Intraductal tubulopapillary neoplasm is a recently recognized distinct and rare entity of the pancreas, which may be unfamiliar to many physicians and laboratory personnel. However, recognizing this disease is critical for its proper clinical management and further study. Here, we discuss the clinical and pathological features of this neoplasm.
by Dr Shula Schechter and Dr Jiaqi Shi
Presentation and definition of intraductal tubulopapillary neoplasm of the pancreas
Intraductal tubulopapillary neoplasm (ITPN) was recently recognized as a distinct neoplastic entity of the pancreas in the 2010 edition of the World Health Organization (WHO) classification [1]. It was defined as an intraductal, grossly visible, tubule-forming epithelial neoplasm with high-grade dysplasia and ductal differentiation without overt production of mucin, although focal tubulopapillary growth is also acceptable [1].
ITPN is a rare entity. Although it was first described in the mid-1990s by Japanese investigators and has been termed ITPN since 2009 [2], its diagnostic criteria need to be refined and recognition of this disease needs to be improved. The differential diagnosis of ITPN can be complex because its features overlap with other more common intraductal neoplasms, such as intraductal papillary mucinous neoplasm (IPMN). A recently published literature review and a large study of 33 cases of ITPN have shed some light on the clinicopathologic and immunohistochemical features of this disease and further advance our knowledge of its diagnosis [3, 4].
The majority of the patients with ITPN present with abdominal pain, nausea, vomiting, weight loss and steatorrhea. A few patients have diabetes mellitus, acute pancreatitis, jaundice and fever. Incidental discovery of ITPN occurs in about one-third of patients. The risk factors for ITPN are not well defined, but there are reports of an association of ITPN with radiation exposure and with a family history of pancreatic cancer [4–6]. The incidence of ITPN in men and in women is comparable. Most ITPNs occur in the sixth decade with a range in age of 25 to 79 years. Nearly half of reported ITPNs are located in the head of the pancreas. In the remainder of cases, the location of the ITPN is divided between the body and tail with about one-quarter of lesions showing more extensive involvement of the entire pancreas [4]. ITPNs are often slow growing tumours and large at the time of discovery.
Imaging studies with dynamic contrast-enhanced computed tomography and magnetic resonance imaging are commonly used to assist with preoperative diagnosis. A helpful imaging clue for the diagnosis of ITPN is the two-tone duct sign, which is a reflection of tumour in the main pancreatic duct with ductal dilation upstream [7]. With magnetic resonance cholangiopancreatography and endoscopic retrograde cholangiopancreatography, ITPN also has a characteristic finding, the so called ‘cork-of-wine-bottle’ sign, which results from intraductal growth of the tumour [7].
Information on the prognosis of ITPNs is limited by the small number of reported cases, although data have suggested an excellent prognosis for patients without invasion (overall 5-year survival rate of 100%) and a significantly more favourable prognosis for ITPNs with a component of invasive carcinoma (overall 5-year survival rate of 71%) relative to the traditional invasive pancreatic ductal adenocarcinoma (overall 5-year survival rate <10%) [2, 8, 9]. However, the extent of invasion does not necessarily correlate with clinical outcome. Patients with minimal invasion can die of disease, whereas patients with a large volume of invasion can achieve long-term survival [4]. Unfortunately, invasive carcinoma is present in most (54–71%) ITPNs and may be more likely in men [3, 4, 10]. In addition, tumours that are large in size, or have increased mitosis and a high Ki-67 proliferation index may have an increased association with invasive carcinoma [2]. Despite the favourable prognosis, the possibility of invasive carcinoma, recurrence and metastasis has led to the general recommendation of surgery as treatment in most ITPN patients.
Diagnostic features of ITPN based on histology and immunohistochemistry
Macroscopically, the mean size of the tumour is 3.8 cm (range 0.5–15 cm). Most ITPNs are circumscribed solid or polypoid masses obstructing pancreatic ducts. They generally arise in the main pancreatic duct, but approximately 5% arise within the branch ducts [4, 10]. ITPNs may be cystic, this occurs in less than half of cases. However, ITPNs do not have grossly identifiable mucin.
