Reviewer's report
 Risk factors for hepatitis C virus infection among blood donors in southern Brazil: a case-control Title:
study
Authors:
Ajacio BM Brandao (ajacio@via-rs.net )
Sandra C Fuchs (scfuchs@zaz.com.br )
 2  17 May 2002 Version: Date:
 Prof Charles Hoff Reviewer:
 A paper whose findings are important to those with closely related research interests Level of interest:
 Accept after discretionary revisions Advice on publication:
Since my task is to critique the design and statistical aspects of this ms., I will confine my remarks to 
these topics. 
In my opinion, this is an appropriately designed study with a thoughtful approach to statistical analysis 
and interpretation of results. The authors acknowledge aEoethat the eligible donors were in good health
and did not represent the general populationaE. Thus, they recognize that findings are not completely 
generizable to the population-at-large. I note that in the abstract-results section, they state that a 
aEoerepresentative sample of 178 anti-HCV positive cases and 356 controls were investigated.aE 
However, in the abstract-methods section the numbers are 137 and 274, respectively. I could not find 
an explanation as to why these numbers are different and, unless I have missed it, the authors should 
address this in the ms. 
Sample size estimates for controls and cases were based on a 2:1 ratio of controls to cases and 
acceptable parameters for univariate comparisons. The sample estimates were then increased 30% to 
allow for multivariate analyses and adjustment for confounding factors. Multivariate sample size 
estimation is a bit problematic, but I am inclined to accept their argument. Multivariate analytic approaches were hierarchical in nature and the authors have not chosen stepwise models. An 
hierarchical approach seems justified since larger sample sizes would probably be required for stepwise
regression and, if conducted, Type I error rates could be inflated. Still, for exploratory purposes, it would
have been interesting to see whether the same models were generated in both a forward and backward 
stepwise regression. The use of P values ranging between .05 and .10 as indicating possible trends 
also seems justified in my opinion. 
In general, this is a well-written ms., but I noted a few minor typos/syntactical errors. According to the 
ms. I downloaded, they are: (i) page 2, next-to-last line from the bottom: aEoeeighthaE should be 
aEoeeightaE; (ii) page 6, next-to-last line from the bottom: aEoeSince have being incarcerated doaE, 
this portion of the sentence needs to be rewritten; (iii) page 6, last-line: aEoeassociated toaE should be aEoeassociated withaE. 
Competing interests:
None declared.
Reviewer's report
 Risk factors for hepatitis C virus infection among blood donors in southern Brazil: a case-control Title:
study
Authors:
Ajacio BM Brandao (ajacio@via-rs.net )
Sandra C Fuchs (scfuchs@zaz.com.br )
 2  17 May 2002 Version: Date:
 Prof Charles Hoff Reviewer:
 A paper whose findings are important to those with closely related research interests Level of interest:
 Accept after discretionary revisions Advice on publication:
Since my task is to critique the design and statistical aspects of this ms., I will confine my remarks to 
these topics. 
In my opinion, this is an appropriately designed study with a thoughtful approach to statistical analysis 
and interpretation of results. The authors acknowledge aEoethat the eligible donors were in good health
and did not represent the general populationaE. Thus, they recognize that findings are not completely 
generizable to the population-at-large. I note that in the abstract-results section, they state that a 
aEoerepresentative sample of 178 anti-HCV positive cases and 356 controls were investigated.aE 
However, in the abstract-methods section the numbers are 137 and 274, respectively. I could not find 
an explanation as to why these numbers are different and, unless I have missed it, the authors should 
address this in the ms. 
Sample size estimates for controls and cases were based on a 2:1 ratio of controls to cases and 
acceptable parameters for univariate comparisons. The sample estimates were then increased 30% to 
allow for multivariate analyses and adjustment for confounding factors. Multivariate sample size 
estimation is a bit problematic, but I am inclined to accept their argument. Multivariate analytic approaches were hierarchical in nature and the authors have not chosen stepwise models. An 
hierarchical approach seems justified since larger sample sizes would probably be required for stepwise
regression and, if conducted, Type I error rates could be inflated. Still, for exploratory purposes, it would
have been interesting to see whether the same models were generated in both a forward and backward 
stepwise regression. The use of P values ranging between .05 and .10 as indicating possible trends 
also seems justified in my opinion. 
In general, this is a well-written ms., but I noted a few minor typos/syntactical errors. According to the 
ms. I downloaded, they are: (i) page 2, next-to-last line from the bottom: aEoeeighthaE should be 
aEoeeightaE; (ii) page 6, next-to-last line from the bottom: aEoeSince have being incarcerated doaE, 
this portion of the sentence needs to be rewritten; (iii) page 6, last-line: aEoeassociated toaE should be aEoeassociated withaE. 
Competing interests:
None declared.
Please review this paper.
user
Reviewer's report
 Risk factors for hepatitis C virus infection among blood donors in southern Brazil: a case-control Title:
study
Authors:
Ajacio BM Brandao (ajacio@via-rs.net )
Sandra C Fuchs (scfuchs@zaz.com.br )
 2  17 May 2002 Version: Date:
 Prof Charles Hoff Reviewer:
 A paper whose findings are important to those with closely related research interests Level of interest:
 Accept after discretionary revisions Advice on publication:
Since my task is to critique the design and statistical aspects of this ms., I will confine my remarks to 
these topics. 
In my opinion, this is an appropriately designed study with a thoughtful approach to statistical analysis 
and interpretation of results. The authors acknowledge aEoethat the eligible donors were in good health
and did not represent the general populationaE. Thus, they recognize that findings are not completely 
generizable to the population-at-large. I note that in the abstract-results section, they state that a 
aEoerepresentative sample of 178 anti-HCV positive cases and 356 controls were investigated.aE 
However, in the abstract-methods section the numbers are 137 and 274, respectively. I could not find 
an explanation as to why these numbers are different and, unless I have missed it, the authors should 
address this in the ms. 
Sample size estimates for controls and cases were based on a 2:1 ratio of controls to cases and 
acceptable parameters for univariate comparisons. The sample estimates were then increased 30% to 
allow for multivariate analyses and adjustment for confounding factors. Multivariate sample size 
estimation is a bit problematic, but I am inclined to accept their argument. Multivariate analytic approaches were hierarchical in nature and the authors have not chosen stepwise models. An 
hierarchical approach seems justified since larger sample sizes would probably be required for stepwise
regression and, if conducted, Type I error rates could be inflated. Still, for exploratory purposes, it would
have been interesting to see whether the same models were generated in both a forward and backward 
stepwise regression. The use of P values ranging between .05 and .10 as indicating possible trends 
also seems justified in my opinion. 
In general, this is a well-written ms., but I noted a few minor typos/syntactical errors. According to the 
ms. I downloaded, they are: (i) page 2, next-to-last line from the bottom: aEoeeighthaE should be 
aEoeeightaE; (ii) page 6, next-to-last line from the bottom: aEoeSince have being incarcerated doaE, 
this portion of the sentence needs to be rewritten; (iii) page 6, last-line: aEoeassociated toaE should be aEoeassociated withaE. 
Competing interests:
None declared.
assistant