Reviewer's report
Title:Susceptibility to intestinal infection and diarrhoea in Zambian adults in
relation to HIV status and CD4 count
Version: 2Date:9 October 2008
Reviewer: Joanna Stewart
Reviewer's report:
The following is limited to a statistical review of the paper
Major
1. The data reported is clustered by individual as there are up to 36 data points
reported per person. The authors demonstrate that in fact there is a strong
cluster effect at least in occurence of disease but it appears many of the
statistical analyses quoted have not included a random person effect in the
model. Ignoring the person effect could possibly make the p values quoted quite
incorrect if in fact for example the relationship of infection and diarrhoea differs in
different people. All p values quoted should come from analyses including a
person effect.
2. What was the timing of the measure of infection compared to diarrhoea? Was
it the data from the end of the month with the diarrhoea being from during the
preceeding month? Is this timing issue going to cause a problem in that the
diarrhoea episode may have occured 4 weeks earlier? In fact an episode may
occur a couple of days after the stool collection but would be associated with the
infections a month later. At the very least the timing issue needs discussion
Minor
Table 3 in the third line of the paragraph 'Association between infection and
reported symptoms of diarrhoea' should be table 4
Discretionary
It is not clear why there are p values in table 1. Are these testing the difference of
each of the other factors by gender? If this is so they would seem unnecessary
are this would not seem relevant to the study. Simply displating the
demographics is all that is required.
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
Reviewer's report
Title:Susceptibility to intestinal infection and diarrhoea in Zambian adults in
relation to HIV status and CD4 count
Version: 2Date:9 October 2008
Reviewer: Joanna Stewart
Reviewer's report:
The following is limited to a statistical review of the paper
Major
1. The data reported is clustered by individual as there are up to 36 data points
reported per person. The authors demonstrate that in fact there is a strong
cluster effect at least in occurence of disease but it appears many of the
statistical analyses quoted have not included a random person effect in the
model. Ignoring the person effect could possibly make the p values quoted quite
incorrect if in fact for example the relationship of infection and diarrhoea differs in
different people. All p values quoted should come from analyses including a
person effect.
2. What was the timing of the measure of infection compared to diarrhoea? Was
it the data from the end of the month with the diarrhoea being from during the
preceeding month? Is this timing issue going to cause a problem in that the
diarrhoea episode may have occured 4 weeks earlier? In fact an episode may
occur a couple of days after the stool collection but would be associated with the
infections a month later. At the very least the timing issue needs discussion
Minor
Table 3 in the third line of the paragraph 'Association between infection and
reported symptoms of diarrhoea' should be table 4
Discretionary
It is not clear why there are p values in table 1. Are these testing the difference of
each of the other factors by gender? If this is so they would seem unnecessary
are this would not seem relevant to the study. Simply displating the
demographics is all that is required.
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
Please review this paper.
user
Reviewer's report
Title:Susceptibility to intestinal infection and diarrhoea in Zambian adults in
relation to HIV status and CD4 count
Version: 2Date:9 October 2008
Reviewer: Joanna Stewart
Reviewer's report:
The following is limited to a statistical review of the paper
Major
1. The data reported is clustered by individual as there are up to 36 data points
reported per person. The authors demonstrate that in fact there is a strong
cluster effect at least in occurence of disease but it appears many of the
statistical analyses quoted have not included a random person effect in the
model. Ignoring the person effect could possibly make the p values quoted quite
incorrect if in fact for example the relationship of infection and diarrhoea differs in
different people. All p values quoted should come from analyses including a
person effect.
2. What was the timing of the measure of infection compared to diarrhoea? Was
it the data from the end of the month with the diarrhoea being from during the
preceeding month? Is this timing issue going to cause a problem in that the
diarrhoea episode may have occured 4 weeks earlier? In fact an episode may
occur a couple of days after the stool collection but would be associated with the
infections a month later. At the very least the timing issue needs discussion
Minor
Table 3 in the third line of the paragraph 'Association between infection and
reported symptoms of diarrhoea' should be table 4
Discretionary
It is not clear why there are p values in table 1. Are these testing the difference of
each of the other factors by gender? If this is so they would seem unnecessary
are this would not seem relevant to the study. Simply displating the
demographics is all that is required.
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
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