Endoscopic biopsy pathology of Helicobacter pylori gastritis. Comparison of bacterial detection by immunohistochemistry and Genta stain

A comparative systematic review and meta-analysis on the diagnostic accuracy of non-invasive tests for Helicobacter pylori detection in elderly patients

Background

Helicobacter pylori (H. pylori) infection, a type I carcinogen, affects approximately 50% of the global population, correlating with various gastric pathologies. Notably, diagnostic sensitivities of non-invasive methods, such as the stool antigen test (HpSA), Serology, and Urea Breath Test (UBT), have been suggested to be less effective in older age groups. This study systematically reviews and meta-analyzes the diagnostic accuracy of these tests within the elderly population.

Methods

A comprehensive literature search was performed across multiple databases, including PubMed, Medline, and Web of Science, up to July 2023. Data were pooled and analyzed using random-effects models. Sensitivity, specificity, and Diagnostic Odds Ratios (DOR) were computed for the tests. Heterogeneity and risk of bias were assessed.

Results

Eight studies involving diverse geographic locations and totaling between 46 and 1,441 participants per study were included. The pooled sensitivity and specificity for HpSA were 72.5 and 94.7%, for Serology 83.7 and 73.3%, and for UBT 96.4 and 88.3%, respectively. DOR for UBT, HpSA, and Serology were 94.5, 47.9, and 14.2, respectively. High levels of heterogeneity were observed across the studies.

Conclusion

UBT and HpSA proved effective for diagnosing H. pylori in those over 60, while serology showed lower specificity. Despite methodological variations in available studies, these non-invasive tests offer reliable alternatives, especially for older patients who recently undergone endoscopy or without an indication for it, warranting consideration by healthcare practitioners.

Practice guidelines for the management of Helicobacter pylori infection: The Saudi H. pylori Working Group recommendations

The eradication rates for Helicobacter pylori globally are decreasing with a dramatic increase in the prevalence of antibiotic resistant bacteria all over the world, including Saudi Arabia. There is no current consensus on the management of H. pylori in Saudi Arabia. The Saudi Gastroenterology Association developed these practice guidelines after reviewing the local and regional studies on the management of H. pylori. The aim was to establish recommendations to guide healthcare providers in managing H. pylori in Saudi Arabia. Experts in the areas of H. pylori management and microbiology were invited to write these guidelines. A literature search was performed, and all authors participated in writing and reviewing the guidelines. In addition, international guidelines and consensus reports were reviewed to bridge the gap in knowledge when local and regional data were unavailable. There is limited local data on treatment of H. pylori. The rate of clarithromycin and metronidazole resistance is high; therefore, standard triple therapy for 10-14 days is no longer recommended in the treatment of H. pylori unless antimicrobial susceptibility testing was performed. Based on the available data, bismuth quadruple therapy for 10-14 days is considered the best first-line and second-line therapy. Culture and antimicrobial susceptibility testing should be considered following two treatment failures. These recommendations are intended to provide the most relevant evidence-based guidelines for the management of H. pylori infection in Saudi Arabia. The working group recommends further studies to explore more therapeutic options to eradicate H. pylori.

Immunohistochemical diagnosis of human infectious diseases: a review

BACKGROUND

Immunohistochemistry (IHC) using monoclonal and polyclonal antibodies is a useful diagnostic method for detecting pathogen antigens in fixed tissues, complementing the direct diagnosis of infectious diseases by PCR and culture on fresh tissues. It was first implemented in a seminal publication by Albert Coons in 1941.

MAIN BODY

Of 14,198 publications retrieved from the PubMed, Google, Google Scholar and Science Direct databases up to December 2021, 230 were selected for a review of IHC techniques, protocols and results. The methodological evolutions of IHC and its application to the diagnosis of infectious diseases, more specifically lice-borne diseases, sexually transmitted diseases and skin infections, were critically examined. A total of 59 different pathogens have been detected once in 22 different tissues and organs; and yet non-cultured, fastidious and intracellular pathogens accounted for the vast majority of pathogens detected by IHC. Auto-IHC, incorporating patient serum as the primary antibody, applied to diseased heart valves surgically collected from blood culture-negative endocarditis patients, detected unidentified Gram-positive cocci and microorganisms which were subsequently identified as Coxiella burnetii, Bartonella quintana, Bartonella henselae and Tropheryma whipplei. The application of IHC to ancient tissues dated between the ends of the Ptolemaic period to over 70 years ago, have also contributed to paleomicrobiology diagnoses.