Microscopically, ITPNs are characterized by back-to-back tubules forming complex cribriform structures (Fig. 1a, c) with focal areas of papillary architecture seen in 36% of ITPN cases [4]. Solid growth with necrotic foci can occur, occasionally with areas of comedo-like necrosis (Fig. 1b). Occasionally, there are apical apocrine snouts and intraluminal secretion; however, cytoplasmic and intraluminal mucin is scant to absent. The tubules are lined by cuboidal to low columnar epithelial cells with minimal to moderate amounts of eosinophilic or amphiphilic cytoplasm and round to oval nuclei with moderate to marked atypia (Fig. 1d). ITPNs classically have uniform high-grade dysplasia and increased mitotic figures. Uncommon clear cell morphology or stromal osseous and cartilaginous metaplasia has also been reported in an ITPN.
By immunohistochemistry, all ITPNs to date have stained positively with anti-cytokeratin (CK) 7 (Table 1) and CAM5.2 antibodies. CK19 is positive in 92% of the cases. Tumour markers CA19.9 and CEA (carcinoembryonic antigen) are expressed in 93% and 50% of the cases respectively. In contrast, CK20 and CDX2 (homeobox protein CDX-2) only stain rare cells in a minority of ITPNs. The mucin (MUC) family has a particular staining pattern in ITPNs (Table 1), which is sometimes helpful in its differential diagnosis. MUC1 and MUC6 are positive in the majority of cases (88% and 77% respectively) whereas MUC2 and MUC5AC are usually negative (only 2% and 6% ITPNs are positive respectively). Nuclear p53 and p16-INK4 (cyclin-dependent kinase inhibitor 2A) are expressed in 27% and 33% of the cases. Rare focal or scattered cells can be positive for HepPar-1 antigen, chromogranin or nuclear β-catenin. However, ITPNs do not express pancreatic enzymes, trypsin and chymotrypsin, or loss of E-cadherin or Smad4.
Recent molecular findings
Recent genetic studies have found evidence that ITPN is molecularly distinct from IPMN. The most commonly mutated genes in ITPN include PIK3CA, TP53 and CDKN2A, among others [8–18]. Other rare mutations in histone H3 methyltransferase genes, MLL2 and MLL3 (also known as KMT2A and KMT2C), and MCL1 amplification have also been identified in ITPN [19]. However, ITPNs have been shown to have no or rare mutations in KRAS, BRAF, or GNAS. In contrast, IPMNs have high mutation rates in multiple genes [20]. KRAS mutation is thought to be one of the driver genes during IPMN development and mutations in GNAS and RNF43 are also common.
Differential diagnosis
Despite its distinct molecular features, the histology of ITPN can resemble that of IPMN, especially the pancreatobiliary and oncocytic type, making it difficult to distinguish ITPNs from IPMNs by morphology alone. The key morphologic features that characterize ITPNs as compared to IPMNs are shown in Table 2 and Figure 2. Overall, cystic components are infrequent with ITPNs in contrast to IPMNs, which are predominantly cystic lesions. Mucin is another distinguishing feature, which is sparse or absent with ITPNs but abundant with IPMNs. IPMNs also have significantly more morphologic variation according to epithelial subtype, and their degree of cytologic and architectural atypia varies from low- to high-grade dysplasia, whereas ITPNs typically demonstrate uniform high-grade dysplasia. On the other hand, comedo-like necrosis is frequent with ITPNs but rare with IPMNs.
