Interobserver variability and feasibility of polymerase chain reaction-based assay in distinguishing ischemic colitis from Clostridium difficile colitis in endoscopic mucosal biopsies

[Severe pseudomembranous colitis in patients with previous coronavirus infection]

OBJECTIVE

To analyze treatment outcomes in patients with severe pseudomembranous colitis and previous coronavirus infection.

MATERIAL AND METHODS

We retrospectively analyzed treatment outcomes, clinical, laboratory and histological data in convalescents of COVID-19 who admitted to the department of coloproctology for moderate-to-severe pseudomembranous colitis confirmed by endoscopic examination between 2020 and 2021.

RESULTS

There were 13 patients with moderate pseudomembranous colitis and 6 ones with severe pseudomembranous colitis. Mean period after recovery from coronavirus infection was 19 days. Endoscopy revealed whitish-yellow or gray raised plaques on colonic mucosa in all cases. Four patients with signs of peritonitis underwent emergency surgery. Three patients had perforation of caecum; one patient had perforation of sigmoid colon and widespread peritonitis. Two patients underwent urgent surgery for progressive toxic megacolon and ineffective therapy. Subtotal colectomy and ileostomy were performed in all cases. Histological examination revealed necrosis of not only superficial layer of colon mucosa typical for clostridial colitis, but also the entire thickness of mucosa, as well as submucosal and partially muscular layers in some cases. Mucosal crypt atrophy, fibrinoid effusion in muscular layer, diffuse polymorphonuclear cell infiltration and necrosis of muscular and submucosal nerve plexuses, as well as necrosis of vascular walls with deposition of hyaline-like structures characterize microcirculatory ischemic processes in the colon wall.

CONCLUSION

Severe pseudomembranous colitis associated with COVID-19 may not be associated with clostridial infection. Further analysis of possible ischemic etiology and pathogenesis of gastrointestinal lesions in COVID-19 is needed for preventive and therapeutic measures.

Analysis of TaqMan Array Cards Data by an Assumption-Free Improvement of the maxRatio Algorithm Is More Accurate than the Cycle-Threshold Method

Quantitative PCR diagnostic platforms are moving towards increased sample throughput, with instruments capable of carrying out thousands of reactions at once already in use. The need for a computational tool to reliably assist in the validation of the results is therefore compelling. In the present study, 328 residual clinical samples provided by the Public Health England at Addenbrooke's Hospital (Cambridge, UK) were processed by TaqMan Array Card assay, generating 15 744 reactions from 54 targets. The amplification data were analysed by the conventional cycle-threshold (CT) method and an improvement of the maxRatio (MR) algorithm developed to filter out the reactions with irregular amplification profiles. The reactions were also independently validated by three raters and a consensus was generated from their classification. The inter-rater agreement by Fleiss' kappa was 0.885; the agreement between either CT or MR with the raters gave Fleiss' kappa 0.884 and 0.902, respectively. Based on the consensus classification, the CT and MR methods achieved an assay accuracy of 0.979 and 0.987, respectively. These results suggested that the assumption-free MR algorithm was more reliable than the CT method, with clear advantages for the diagnostic settings.

Ischemic enterocolitis and its differential diagnosis

Ischemia is a common type of gastrointestinal injury that can be clinically misdiagnosed due to its often mild and transient clinical presentation as well as a tendency to masquerade as other disorders. A wide range of etiologies can contribute to the development of ischemia. These include hypovolemic states, systemic diseases such as vasculitis and hypercoagulable states, mechanical obstruction, therapeutic drug effects, infection, and a host of other diseases. An accurate diagnosis of ischemia relies on a strong clinical suspicion in combination with endoscopic and pathologic findings. Most cases show histologic features that are diagnostic of ischemia, but do not point to a specific differential diagnosis, whereas the cause of ischemia can be recognized or suspected based on careful review of vascular changes in others. This review is focused on providing an overview of ischemic enterocolitis and its differential diagnosis.