CONCLUSION

IHC plays an important role in diagnostic of infectious diseases in tissue samples. Paleo-auto-IHC derived from auto-IHC, is under development for detecting non-identified pathogens from ancient specimens.

Efficacy of immunohistochemical staining in detecting <em>Helicobacter pylori</em> in Saudi patients with minimal and atypical infection

Gastric Helicobacter pylori infection is diagnosed based on histopathological evaluation of gastric mucosal biopsies, urease test, urea breath test, H. pylori culturing, or direct detection using polymerase chain reaction (PCR). This study aimed to evaluate the efficacy of immunohistochemical (IHC) staining in detecting H. pylori in gastric biopsies from patients with chronic gastritis and minimal or atypical infection. Gastric biopsies from 50 patients with chronic gastritis were subjected to routine haematoxylin and eosin (H-E), modified Giemsa, and IHC staining. The results of staining were compared with those of quantitative real-time PCR (qRT-PCR). The qRT-PCR analysis identified 32 (64%) H. pylori-positive cases, whereas IHC, H-E, and modified Giemsa staining identified 29 (58%), 27 (54%), and 21 (42%) positive cases. The sensitivity of IHC staining (87.50%) was higher than that of H-E (59.38%) and modified Giemsa (43.75%) staining. The specificity of H-E, modified Giemsa, and IHC staining was 55.56%, 61.11%, and 94.44%, respectively. IHC staining exhibited the highest diagnostic accuracy (90%), followed by H-E (58%) and modified Giemsa (50%) staining. Active gastritis, intestinal metaplasia, and lymphoid follicles were detected in 32 (64%), 4 (8%), and 22 (44%) cases, respectively, and all of these cases were H. pylori positive. In contrast to routine H-E and modified Giemsa staining, IHC allows for the accurate H. pylori detection in cases with minimal or atypical infection. Moreover, IHC can be an alternative diagnostic method to qRT-PCR for detection of H. pylori in such cases.

[Diagnosis of Helicobacter pylori Infection]

Accurate diagnosis of Helicobacter pylori (H. pylori) infection is mandatory for the effective management of many gastroduodenal diseases. Currently, various diagnostic methods are available for detecting these infections, and the choice of method should take into account the clinical condition, accessibility, advantage, disadvantage, as well as cost-effectiveness. The diagnostic methods are divided into invasive (endoscopic-based) and non-invasive methods. Non-invasive methods included urea breath test, stool antigen test, serology, and molecular methods. Invasive methods included endoscopic imaging, rapid urease test, histology, culture, and molecular methods. In this article, we provide a review of the currently available options and recent advances of various diagnostic methods.

Contribution of genetic amplification by PCR for the diagnosis of Helicobacter pylori infection in patients receiving proton pump inhibitors

Background

Helicobacter pylori detection by standard methods may be altered by proton pump inhibitor (PPI) use. However, some patients cannot or should not interrupt PPI use before undergoing testing for H. pylori. Polymerase chain reaction (PCR) could allow more reliable H. pylori detection even in patients taking PPIs.

Objective

The aim of our study is to compare the H. pylori infection diagnostic value of histological examination without and with immunohistochemical staining, bacterial culture and PCR, in PPI-treated vs untreated patients.

Methods

Patients undergoing a gastric endoscopy for upper digestive symptoms were included. Gastric biopsy samples were obtained. The impact of taking PPI on the diagnostic performance of the different methods was studied. PCR results were confirmed by sequencing the glmM gene.

Results

A total of 497 patients were included, of whom 192 were H. pylori positive. Fifty-two patients received PPIs during the 14 days preceding the endoscopy while 140 did not. All methods had lower sensitivity than PCR, in all cases (PPI treatment or not). PPI use did not change significantly the methods' sensitivities.

Conclusion

The PCR method showed the best performance for the detection of H. pylori in gastric samples, whether or not patients received previous PPI treatment. This diagnosis test could become a new gold-standard test, especially in patients undergoing PPI treatment.

