Teste respiratório com uréia marcada com carbono-13 no diagnóstico da infecção gástrica por helicobacter pylori: análise de um banco de dados com ênfase especial na diferença dos valores do teste entre os sexos

Abstract

13C labelled urea breath test (UBT) is regarded as excellent tool in the diagnosis of infection caused by H. pylori, because of its high accuracy level, sensitivity and specificity higher than 95%. There are, however, doubts concerning the correspondence between the absolute values of the tests in men and women. Aims: To evaluate how UBTs absolute values and sex relate, by taking into account variables such as age, weight, height, body mass index (BMI) aiming at contributions to the epidemiologic and pathogenic aspects of gastric infection caused by H. pylori in the human being. Patients and Methods: A retrospective cross-sectional study, based on the analysis of the database of Breath Tests Laboratory from University Hospital at Federal University of Minas Gerais (UFMG), containing 18.489 UBT, carried out between July 1998 and November 2010. The variables analyzed were age, sex, height (cm), weight (Kg), body mass index (BMI) (Kg/m2) and the absolute value of UBT as delta over baseline (DOB). UBT was carried out with the use of an infrared isotope analyzer (IRIS®, Wagner Analysen-Technik, Bremen, Germany). To sum up, after an overnight fast the patients drank 75mg of 13C-urea in 200 ml orange juice. Samples of the air exhaled were collected before and 30 minutes after the ingestion of the substrate. Values above 4 DOB at 30 min were considered positive. A statistical analysis was conducted with the use of Minitab-16, Excel-2007, Mann-Whitney test and qui-square test. For all these tests significance = 0.05 was adopted. The study was approved by UFMGs Ethics Committee. Results: 12,902 patients [7,612 women (59%) and 5,290 men (41%), average age of 46.4 (1- 96, SD:16.8)] years met the criteria of the investigation and were included in the study. UBT was positive in 3,904 (30%) and negative 8,998 (70%) patients. Among the patients infected by H. pylori, UBT median absolute values were significantly higher for the women (23.3 DOB) than for men (18.4 DOB) (p<0,000), except in the 0-10 age range, where there was no statistical difference. The other variables studied in the infected population revealed: the median age of women was 46 years old and mens was 44 years old (p=0.0093), the median height of 159cm among women and 170cm among men (p<0,000), the median weight of 62Kg among women and 70Kg among men (p<0.000) and the median BMI of 24.8 Kg/m2 among women and 24.2 Kg/m2 among men (p=0.0093), the differences observed being somehow irrelevant from a clinical point of view. All of the positive patients (n=3.904) were allocated in four quartiles, with ascending values of DOB, demonstrating that as UBT absolute values ascend, so does the percentile of female patients in the quartile groups (p=0.000). Conclusion: Among adult women the UBT absolute values found were significantly higher than the value for men, suggesting that they are more densely infected than men. Such findings may have clinical consequences and the epidemiological and therapeutic studies should take the findings reported here into consideration. Future studies should be carried out in order to throw light on the bacterial load observed among the female population