Suggested new breakpoints of anti-MERS-CoV antibody ELISA titers: performance analysis of serologic tests

Area of Science:

• Virology
• Immunology
• Epidemiology

Background:

• Middle East respiratory syndrome coronavirus (MERS-CoV) poses a significant public health threat.
• Accurate serologic diagnostic and surveillance tools are crucial for MERS-CoV management.
• Existing serologic test cut-off values require optimization for improved performance.

Purpose of the Study:

• To establish optimal cut-off values for MERS-CoV serologic tests, including ELISA IgG, ELISA IgA, IFA IgM, and IFA IgG.
• To evaluate test performance for predicting neutralization activity in infected patients.
• To assess test utility for epidemiologic surveillance of MERS-CoV infections.

Main Methods:

• Performance evaluation of ELISA and IFA assays using 138 serum samples from MERS-CoV-infected patients and 219 from MERS-CoV-exposed individuals.
• Analysis of test performance based on serum collection time (days post onset of illness and days post exposure).
• Determination of optimal cut-off values for sensitivity and specificity.

Main Results:

• Serologic test performance improved with delayed sampling, peaking post-seroconversion.
• For neutralization activity prediction, ELISA IgG after 21 days post onset of illness (dpoi) showed 100% sensitivity/specificity at OD ratio 0.4.
• For infection diagnosis, ELISA IgG after 28 days post exposure (dpex) showed 97.3% sensitivity and 92.9% specificity at OD ratio 0.2.

Conclusions:

• New, lower cut-off values for ELISA IgG (OD ratio 0.2 at 28 dpex) and ELISA IgA (OD ratio 0.2 at 14 dpoi) significantly enhance MERS-CoV diagnosis and surveillance.
• Optimized serologic tests provide valuable tools for practical MERS-CoV management.
• The findings support the wider application of serologic testing in MERS-CoV epidemiology and clinical settings.