Management of Helicobacter pylori infection-the Maastricht V/Florence Consensus Report

Important progress has been made in the management of Helicobacter pylori infection and in this fifth edition of the Maastricht Consensus Report, key aspects related to the clinical role of H. pylori were re-evaluated in 2015. In the Maastricht V/Florence Consensus Conference, 43 experts from 24 countries examined new data related to H. pylori in five subdivided workshops: (1) Indications/Associations, (2) Diagnosis, (3) Treatment, (4) Prevention/Public Health, (5) H. pylori and the Gastric Microbiota. The results of the individual workshops were presented to a final consensus voting that included all participants. Recommendations are provided on the basis of the best available evidence and relevance to the management of H. pylori infection in the various clinical scenarios.

Helicobacter pylori chronic gastritis updated Sydney grading in relation to endoscopic findings and H. pylori IgG antibody: diagnostic methods

Helicobacter pylori (Hp) inhabits the stomach of > 50% of humans and has been established as a major etiological factor in the pathogenesis of chronic gastritis, gastric atrophy, peptic ulcer disease, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. The aim of this study was to provide unequivocal information about Hp-associated gastritis grading according to the Sydney grading system and to compare the histopathological features with the endoscopic findings and anti-Hp immunoglobulin (Ig)G serological status. This analytical study was conducted on 157 patients with dyspeptic gastritis. All patients underwent esophagogastroduodenoscopy, and antrum and corpus biopsies were taken. Blood samples were obtained from all participants. Different stains were performed on formalin-fixed, paraffin-embedded tissue blocks that included hematoxylin and eosin and Giemsa stain for histopathological interpretation. The endoscopic findings of gastritis were observed in 120 patients and most of them showed hyperemia (80 patients), whereas seven patients had normal appearing gastric mucosa. Histologically variable numbers of mononuclear inflammatory cellular infiltrates were seen in 150 cases (95.5%). Most of them showed Grade 1 gastritis (80 patients), whereas Grades 2 and 3 were found in 43 and 27 biopsies, respectively. Hp colonization was observed in most of the examined biopsies (93.7%). Hp-IgG seropositivity was found in 80.9% of cases and 19.1% were seronegative. The relationship between endoscopic and histological findings was significant (p < 0.001).

Helicobacter pylori is a risk factor for colonic neoplasms

OBJECTIVES

It has been suggested that Helicobacter pylori (H. pylori) constitutes a risk for the development of adenomatous polyps and adenocarcinoma of the colon. Our aim was to study the association between H. pylori-positive gastritis and the occurrence of any colonic neoplasm.

METHODS

From a computerized database of surgical pathology reports, we selected 156,000 subjects who underwent colonoscopy and esophago-gastro-duodenoscopy with biopsy results from both procedures.

RESULTS

Compared with normal gastric mucosa, H. pylori gastritis occurred more frequently among patients with hyperplastic polyps (OR=1.24, 95% CI: 1.18-1.30), adenomatous polyps (1.52, 1.46-1.57), advanced adenomas (1.80, 1.69-1.92), villous adenomas or adenomas with high-grade dysplasia (1.97, 1.82-2.14), and adenocarcinomas (2.35, 1.98-2.80). Similarly, the strength of the association between H. pylori-positive gastritis and colonic neoplasm increased with size and number of the adenomas. The association between H. pylori gastritis and the occurrence of colonic neoplasm was similar for different locations of the large bowel. Other gastric conditions etiologically associated with H. pylori, such as intestinal metaplasia, adenoma, lymphoma, and adenocarcinoma, were also significantly associated with an increased risk of colonic neoplasm.

CONCLUSIONS

Various forms of gastritis related to H. pylori infection confer an increased risk for colonic neoplasm. In the past, when H. pylori infection was more prevalent, its attributable risk to the occurrence of colorectal neoplasm may have been quite substantial.

