View in Browser
Measles Update: Measles IgG New Cut-off

The CDC reports that from Jan. 1 to Oct. 3, 2019, there have been 1,250 individual cases of measles confirmed in 31 states1. This is the greatest number of measles cases reported in the U.S. since 1992 and highlights a new environment of lower measles vaccinations in specific populations and ongoing community exposure. Therefore, increased testing and communications with Public Health, CDC, clinicians and laboratorians has prompted a review of the optimal specificity and sensitivity for Measles IgG assays.

Re-exposure to the measles virus induces a strong anamnestic immune response with a rapid boosting of IgG antibodies, which prevents clinical disease2 suggesting lower positive IgG responses may provide appropriate protection. Unnecessary quarantine post-exposure is given as the reason for a sensitive Measles IgG assay by Public Health at both the state and county level. Consensus is that an assay for Measles IgG should be as sensitive as practicable to avoid unnecessary vaccination or unnecessary quarantine of those exposed to measles and thus reduce the overall individual and public health economic impact of measles outbreaks in the community.

DiaSorin, the manufacturer of the current assay used in the Microbiology Division, has reassessed the comparator data in light of these new needs and has lowered the cut-off and equivocal zone for the assay to increase the agreement for positive results with the comparator assay. There have been no changes to the assay formulation or performance.

Effective date: immediatley 

Methodology and reporting:
The DiaSorin LIAISON Measles IgG assay uses chemiluminescent immunoassay (CLIA) for the qualitative determination of IgG antibodies to measles virus in human serum. It is intended to be used as an aid in the determination of serological status to the measles virus. See below for the new assay cut-off:
New cut-off
AU/mL Value
New cut-off
Old cut-off
AU/mL Value
Old cut-off
<13.5 Negative < 25.0 Negative
 ≥  13.5 to < 16.5 Equivocal  ≥  25.0 to < 30 Equivocal
 ≥  16.5 Positive  ≥  30 Positive

Specimen requirements:
Collect: 4.0 mL blood in gold-top
Preparation: spin down and separate serum
Specimen required: 2.0 mL serum
Minimum volume: 1.0 mL serum

Test codes: VISMEG (Measles Antibody, IgG) or VISMEP (Measles Antibody IgG & IgM)

Stability (after separation from cells):
Ambient: 8 hours
Refrigerated: 48 hours
Frozen: 1 year

Turnaround time (TAT): 1 – 5 days

Rejection criteria:
Specimens that exceed stated stability, unlabeled/mislabeled/mismatched specimens, specimens submitted in leaking containers, icteric, contaminated, heat-inactivated or hemolyzed specimens.

References: click here

A summary of all tests offered by our laboratory services can be found here:


Cassiana Bittencourt, MD
Division of Clinical Microbiology

Edwin S. Monuki, MD, PhD
Department of Pathology & Laboratory Medicine
© 2019 The Regents of the University of California. All rights reserved. Proprietary and Confidential. For Internal Distribution Only.