The cytologic and architectural distinctions between ITPNs and IPMNs are confounded by the wide spectrum of morphologies and degree of dysplasia that are seen with IPMNs. Among the four recognized epithelial subtypes of IPMN, the pancreatobiliary and oncocytic type IPMN are the types that are most easily confused with ITPN. Similar to ITPN, both pancreatobiliary and oncocytic type IPMNs have high-grade dysplasia and often complex architecture. Nevertheless, the architecture of these IPMN subtypes remains predominantly papillary in nature as compared to the tubular or tubulopapillary architecture of ITPNs. In addition, the oncocytic IPMN has intraepithelial lumens as well as cells with abundant granular eosinophilic cytoplasm. Subtypes of IPMN also differ from ITPN in their immunohistochemical profiles. Most ITPNs are MUC6 positive and MUC5AC negative, whereas the opposite is true for most IPMNs (MUC6 negative and MUC5AC positive). The immunohistochemical findings with the oncocytic subtype of IPMN are most similar to findings with ITPNs, although some studies found MUC5AC can be positive with oncocytic IPMNs. Use of a mitochondrial stain (e.g. phosphotungstic acid–hematoxylin, Novelli stain, anti-apoptin 111.3 antibody) may allow an oncocytic IPMN to be distinguished from an ITPN on the basis of abundant mitochondria in cytoplasm [12].
Intraductal acinar cell carcinoma can also be confused with ITPN due to its occasional intraductal growth pattern. However, intraductal acinar cell carcinoma will typically stain positively for pancreatic enzymes such as trypsin, chymotrypsin or Bcl-10 (B-cell lymphoma/leukemia 10), and negatively for CK7 and CK19 by immunohistochemistry [4, 21].
Conclusion
ITPN is a relatively new diagnostic entity that occurs infrequently, predominantly in older patients. One-third of patients can be asymptomatic. Although invasive carcinoma is present in most ITPNs, the prognosis of these tumours appears to be significantly more favourable than pancreatic ductal adenocarcinoma. ITPNs generally arise in and obstruct the main pancreatic duct with circumscribed, solid nodules that are grossly visible. Histologically, these tumours are characterized by back-to-back tubules forming complex cribriform structures and uniform high-grade dysplasia. Necrosis is frequent but cytoplasmic and intraluminal mucin is scant to absent, which is in contrast with IPMNs. Molecular studies support that ITPN is a distinct entity from other intraductal neoplasms of pancreas, such as IPMN. With increased recognition of ITPNs, we expect to learn more information about its pathological features and prognostic implications.
References
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The authors
Shula Schechter MD; Jiaqi Shi* MD, PhD
Department of Pathology, University of Michigan,
Ann Arbor, MI 48109 USA
*Corresponding author
E-mail: jiaqis@med.umich.edu
The prevalence of T2DM has reached epidemic levels, affecting about 7% of the U.S. population, and is growing.
The Randox automated immunoturbidimetric adiponectin test offers an improved method for assessing T2DM risk, with a convenient format for routine clinical use. The Randox Adiponectin assay is available for use on most biochemistry analysers, including the RX series.
Background
The prevalence of type 2 diabetes mellitus (T2DM) has reached epidemic levels, affecting ~7% of the U.S. population, and current epidemiological trends indicate that the prevalence will continue to increase dramatically (Blonde, 2007).
The global prevalence of diabetes among adults over 18 years of age has risen from 4.7% in 1980 to 8.5% in 2014 (WHO, 2016). About 422 million people worldwide have diabetes (WHO, 2016). Furthermore, the prevalence of diabetes is growing most rapidly in low and middle-income countries (WHO, 2016).
Millions more people are also at risk. One in three adults have prediabetes, and 9 out of 10 of those with prediabetes don’t know they have it (CDC, 2016).
Early risk assessment is vital for a number of reasons. Diabetes is one of the leading causes of death in the world – in 2012 it was the direct cause of 1.5 million deaths (WHO, 2016). 50% of people with diabetes die of CVD (WHO, 2016). Additionally, diabetes is the leading cause of newly diagnosed adult blindness for people between the ages of 20 and 74 (NIDDK, 2016).
Economically, diabetes and its complications bring about substantial economic loss to people with diabetes and their families, and to health systems and national economies through direct medical costs and loss of work and wages. While the major cost drivers are hospital and outpatient care, a contributing factor is the rise in cost for analogue insulins 1 which are increasingly prescribed despite little evidence that they provide significant advantages over cheaper human insulins (WHO, 2016).