The role of routine immunohistochemistry for Helicobacter pylori in gastric biopsy

Helicobacter pylori infection is associated with gastritis, gastric ulcer, gastric adenocarcinoma, and mucosal associated lymphoid tissue lymphoma. Documenting the presence of H pylori in a gastric biopsy is essential for appropriate patient care. Several special stains and immunohistochemistry (IHC) stain for H pylori are available, and many laboratories are routinely using one of them. We introduced routine IHC for H pylori about a year ago, and this study aims to investigate the value of this protocol. A total of 224 patients qualified for the study criteria during this period. The diagnoses were chronic active gastritis (68), chronic gastritis (76), no pathologic abnormality (50), reactive gastropathy (24), and polyps (6). Fifty-four cases were positive for H pylori on IHC, including 50 chronic active gastritis and 4 chronic gastritis. The IHC positive rate was 73.5% (50/68) in chronic active gastritis, 5.3% (4/76) in chronic gastritis, and 0% (0/80) in other diagnoses. The sensitivity/specificity of finding H pylori by blindly reviewing hematoxylin and eosin slides was 100%/100%, 100%/100%, 95%/100%, and 100%/100% from the 4 authors. Our results showed that many gastric biopsies (35.7%, 80/224) had no pathologic abnormality or reactive gastropathy and did not need a routine IHC for H pylori. Hematoxylin and eosin slide review had a very good sensitivity and specificity with all levels of observers. In summary, IHC for H pylori should not be routinely used, especially during these economically challenging times. Immunohistochemistry should be reserved for unexplained gastritis and previously treated patients with likely low organism density.

Practical approach to the pathologic diagnosis of gastritis

CONTEXT

Most types of gastritis can be diagnosed on hematoxylin-eosin stains. The most common type of chronic gastritis is Helicobacter pylori gastritis. Reactive or chemical gastropathy, which is often associated with nonsteroidal anti-inflammatory drug use or bile reflux, is common in most practices. The diagnosis of atrophic gastritis can be challenging if few biopsy samples are available and if the location of the biopsies in the stomach is not known, such as when random biopsies are sampled in one jar. If the biopsy site is not known, immunohistochemical stains, such as a combination of synaptophysin and gastrin, are useful in establishing the biopsy location.

OBJECTIVE

To demonstrate a practical approach to achieving a pathologic diagnosis of gastritis by evaluating a limited number of features in mucosal biopsies.

DATA SOURCE

In this article, we present several representative gastric biopsy cases from a gastrointestinal pathology practice to demonstrate the practical application of basic histopathologic methods for the diagnosis of gastritis.

CONCLUSIONS

Limited ancillary tests are usually required for a diagnosis of gastritis. In some cases, special stains, such as acid-fast stains, and immunohistochemical stains, such as for H pylori and viruses, can be useful. Helicobacter pylori immunohistochemical stains can particularly contribute (1) when moderate to severe, chronic gastritis or active gastritis is present but no Helicobacter organisms are identified upon hematoxylin-eosin stain; (2) when extensive intestinal metaplasia is present; and (3) in follow-up biopsies, after antibiotic treatment for H pylori.

Sleeve gastrectomy leads to Helicobacter pylori eradication

BACKGROUND

The role of Helicobacter pylori (HP) in patients scheduled and undergoing laparoscopic sleeve gastrectomy (LSG) has not been previously evaluated.

METHODS

Included were obese patients presenting to our institution for LSG over 24 months. All patients had presurgical HP breath test, and the symptomatic ones received triple therapy with symptom follow-up. Post surgery, all excluded stomachs were evaluated for HP, and those that were positive performed a second 13C-urea breath test (UBT) 3 months later.

RESULTS

Forty patients underwent LSG. Male to female sex ratio was 1:3; mean age-42 years; mean weight-122 kg; and mean BMI of 43.4 kg/m2. Presurgical HP was positive in 15 (37.5%) patients (11 symptomatic and four asymptomatic). Only these 11 patients were given HP eradication therapy and all experienced complete subsequent symptom resolution. HP was detected in 17 out of the 40 (42.5%) cases of excluded stomachs. All performed a 13C-UBT 3 months post operation and only three (17.6%) tested positive.

CONCLUSIONS

HP infection is frequent in biopsies from patients with previous LSG and the majority of follow-up 13C-UBT were negative. In our small initial sample, we treated only symptomatic patients preoperatively. Routine screening for HP for all LSG patients and/or treatment for all positive ones would subject patients to expensive and unnecessary investigations. We propose that this stomach-reducing, pylorus-preserving surgery might even lead to HP eradication. The clinical implications of HP and this gastrectomy for a non-neoplastic, non-peptic indication deserve further study.

