Review for 10.1186/1471-230X-12-13 (2012)

Reviewer's report
Title:Chronic fatigue syndrome after Giardia enteritis: clinical characteristics,
disability and long-term sickness absence.
Version: 1Date:25 April 2011
Reviewer: Panayotis Ferentinos
Reviewer's report:
This is an interesting report about clinical characteristics of CFS developing after
a Giardia lamblia epidemic in Norway. I have some questions on sample
recruitment and suggest several points to improve the presentation of the
findings.
- Discretionary Revisions
1. Methods, par. 4: Abbreviations for SF-36 subscales (in accordance with those
used in Fig.1) would be helpful (e.g. PF, RP, BP, etc).
2. Table 3: Abdominal complaints at referral had better be moved to a separate
table and their method of coding briefly explained in a table footnote.
- Minor Essential Revisions
1. Tables 2 and 3 had better been numbered 1 and 2 as they are mentioned
before table 1.
2. Methods, par. 3: the FSS cut-off score of #5 (not >5) is not referred in the
original Krupp paper (where the cut-off score of 4 is reached) but in a paper by
Lerdal et al 2005, which should be cited.
3. Methods: Type of fatigue onset is first mentioned in the discussion section. A
mention about type of fatigue onset (acute, taking weeks and taking months)
should be added and further explained (with preferably more precise time
boundaries) in the Methods section first. For example, if a pt reported fatigue
onset within 6-7 weeks should that be with weeks or months?
4. Methods, Results, par. 1: The gender distribution of the 1262 infected subjects
as well as of the 96 referred participants should be added.
5. Results, par. 2: the percentages reported for depression and anxiety
correspond to n=57 (not 58) pts (11/58=19.0%, 9/58=15.5%). Either correct
percentages or otherwise explain (e.g. Was 1 pt not asked about prior
depression or anxiety?).
6. Results: Add the specifier pts or participants as appropriate everywhere in the
results section.
7. Results, par. 6: the cut-off score for both depression and anxiety in the HADS
subscales is 8 (not 15) (Bjelland et al 2002). Please correct percentages or
explain otherwise. The two HADS subscales had better be named HADS-A and
HADS-D, according to the literature.
8. Discussion, par. 4 (‘There were little differences between the sexes both
regarding concomitant symptoms such as abdominal symptoms and other
symptoms in the early phase of the disease’): A mention of this finding should
first be made in the results and then discussed here.
9. Discussion, par. 4 (‘at the time of referral females reported significantly more
severe abdominal symptoms’): Again, the finding should first be mentioned in the
results. Also, as shown in table 3, abdominal symptoms were only marginally (not
significantly) different between males and females (p=0.06).
10. Discussion, par.2 & conclusion: I may have not understood correctly but pts
in this study were previously exposed to Giardia (and not ‘never exposed to
Giardia’ as stated).
11. Table 1: It should be somehow stated that employment status refers to 38
workers only and education status to 20 students only.
12. Table 2: the word ‘problems’ or ‘difficulties’ should be added to education,
work and house or car items. Moreover, it should be somehow explained that
figures correspond to n (%).
13. Table 3: Again, it should be somehow explained that figures correspond to n
(%).
- Major Compulsory Revisions
1. Methods-patients: How were the 96 pts referred to the fatigue clinic? Were
they previously assessed with e.g. a postal questionnaire? Sampling method
should be further described. Moreover, calculation of the prevalence of CFS on
the basis of the convenience sample of 96 pts only is wrong; A random sample of
non-referrals should also be evaluated for CFS. Therefore, this should be
included in a limitations section in the discussion.
2. Discussion, par. 3 (‘the frequency of CFS was significantly higher among
females’): we cannot reach such a conclusion unless we know the gender
distribution of the 1262 infected subjects.
3. Figure 1b (for male pts and controls) is missing!
Level of interest: An article of importance in its field
Quality of written English: Acceptable
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