Review for 10.1186/1471-230X-2-12 (2002)

Reviewer's report
 13C-Urea Breath Test Threshold Calculation and Evaluation for the Detection of Helicobacter Title:
pylori Infection in Children
Authors:
Ralf Herold (ralf.herold@charite.de )
Michael Becker (michael.becker@charite.de )
 1  8 Jan 2002 Version: Date:
 Prof Francois Mion Reviewer:
 A paper whose findings are important to those with closely related research interests Level of interest:
 Unable to decide on acceptance or rejection until the authors have responded Advice on publication:
to the compulsory revisions
This study deals with the question of threshold calculation of the urea breath test in children. 
As mentioned by the authors, several articles have already been published on this subject, both in the 
adult and pediatric population. 
The authors use original statistical methods to calculate the optimal threshold of the test: I am not very 
familiar with these methods, and a review of their manuscript by a statistician would be advisable. 
I have several concerns regarding the work presented here, that should be addressed by the authors before a decision of publication is made: 
1) first, the proposed threshold of 5.3 or 5.8 delta is significantly higher than recently published threshold
around 3 delta (the authors should add the threshold of the Gambian study (ref 16) that is missing in the
background section): the authors should comment on these discrepancies in the discussion section. Of note is the fact that their Hp negative population has a much higher delta value (median at 2.4) than 
what is usually reported in the literature (see Delvin et al. JPGN 1999;25:59-62, mean delta value of Hp 
negative children at 0.97). My feeling is that differences are mainly due to the way UBTs are performed 
(test meal, citric acid and so on), and that thresholds should be validated by each lab for its own population rather than looking for universal standardisation. 2) Methods are not adequately described: it is unclear whether citric acid was given with the urea, and 
this is an important point, since it has been shown that citric acid solution may increase the distinction 
between Hp positive and negative subjects (see Eggers et al. Eur J Gastroenterol Hepatol 1990;2:437-44, or Leodolter et al. Aliment Pharmacol Ther 1999;13:1057-62 ) (the meal may also decrease the efficacy of the test to distinguish between positive and negative subjects as it may 
increase the 13CO2 enrichment per se ) ; it is unclear whether the presence of Hp on the four biopsy 
specimens was required to state that a patient was Hp positive (in this case, this may explain why their cut-off value is so high), or if the presence of Hp on one biopsy was regarded as sufficient. A second lecture of histological slides with predefined criteria for the diagnosis of Hp infection would be of 
interest, and the pathologist could then be associated as an author of the paper; it is also unclear how 
urea was administered and how breath sampling was managed in children younger than 4 (difficulties may arise in this population for the ingestion of urea and to obtain adequate breath samples at the correct time: this may explain the much larger SD of their threshold compared to the other age groups); 
authors should comment on the fact that the UBT comparison with histology was performed in children 
older than 5, while a significant proportion of UBTs performed alone were so in children much younger. 
3) Minor points: instead of "Hp-antigens" (line 4 of background section), probably read "anti-Hp 
antibodies"; table 1: what "BM (methods of analysis)" stands for ? it is not clear to me what the values of
the vertical axis of figure 1 represent: it would be better is actual number of patients were represented 
(otherwise indicate on the figure the significance of the scale); in figures 2 and 3, plots A and B are probably inverted, if I understand correctly the legends; in figure 3, adding the words sensitivity and 
specificity under their corresponding curves will increase the understanding of the figure. 
Competing interests:
This reviewer was a member of the European BIOMED project which funding helped for the realisation 
of this study. This reviwer was however not involved in the design, realisation or interpretation of this work.