Helicobacter pylori invades the gastric mucosa and translocates to the gastric lymph nodes

Helicobacter pylori has been considered to be non-invasive and to rarely infiltrate the gastric mucosa, even though there is an active Th1 immune response in the lamina propria of the H. pylori-infected stomach. To elucidate whether H. pylori invades the lamina propria and translocates to the gastric lymph nodes, we examined H. pylori in formalin-fixed and paraffin-embedded tissue sections of stomach and gastric lymph nodes obtained from 51 cancer patients using real-time PCR and immunohistochemistry (IHC) with a novel anti-H. pylori monoclonal antibody that recognizes lipopolysaccharides. Fresh gastric lymph nodes were used to culture for H. pylori. In 46 patients with H. pylori in the stomach, the bacterium was found in the lymph nodes from 21 patients by culture, 37 patients by PCR, and 29 patients by IHC. H. pylori captured by macrophages was found in the lamina propria of 39 patients. In the lymph nodes, the bacterium was found in many macrophages and a few interdigitating dendritic cells at the paracortical areas. H. pylori was also found in the intracellular canaliculi of parietal cells in 21 patients, but intracytoplasmic invasion into gastric epithelial cells was not identified. When compared to the commercially available anti-H. pylori antibodies, the novel antibody showed the highest sensitivity to detect H. pylori-positive macrophages, whereas no difference was found for H. pylori in the mucous layer. The H. pylori-positive macrophages in the lamina propria correlated with chronic gastritis as well as translocation of such cells to the lymph nodes. These results suggest that H. pylori-induced gastric epithelial damage allows the bacteria to invade the lamina propria and translocate to the gastric lymph nodes, which may chronically stimulate the immune system. The bacteria captured by macrophages, whether remaining alive or not, may contribute to the induction and development of H. pylori-induced chronic gastritis.

Application of immunohistochemistry to infections

CONTEXT

Pathologists play an important role in the diagnosis or exclusion of infectious diseases. Traditionally, the diagnosis of infectious diseases rely on serologic assays and cultures. Serologic results may be difficult to interpret in the setting of immunosuppression, fresh tissue is not always available for culture, and culture of fastidious pathogens can be difficult and may take weeks or months to yield a result. Although some microorganisms or their cytopathic effects may be readily identifiable on routine and/or histochemical stains, often these changes are not specific or are sparse in the sample evaluated. In these cases, additional immunohistochemical stains are often needed to establish the diagnosis of infection.

OBJECTIVE

To review the current value and limitations of the use of immunohistochemistry in the diagnosis of infectious diseases in formalin-fixed tissue samples.

DATA SOURCES

Literature in Medline and the authors' own experience.

CONCLUSIONS

Immunohistochemistry has proven to be a useful tool in the diagnosis of infectious diseases in tissue samples. Immunohistochemistry is especially useful in the identification of microorganisms that are present in low numbers, stain poorly, are fastidious to grow, are noncultivable, or exhibit an atypical morphology. Finally, it is important to remember that there may be widespread occurrence of common antigens among bacteria and pathogenic fungi and both monoclonal and polyclonal antibodies must be tested for possible cross-reactivity with other organisms.

Immunoperoxidase in the interpretation of discordant histologic and urease findings for Helicobacter pylori

