B-100 Utilization and Performance of Monospot and Epstein-Barr Virus Antibody Profile Testing for Diagnosis of Infectious Mononucleosis in Adolescents and Adults
Authors: Zhang X , Frisky C , Meyers J , Qureshi A , Stempak L , Schmotzer C , Noguez J 
Published: October 2024

Abstract

Background
Epstein-Barr virus (EBV) antibody profile, which includes IgM and IgG antibodies against EBV viral capsid antigen (VCA), IgG antibodies against early antigen (EA) and nuclear antigen (EBNA), is recommended by the CDC for diagnosing infectious mononucleosis (IM) and differentiating acute versus past infection. Conversely, the monospot test, which detects reactive heterophile antibodies, is not recommended by the CDC due to its low sensitivity in young children and non-specific nature. However, monospot tests remain widely used, especially as point-of-care testing at emergency department visits, likely related to their technical ease, rapid turnaround, and low cost. In this study, we compared the utilization and performance of the monospot test and EBV profile for the diagnosis of primary IM in adolescent and adult patients.

Methods
A retrospective review was conducted on consecutive monospot tests (Acceava Mono Cassette, Abbott) and EBV profiles (multiplex assay on Bioplex analyzer, Bio-Rad) performed between August 16, 2020, and August 15, 2021 in our hospital system. Cases with concurrent monospot and EBV profile testing were evaluated for qualitative agreement between the two methods. A chart review was conducted for cases with discrepant results between monospot and EBV antibody profile tests to assess the performance of these two methods. The final EBV infection status for each case was determined by clinical manifestation, relevant lab findings, and EBV profile results.

Results
A total of 1,524 monospot tests were performed, with an overall positive rate of 12.4%. The majority of tests were from the emergency departments (ED, 47.5%) and outpatient settings (48.7%), with inpatient tests comprising 3.8%. Notably, the positive rate was highest among outpatients (13.4%), followed by ED patients (12.3%), and lowest among inpatients (1.5%). In contrast, 3,769 EBV profile tests were performed, yielding an overall VCA IgM positive rate of 11.8% and 2.9% equivocal cases. Outpatient settings accounted for the majority of EBV profile tests (81.5%), followed by inpatients (16.2%) and ED patients (2.3%). Inpatients also exhibited a lower positive rate (7.5%) than ED (13.1%) or outpatients (13.1%). Among 364 cases concurrently tested by both the mono spot and the EBV profile, the negative agreement between the two tests was 97.7%, while the positive agreement was 52.8%. Discrepancies included 8 monospot-positive but VCA IgM-negative cases and 58 VCA IgM-positive but monospot-negative cases. Chart review revealed that monospot and EBV profiles missed 4 and 40 cases of primary IM, respectively. Additionally, 7 cases of past EBV infection exhibited prolonged VCA IgM positivity, and 2 cases of VCA IgM were falsely positive, likely due to cross-reaction with cytomegalovirus or B. burgdorferi IgM. Sensitivity/specificity for EBV profile and monospot were 96.4%/97.4% and 64.0%/100.0%, respectively.

Conclusions
The EBV profile demonstrates high sensitivity and specificity and is suitable as the primary test for diagnosing IM. While the monospot test exhibits good specificity, its lower sensitivity necessitates further testing with the EBV profile, particularly for patients with a high suspicion of IM, to avoid missed diagnoses.