract | Full Text | PDF-195K |
I think the paper would be enhanced by some reference to comparative
cost effectiveness. The authors may find this recently published paper
useful
Cost-Effectiveness of Screening Strategies for Chlamydia trachomatis
Using Cervical Swabs, Urine, and Self-Obtained Vaginal Swabs in a
Sexually Transmitted Disease Clinic Setting
Diane R. Blake, Nancy Maldeis, Mathilda R. Barnes, Andrew Hardick,
Thomas C. Quinn, and Charlotte A. Gaydos Sex Transm Dis. Author
manuscript; available in PMC 2009 July 16.
PMCID: PMC2711851 Published in final edited form as: Sex Transm Dis.
2008 July; 35(7): 649-655. doi: 10.1097/OLQ.0b013e31816ddb9a.
Manuscript: | Abstract | Full Text | PDF-1.3M |
Small point - so as not to overstate the case, it may be better to use
"proportion of positive tests" rather than "prevalence" in paragraph 3
on page 11 in the Discussion.
6. Are limitations of the work clearly stated?
7. Do the authors clearly acknowledge any work upon which they are
building, both published and unpublished?
Yes to both, but see points above about vaginal swabs and cost
effectiveness.
8. Do the title and abstract accurately convey what has been found?
Yes and No
1. All abbreviations need to be spelt out in full i.e. SDA, CT,
BDPT PCR and BC.
2. Aim rather than Background may better describe the first section
of the abstract.
3. It would be good to know how many Bootstrap replications were
computed and also to see the Bootstrap confidence intervals in the
abstract.
9. Is the writing acceptable?
Yes, some minor grammatical changes required.