Azure A and methylene blue ("Diff-Quik," DQ) and tissue urease (U) tests are popular methods to diagnose Helicobacter pylori. These tests usually correlate well but sometimes produce discordant results. This study evaluates the DQ and U tests by comparing them with the immunoperoxidase reference method to resolve discordant results. DQ and U tests were performed on gastric biopsies. Results were tabulated as DQ(+)/U(+), DQ(+)/U(-), DQ(-)/U(+), and DQ(-)/U(-). Cases that were DQ(+)/U(+) were recorded as positive and not tested with immunoperoxidase. Cases that had discordant DQ/U results were tested by immunoperoxidase to resolve the discordance. Cases which were negative for both DQ/U were evaluated by immunoperoxidase to confirm the validity of DQ(1-)/U(-). The groups were compared with concordant results (DQ(1-)/U(-) group) and immunoperoxidase versus discordant DQ/U results and immunoperoxidase. There were 56 gastric biopsy specimens. Among all cases, 6 were DQ(+)/U(+). Of the remaining 50 cases, 38 were concordant DQ(-)/U(-), whereas 12 showed discordant DQ/U results. All 38 concordant DQ(-)/U(-) specimens were confirmed negative, 11 discordant DQ/U cases were confirmed negative, and 1 DQ(+)/U(-) specimen was confirmed positive by immunoperoxidase. Comparison of concordant versus discordant results was not statistically significant (P=0.10). Among all discordant DQ and U, 11/12 (92%) were confirmed negative by immunoperoxidase. Thus, both concordant negative results and discordant results can be considered negative. Such interpretation of discordant results might prevent unnecessary additional procedures or treatment.

Helicobacter pylori detection and antimicrobial susceptibility testing

The discovery of Helicobacter pylori in 1982 was the starting point of a revolution concerning the concepts and management of gastroduodenal diseases. It is now well accepted that the most common stomach disease, peptic ulcer disease, is an infectious disease, and all consensus conferences agree that the causative agent, H. pylori, must be treated with antibiotics. Furthermore, the concept emerged that this bacterium could be the trigger of various malignant diseases of the stomach, and it is now a model for chronic bacterial infections causing cancer. Most of the many different techniques involved in diagnosis of H. pylori infection are performed in clinical microbiology laboratories. The aim of this article is to review the current status of these methods and their application, highlighting the important progress which has been made in the past decade. Both invasive and noninvasive techniques will be reviewed.

Identification ofHelicobacter sp. in gastric mucosa from captive marmosets (Callithrix sp.; callitrichidae, primates)

The aim of this study was to identify the presence of Helicobacter sp. in the gastric mucosa of captive marmosets (Callithrix sp.). Histologic specimens from the fundic, corpus, and antral gastric regions of six Callithrix jacchus, 12 C. kuhli, and 12 C. geoffroyi specimens were evaluated. The sections were stained with hematoxylin-eosin (H&E) and the Warthin-Starry silver impregnation method, and immunostained with rabbit anti-H. pylori polyclonal antibody. Helicobacter-like organisms (HLOs) and coccoid forms were present in silver-stained sections from 29 stomachs, whereas immunohistochemistry (IHC) tests revealed bacterial aggregates in 15 stomachs. No statistical difference relative to the presence of Helicobacter sp. was found among the gastric regions or marmoset species. Gastric lesions were found in the groups of marmosets that had positive and negative IHC results, but no correlation between inflammation and Helicobacter sp. infection was established. These findings demonstrate that marmosets are susceptible to naturally-occurring Helicobacter sp. infection, and open the way to the development of comparative studies on Helicobacter sp. infection in humans.

Is immunostaining for Helicobacter pylori superior to the special stain thiazine in detecting small numbers of H. pylori in gastric biopsies?

Helicobacter pylori is implicated in the pathogenesis of gastritis and duodenal ulcers, gastric lymphoma of the mucosa-associated lymphoid tissue (MALT) type, and gastric adenocarcinoma. Eradication of H. pylori with antibiotic therapy therefore is essential, not only for the successful treatment of active gastritis, but also for the treatment and prevention of the MALT lymphoma. It has been suggested recently that immunostaining for H. pylori is more sensitive than special stains for the detection of the organism in the gastric biopsies after triple therapy. Fifty-five endoscopic mucosal biopsies from 38 patients, including 18 treated with H. pylori eradication therapy, were selected for immunostaining because they were either negative or contained rare H. pylori organisms by thiazine stain. Formalin-fixed, paraffin-embedded tissue sections were immunostained for H. pylori using a polyclonal antibody using standard immunoperoxidase technique. The results were compared with those obtained with the thiazine stain. Detection of H. pylori by immunostaining was easier and less time-consuming than by thiazine stain. There was complete agreement between immunostaining and thiazine stain in 48 (87%) cases. Of the 7 discordant cases, 3 (42%) were positive for H. pylori with thiazine only and 4 (48%) with immunostaining only. Given the nature of the selection of the study sample (absent to rare by thiazine stain), the discordance most likely represents a sampling error. The authors concluded that immunostaining for H. pylori did not appear to be more sensitive than special stains. Three cases with bacterial clumps were diagnosed previously as positive for H. pylori, but identified correctly as negative using both staining methods. Pathologists, however, should balance the added cost to patients of immunostaining against the time saved by the easier screening of the immunostained slides and the possibility of false positive results when special stains are interpreted by inexperienced pathologists.

Infectious disease pathology

The anatomic pathologist performs an important role in the diagnosis or exclusion of infectious diseases. The morphologic interpretation of biopsies and cytologic preparations allows for the definitive establishment or exclusion of a wide variety of diseases. Once the pathologist has determined that a disease is likely to be due to an infection and has characterized the inflammatory response, associated microorganisms or viral-associated cytopathic effects should be recorded. Although some microorganisms or their cytopathic effects may be clearly visible on routine hematoxylin and eosin-stained sections, additional histochemical stains are often needed for their complete characterization. Highly specific molecular techniques, such as immunohistochemistry, in situ hybridization, and nucleic acid amplification, may be needed in certain instances to establish the diagnosis of infection. Through appropriate morphologic diagnoses and interlaboratory communication and collaboration, the anatomic pathologist contributes greatly to the diagnosis and treatment of infectious diseases.

Comparison of immunohistochemistry and silver stain for the diagnosis of pediatric Helicobacter pylori infection in urease-negative gastric biopsies

We compared immunohistochemical and silver stains of pediatric gastric biopsy sections for the identification of Helicobacter pylori infection with chronic inflammation and a negative urease screening test. Thirty-seven patients (age range 10 months to 21 years) whose gastric antral biopsies were negative for the rapid urease test (CLO(R)) but positive for lymphocytic infiltration were selected for a retrospective study. Specimens had been subjected to a rapid urease test (CLO(R)) and hematoxylin and eosin staining, and Dieterle silver staining and immunohistochemical staining specific for H. pylori were also performed. Twelve additional patients with urease-positive biopsies were used as controls. With Dieterle staining, 8/37 (22%) urease-negative biopsies contained organisms morphologically compatible with H. pylori, 21/37 (56%) contained organisms not compatible with H. pylori, and 8/37 (22%) were negative for organisms. Immunostaining confirmed 6/8 (75%) Dieterle-positive cases as being H. pylori, was negative in 2/8 (25%) Dieterle-positive cases, and was positive in 2/8 (25%) Dieterle-negative cases. Biopsies from 8/12 (67%) urease-positive specimens contained organisms seen with both Dieterle and immunohistochemical stains, and 4/12 (33%) were negative with both stains. Although both stains yielded comparable results with H. pylori-positive biopsies, Dieterle staining was potentially confusing because of nonspecific staining of other organisms. A significant proportion of (CLO(R))-negative biopsies was positive for H. pylori with special stains. We therefore recommend the use of immunohistochemical staining rather than silver staining in the evaluation of urease-negative gastric biopsies demonstrating chronic inflammation in children.

Effect of formalin tissue fixation and processing on immunohistochemistry

Although immunohistochemistry is routinely performed by many pathology laboratories, its standardization still lags behind. A major cause of variation in the reproducibility of immunohistochemical staining is induced by tissue fixation and, to a lesser degree, tissue processing. This report, stemming from the first meeting of the International Consensus Group on Standardization and Quality Control (ICGSQC) in Nice, France, summarizes the problem and suggests solutions to begin to achieve standardization of fixation and processing. Most laboratories use neutral-buffered formalin (10%) for tissue fixation which introduces cross-links, whereas coagulative fixatives are less popular. Problems with formalin fixation comprise delay of fixation and variations in the duration of the fixation mainly. Solutions to these problems could be to start fixation soon (<30 min) after surgical removal of the tissue and to avoid overfixation (>24-48 hrs). For tissue processing, the most important problem is inadequate tissue dehydration prior to paraffin embedding. This can be prevented by preparing all solutions freshly every week, depending on the volume of tissue processed. If consistently applied, these procedures could eliminate some of the sources of variation in immunohistochemical stains.