Reviewer's report
Title:The incidence and risk factors of herpes simplex virus type 2 after delivery
amongst Zimbabwean women.
Version: 1Date:10 September 2009
Reviewer: Ahti Anttila
Reviewer's report:
The paper focuses on an essential public-health problem by showing a very high
prevalence and incidence of HSV-2 in Zimbabwean women having a birth and
after it. The research question is posed clearly, study materials and data
collection methods well established. There are still some deficits in the
manuscript in the data reporting and statistical analysis, deserving further
attention.
Suggested major compulsory revisions
1. The paper deals both with prevalence and incidence of HSV2. Prevalence
could be added also to the title.
2. Concerning use of prevalence odds ratios, because the studied outcome
(HSV2) is so common, that the prevalence odds ratios (point estimates) are not
interpretabpe as an indication of the size of the risk. It might be more relevent to
use prevalence (risk) ratios instead. Analyses might be straightforward to do e.g.
by using log-binomial regression or a link function.
3. For the incidence RRs (Statistical analyses, page 7 first paragraph) mention
specifically which analysis method was used to calculate significance/CIs?
4. The results of the multivariate analyses on prevalence should also be added to
a new table 2.
5. Recruitment and follow-up of the study materials should be explained in a
more detailed manner: how many women were asked for to participate, how
many refused, how the follow-up was defined, how many were censored due to
drop-out during the follow-up time. This information would be crucial to
understand whether the data represented the pregant female population.
Minor essential revisions
6. Methods, page 5 line 5 (also in the abstract): Why pregancies with 34-36
weeks of gestation were chosen, i.e., pregnancies with rather short gestational
times. Is this average in Zimbabwe, or did you concentrate to a selected group?
7. Statistical analysis page 6 lines 4-5 of the last paragraph: I think that the
infection in the target tissues starts possibly some 4 weeks (?) earlier than the
seroconversion can be observed. When defining the time of infection, please
specify the terminology (you elaborated serological outcome). The alternative is
that you would subtract the estimated delay time from the time of serological
conversion in order to get information on the infection itself. Also information on
the infections is relevant, see the next comment:
8. Possibly the women who had seroconversion observed shortly (6 weeks) after
the delivery had the infection already during the pregnancy? Please discuss this.
9. For table 1. mention in the title that the analyses were done for univariate or
unifactorial level. Showing both the p-value and confidence interval for lines is
not needed, confidence interval should be enough. For marital status, you should
preferably use Married as the reference group because the there were so few
single women in the material.
10. Current table 2, add a line showing person-time. The reader is not yet aware
how did you count the person time, as some women apparently did not give all
the requested samples. On the other hand by assuming that all the 171 women
had a 9-month follow-up one wouldn't get the 15.2 point estimate (neither
assuming a 10 month interval).
11. Current table 2, I didn't understand why the 'Total' column included 10
months, as it was detailed in the text that the last measurement was done nine
months after the delivery. Concerning the two first columns it would have been
more informative to show the data at 6 weeks, 4 months and 9 months as
measured according to the Methods section.
12. Current table 3, delete the P-value as the confidence interval is already
shown. Add that the analyses were done by univariate/unifactorial level (if so).
13. Did you do try any multivariate analysis for the incidence RRs?
Discretionary revisions
14. Introduction 2nd line and the discussion: HSV2 has also many other health
aspects than mentioned, e.g. possibility to contribute to cervical cancer risk;
concerning pregant women particularly possibility to neonatal infection. These
should be discussed.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that U have no competing interests.