Rubella Surveillance and Diagnostic Testing among a Low-Prevalence Population, New York City, 2012-2013

Appropriateness of Immunoglobulin M Testing for Measles, Mumps, and Rubella

INTRODUCTION

Testing for immunity to measles, mumps, and rubella should include only immunoglobulin G (IgG); immunoglobulin M (IgM) testing is appropriate only if acute illness is suspected. The appropriateness of measles, mumps, and rubella IgM testing was evaluated in a national administrative dataset.

METHODS

Laboratory testing for measles, mumps, and rubella during 2019-2022 was analyzed in 2024 using HealthVerity administrative claims and laboratory data. IgG, IgM, and reverse-transcriptase polymerase chain reaction (RT-PCR) testing are described by year, demographics, and region. IgM testing was examined for appropriateness, defined as an IgM test combined with diagnostic codes indicative of acute illness.

RESULTS

During 2019-2022, IgM testing represented a small proportion of serologic testing (measles: 3.3%, mumps: 2.4%, rubella: 2.1%) but appeared to be appropriately performed in only 15.4% of cases for measles, 32.8% of cases for mumps, and 10.2% of cases for rubella. IgM testing was more commonly performed for female patients, with the largest discrepancy seen for rubella (90.5% female vs 9.5% male). IgM for measles and mumps was more often performed appropriately for persons aged 0-19 years (37.6% and 60.1%) compared with persons aged 20-49 years (11.8% and 22.0%) and 50+ years (16.5% and 33.8%).

CONCLUSIONS

The majority of IgM testing for measles, mumps, and rubella during this period appeared inappropriate. Clinicians and health systems could ensure that IgG testing alone is performed when evaluating for immunity through modifications to electronic medical records and commercial laboratories could ensure that providers are able to test for IgG alone when evaluating immunity.

The path to eradication of rubella

Since 1969, rubella and its harmful effect on fetuses infected in utero can be prevented by rubella vaccine, usually given in combination with measles vaccine. The rubella vaccine is highly protective both in children and in adults including women intending to become pregnant. Owing to the use of combined measles and rubella vaccines, congenital rubella infection has been eliminated from the Western Hemisphere and nearly all of Europe. Such combined vaccination is now being applied throughout the world, posing the possibility of eventual rubella eradication. The existence of viruses of animals related to rubella does not appear to be a barrier to eradication of the human virus. However, persistent rubella virus in infants infected in utero and of immunosuppressed patients with granulomas may pose a problem for eradication. Nevertheless, this review posits that eradication of rubella is now feasible if routine vaccination of infants and surveillance for chronic infection are correctly applied.

Pitfalls of rubella serology while on the brink of elimination: evaluation of national data, Belgium, 2017

BackgroundIn Belgium, rubella serology is frequently requested in women of childbearing age, despite high vaccination coverage and a near-absence of congenital rubella cases. Different test kits are available and should be standardised by an international standard preparation.AimTo analyse and compare rubella serology practices in Belgian laboratories.MethodsAs part of the mandatory External Quality Assessment programme for rubella serology in Belgium, the national public health institute, Sciensano, sent a voluntary questionnaire concerning anti-rubella IgM/IgG analyses in women aged 15 to 45 years in 2017 to 130 laboratories.ResultsThe questionnaire response rate was 83.8% (109/130). The majority of 169,494 IgG analyses were performed on Roche (55%), Abbott (17%) and Diasorin (13%) analysers. Not all laboratories used the proposed international cut-off of 10 IU/mL. Assumed median seroprevalence ranged from 76.3% with Liaison (Diasorin) to 96.3% with Modular (Roche). Despite very low rubella incidence in Belgium, 93 laboratories performed 85,957 IgM analyses, with 748 positive and 394 grey zone results. The National Reference Centre for Measles, Mumps and Rubella virus and the National Reference Centre for Congenital infections did not confirm any positive rubella cases in 2017.ConclusionThis retrospective analysis shows that rubella serology results may differ considerably according to the assay used. It is therefore important to use the same test when comparing results or performing follow-up testing. The number of anti-rubella IgM analyses was very high. Incorrect use of IgM for screening women of childbearing age can lead to unwarranted anxiety and overuse of confirmation tests.

Positive predictive value of seroconversion or positive rubella IgM in diagnosis of maternal rubella infection: Seven-years review of French National Reference Laboratory for Rubella

BACKGROUND

In France, as in most developed countries, childbearing age women are routinely screened for rubella antibodies to identify and vaccinate susceptible women. Immunity to rubella is usually determined by measuring the rubella virus-specific immunoglobulin G (RV-IgG). In case of seroconversion for RV-IgG and/or positive RVIgM during pregnancy, laboratories usually send serum samples to the French National Reference Laboratory (FNRL) for Rubella in order to perform complementary investigations and confirm or exclude rubella infection during pregnancy.

