Question

Hospital Setting: The facility is a 300-bed hospital which includes general medical, obstetrical, surgical and emergency services. You are one of two technologists working first shift in immunology. Routine and high complexity testing is performed.

Patient Information: Janet Carson is a 56-year old female presenting to the emergency department with right upper quadrant pain that is penetrating to her back. She states that this is independent of eating. She also states that she has lost 10 lb. involuntarily in the last 4 or 5 months. The physician has ordered serologic testing for H. pylori.

1.      What is the suspected diagnosis leading to the H. pylori test order?

2.      Describe the advantages of serologic testing for H. pylori over more direct methods, such as culture.

3.      Describe how the serologic testing may be of use after treatment with antibiotics and antisecretory agents.

can you answer these questions for this case study, detailed please.

Answer 1

1. Helicobacter pylori infections usually do not lead to signs or symptoms. But if someone develops signs or symptoms, it is more like peptic ulcer symptoms. In this case study, the patient has pain in the right upper quadrant, which is penetrating to her back. The pain is not associated with eating. The most striking symptom which leads to the H. pylori test order is the unintentional weight loss over a span of 4-5 months. The patient reports that she has lost over 10 lb in the aforementioned time span involuntarily. Serological testing will provide evidence of H. pylori infection in the patient's body and gives an idea of the global distribution of H. pylori inside the stomach, even if irregularly distributed.

2. Diagnosis of H. pylori infection is done by various invasive and non-invasive techniques. Invasive techniques include endoscopy and biopsy (for example, histological examination, culture or rapid urease test). Non invasive techniques are of two types : active and passive tests. Active non-invasive tests include urea breath test and the stool antigen test that detects active infection. Serology, urine examination and near-patient tests are in nature passive tests as these serve as markers of exposure to H. pylori infection but do not provide indications of active infection.

Culturing of Helicobacter is quite cumbersome, as they can be obtained and cultured from gastric biopsies (invasive). Helicobacter is very fragile when taken outside the gastric environment. Therefore even after biopsy samples are collected they need to be transported quickly and steps need to be taken immediately for isolation of the bacterial colonies. The biopsies can be kept in transport medium for for at most 24h at 4^oC. The culture plates need to be incubated for 5 days, even though H. pylori colonies appear after 3 days. Although the culture technique is highly specific, it is less sensitive and is associated with a number of problems.

In contrast, serological testing is cost-effective, far more accurate, requires minimal equipments and are very rapid. Serological testing involves three formats: enzyme linked immunosorbent assay (ELISA), latex agglutination tests and another test based on Western blotting. ELISA detects the total content of immunoglobulin in patients' serum samples and can also detect any of the isotypes. Any particular antibody response to a specific antigen can also be probed. Latex agglutination tests can also detect all immunoglobulin isotypes. In the third test, specific antigens are subjected to gel electrophoresis and transferred to membrane and probed with patient's serum sample to detect the presence of the antibody / immunoglobulin. Allisotypes can be detected by this test as well. Therefore serological testing is cheaper, convenient, does not require elaborate apparatus or experimental set up, and can be used in situations where additional information by endoscopy or other invasive techniques is not needed. It can be used as a routine test.

3. After the patient is treated with recommended antibiotics and anti-secretory agents to treat H. pylori infection, she can be recommended to repeat the serological testing four weeks after treatment. Since serological tests are based on the presence of specific anti-H. pylori IgG antibodies in the patient's serum sample, a post -treatment testing can provide an idea of the antibody titer. Usually if the treatment has worked then the titer should be less, but if the infection is still persistent, then the antibody titer will increase. This can highlight the efficacy of the ongoing treatment, and may indicate a change of drugs, if required.