Performance of Four IgM Antibody Assays in the Diagnosis of Measles Virus Primary Infection and Cases with a Serological Profile Indicating Reinfection.

The object of this study was to determine the diagnostic performance of four commercially available IgM tests in the diagnosis of measles virus (MeV) primary infection and cases with a serological profile indicating reinfection. Sera from 187 patients with MeV primary infection, 30 patients with suspected reinfection (after vaccine failure), and 153 patients with rash-like symptoms after exclusion of MeV infection were retested with four IgM tests. MeV infection was verified by reverse transcriptase PCR (RT-PCR), and primary and suspected reinfections were differentiated by IgG avidity and neutralization assays. All IgM assays displayed significant agreement (Cohen's κ, ≥0.604; all P < 0.001) and a higher diagnostic accuracy in primary infection than in suspected reinfection (indicated by high IgG avidity and significantly higher anti-MeV-IgG and neutralizing titers). In the overall cohort, the areas under the curve (AUC) were comparable among all tests, ranging from 0.875 to 0.931, with ranges increasing to 0.911 to 0.930 in the primary infection and decreasing to 0.765 to 0.940 in the setting of high anti-MeV-IgG avidity, and all tests displayed high specificity (81.1 to 92.2%). Of note, IgM tests with the highest diagnostic accuracy had discriminatory abilities not significantly different than PCR from serum. Although reinfections pose a challenge for IgM testing, IgM assays remain a cornerstone in the diagnosis of MeV infections. Especially in samples with a serological profile indicating reinfections, IgM tests displayed an equal or even superior diagnostic ability compared to PCR from serum.

Elevated CXCL10 Serum Levels in Measles Virus Primary Infection and Reinfection Correlate With the Serological Stage and Hospitalization Status.

We quantified serum concentrations of chemokine CXCL10 in 288 patients with measles virus (MeV) primary infection and 16 patients with reinfection (vaccine failure). CXCL10 peaked with emergence of IgM antibodies and was elevated in hospitalized patients (3233 vs 1930 pg/mL, P < .0001). CXCL10 differed between primary and reinfection (1958 vs 932 pg/mL, P = .0402). In comparison to other viral infections with rash-like symptoms, CXCL10 was highly elevated in MeV infection (area under the curve = 0.935; 95% confidence interval, .905-.965; P < .0001). CXCL10 is a potential marker for diagnosis, stage, and severity of MeV infection.

Performance of Severe Acute Respiratory Syndrome Coronavirus 2 Antibody Assays in Different Stages of Infection: Comparison of Commercial Enzyme-Linked Immunosorbent Assays and Rapid Tests.

We comparatively assessed sensitivities and specificities of 4 commercial enzyme-linked immunosorbent assays (ELISAs) and 2 rapid tests in 77 patients with polymerase chain reaction-confirmed severe acute respiratory syndrome coronavirus 2 infection, grouped by interval since symptom onset. Although test sensitivities were low (<40%) within the first 5 days after disease onset, immunoglobulin (Ig) M, IgA, and total antibody ELISAs increased in sensitivity to >80% between days 6 and 10 after symptom onset. The evaluated tests (including IgG and rapid tests) provided positive results in all patients at or after the 11th day after onset of disease. The specificities of the ELISAs were 83% (IgA), 98% (IgG), and 97% (IgM and total antibody).