Non-invasive indirect tests
Ureolytic based tests
13C-urea breath technique
UBT as a direct non-invasive test with diagnostic accuracy of >95% (sensitivity >95%, Specificity >95%) is easy to perform and based on urea hydrolysis achieving within gastric mucosal epithelial cells produces ammonia and CO2. In this test, when an individual with H.pylori infection ingests 13C-labled urea, H.pylori as a famous urease enzyme producer breaks down the urea and the labeled CO2 will be monitored within a short time. It takes 2h for collecting the breath samples of patients. Also, a single sample is collectable in 40 min by the help of hyamine as a CO2 trapping agent for exhaling into it. Finally, the percentage of radioactivity of each sample is calculated by a scintillation counter. 13C has a non-radioactive property; so, the test is safe for children and pregnant women. UBT is occurred in different manners such as meal-based 13C UBT, tablet-based 13C UBT and, 14C UBT. Recently, the tablet-based 13C UBT is recommended. Different reports confirm UBT as an accessible, accurate, safe and practical test (45, 48, 58-62).
Serum bicarbonate and Ammonia vapor tests
In addition to UBT, there are other ureolytic techniques including serum bicarbonate and ammonia vapor which have their special applications. In serum bicarbonate test, the measure of serum 13C-carbonate is evaluated. This test is reliable and suitable as post-treatment setting (46).
Ammonia vapor test is used for assessing the level of ammonia gas in the patient breath. This method is absolutely cost effective method (46, 63).
Serologic tests are divided into four formats including the Enzyme-Linked ImmunoSorbant Assay (ELISA), agglutination, Western blotting, and immunochromatography (45, 46, 64).
Serologic tests regarding to H.pylori infection diagnosis, are designed for detecting specific antibodies such as anti- H.pylori IgG antibodies or anti- CagA and anti- VacA antibodies. In adults, the preferable sample is serum, while in children is saliva or urine. Serologic diagnostic tools are cheap with high limitations. However, the serologic tests are common and accessible in a wide range. Depending on the type of serologic tests, their sensitivity is up to 90-97% and the specificity of them varies from 50-96%. Thus, each serologic test must be used in validated settings. Some of the serological commercial kits are suitable and available (43, 45, 46, 48, 65).
Serologic tests are not capable to distinguish active infection from previous contact. Today, serologic tests are the third common techniques between non-invasive tools for diagnosing H.pylori infection. According to previous reports, the use of combined serologic methods may increase the sensitivity and the specificity of the tests (45, 46, 48, 65, 66).
Salivary and urinary tests
For decreasing the stressful condition of venipuncture in children, serum test is replaced by saliva or urine tests in...