Performance and reliability of the Enzygnost measles enzyme-linked immuno-sorbent assay for detection of measles virus-specific immunoglobulin M antibody during a large measles epidemic

Abstract

Evaluation of the Enzygnost Measles Enzyme-Linked Immuno-Sorbent Assay kit (Behring) performance to detect specific immunoglobulin M (IgM) was carried out with 3,297 single serum samples and 898 paired serum samples collected during a measles epidemic (10,184 reported cases) in Quebec, Canada. Anti-measles IgM and IgG were detected by using the Enzygnost kit with the appropriate conjugates. Complement-fixing (CF) antibody (Ab) titers were assessed by the laboratory branch complement fixation micromethod. The Centers for Disease Control's clinical measles case definition was used. A modification of the manufacturer's optical density interpretation algorithm was introduced to allow for equivocal results, in addition to positive and negative ones. These three categories differed as to their association with a significant increase in CF Ab titer and the time between the onset of symptoms and phlebotomy. The IgM positivity rate for complement fixation-confirmed measles cases was 96.6% for vaccinated subjects and 100% for nonvaccinated subjects. The daily percentage of IgM seropositivity that was detected for subjects who became IgM positive within 30 days increased gradually from 40 to 90% for sera taken 1 to 7 days after the onset of symptoms, and it plateaued at 100% for sera taken 16 to 30 days after the onset of symptoms. IgM seropositivity was strongly associated with IgG seroconversion, CF Ab titer increase, and clinical measles (P less than 0.0001). Reproducibility was 100% for nonreactive sera and 99.1% for reactive sera. In conclusion, the Enzygnost Measles Enzyme-Linked Immuno-Sorbent Assay kit performed adequately to confirm measles virus infection during this epidemic. A second serum sample should be tested when an early-acute-phase serum sample is IgM negative.

Evaluation of Hemagglutinin Protein-Specific Immunoglobulin M for Diagnosis of Measles by an Enzyme-Linked Immunosorbent Assay Based on Recombinant Protein Produced in a High-Efficiency Mammalian Expression System

“…The high sensitivity seems to agree with the results of Ozanne and d'Halewyn (26), who reported a sensitivity of 91.9% for Enzygnost between days 1 and 56. However, the overall sensitivity strongly depends on the number of sera collected during the later time points.…”

“…However, the overall sensitivity strongly depends on the number of sera collected during the later time points. In some studies only 0, 8, 5, or 4.5% of the samples were collected after day 15 (32), day 19 (23), day 25 (26), or day 30 (1), respectively. In contrast, 37% of the samples in our study were drawn after day 20 and 25% of the samples were collected after day 30.…”

“…Since IgM is transient, the demonstration of spe-cific IgM corresponds to a recent primary measles infection (14,21). A single serum specimen collected at the appropriate time (14) is now generally accepted to be sufficient to diagnose measles (10,12,14,17,26,32,34,37).…”

Immunosorbent Assay Based on Recombinant Hemagglutinin Protein Produced in a High-Efficiency Mammalian Expression System for Surveillance of Measles Immunity

“…Different serological assays measure diverse subsets of MV antibodies, and it is not clear which subset reflects the cellular immune response best. Whole MV-based ELISAs detect a broad range of immunoglobulins, irrespective of their functional activities (8,15,35,50). Functional assays, such as HI and NT, are therefore considered to provide a better estimate of the immune status.…”

“…Monitoring of immunity to measles relies solely on the detection of specific antibodies, but it is not clear to what extent antibody titers reflect protective cellular immunity. Past experience with enzyme-linked immunosorbent assays (ELISAs) based on whole measles virus (MV) suggests that antibodies directed against whole virus are a reliable measure of measles immunity (8,15,35,50). Assays for immunity based on recombinant proteins may offer a number of advantages over whole-virus-based ELISAs.…”