Traditional methods for diabetes risk assessment
Non-biochemical methods for assessing a patient’s risk of developing T2DM traditionally take into account gender; age; family history of T2DM; BMI waist size; and high blood pressure to give a risk score. Other factors which health services may take into account include ethnicity (UK NHS); history of gestational diabetes (GDM) (American Diabetes Association (ADA)); physical activity (ADA and Finnish Diabetes Association (FDA)); blood glucose history (FDA) and diet (FDA).
It is widely recognized that people who are overweight are at higher risk of developing T2DM. However, assessing those who are overweight can be challenging. Studies have shown that measuring waist circumference alone measures total abdominal fat reliably, but its association with visceral fat depends on visceral fat/ subcutaneous fat ratios that vary by gender and ethnicity (Grundy et al, 2013). Body mass index (BMI) (weight kg / height m2) is another common method of determining which patients are classed as overweight or obese, however it has limitations in measuring athletes and varies in reliability based on age, sex, and race.
Furthermore, it has been found that risk prediction for T2DM and cardiovascular disease (CVD) remains suboptimal even after the introduction of global risk assessment by various scores. This has prompted the search for additional biomarkers (Herder et al, 2011).
The most commonly used biochemical method of assessing risk of T2DM is measuring fasting plasma glucose (FPG); however, the specificity of this test is poor (Genuth et al, 2003; Nichols et al, 2007). Although many individuals are identified as having impaired fasting glucose (IFG), their absolute risk of conversion to diabetes is only 5–10% per year (Gerstein et al, 2007). The oral glucose tolerance test (OGTT) is more accurate for risk assessment. However, it is rarely used in practice because it is unpleasant for the patient and requires 2 hours to perform. Another challenge is that by the time glucose regulation is abnormal, the underlying disease has been progressing for many years, and complications have already occurred in a significant number of individuals (Wong et al, 2008). Thus, the rationale of using one variable to assess risk is questionable, when the risk of harm actually varies based on a range of variables and would be better assessed using a multivariable individualized risk score (Mohamed and Evans, 2008).
Given the limitations of the OGTT, FPG, and indexes that the clinician must calculate, it is clear that an improved method for assessing T2DM risk, with a convenient format for routine clinical use, would enable physicians to accurately evaluate more individuals (Kolberg et al, 2009).
Clinical significance
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Implications for clinicians
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When risk via adiponectin measurement is identified, lifestyle modification to reduce visceral fat should become a primary measure for the prevention of the development of cardiovascular diseases as well as its risks including T2DM in metabolic syndrome with visceral fat accumulation (metabolic syndrome in the narrow sense) through the improvement of adiponectin production (Matsuzawa, 2014).
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Multiplex RT-PCR for rapid detection of viruses commonly causing diarrhoea in pediatric patients
Thongprachum A, Khamrin P, Pham NT, Takanashi S, Okitsu S, et al. J Med Virol 2017; 89(5): 818–824
Multiplex RT-PCR method using five sets of panel primers was developed for the detection of diarrhoeal viruses, including rotavirus A, B, and C, adenovirus, astrovirus, norovirus GI and GII, sapovirus, Aichi virus, parechovirus, enterovirus, cosavirus, bocavirus, and Saffold virus. The sensitivity of the method was evaluated and tested with 751 fecal specimens collected from Japanese children with acute diarrhoea. Several kinds of viruses were detected in 528 out of 751 (70.3%) fecal specimens. Mixed-infection with different viruses in clinical specimens could also be effectively detected. The method proved to be reliable with highly sensitive and specific and useful for routine diagnosis.
