Med Sci Monit 2004; 10(9): LE17-18
Available online: 2004-09-01
Thank you for the opportunity to answer the interesting comments raised by C.M. Pathak, Ph.D. et al, referring to the article pertaining to our group .
1) First of all I want to thank C.M. Pathak, Ph.D. et al. for his thorough analysis, comments and discussion.
2) I am very happy of their letter title, which overall I agree with, because they also believe 14C-urea breath test largely qualifies to be gold standard for H. Pylori detection, even though the grounds for their statement may be different.
3) The options indicated by C.M. Pathak, Ph.D. et al to explain false positive cases were discarded by us. In brief, a) Contaminated vials were not employed and all our material was new and disposable; b) We did not prepare any standard and results were given in DPM; c) We used a capsule, which only dissolves in the stomach; d) Capsules were checked carefully at the time of preparation as they were provided directly by the laboratory (Tri-Med Specialists) applying for FDA approval at the moment of the research; E) It was our very same hypothesis.
4) All possible causes producing chemiluminescence were also ruled out before starting clinical studies:
We used Econo-Safe as scintillation liquid, also recommended by Tri-Med Laboratories. Regarding other factors increasing chemiluminescence, especifically as CM Pathak, Ph.D. et al. mention, our samples were measured after 24 h storage and at room temperature (rather cool in our city). Background was measured routinely and substracted from the patient sample counts. Again, all material was new, used once and discarded after utilization in every patient.
5) The higher DPM (range 214–4253) in 14 biopsy based H.pylori negative patients (Table 3) are clearly coming from the samples themselves because contamination was ruled-out.
6) In relation to Figure 1, indeed it only contains 10 duplicate measurements. Dot 11 mentioned by C.M. Pathak, Ph.D. et al, is part of the identity line, as it is dot at 0 value. Something occurred when plotting the graph in final electronic format. I enclose same graph with values included, without these 2 dots.
7) As our data is from the real world, we have 1 outlier point out of the 10 samples, commented by CM Pathak, Ph.D. et al. This sample gave higher counts at Tri-Med Specialities Laboratory (USA) and lower counts in our laboratory. Needless, to say that only these 10 cases were sent abroad and all patients part of the work published, were measured in Chile at the University of Chile laboratories, so there is no reason to anticipate higher counts, but on the contrary.
8) “Average radioactive count in breath samples was found to be 649±1029 DPM in patients considered negative for H. pylori by two or more invasive techniques using one 14C-UBT as a tracer dose”. High counts in this group are easily explained, because some of these cases are the false positive according to the gold standard we are challenging.
9) Regarding the amount of water used, we missed to mention in the publication that a second bolus of 20 mL was given to the patient after the first swallow, totaling 40 mL. We agree that it is probably better to use 200–300, but as these patients were part of a protocol previously designed, we did not want to modify this parameter.
10) Again, the protocol we followed required the results be delivered in DPM, used also in several other publications. We do not believe this factor could explain any of the results found by us.
Finally, We agree “that [sup]14[/sup]C-UBT is a very accurate test for detecting H. pylori infection with sensitivity and specificity better than many other tests for H.pylori. [sup]14[/sup]C-UBT detects much lower levels of active H.pylori infection and by assessing the entire gastric mucosa avoids the risks of sampling error. [sup]14[/sup]C-UBT is a readily available simple test that can be used as a ‘gold standard’ against which the other tests for H.pylori can be compared”.
1. Gonzalez P, Galleguillos C, Massardo T et al: Could the [14C]
urea breath test be proposed as a ‘Gold Standard’ for detection of
Helicobacter pylori infection ? Med Sci Monit, 2003; 9(8): 363–368
Keywords: Tri-Med Laboratories