Diagnostic accuracy of commercially available serological tests for the detection of measles and rubella viruses: a systematic review and meta-analysis.

Measles and rubella serological diagnoses are done by IgM detection. The World Health Organization Global Measles and Rubella Laboratory Network previously endorsed Siemens Enzygnost enzyme-linked immunosorbant assay kits, which have been discontinued. A recommended replacement has not been determined. We aimed to search for suitable replacements by conducting a systematic review and meta-analysis of IgM detection methods that are currently available for measles and rubella. A systematic literature search was performed in Medline, Embase, Global Health, Cochrane Central, and Scopus on March 22 and on 27 September 2023. Studies reporting measles and/or rubella IgM detection with terms around diagnostic accuracy were included. Risk of bias was assessed using QUADAS tools. Meta-DiSc and R were used for statistical analysis. Clinical samples totalling 5,579 from 28 index tests were included in the measles meta-analysis. Sensitivity and specificity of the individual measles studies ranged from 0.50 to 1.00 and 0.53 to 1.00, respectively. Pooled sensitivity and specificity of all measles IgM detection methods were 0.94 (CI: 0.90-0.97) and 0.94 (CI: 0.91-0.97), respectively. Clinical samples totalling 4,983 from 15 index tests were included in the rubella meta-analysis. Sensitivity and specificity of the individual rubella studies ranged from 0.78 to 1.00 and 0.52 to 1.00, respectively. Pooled sensitivity and specificity of all rubella IgM detection methods were 0.97 (CI: 0.93-0.98) and 0.96 (CI: 0.93-0.98), respectively. Although more studies would be ideal, our results may provide valuable information when selecting IgM detection methods for measles and/or rubella.

Evaluation of Diagnostic Accuracy of Eight Commercial Assays for the Detection of Rubella Virus-Specific IgM Antibodies.

Rubella and congenital rubella syndrome are caused by the rubella virus and are preventable through vaccination, making disease eradication possible. Monitoring of progress toward global eradication and local elimination requires high-quality, sensitive disease surveillance that includes laboratory confirmation of cases. Previous evaluations of anti-rubella IgM detection methods resulted in the broad adoption of the Enzygnost (most recently manufactured by Siemens) enzyme-linked immunosorbent assay (ELISA) kits within WHO's global measles and rubella laboratory network, but they have been discontinued. This study evaluated seven comparable ELISAs from six manufacturers (Trinity Biotech, Euroimmun, Clin-Tech, NovaTec and Virion\Serion) as well as one automated chemiluminescent assay (CLIA) from DiaSorin. These assays include three IgM capture assays and five indirect ELISAs. A panel of 238 sera was used for the evaluation that included 38 archival rubella IgM-positive sera and 200 sera collected from patients with symptomatically similar diseases, such as measles, dengue, parvovirus B19 infection, and roseola. With this panel of sera, the sensitivity of the methods ranged from 63.2% to 100% and the specificity from 80.0% to 99.5%. No single method had both sensitivity and specificity of >90%, unless sera with equivocal results were considered presumptively positive. Some assays, particularly the Serion ELISA, had a large number of false positives with parvovirus B19 IgM-positive sera as well as sera from confirmed measles cases. The performance characteristics identified in this evaluation serve as a reminder to not rely solely on rubella IgM results for case confirmation in elimination settings.

Evaluation of Diagnostic Accuracy of Eight Commercial Assays for the Detection of Measles Virus-Specific IgM Antibodies.

The World Health Organization (WHO) has targeted measles for global eradication through mass immunization. For effective monitoring of eradication targets, high-quality surveillance is needed. The detection of IgM antibodies, specific to the measles virus, with the use of commercial enzyme-linked immunosorbent assays (ELISA or EIA) is broadly used within the WHO global measles and rubella laboratory network for laboratory confirmation, and in particular, ELISA kits manufactured by Siemens (Enzygnost kits) have been primarily used. Spurred by the discontinuation of these kits, this study aims to report on the clinical sensitivity and specificity of comparable commercial ELISA kits and one automated chemiluminescent immunoassay (CLIA) method. A panel of 239 serum samples was assembled that included sera from confirmed measles cases (n = 50) and probable post-MMR vaccine response (n = 2). Measles-negative sera (n = 187) were collected from individuals presenting with other fever and rash illnesses. A total of 7 ELISA kits (Euroimmun native antigens and recombinant nucleoprotein, IBL, Clin-Tech Microimmune, NovaTec NovaLisa, Serion, and Siemens Enzygnost) and one CLIA method (DiaSorin LIAISON XL) were evaluated. The ELISA kits included two IgM capture methods and five indirect methods. Calculated sensitivities and specificities ranged from 75.0% to 98.1% and 86.6% to 99.5%, respectively. The parvovirus B19 IgM positive sera were noted to cause false-positive results, particularly for the ELISA kits from Serion and NovaLisa; specificities for this subset of samples ranged from 51.4% to 100.0%. The capture IgM ELISA methods provided the best combination of sensitivity and specificity.

Simultaneous Detection and Differentiation between Wild-Type and Vaccine Measles Viruses by a Multiplex Real-Time Reverse Transcription-PCR Assay.

Measles is one of the most contagious viral respiratory infections and was declared to be eliminated from Canada in 1998; however, measles cases and outbreaks still occur every year through reintroduction from other parts of the world. Laboratory confirmation of measles virus (MV) RNA by real-time PCR provides a definitive diagnosis, and molecular analysis to determine the genotype is the only way to distinguish between wild-type and vaccine strains. This distinction is important since live attenuated vaccine strains are able to replicate in the patient and can be associated with rash and fever but are poorly transmissible, if at all. Prompt reporting of measles cases to local authorities, including differentiation between wild-type and vaccine strains, allows for optimal management and contact tracing. The development and validation of a multiplex real-time reverse transcription-PCR (rtRT-PCR) assay for the simultaneous detection and differentiation of the Moraten and Schwarz vaccine strains from presumptive wild-type MV in a format that can be easily implemented for high-throughput testing of patient samples are reported here. This assay is sensitive, specific, reproducible, and 100% accurate in comparison with the gold standard comparator assay.

Cost-effectiveness of measles control during elimination in Ontario, Canada, 2015.

BackgroundGiven that measles is eliminated in Canada and measles immunisation coverage in Ontario is high, it has been questioned whether Ontario's measles outbreak response is worthwhile.AimOur objective was to determine cost-effectiveness of measles containment protocols in Ontario from the healthcare payer perspective.MethodsWe developed a decision-analysis model comparing Ontario's measles containment strategy (based on actual 2015 outbreak data) with a hypothetical 'modified response'. The modified scenario assumed 10% response costs with reduced case and contact tracing and no outbreak-associated vaccinations; it was based on local and provincial administrative and laboratory data and parameters from peer-reviewed literature. Short- and long-term health outcomes, quality-adjusted life years (QALYs) and costs discounted at 1.5%, were estimated. We conducted one- and two-way sensitivity analyses.ResultsThe 2015 outbreak in Ontario comprised 16 measles cases and an estimated 3,369 contacts. Predictive modelling suggested that the outbreak response prevented 16 outbreak-associated cases at a cost of CAD 1,213,491 (EUR 861,579). The incremental cost-effectiveness ratio was CAD 739,063 (EUR 524,735) per QALY gained for the outbreak response vs modified response. To meet the commonly accepted cost-effectiveness threshold of CAD 50,000 (EUR 35,500) per QALY gained, the outbreak response would have to prevent 94 measles cases. In sensitivity analyses, the findings were robust.ConclusionsOntario's measles outbreak response exceeds generally accepted cost-effectiveness thresholds and may not be the most efficient use of public health resources from a healthcare payer perspective. These findings should be balanced against benefits of increased vaccine coverage and maintaining elimination status.

Evaluation of 5 Commercially Available Zika Virus Immunoassays.

Because of the global spread of Zika virus, accurate and high-throughput diagnostic immunoassays are needed. We compared the sensitivity and specificity of 5 commercially available Zika virus serologic assays to the recommended protocol of Zika virus IgM-capture ELISA and plaque-reduction neutralization tests. Most commercial immunoassays showed low sensitivity, which can be increased.

Measles Outbreak with Unique Virus Genotyping, Ontario, Canada, 2015.

The province of Ontario continues to experience measles virus transmissions despite the elimination of measles in Canada. We describe an unusual outbreak of measles in Ontario, Canada, in early 2015 that involved cases with a unique strain of virus and no known association among primary case-patients. A total of 18 cases of measles were reported from 4 public health units during the outbreak period (January 25-March 23, 2015); none of these cases occurred in persons who had recently traveled. Despite enhancements to case-patient interview methods and epidemiologic analyses, a source patient was not identified. However, the molecular epidemiologic analysis, which included extended sequencing, strongly suggested that all cases derived from a single importation of measles virus genotype D4. The use of timely genotype sequencing, rigorous epidemiologic investigation, and a better understanding of the gaps in surveillance are needed to maintain Ontario's measles elimination status.

Rapid Identification of Measles Virus Vaccine Genotype by Real-Time PCR.

During measles outbreaks, it is important to be able to rapidly distinguish between measles cases and vaccine reactions to avoid unnecessary outbreak response measures such as case isolation and contact investigations. We have developed a real-time reverse transcription-PCR (RT-PCR) method specific for genotype A measles virus (MeV) (MeVA RT-quantitative PCR [RT-qPCR]) that can identify measles vaccine strains rapidly, with high throughput, and without the need for sequencing to determine the genotype. We have evaluated the method independently in three measles reference laboratories using two platforms, the Roche LightCycler 480 system and the Applied Biosystems (ABI) 7500 real-time PCR system. In comparison to the standard real-time RT-PCR method, the MeVA RT-qPCR showed 99.5% specificity for genotype A and 94% sensitivity for both platforms. The new assay was able to detect RNA from five currently used vaccine strains, AIK-C, CAM-70, Edmonston-Zagreb, Moraten, and Shanghai-191. The MeVA RT-qPCR assay has been used successfully for measles surveillance in reference laboratories, and it could be readily deployed to national and subnational laboratories on a wide scale.

Genomic diversity of mumps virus and global distribution of the 12 genotypes.

The WHO recently proposed an updated nomenclature for mumps virus (MuV). WHO currently recognizes 12 genotypes of MuV, assigned letters from A to N (excluding E and M), which are based on the nucleotide sequences of small hydrophobic (SH) and haemagglutinin-neuraminidase (HN) genes. A total of 66 MuV genomes are available in GenBank, representing eight of the 12 genotypes. To complete this dataset, whole genomes of seven isolates representing six genotypes (D, H, I, J, K and L) and one unclassified strain were sequenced. SH and HN genes of other representative strains were also sequenced. The degree of genetic divergence, predicted amino acid substitutions in the HN and fusion (F) proteins and geographic distributions of MuV strains were analysed based on the updated dataset. Nucleotide heterogeneity between genotypes reached 20% within the SH gene, with a maximum of 9% within the HN gene. The geographic and chronologic distributions of the 12 genotypes were summarised. This review contributes to our understanding of strain diversity for wild type MuV, and the results support the current WHO nomenclature.

Genome sequence of a measles virus strain with a novel loss of stop codon mutation in the phosphoprotein gene.

Measles virus genotype B3 coding-complete genome sequence from a 2019 case showed a novel mutation in the phosphoprotein (P) gene that abrogates the established stop codon. A downstream stop codon has been identified, resulting in a putative P that would be 19 amino acids longer than wild type.

Dimeric immunoglobulin A as a novel diagnostic marker of measles infection.

IMPORTANCE: The world is facing a measles resurgence, and improved diagnostic tests for measles infection are an urgent World Health Organization research priority. Detection of measles-specific immunoglobulin M (IgM) as a standard diagnostic test has low positive predictive value in elimination settings, and there is a need for new biomarkers of measles infection to enable enhanced surveillance and response to outbreaks. We demonstrate the detection of measles-specific dimeric immunoglobulin A (dIgA) in patients with confirmed measles infections using a new indirect enzyme-linked immunosorbent assay protocol that selects for the dIgA fraction from total IgA in the blood. The magnitude of measles-specific dIgA responses showed a low correlation with IgM responses, and our results highlight the potential of dIgA for further development as an alternative and/or complementary biomarker to IgM for serological diagnosis of measles infection.

Genomic Characterization of Three Canadian Mumps Outbreaks Demonstrates Endemic Transmission in Canada.

Despite the provision of a mumps vaccination program in Canada for over three decades, mumps has not reached elimination. Instead, a re-emergence has been observed in vaccinated populations, particularly in young adults. These outbreaks have been almost exclusively due to genotype G infections, a trend that has been seen in other countries with high mumps vaccination rates. To characterize mumps outbreaks in Canada, genomes from samples from Manitoba (n = 209), Newfoundland (n = 25), and Nova Scotia (n = 48) were sequenced and analysed by Bayesian inference. Whole genome sequencing was shown to be highly discriminatory for outbreak investigations compared to traditional Sanger sequencing. The results showed that mumps virus genotype G most likely circulated endemically in Canada and between Canada and the US. Overall, this Canadian outbreak data from different provinces and ancestral strains demonstrates the benefits of molecular genomic data to better characterize mumps outbreaks, but also suggests genomics could further our understanding of the reasons for potential immune escape of mumps genotype G and evolution in highly vaccinated populations. With a possible endemic circulation of mumps genotype G and the remaining risk of new imported cases, increased surveillance and alternative vaccination strategies may be required for Canada to reach the current target for mumps or a future elimination status.

Congenital rubella syndrome, a case series.

Rubella, or German measles, is a vaccine-preventable disease. Rubella infection is usually mild; however, infection in pregnancy is associated with severe outcomes for the baby, including pregnancy loss or a combination of developmental defects called congenital rubella syndrome. Within the last ten-year period, two cases of congenital rubella syndrome in Saskatchewan were reported to the provincial ministry and the Public Health Agency of Canada of the newborns of mothers who had recently arrived from Sub-Saharan Africa. Both infants had multiple health complications at birth consistent with congenital rubella and tested positive for the rubella virus. The article discusses the challenges encountered by the healthcare system in diagnosing, investigating, monitoring and managing cases of congenital rubella syndrome to prevent further sporadic transmission. The article emphasizes the need to provide additional support for cases and their households, especially new Canadians with less support to comply with public health advice and the importance of routine immunization to eliminate rubella globally.

Local public health response to vaccine-associated measles: case report.

BACKGROUND: The most appropriate public health approach to vaccine-associated measles in immunocompromised patients is unknown, mainly because these cases are rare and transmission of vaccine-associated measles has not been previously documented. In this case report, we describe Peel Public Health's response to a vaccine-associated measles case in an immunocompromised child in Ontario, Canada. CASE PRESENTATION: A five-year-old Canadian-born boy with a history of a hematopoetic stem cell transplant three years previously received live attenuated measles, mumps, and rubella (MMR) vaccine. Over the subsequent 7 to 14 days, he developed an illness clinically consistent with measles. There was no travel history or other measles exposure. Serology and polymerase chain reaction (PCR) testing confirmed acute measles infection. Following discussion with pediatric infectious diseases specialists, but prior to the availability of virus sequencing, it was felt that this case was most likely due to vaccine strain. Although no microbiologically confirmed secondary cases of vaccine-associated measles have been previously described, we sent notification letters to advise all contacts of measles symptoms since the likelihood of transmission from an immunocompromised patient was low, but theoretically possible. We decided to stratify contacts into immune competent and compromised and to deal with the latter group conservatively by excluding them as if they were exposed to wild-type measles because the risk of transmission of disease in this population, while presumably very low, is unknown. However, no contacts self-identified as immunocompromised and there were no secondary cases. Subsequent genotyping confirmed that this case was caused by vaccine strain measles virus. CONCLUSION: The public health approach to contact tracing and exclusions for vaccine-associated measles in immunocompromised patients is unclear. The rarity of secondary cases provides further evidence that the risk to the general public is likely extremely low. Although the risk appears negligible, exclusion and administration of immune globulin may be considered for susceptible, immunocompromised contacts of cases of vaccine-associated measles in immunocompromised patients.

Mumps resurgence in a highly vaccinated population: Insights gained from surveillance in Canada, 2002-2020.

Although mumps vaccination has been routine in Canada for decades, mumps cases and outbreaks continue to occur periodically. Mumps surveillance, including monitoring of the mumps virus genotype associated with disease activity, is important to document baseline activity and to advance further research into vaccine effectiveness. Here we describe a detailed analysis of mumps cases that have been detected in Canada from 2002 to 2020, with a focus on the mumps molecular epidemiology. In total, 7395 cases of mumps were reported to the surveillance system, with outbreaks occurring in the years 2007, 2010 and 2016 to 2018. Adolescents and young adults aged 15 to 29 years had the highest risk of being a case (rate ratios ranging from 1.50 to 2.29), compared to adults aged 30 to 39. Genotypes of mumps viruses were determined in 3225 specimens. Genotype G was predominantly detected (96% of genotyped specimens) and was first reported in 2005. Other genotypes were more likely to be detected in cases that also reported travel (or were linked to imported cases) than the cases with genotype G detected (p < 0.0001). The genotype G viruses had little sequence diversity in the 316 nucleotide window used for genotyping (the small hydrophobic protein gene) and mainly belonged to a single phylogenetic lineage that included the MuVi/Sheffield.GBR/1.05 reference sequence. The analysis of over ten years of data has demonstrated that mumps genotype G, specifically belonging to a single lineage, the Sheffield lineage, is the endemically circulating virus in Canada. This lineage is seen also in other countries using the genotype A vaccine. Mumps remains endemic despite high MMR vaccination coverage which has been sufficient to eliminate circulation of measles and rubella in Canada, raising the hypothesis of the evolution towards a vaccine escape mumps virus.

Development of a rapid, internally controlled, two target, real-time RT-PCR for detection of measles virus.

Vaccination has greatly reduced global measles incidence, however measles remains endemic in many regions worldwide. Measles surveillance relies on high performance molecular detection of the virus. We have developed and validated a multiplex rRT-PCR assay for the detection of measles virus. The assay includes three independent probes with unique reporter dyes for the simultaneous detection of the measles hemagglutinin gene, nucleoprotein gene and endogenous RNaseP control. Using dilution series of synthetic RNAs the limits of detection were determined to be approximately 20 copies of measles RNA. The assay is extremely reproducible with very low intra-assay and inter-assay coefficients of varation for both the N and the H targets. After testing 68 confirmed measles positive and 86 measles negative archival clinical samples our data shows the multiplex assay has a sensitivity and specificity of 100 %, and a 100 % concordance with the expected results. No cross reactivity was identified with clinical specimens positive for six other viruses. According to the WHO, currently only the B3, D4, D8, H1 measles genotypes of the 24 recognized genotypes continue to circulate and this new multiplex assay successfully detected all four of those genotypes as well as six other genotypes.

Optimisation of methodology for whole genome sequencing of Measles Virus directly from patient specimens.

In an era of decreasing genetic diversity of Measles Virus (MeV), effective surveillance requires a higher-resolution genotyping method or whole genome sequencing (WGS) to document elimination. Through optimization of MeV WGS protocol, we developed a MeV-specific probe enrichment method that allows next generation sequencing from clinical specimens. With the probe enrichment method, 70% of specimens can be sequenced at a read depth of greater than 10 reads with minimal off-target sequences.

Development of a rapid, internally controlled, two target, real-time RT-PCR for detection of rubella virus.

Rubella surveillance in elimination setting relies on rapid molecular detection of the virus. In this study a multiplex real-time RT-PCR assay for the detection of rubella virus was validated. The assay includes three independent probes with unique reporter dyes for the simultaneous detection of the rubella viral coding regions for envelope glycoprotein E1 and non-structural p150 protein, and an endogenous control (human RNaseP). Using dilution series of synthetic RNAs, the limits of detection were determined to be at least 50 copies of rubella RNA. The assay is reproducible with low intra-assay and inter-assay coefficients of variation for both the E1 and the p150 targets. After testing 62 confirmed rubella positive and 165 rubella negative archival clinical samples, the sensitivity and specificity of the multiplex assay were 98.4 and 100 %, respectively. No cross reactivity was identified with clinical specimens positive for eleven other viruses. This multiplex assay successfully detected nine viral genotypes including the predominant genotypes 1E, 1G, 1J, and 2B as well as the 1a vaccine genotype.

Measles surveillance in Canada, 2019.

BACKGROUND: The Public Health Agency of Canada (PHAC) has conducted enhanced measles surveillance since 1998, the year endemic measles transmission was eliminated in Canada. The objective of this annual national measles surveillance report is to provide an epidemiologic summary of measles activity reported in Canada for 2019 in order to provide evidence to support the continued verification of Canada's measles elimination status. METHODS: Measles surveillance data are housed in the Canadian Measles and Rubella Surveillance System (CMRSS) database. Descriptive analyses of demographics and risk factors were performed. Outbreak characteristics were summarized and genotypic analyses conducted. Surveillance, laboratory and vaccine coverage data for 2019 were used to assess Canada's status against the Pan American Health Organization (PAHO) essential criteria for the verification of measles elimination. RESULTS: In 2019, 113 measles cases were reported in Canada (crude incidence rate of 3.0 cases per 1,000,000 population). Of these cases, 42 (37%) were imported into Canada, and of the imported cases, 12 (29%) resulted in further transmission. Infants younger than one year had the highest age-specific incidence rate at 13.1 cases per 1,000,000 population. Only 29% of cases had one or more documented doses of measles-containing vaccine. One-fifth (19%) of cases were hospitalized; no deaths were reported. Genotype information was available for 100% of outbreaks reported in 2019 and 90% of non-outbreak-related measles cases; of cases with genotype information available, 27% were B3 and 73% were D8. CONCLUSION: Despite meeting/partially meeting only three out of four of PAHO's essential criteria for measles elimination status, there is no evidence that endemic measles transmission has been reestablished in Canada.