Evaluation of diagnostic accuracy of two rapid stool antigen tests using an immunochromatographic assay to detect Helicobacter pylori
da Silva-Etto JMK1, Mattar R2, Villares-Lopes CA1, Marques SB1, Carrilho FJ. Clin Biochem 2017; pii: S0009–9120(17)30129–7
OBJECTIVES: The stool antigen assay for H. pylori infection diagnosis with monoclonal antibodies is a simple and recommended technique by the Maastricht V/Florence consensus report. Recently, Pylori K-Set K-1219 (Coris Bioconcept Sprl, Belgium) and HP-F23 (Symbiosys, Brazil) have been made commercially available in Brazil. Thus, the aim of this study was to evaluate the diagnostic accuracies of these two rapid stool antigen tests by immunochromatographic assays (index tests) for the clinical practice.
DESIGN AND METHODS: A total of 98 patients who underwent upper gastrointestinal endoscopy and 13C-urea breath test entered the study. H. pylori infection status was defined by the combination of the rapid urease test and the 13C-urea breath test (reference standard). Two observers who were aware of H. pylori status performed the reading of index tests. Diagnostic accuracy (sensitivity, specificity, positive predictive value, negative predictive value with 95% confidence intervals, positive likelihood ratio, negative likelihood ratio and kappa index measure of agreement) were determined.
RESULTS: The index tests where in perfect agreement with the H. pylori status with kappa values of 0.87 for Pylori K-Set K-1219 and 0.92 for HP-F23. The sensitivity of HP-F23 was 97.9% (IC95%: 87.5–100) and specificity was 93.8% (IC95%; 84-97.2).The positive likelihood ratio was 15.8, and the negative likelihood ratio was 0.02. The Pylori K-Set K-1219 had a sensitivity of 87.7% (IC95%: 74.5–94.9) and a specificity of 100% (IC95%: 91.6-100); the positive likelihood ratio was infinity, and the negative likelihood ratio was 0.1. The test line on the cassette device of HP-F23 was stronger than of the Pylori K-Set K-1219.
CONCLUSION: The HP-F23 test performed better in clinical practice. Nonetheless, the 13C-urea breath test is more reliable technique. Moreover, caution must be paid to the trace or clear pale test line readings that were observed in false positive and false negative results, leading to incorrect management of the patient.
Development of an LPS-based ELISA for diagnosis of Yersinia enterocolitica O:3 infections in Danish patients: a follow-up study
Dalby T, Rasmussen E, Schiellerup P, Krogfelt KA. BMC Microbiol 2017; 17(1): 125
BACKGROUND: The bacterium Yersinia enterocolitica causes gastroenteritis in humans. The study aimed to develop a diagnostic enzyme-linked immunosorbent assay (ELISA) for detection of Y. enterocolitica O:3 LPS antibodies in sera from Danish patients with suspected Y. enterocolitica O:3 gastrointestinal infection. As a part of this, antibody decay profiles after culture confirmed Y. enteritis were studied.
RESULTS: An ELISA using Y. enterocolitica O:3 LPS as the coating antigen was developed for measuring IgA, IgG and IgM specific antibodies. A longitudinal collection of 220 sera drawn between 20 and 1053 days after onset of symptoms from 85 adult Danish patients with verified Y. enteritis were examined. A control group of 100 sera from healthy Danish blood-donors were analysed in order to determine the cut-off for interpretation of results. Serum samples from 62 out of 81 patients who delivered either the first or the second sample were found positive for specific antibodies against Y. enterocolitica O:3 LPS (77%). For samples collected within 60 days after onset of symptoms (n = 48) sensitivities of 58%, 42% and 79% for IgA, IgG and IgM antibodies were found. A sensitivity of 81% was found for these samples when using the definition of a positive result in either IgA, IgG or IgM as a combined positive. All samples received up to 36 days after onset of symptoms (n=10) were found to be positive using this definition. For the period 61 to 90 days after onset of symptoms (n=32), a combined sensitivity of 63% was found. The antibody levels as well as decay profiles for the three different immunoglobulin classes for the individual patients exhibited a large degree of variation.
CONCLUSIONS: Using a definition of positive as a positive result for either IgA, IgG or IgM antibodies, a diagnostic sensitivity of 81% was achieved for samples received within 60 days after onset of symptoms. In particular, the levels of specific IgM antibodies were elevated. In comparison, the standard tube-agglutination assay achieved a sensitivity of 60% on the same samples. The sensitivity of the ELISA decreased the longer the duration of time since onset of symptoms. The ELISA was highly specific for Yersinia when testing sera from individuals with confirmed gastrointestinal infections by other bacteria. Moreover, the knowledge gained from this longitudinal study of antibody decay profiles can be used in future epidemiological studies of seroprevalence.
The development of a multiplex real-time RT-PCR for the detection of adenovirus, astrovirus, rotavirus and sapovirus from stool samples
Bennett S, Gunson RN. J Virol Methods 2017; 242: 30–34
Viral gastroenteritis is a major health problem with significant morbidity and economic consequences. Viral gastroenteritis is caused by a number of viruses, including norovirus, rotavirus, adenovirus, astrovirus, and sapovirus. Conventional diagnosis is based on direct antigen detection and electron microscopy, however enzyme immunoassay’s are insensitive and not available for all relevant pathogens, and electron microscope (EM) is no longer routinely carried out in most laboratories. Most laboratories now offer norovirus real-time PCR testing however the availability of other assays is variable. Commercial methods for the detection of inflectional intestinal disease (IID) are available but these can be expensive and are not commonly used. This paper describes the development of a single multiplex assay for the simultaneous detection of adenovirus, astrovirus, rotavirus and sapovirus from stool samples. The multiplex was evaluated by assessing endpoint sensitivity, specificity, panel of clinical samples, quality control (QC) panel and the robustness and reproducibility of the multiplex.
Cholera rapid test with enrichment step has diagnostic performance equivalent to culture
Ontweka LN, Deng LO, Rauzier J, Debes AK, Tadesse F, et al. PLoS One 2016; 11(12): e0168257
Cholera rapid diagnostic tests (RDT) could play a central role in outbreak detection and surveillance in low-resource settings, but their modest performance has hindered their broad adoption. The addition of an enrichment step may improve test specificity. We describe the results of a prospective diagnostic evaluation of the Crystal VC RDT (Span Diagnostics, India) with enrichment step and of culture, each compared to polymerase chain reaction (PCR), during a cholera outbreak in South Sudan. RDTs were performed on alkaline peptone water inoculated with stool and incubated for 4-6 hours at ambient temperature. Cholera culture was performed from wet filter paper inoculated with stool. Molecular detection of Vibrio cholerae O1 by PCR was done from dry Whatman 903 filter papers inoculated with stool, and from wet filter paper supernatant. In August and September 2015, 101 consecutive suspected cholera cases were enrolled, of which 36 were confirmed by PCR. The enriched RDT had 86.1% (95% CI: 70.5–95.3) sensitivity and 100% (95% CI: 94.4–100) specificity compared to PCR as the reference standard. The sensitivity of culture versus PCR was 83.3% (95% CI: 67.2–93.6) for culture performed on site and 72.2% (95% CI: 54.8–85.8) at the international reference laboratory, where samples were tested after an average delay of two months after sample collection, and specificity was 98.5% (95% CI: 91.7–100) and 100% (95% CI: 94.5–100), respectively. The RDT with enrichment showed performance comparable to that of culture and could be a sustainable alternative to culture confirmation where laboratory capacity is limited.
