Disease condition and impact on patients HEV is an RNA virus and a leading cause of acute viral hepatitis worldwide (1). Hepatitis E disease presents as acute, viral hepatitis. During the first week of illness, many symptoms are nonspecific, including fever, malaise, nausea and vomiting. After the prodromal phase, patients experience a period of acute, icteric hepatitis, including jaundice, dark urine, pale stools and prolonged cholestasis with elevated liver enzymes. Symptoms can last 4–6 weeks (2). Most cases occur in older adolescents and adults. In general, these cases are mild and self-limiting, yet approximately 1–2% of cases die. However, some populations are more prone to severe disease. Women infected during pregnancy are at increased risk of fulminant hepatic failure and its associated complications, including hepatic encephalopathy, cerebral oedema and disseminated intravascular coagulation. HEV infection during pregnancy also has poor outcomes for the fetus, including low birth weight, small for gestational age, preterm birth and intrauterine death (3). A recent meta-analysis found the case fatality rate of hepatitis E during pregnancy to be 26% (IQR: 17–41%) for the mother, 33% (IQR: 19–37%) for the fetus and 8% (IQR 3–20%) for the neonate (4). HEV is a pathogen of global concern (5). However, the burden of disease is not distributed evenly; HEV is very common in low-income countries, where it causes substantial burden of disease, while relatively few cases are reported from high-income countries (5). There are four genotypes of HEV that infect humans. Genotypes 1 and 2 only infect humans and are thought to be transmitted primarily via contaminated drinking water. These genotypes are most common in South-East Asia and Africa (6). They are responsible for large outbreaks, with cases numbering in the tens of thousands. Outbreaks have been reported from East and South-East Asia, and protracted outbreaks have occurred in Africa, often affecting displaced populations (7). However, genotypes 1 and 2 also cause substantial disease outside of outbreaks (6). In India, between 25% and 50% of clinical hepatitis cases are caused by HEV, even in the absence of an outbreak (6). Genotypes 3 and 4 infect humans and a wide range of mammals, notably wild and domestic swine. These genotypes are usually transmitted zoonotically from eating infected meat and are largely reported from Europe, East Asia and the Americas. Here, HEV is responsible for sporadic cases and small foodborne outbreaks (8). Does the test meet a medical need? The availability of HEV diagnostic tests will improve differential diagnosis capability in the case of acute jaundice syndrome. Early diagnosis will alert authorities to the possibility of an outbreak, which can mobilize mitigation efforts. Due to the lack of diagnostic testing in areas where HEV is most common, the burden of HEV disease is underestimated and often poorly understood at the country level. This lack of awareness and understanding by country officials has prevented the use of a vaccine during outbreaks. How the test is used When a suspect HEV case presents at the community level, defined as any person presenting with an acute (recent, new or abrupt) onset of jaundice (yellowing of whites of eyes or skin) or dark urine and pale clay stools, a rapid IgM test should be performed, if available, to confirm the diagnosis (9). If the rapid IgM test is positive, this can be considered case confirmation. If the rapid test is positive early in an outbreak, samples may still be sent to a reference laboratory for IgM ELISA or PCR confirmation. If the patient tested negative on the rapid IgM test and no other cause for the acute jaundice has been found, an IgM ELISA or PCR should be performed to confirm the negative diagnosis. Note: the following algorithm was provided by the applicant as part of this application and is not a WHO algorithm. Diagnostic algorithm for HEV infection: https://docs.google.com/presentation/d/ 10Yd0I67LoepbYSHxIIZwrMEKUJttU9OA/edit#slide=id.p1 (accessed 1 August 2023). Anti-HEV IgM antibodies appear early during infection and indicate a current or recent infection. They are detectable in blood about 3–7 days after symptom onset (after approx. 1 month incubation period) and persist for several months (10). IgM EIAs that use an antibody capture technique are more specific than indirect antibody assays. IgM assays use recombinant antigens from the ORF2 or ORF3 region of HEV. ORF2-specific assays can detect antibodies in serum earlier in the course of infection and are more useful for diagnosis during the acute phase of the illness (11). Anti-HEV IgM antibody assays have high sensitivity (up to 98%) and specificity (up to 96%) and high PPV in patients with acute hepatitis in highly endemic areas (9). Additionally, where POC testing is not an option (dependent on setting and available lab infrastructure), specimens can be preserved so that ELISAs can be performed retrospectively.

Prevalence A commonly cited meta-analysis estimated that HEV causes 20.1 million infections, 3.4 million clinical cases, 70 000 deaths and 3000 stillbirths annually due to the epidemic-prone genotypes 1 and 2 (12). While there is increasing recognition of HEV in genotype 3 and 4 endemic areas, the burden of disease has not been well classified. However, the burden of disease of HEV is vastly underestimated due to the lack of diagnostic capabilities in areas where HEV is most common. Socioeconomic impact Poor understanding of the global burden of disease has hindered efforts to implement control and prevention strategies. Few studies have looked at the economic impact of hepatitis E. In Nepal, acute HEV infection led to an average of 10 bedridden days and 22 sick days; wage earners lost nearly 20% of their yearly income (13). An estimated 108 YLL per 1000 individuals, 144 years lived with disability per 1000 individuals and 252 DALYs per 1000 individuals were attributed to an HEV outbreak in Uganda (14). However, this estimate used disability weights for untreated diarrhoeal disease and did not account for differential severity among pregnant women and neonates, therefore underestimating the true economic impact.

The use of ELISA to diagnose acute hepatitis E in suspected cases is supported by the WHO guidance document Waterborne outbreaks of hepatitis E: recognition, investigation and control (9, 15). The ELISA is one of the first-line laboratory tests recommended for this purpose.

There are currently no systematic reviews that detail the clinical accuracy of HEV IgM ELISAs. For the purposes of this application, it was therefore necessary to conduct a systematic review. To do so, a search was conducted through PubMed using the search terms ((HeV) OR (Hepatitis E Virus)) AND (ELISA) AND (specificity), which yielded 205 results. Results were limited to English language. Initial searching made it necessary to narrow search results by filtering out articles with (latex) or (Hendra), limiting results to those published after 2000 and only using human sera, resulting in 178 hits. After review, 15 publications were found to be relevant to HEV IgM ELISAs specifically. Three further articles were found through snowballing. Clinical accuracy was examined in these 18 studies, including 12 commercial ELISAs and three in-house tests. Twelve articles discussed the Wantai HEV IgM ELISA (10, 11, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25): Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. Four studies involved Asian populations, two studies were of European populations, one involved an African population, and the rest did not specify the geographic location of their participants. The test was evaluated in patients infected with genotypes 1, 3 and 4, although many of the studies did not specify the infecting genotype. Two studies had study designs that were likely to give low sensitivity values. One study included a mix of immunocompromised and immunocompetent participants but did not separately report test performance by immune status. Antibody assays are less sensitive in immunocompromised populations. The other study tested the ELISA using serial dilutions from a few patients but did not separately report sensitivity for the undiluted samples. The undiluted samples would most accurately reflect clinical sensitivity. When these two studies are eliminated, the range of sensitivity is 82–98%. One study had a study design that was likely to give a low specificity. The ELISA was evaluated in acute hepatitis patients within 4 weeks of symptom onset. The specificity was evaluated in the acute hepatitis patients who were HEV RNA negative. HEV RNA may not persist in the blood for 4 weeks, whereas IgM lasts for several months. When this study is eliminated, the range of specificity is 97–100%. Range of sensitivity: 65–100% Range of specificity: 28–100% Range of PPV: 41–100% Range of NPV: 83–98% Seven articles discussed MP Biomedical’s Assure HEV IgM ELISA (11, 19, 23, 25, 26, 27, 28): Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA-negative blood donors. Two studies involved Asian populations, two studies were in European populations, one study included participants from six countries, and two studies did not specify the geographic location of their participants. The test was evaluated in patients infected with all four genotypes. Two studies had study designs that were likely to give low sensitivity values. One study included a mix of immunocompromised and immunocompetent participants but did not separately report test performance by immune status. Antibody assays are less sensitive in immunocompromised populations. The other study tested the ELISA using serial dilutions from a few patients but did not report the sensitivity for the undiluted samples. The undiluted samples would most accurately reflect clinical sensitivity. When these two studies are eliminated, the range of sensitivity is 72–96%. Range of sensitivity: 60–96% Range of specificity: 84–99% Range of PPV: 17–96% Range of NPV: 98–99% Five articles discussed Mikrogen’s recomWell HEV IgM ELISA (11, 23, 27, 28, 29): Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. Two studies involved Asian populations, one study was in a European population, and two studies did not specify the geographic location of their participants. One study included only genotype 3 patients, one study included genotype 1 and 2 patients, one study included genotype 1 and 3 infections as well as a few patients with an unknown infecting genotype, one study included genotype 1, 2 and 3 infections, and the fifth included genotype 1, 3 and 4 infections. Two studies had study designs that were likely to give low sensitivity values. One study included a mix of immunocompromised and immunocompetent participants but did not separately report test performance by immune status. Antibody assays are less sensitive in immunocompromised populations. The other study tested the ELISA using serial dilutions from a few patients but did not separately report sensitivity for the undiluted samples. The undiluted samples would most accurately reflect clinical sensitivity. When excluding these two studies, the range of sensitivity is 92–100%. Range of sensitivity: 74–100% Range of specificity: 88–99% PPV: 24% NPV: 100% Three articles discussed the DSI HEV IgM ELISA (11, 23, 29): * Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. One study included participants from six countries, and two studies did not specify the geographic location of their participants. One study included genotype 1, 2 and 3 patients, one study included only genotype 3 patients, and the third study included genotype 1 and 3 infections as well as a few patients with an unknown infecting genotype. Two studies had study designs that were likely to give low sensitivity values. One study included a mix of immunocompromised and immunocompetent participants but did not separately report test performance by immune status. Antibody assays are less sensitive in immunocompromised populations. The other study tested the ELISA using serial dilutions from a few patients but did not separately report sensitivity for the undiluted samples. The undiluted samples would most accurately reflect clinical sensitivity. The third study, without these study design issues, reported a clinical sensitivity of 98%. Range of sensitivity: 71–98% Range of specificity: 90–95% Range of PPV: not given Range of NPV: not given Two articles discussed the Adaltis EIAgen HEV IgM ELISA (26, 27): Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses. One study included participants from Europe, and the other from Asia. One study included genotype 1, 3 and 4 patients; the other study included genotype 1 and 3 patients. Range of sensitivity: 80–90% Range of specificity: 87–100% Range of PPV: 18–100% Range of NPV: 98–99% Two articles discussed Dia.Pro’s HEV IgM ELISA (11, 21): Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. Neither study specified the geographic location of their participants. One study included only genotype 3 patients; the other study included genotype 1 and 3 infections as well as a few patients with an unknown infecting genotype. The low sensitivity values reflect the study designs. One study included a mix of immunocompromised and immunocompetent participants but did not separately report test performance by immune status. Antibody assays are less sensitive in immunocompromised populations. The other study tested the ELISA using serial dilutions from a few patients but did not separately report sensitivity for the undiluted samples. The undiluted samples would most accurately reflect clinical sensitivity. Range of sensitivity: 60–81% Specificity: 98% Range of PPV: not given Range of NPV: not given Two articles discussed Genelabs HEV IgM ELISA (17, 30): * Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. One study used a European population, and the other an Asian population. One study included genotype 1 and 3 patients; the other study did not specify the infecting genotype. Range of sensitivity: 79–83% Range of specificity: 94–99% PPV: 97% NPV: 94% Two articles discussed the Kehua anti-HEV IgM ELISA (17, 25): * Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. Both studies were completed in an Asian population and did not specify the infecting genotype. Range of sensitivity: 86–98% Range of specificity: 89–100% PPV: 100% NPV: 95.9% One article discussed the Bioelisa Biokit HEV IgM ELISA (19): * Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. This study was completed in a European population with mostly genotype 3 infections and a few genotype 1 infections. Sensitivity: 92% Specificity: not given PPV: not given NPV: not given One article discussed the Euroimmun HEV IgM ELISA (11): Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. The geographic location of the participants was not specified, and only genotype 3 infections were included. The low sensitivity value reflects the study design. This study tested the ELISA using serial dilutions from a few patients but did not report sensitivity for the undiluted samples. The undiluted samples would most accurately reflect clinical sensitivity. Sensitivity: 62% Specificity: not given PPV: not given NPV: not given One article discussed International Immuno-Diagnostics’ Anti-HEV IgM ELISA (28): * Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. This study was completed in participants from six countries, and included genotype 1, 2 and 3 infections. Sensitivity: 82% Specificity: 91% PPV: not given NPV: not given One article discussed the Lizhu HEV ELISA kit (17): * Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA- negative blood donors. The study was performed in an Asian population and did not specify the infecting genotype. Sensitivity: 84% Specificity: 100% PPV: 100% NPV: 95.2% Three articles developed and examined in-house immunoassays (27, 29, 31): Sensitivity was assessed by comparing the ELISA to PCR-positive, acute hepatitis E patients early in the course of symptoms. Specificity was assessed using patients with acute infections from other viruses or healthy, HEV RNA-negative blood donors. Two studies were in Asian populations; one was completed in participants from six countries. One study included genotype 1, 3 and 4 patients, one study included genotype 1, 2 and 3 patients, and the third did not specify the infecting genotype. Range of sensitivity: 67–98% Range of specificity: 78–96% PPV: 40% NPV: 98.9% Note: the table of commercially available IVD products is required as part of all applications to add new IVDs to the EDL. _________________________________________________________________________________________________________ * Footnote 2 -The commercial information for these ELISAs could not be obtained for inclusion in the commercially available IVD products table either because the ELISA was discontinued or because the company did not respond after repeated inquiries.

A systematic search across several databases at the time of submission of this application found no systematic reviews that examined the direct clinical utility of anti-HEV IgM ELISAs on patient care and management. However, one recent systematic review examined data on the epidemiology of HEV in LMICs of Africa and Asia based on seroprevalence, outbreaks and risk factors for infection (32). The lack of routine testing is a major limiting factor to understand the burden of HEV disease in LMICs. Ninety-one studies from 29 countries examined seroprevalence, with seroprevalence generally increasing by age. Forty-nine completed or ongoing HEV outbreaks from 18 countries were reported from 1988 to 2017. However, most outbreaks are not reported in the published literature, and alternative sources were not used for this systematic review. Risk factors for HEV infection included increased exposure to contaminated water sources and poor hygiene (although not all studies found this association). Risk factor data suggested an increased likelihood of current or recent HEV infection and disease associated with faecal-oral transmission of HEV, as well as exposure to blood and animals. However, the authors emphasized that most data on HEV prevalence and risk factors come from specialized studies or outbreak reports. There are no primary studies specific to the clinical utility of the HEV IgM ELISA on patient management and care. However, several preventative strategies could reduce the number of future HEV cases and deaths, especially if these preventative measures are introduced early in an outbreak. The applicant identified 12 studies that point to the clinical utility of an HEV diagnosis and greater understanding of the epidemiology and burden of HEV disease in the local context. Better understanding of the local epidemiology and disease burden caused by HEV will allow country officials to make evidence-based decisions on intervention implementation both prior to and during outbreaks.

No data available.

HEV IgM ELISAs have been demonstrated to have reduced sensitivity in transplant recipients, an immunocompromised population. In areas where HEV is endemic, HIV is likely to be the most common immunocompromising cause. ELISAs have not been evaluated in HIV-positive populations except for one study that included six HIV-positive patients. That study did not report lower sensitivity in these six patients; however, a systematic evaluation in HIV-positive patients is needed. The IgM ELISAs require a continuous power supply and basic laboratory infrastructure. These facilities may not be available in all areas and may be inaccessible to some populations. Increased availability of diagnostic testing would allow country officials to better understand the local burden of HEV, and therefore to make evidence-based decisions, for example regarding the routine use of HEV vaccine and its use during outbreaks. No ethical issues were identified.