Reviewer's report
Title:Menstrual bleeding patterns: a community-based cross-sectional study
among women aged 18-45 years in Southern Brazil
Version: 1Date:4 August 2010
Reviewer: Mark Shapley
Reviewer's report:
This was an interesting paper on the symptoms of menstrual loss in women
attending primary care. I enjoyed reading the study and clearly the authors have
put considerable effort in to undertaking the study for which they should be
congratulated. Whilst I liked some aspects of the study very much I had some
concerns regarding others.
There are a number of methodological issues that need to be taken in to account
when considering the validity of the findings.
Major compulsory revision
1. The questionnaire
Information is lacking concerning the actual question that was used to determine
the heaviness of menstrual bleeding and how the women were classified into
heavy, normal or light.
It was good to see an attempt to validate the questionnaire with an objective
measure but I am not sure that used adds much for two reasons.
There is controversy concerning whether or not assessment of heavy menstrual
bleeding should be via objective or subjective means with the argument for the
former being that there is poor correlation between the subjective assessment
and actual loss whilst the latter is the currency of the consultation. Thus
self-reported symptoms have validity in their own right provided they are used in
the appropriate context. This would suggest that there was no need to undertake
an “objective” assessment.
The method used to “objectively” measure the degree of blood loss is not the
accepted “gold standard” (the alkaline haematin method) and may correlate
better with fluid rather than blood loss. The authors report a correlation and dose
response curve between degree of reported menstrual loss and objective
assessment but they do not report the degree of misclassification (e.g. in results
the “average” weight is probably the median as the weights are probably not
normally distributed and no inter quartile range is given). There are already
several studies showing that there is a poor correlation between subjective and
objective assessment of menstrual blood loss. I feel they have over-interpreted
their results in the discussion with comments such as “self-perception is a
reliable estimate of blood loss” as the study was not set up to test this. I do not
believe they can claim that the “woman self-perception of the intensity of
bleeding is a reliable estimate of blood loss” as they have not used the gold
standard, nor done the appropriate analyses and these statements contradicts
several studies in the established literature.
Discretionary revision
2. The sample
The women were selected from those in primary care waiting rooms who were
consulting for any reason and those accompanying them. They were thus not
strictly a community population and not a consulting population but a mixture.
Consulting behaviour is known to be associated with the reporting of symptoms
in general and this is relevant in comparing the results of studies.
It is difficult to ascertain as to how the women were selected in the waiting room
(all? random? consecutive?) but it is implied that all were approached. There is
no information as to how the non-responders differed from the participants
(?age).
There are good statements in the discussion concerning other aspects of the
generalisability of the study.
3. Power calculation
The sample size was determined by another study and this needs to be stated
but I am not sure doing a power calculation for this study adds anything as
confidence intervals are given in the results.
4. Menstrual morbidity
In the discussion this term is used when the authors have not detected “illness”
but reported symptoms. It should not be assumed that just because a symptom is
reported it constitutes morbidity as it may not be causing physical, social or
emotional distress or interfering with function or lead on to any of these.
Minor essential revisions
5. Typos/use of English
Several typos exist (e.g. methods: alfa for alpha, results: average number of
formal education … IC95% for CI 95%) and it may be better to use the term
“male barrier contraception” rather than “preservatives”.
In summary the data on the prevalence of subjective heavy menstrual bleeding
and its associations are interesting but constrained by some concerns regarding
generalisability. The data and conclusions regarding the objective assessment of
menstrual loss are tenuous, as the study was not originally set up to investigate
this.
Level of interest: An article whose findings are important to those with closely
related research interests
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