Reviewer's report
Title:Determinants of Consistent Condom Use among Female Sex Workers in
Savannakhet, Lao PDR
Version:4Date:31 October 2014
Reviewer: Thanh Bui
Reviewer's report:
Manuscript ID:
Title: Determinants of Consistent Condom Use among Female Sex Workers in
Savannakhet, Lao PDR
Major Compulsory Revisions
1. In ‘Results’\‘Condom practices with non-regular and regular partners’, and in
Table 1, the authors provided descriptive statistics of condom initiation and
condom use with non-regular versus regular partners. Please test if these
differences are statistically significant and provide p-values for these differences.
If these differences are not statistically significant, the authors cannot make such
conclusions as ‘Consistent condom use decreased the closer the relationship
was between the FSWs and their partners”.
Author response: To be able to show the significance of the variable of having
regular or non-regular partners as a determinant for condom use we expanded
the logistic regression to include all FSW instead of only the FSWs with regular
partners. In this new model you can see that not having a regular partner is
highly significant for consistent condom use. See Table 5 and the results section
“Association between independent variables and consistent condom use”.
Comments: Please carefully address each of these comments below.
1.1. The authors still need to provide statistical tests for differences and p-values
when contrasting condom use with regular versus non-regular partners in the
Table 1. Measures and purposes of the Table 1 are not similar to the Table 5
(see more details in the comments below). At least, in term of statistics, the Table
1 compares condom use with different types of partners of the same individuals
(i.e., female sex workers), mostly; while the independent variable of “having
regular partners” in the Table 5 implies 2 groups: those who had regular partners
versus those who did not.
1.2. What were exactly the questions for consistent condom use in previous 30
days in the Table 1? I assume that there must have been at least 3 different
questions regarding consistent condom use with all sexual partners, with regular
partners, and with non-regular partners; is this correct? If so, please specify
these in the “measure” section. If not, please explain how the percentages of
condom use with regular vs. non-regular partners in the Table 1 were calculated?
1.3. What question/variable was used as the dependent variable in Table 5? I
assume that it is “consistent condom use in previous 30 days with all sexual
partners”, is this correct? Please specify the dependent variable in the “Data
Analysis” section and also in the Table 5. And if so, why is the n only 82 (i.e.,
regular-partner group only)?
2. In ‘Data Analysis’, given the descriptive aim of this study, why did the authors
need to perform multiple regression? Even if the authors chose to do so, which
variable were selected into the multiple regression models, based on which
criteria, and using which methods? The authors said that ‘Number of sexual
partners last week was included in the multiple logistic regression as a
confounding variable.’ If number of sexual partners last week was considered a
potential confounder, then it was confounding an association between the
outcome (consistent condom use) and which main independent variable? Why
was it so? This section needs to be carefully rewritten.
Authors’ response: We decided to use a logistic regression model for analysis to
establish the determinants of consistent condom use. We have after your review
comments developed a new logistic regression model; we decided to exclude
number of sexual partners as a confounding variable in the new model. Please
see the revisions in the “Data analysis” section.
Comments:
2.1. As in my comment # 1.3. above, the purpose and the methods for Table 5
(or more correctly, for building logistic regression models) are still unclear. The
“Data analysis” section needs to be edited and elaborated in details.
2.2. In my initial comment, I did not mean to include “number of sexual partners”
in the regression model. It was just the term (e.g. confounding) and the way the
authors wrote it was not appropriate. In this revision, the authors remove
“number of sexual partners” out of the model. Why is it so?
2.3. The authors wrote that “The independent variables that were significant
(p-value <0.05) in the bivariate analysis were included in a multiple logistic
regression analysis.” Please cite a statistical method paper that suggests a
cut-off point of <.05. To my knowledge, common cut-off points for inclusion into
multiple regression models (not for conclusion of significance) are .20 or .25.
2.4. The authors write that “Bivariate logistic regression was first applied to see
the association between consistent condom use and the independent variables:
age, time in sex work, having regular partners, education level, marital status,
having children, number of sexual partners, had received information on
condoms from the drop-in centre, if condoms were received for free, affordability
of condoms and having enough condoms.” Please report all of these association
results and p-values in the Table 5 (in the Crude OR column), even though some
of them are not statistically significant. These results will be very informative for
readers who want to know about what are risk factors and what may be not risk
factors of condom use among female sex workers in Laos.
3. The authors have addressed my initial comment adequately. However, please
consider the new comment #2.4 above.
4. The authors have addressed my initial comment adequately.
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests.