Laboratory diagnosis of measles infection using molecular and serology during 2019-2020 outbreak in Brazil: RUNNING TITLE: Measles and PCR

Available online 29 November 2023, 105623

Author links open overlay panel, ABSTRACTIntroduction

Laboratory diagnosis of measles can be challenging, and the reintroduction of the measles virus in Brazil has brought about new issues. The aim of this study was to analyze the qPCR results of swab and urine samples and compare them with those of immunological methods for the diagnosis of measles.

Methods

This was a cross-sectional study based on a retrospective analysis of 3,451 suspected cases using laboratory test surveillance databases for qPCR (respiratory swabs and urine) and serologic tests for IgM and paired IgG. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and agreement through kappa and adjusted kappa coefficients (PABAK) were calculated using different diagnostic strategies.

Results

The swab and urine samples obtained using real-time qPCR were equivalent. Samples collected simultaneously and the combined samples showed moderate agreement between IgM ELISA and real-time qPCR; however, 48.9% of the IgM ELISA analyses did not demonstrate detectable qPCR concentrations during simultaneous collections and 43.9% of combined collections. The paired analysis of IgG showed an accuracy of 67.5% for IgM and 90.7% for real-time qPCR.

Conclusions

Diagnosis based on IgM presents detection delimitation in samples collected early (1–5 days), suggesting that these individuals satisfy at least two criteria. In addition to qPCR, paired analysis of IgG using ELISA can be used to increase the sensitivity and specificity of laboratory diagnoses.

Section snippetsINTRODUCTION

Measles is a viral infection characterized by high fever and exanthema (skin rash). Primarily categorized as a childhood disease, its endemic circulation has been interrupted in most countries in the Americas through vaccination and prevention strategies. However, owing to the highly infectious nature of the virus and its circulation in other countries, imported cases and outbreaks still occur 1.

The ability to diagnose measles clinically becomes increasingly difficult with increase in vaccine

Study design

This was a cross-sectional study based on a retrospective analysis of laboratory test results obtained from the Brazilian Laboratorial Environment Manager System (GAL) and clinical data recorded in the Notifiable Diseases Information System (SINAN), referring to the measles outbreak that occurred in the state of Paraná, state in the south of Brazil, from August 2019 to September 2020. The requirement for informed consent was waived by the local ethics committee (PUCPR, Curitiba, Brazil), which

RESULTS AND DISCUSSION

Of the total 4,433 cases registered in GAL and 3,648 cases reported in SINAN, 3,451 cases were suspected in this study through the analysis of 2,923 respiratory swab samples and 930 urine samples by qPCR, 3,389 IgM, and 576 by paired IgG. For comparative analysis, 783 simultaneous collections of respiratory swab and urine samples by qPCR (group 1), 1,070 simultaneous collections of qPCR and IgM ELISA (group 2), 2,679 combined qPCR and IgM ELISA collections (group 3), and 492 combined qPCR, IgM,

CONCLUSION

The study proposes an evaluation of the performance of the tests used for laboratory diagnosis during an outbreak, using a representative sampling of the target population (individuals with and without the disease). For this reason, all samples were used, despite the high number of cases discarded by both methodologies.

The kappa index, used to assess the concordance rate, can indicate a low level of reliability between the prevalence extremes, even when concordance is high. However, the

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

ACKNOWLEDGEMENTS

None.

Consent to Participate

N/A.

Consent to Publish

All the authors have approved the final version of this manuscript.

Author Contributions

FFT- data analysis and final review of the manuscript; EWC- drafting the manuscript, investigation, and data analysis.

Funding

None.

Availability of data and materials

All data are available upon reasonable request.