OBJECTIVE

Our aim is to report results of these investigations during a seven-year period (2013-2019) and evaluate the positive predictive value (PPV) of RV-IgG seroconversion or positive RV-IgM to diagnose maternal rubella infection in France.

STUDY DESIGN

Between 2013 and 2019, 5398 serum samples collected from 4104 pregnant women, were addressed to FNRL because of RV-IgG seroconversion (N=899) or positive RV-IgM (N=3205). Additional serological tests were performed, mainly immunoblot (to look for the presence of anti-E1 protective antibody) and RV-IgG avidity (to exclude or confirm primary infection).

RESULTS

Overall, for 3724/4104 (90.8 %) women, rubella primary-infection during pregnancy was formally excluded and maternal rubella primary-infection was only confirmed in 46/4104 (1.1 %) cases.

CONCLUSION

Clinicians and biologists should be particularly aware that RV-IgG seroconversion or positive RV-IgM, in the current context of low RV circulation in France are most often not rubella primary infections. PPV of seroconversion to assess maternal rubella primary infection is as low as 0.2 % (95 % CI: 0 %; 0.5 %) and PPV of positive RV-IgM is only of 1.4 % (95 % CI: 0.99 %; 1.81 %).

Mechanism of heparin interference in detection of LIAISON® Rubella IgM

AIMS

To investigate the effects of heparin in detection of LIAISON® Rubella IgM (Rub-M) and the mechanism of interference.

METHODS

Different concentrations of lithium heparin and sodium heparin were added to ten serum samples. The relative light units (RLU) value of Rub-M was measured using the LIAISON XL detection system. Different levels of IgM serum were incubated with magnetic particle in Rub-M detection kit at 4 °C for 4 h, blocking anti-human IgM-specific antibodies coated on the surface of magnetic particle. Separately, the rubella virus antigen in Rub-M detection kit was replaced by phosphate-buffered saline (PBS). The RLU values of LIAISON® Rub-M of original serum and serum containing various concentrations of heparin were measured after the above two different treatments.

RESULTS

The RLU value of LIAISON® Rub-M increased with the increase of heparin content lower than 40 IU/mL, and reached a peak value at 40-50 IU/mL. The RLU value of LIAISON® Rub-M then decreased with the decrease of heparin concentration. When rubella virus antigen was replaced by PBS, the RLU value of LIAISON® Rub-M of serum samples containing 40 IU/mL heparin decreased significantly. The blocking concentration of IgM increased gradually, and the RLU value of LIAISON® Rub-M of seven serum samples containing 40 IU/mL heparin also decreased gradually.

CONCLUSION

Plasma with heparin cannot be used to the detection of LIAISON® Rub-M. Heparin may participate in the reaction by binding with rubella virus antigen and anti-human IgM-specific antibodies coated on the surface of magnetic particle, thus affecting the detection results.

Rubella virus-specific humoral immune responses and their interrelationships before and after a third dose of measles-mumps-rubella vaccine in women of childbearing age

In the U.S., measles, mumps, and rubella vaccination is recommended as two vaccine doses. A third dose of measles-mumps-rubella (MMR) vaccine is being administered in certain situations (e.g., identified seronegativity and during outbreaks). We studied rubella-specific humoral immunity (neutralizing antibody, enzyme-linked immunosorbent assay/ELISA IgG titer and antibody avidity) and the frequencies of antigen-specific memory B cells before and after a third dose of MMR-II in 109 female participants of childbearing age (median age, 34.5 years old) from Olmsted County, MN, with two documented prior MMR vaccine doses. The participants were selected from a cohort of 1117 individuals if they represented the high and the low ends of the rubella-specific antibody response spectrum. Of the 109 participants, we identified four individuals (3.67% of all study participants; 7.14% of the low-responder group) that were seronegative at Baseline (rubella-specific ELISA IgG titers <10 IU/mL), suggesting a lack of protection against rubella before receipt of a third MMR vaccine dose. The peak geometric mean neutralizing antibody titer one month following the third dose of MMR vaccine for the cohort was 243 NT₅₀ (CI; 241, 245), which is expected for a cohort with two doses of MMR, and the peak geometric mean IgG titer was 150 IU/mL (CI; 148, 152) with no seronegative individuals at Day 28. One-third of all subjects (31.8% for the neutralizing antibody; 30.8% for the IgG titer) experienced a significant boost (≥4-fold) of antibody titers one month following vaccination. Antibody titers and other tested immune-response variables were significantly higher in the high-responder group compared to the low-responder group. The frequencies of rubella-specific memory B cells were modestly associated with the antibody titers. Our study suggests the importance of yet unknown inherent biologic and immune factors for the generation and maintenance of rubella-vaccine-induced humoral immune responses.