Clinical and analytical evaluation of a single-vial stool collection device with formalin-free fixative for improved processing and comprehensive detection of gastrointestinal parasites
Couturier BA, Jensen R, Arias N, Heffron M, Gubler E, et al. J Clin Microbiol 2015; 53(8): 2539–2548
Microscopic examination of feces is a standard laboratory method for diagnosing gastrointestinal parasite infections. In North America, the ovum and parasite (O&P) examination is typically performed using stool that is chemically fixed in polyvinyl alcohol (PVA) and formalin, after which the stool is concentrated by filtration to enhance sensitivity. Mini Parasep solvent-free (SF) tubes allow collection and concentration within a single collection vial. The goal of the study was to determine whether consolidated processing and concentration with the Parasep tubes using an alcohol-based fixative (Alcorfix) provide O&P examinations equivalent to or better than those done by processing of PVA-formalin-fixed stool using a SpinCon concentration device. Parasep tubes revealed filtration performance equivalent to that of the SpinCon concentration device using PVA-formalin-fixed stool containing protozoa. Specimens cocollected in Parasep tubes containing PVA-formalin and Alcorfix revealed comparable morphology and staining for various protozoa. Alcorfix effectively fixed live Cryptosporidium and microsporidia such that morphology and staining were conserved for modified acid-fast and modified trichrome stains. A work flow analysis revealed significant time savings for batches of 10 or 30 O&P specimens in tubes with Alcorfix compared to the amount of time that it took to analyse the same number of specimens in tubes with PVA-formalin. The direct hands-on time savings with Mini Parasep tubes were 17 min and 41 s and 32 min and 1 s for batches of 10 and 30 specimens, respectively. Parasep tubes containing Alcorfix provide significant work flow advantages to laboratories that process medium to high volumes of O&P specimens by streamlining processing and converting to a single tube. These improvements in work flow, reduction of the amount of formalin used in the laboratory, and equivalent microscopy results are attractive advancements in O&P testing for North American diagnostic parasitology laboratories.
Chemiluminescent immunoassays for the laboratory diagnosis of Clostridium difficile infection
Makristathis A, Zeller I, Mitteregger D, Kundi M, Hirschl AM. Eur J Clin Microbiol Infect Dis 2017; 36(7): 1253–1259
For the microbiological diagnosis of a Clostridium difficile infection (CDI), a two-test algorithm consisting of a C. difficile glutamate dehydrogenase (GDH)-immunoassay followed by a toxin-immunoassay in positive cases is widely used. In this study, two chemiluminescent immunoassays (CLIAs), one for GDH and the other for the toxins A and B, have been evaluated systematically using appropriate reference methods. Three-hundred diarrhoeal stool specimens submitted for CDI diagnosis were analysed by the LIAISON CLIAs (DiaSorin). Toxigenic culture (TC) and cell cytotoxicity assay (CCTA) were used as “gold standard” reference methods. In addition, GDH and toxin A and B enzyme immunoassays (EIAs), C. diff Chek-60 and toxin A/B II (TechLab), and the Cepheid Xpert C. difficile polymerase chain reaction (PCR) were performed. C. difficile was grown in 42 (14%), TC was positive in 35 (11.7%) and CCTA in 25 (8.3%) cases. CLIAs were more sensitive but less specific than the respective EIAs. Using culture as reference, the sensitivity of the GDH CLIA was 100%. In comparison to CCTA sensitivity, specificity, positive predictive value and negative predictive value of the two-test algorithm were 88, 99.3, 91.7 and 98.9% by CLIAs and 72, 99.6, 94.7 and 97.5% by EIAs. Discrepant results by CLIAs were more frequent than that by EIAs (9% vs. 6.3%); in those cases, PCR allowed for the accurate detection of toxigenic strains. Due to performance characteristics and testing comfort, CLIAs in combination with PCR represent a favourable option for the rapid laboratory C. difficile diagnostics.
Detection and differentiation of norovirus genogroups I and II from clinical stool specimens using real-time PCR
Ramanan P, Espy MJ, Khare R, Binnicker MJ. Diagn Microbiol Infect Dis 2017; 87(4): 325–327
A real-time RT-PCR assay was designed to detect and differentiate norovirus genogroups I (GI) and II (GII), with primers and probes targeting the nonstructural polyprotein gene. Stool samples (n=100) submitted for routine testing by the BioFire FilmArray® GI panel were also tested by the norovirus GI/GII real-time PCR assays. When compared to the FilmArray GI panel, the norovirus real-time PCR assay demonstrated a sensitivity of 77.5% (62/80) and specificity of 95% (19/20). Specimens yielding discordant results (n=19) were tested at two outside laboratories for adjudication. Following discordant resolution, the adjusted sensitivity and specificity of the norovirus real-time PCR assays were 96.9% (63/65) and 100% (35/35), respectively. These results suggest that the real-time PCR assays are able to accurately detect and differentiate norovirus GI/GII from clinical stool specimens. Furthermore, our report highlights a potential issue with the specificity of the BioFire FilmArray® norovirus assay, which warrants additional investigation.
