‘No cyst, no echinococcosis’: a scoping review update on the diagnosis of cystic echinococcosis after the issue of the WHO-IWGE Expert Consensus and current perspectives

Abstract

Purpose of review In 2010, the WHO-Informal Working Group on Echinococcosis (IWGE) published an Expert Consensus on the diagnosis and treatment of echinococcal infections. We provide an update on the diagnosis of cystic echinococcosis through a scoping review of the literature published after the release of the WHO-IWGE document. Recent findings Ultrasound accurately and reliably depicts the pathognomonic signs of cystic echinococcosis (CE) stages compared with other imaging techniques. Among these, T2-wighted MRI is to be preferred to computed tomography, which has poor performance for the etiological diagnosis of CE. A negative serology cannot exclude the diagnosis of CE, while a positive serology, applied after the visualization of a CE-compatible lesion, may confirm a CE diagnosis. Serology alone must not be used to define ‘CE’ nor as ‘screening’ tool for infection. Other imaging and laboratory techniques did not show clinically applicable performances. Summary In the absence of a focal lesion compatible with a CE cyst, no diagnosis of CE should be attempted. There is urgent need to achieve univocal CE case definitions and consensus diagnostic algorithm, as well as standardization of diagnostic methods and issue of a Target Product Profile of CE diagnostics, as advocated by the WHO in the 2021–2030 roadmap for neglected tropical diseases (NTDs).

Ultrasound diagnosis of cystic echinococcosis: updates and implications for clinical management

“…The diagnosis of CE requires experience and skills, but tools currently available allow diagnosis and support clinical decisionmaking in the majority of cases. Unfortunately, they are too often not applied in the appropriate manner, as shown by the still frequent publication of prevalence studies using only serology (Siles-Lucas et al 2023) or misclassification of cysts due to use of inappropriate imaging tools. The publication of WHO guidelines will foster good clinical practice and should be widely disseminated outside the niche of scientists and physicians highly specialized in echinococcosis, including all relevant disciplines (radiology, microbiology, surgery, hepatology, etc).…”

“…Although promising, results to date have unfortunately been inadequate for practical clinical application (Xin et al 2020;Cheng et al 2022;Wu et al 2022). At the laboratory level, diagnostic tests other than seroassays (e.g., cytokine release assays, antigen detection assays, molecular diagnosis on body fluids) have been applied to the diagnosis of CE, so far with unsatisfactory results (Siles-Lucas et al 2017;Siles-Lucas et al 2023). The use of recombinant antigens for the detection of circulating antibodies, which has the advantage of scalability and standardization, has been more extensively explored, although assays' sensitivities thus far have not overcome that of tests based on native antigenic preparations (Siles-Lucas et al 2017).…”

“…Why imaging: "no cyst, no echinococcosis" Because humans are intermediate hosts of E. granulosus harbouring the tissue larval stage of the parasite, classical direct parasitological diagnostic techniques such as coproparasitology are not adequate for its diagnosis and, currently, no molecular or antigen-detection test is able to reliably detect parasitic molecules in excreta or body fluids (Siles-Lucas et al 2017;Siles-Lucas et al 2023). Diagnosis relies on visualization of the cyst by imaging and by detection of circulating antibodies against the parasite using seroassays.…”

“…Seropositivity in single, uncomplicated CE ranges from 64-85% in the presence of hepatic CE1 and from 53-90% in the presence of hepatic inactive CE4-CE5 cysts. In lung CE seropositivity ranges from 17%-80%, and it can be as low as 12% in cysts in uncommon sites (Siles-Lucas et al 2023). Therefore, the theoretical use of serology in screening campaigns for early diagnosis, for capturing people with active infection, and for capturing infection not detectable by portable imaging modalities (i.e., US) is thwarted by its low sensitivity especially in these conditions, and by the high rate of seropositive cases with eventually no detectable CE cysts.…”

Cystic Echinococcosis in the Early 2020s: A Review

“…In light of this endeavor, the WHO aims to reach global disease control by 2030. Specialists worldwide have taken notice of the hyperendemic areas, and an increasing number of countries have joined the WHO efforts to control it [ 21 , 22 , 23 ].…”