Review for 10.1186/1471-230X-12-69 (2012)

Reviewer's report
Title:A low level of serum total testosterone is independently associated with
nonalcoholic fatty liver disease.
Version: 1Date:22 February 2012
Reviewer: Lars Moeller
Reviewer's report:
Kim et al. investigated the association of serum total testosterone with non
alcoholic fatty liver disease in 495 male probands who underwent abdominal
ultrasound, abdominal CT scans (to measure visceral adipose tissue, VAT) and
measurement of total serum testosterone. Patients with alcohol consumption
>140g/d or hepatitis were excluded from the study. The authors find that
probands with NAFLD had significantly lower total testosterone levels. The result
is that the association between total testosterone levels and the odds ratio for
presence of NAFLD was significant, even after adjusting for potential
confounders such as age, BMI, diabetes, HOMA-IR and VAT.
Comments:
The manuscript is well written and the results are clearly presented in three
tables and one figure. The results seem valid, are in accordance with previous
reports from other groups and are of interest, as it goes beyond previous studies
by inclusion of VAT measurement.
Major Revision:
1. Study design: please state whether this cross sectional study was a
prospective or retrospective study.
2. It is understood that the sample is a convenience sample because only the
participants who underwent measurement of testosterone, ultrasound and
abdominal CT scans could be included.
The original population was comprised of healthy men visiting the clinic for
routine health checkups. It appears that roughly 7200 of 28600 men then
received an abdominal CT scan and ultimately 495 of those men could be
included in the study. I wonder why a CT scan was ordered in healthy men at a
routine checkup? What conditions required a CT and what was found? Did these
men then receive a diagnosis from those CTs or the condition leading to the CT
and can therefore not be labeled “healthy” anymore?
My concern is: if the CT scan was not a pre-planned diagnostic tool in a
prospective study, then including only men that required a CT scan for medical
reasons harbours the risk of introducing a strong selection bias. The present
study seems to include only those men that were selected because they received
a CT scan for medical reasons that are left unexplained. As it is exactly this CT
scan that allows measurement of VAT, and that sets this study apart from others,
it is absolutely necessary to explain why a CT scan was ordered in the first place.
The “Methods” part starts with “This study is … one of healthy … men …”. Is that
still true after examining the reasons for and results of the CT scans?
In short, the reader needs to know:
- for what reason were CT scans ordered?
- what were the main findings in the CT scans of these men, the study
population: are they still healthy?
- for the discussion: do the CT scan results suggest a selection bias?
Level of interest: An article of importance in its field
Quality of written English: Acceptable
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.