Limited diagnostic value of a multiplexed gastrointestinal pathogen panel for the detection of adenovirus infection in an oncology patient population
McMillen T, Lee YJ, Kamboj M, Babady NE. J Clin Virol 2017; 94: 37–41
BACKGROUND: Diagnosis of adenovirus infections in transplant patients may be accomplished using either plasma or stool samples. IVD-cleared multiplexed gastrointestinal (GI) PCR panels offer an option for rapid testing of stool samples but most only target adenovirus (HAdV) types F40/41.
OBJECTIVES: Given the potential significance of a positive adenovirus test in an immunocompromised patient, we sought to determine the frequency of type 40/41 in our patient population and the utility of a readily available multiplexed, FDA-cleared GI Panel for the detection of adenovirus infections.
STUDY DESIGN: A total of 215 specimens from immunocompromised patients mostly with hematologic malignancy or transplant recipients were evaluated including 107 plasma samples, 85 stool samples and 23 respiratory samples. Genotyping was performed successfully on 122 specimens.
RESULTS: The most common type detected in all samples including stools was adenovirus C/2. In a subset of patients with multiple specimen types tested, similar types were detected in all samples.
CONCLUSIONS: Although adenovirus F40/41 is the most common enteric type, adenovirus C/2 was the most common type identified in stools and subsequently plasma samples of our patient population. Implementation of assays that have wide reactivity for most adenovirus types is essential for optimal diagnostic yield.
Synergistic effect of hyperglycemia and Helicobacter pylori infection status on colorectal adenoma risk
Hu KC, Wu MS, Chu CH, Wang HY, Lin SC, et al. J Clin Endocrinol Metab 2017; 102(8): 2744–2750
CONTEXT: Both Helicobacter pylori and type 2 diabetes mellitus are possible risk factors for colon adenoma.
OBJECTIVE: The purpose of this study was to assess the interaction between H. pylori and hyperglycemia status on the risk of colon adenoma.
DESIGN, SETTING, AND PARTICIPANTS: This was a cross-sectional, retrospective study conducted at the MacKay Memorial Hospital, Taiwan. The study included 3943 subjects aged >40 years undergoing bidirectional gastrointestinal endoscopy on the same day between July 2006 and June 2015. All subjects had a gastric biopsy specimen tested for H. pylori.
MAIN OUTCOME MEASURE: Colon adenoma with and without H. pylori infection at different hemoglobin A1c (HbA1c) levels.
RESULTS: The prevalence of colorectal adenomas in patients who were H. pylori-positive and H. pylori-negative was 37.3% and 27.29%, respectively. Multivariate logistic regression analysis identified male sex, age, body mass index, H. pylori infection, and HbA1c ≥6.5% as independent risk factors for adenoma; use of hypoglycemic agents decreased this risk. The prevalence of adenoma was increased with elevated HbA1c levels regardless of H. pylori status. The odds ratio (OR) for adenoma was 1.44 (95% confidence interval [CI], 1.20 to 1.73) if H. pylori was present or 1.68 (95% CI, 1.05 to 2.70) in patients who were H. pylori-negative but had HbA1c ≥7.0%. If both conditions were present, the OR was 4.79 (95% CI, 2.92 to 7.84). A 1% increase in HbA1c was associated with an increased prevalence of adenoma by 42.4% in H. pylori-positive subjects.
CONCLUSIONS: The combination of H. pylori infection and elevated HbA1c is associated with an increased risk of colon adenoma.
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