Association between SARS-CoV-2 Symptoms, Ct Values, and Serological Response in Vaccinated and Unvaccinated Healthcare Personnel.

BACKGROUND: SARS-CoV-2 vaccines are effective at reducing symptomatic and asymptomatic COVID-19. Limited studies have compared symptoms, threshold cycle (Ct) values from reverse transcription (RT)-PCR testing, and serological testing results between previously vaccinated vs unvaccinated populations with SARS-CoV-2 infection. METHODS: Healthcare personnel (HCP) with a positive SARS-CoV-2 RT-PCR test within the previous 14 to 28 days completed surveys including questions about demographics, medical conditions, social factors, and symptoms of COVID-19. Ct values were observed, and serological testing was performed for anti-nucleocapsid (anti-N) and anti-Spike (anti-S) antibodies at enrollment and 40 to 90 days later. Serological results were compared to HCP with no known SARS-CoV-2 infection and negative anti-N testing. RESULTS: There were 104 unvaccinated/not fully vaccinated and 77 vaccinated HCP with 2 doses of an mRNA vaccine at time of infection. No differences in type or duration of symptoms were reported (P = 0.45). The median (interquartile range [IQR]) Ct was 21.4 (17.6-24.6) and 21.5 (18.1-24.6) for the unvaccinated and vaccinated HCP, respectively. Higher anti-N IgG was observed in unvaccinated HCP (5.08 S/CO, 3.08-6.92) than vaccinated (3.61 signal to cutoff ratio [S/CO], 2.16-5.05). Anti-S IgG was highest among vaccinated HCP with infection (34 285 aribitrary units [AU]/mL, 17 672-61 775), followed by vaccinated HCP with no prior infection (1452 AU/mL, 791-2943), then unvaccinated HCP with infection (829 AU/mL, 290-1555). Anti-S IgG decreased 1.56% (0.9%-1.79%) per day in unvaccinated and 0.38% (0.03%-0.94%) in vaccinated HCP. CONCLUSIONS: Vaccinated HCP infected with SARS-CoV-2 reported comparable symptoms and had similar Ct values relative to unvaccinated. However, vaccinated HCP had increased and prolonged anti-S and decreased anti-N response relative to unvaccinated.

Method Comparison and Workflow Differences Using the Same Free Light Chain Assay on 2 Analyzer Platforms.

BACKGROUND: The Freelite assay (The Binding Site) is utilized to quantify serum immunoglobulin free light chains (sFLC), which is crucial for diagnosing and monitoring plasma cell dyscrasias (PCDs). Using the Freelite test, we compared methods and evaluated workflow differences across two analyzer platforms. METHODS: sFLC concentrations were measured in 306 fresh serum specimens (cohort A) and 48 frozen specimens with documented sFLC >20 mg/dL (cohort B). Specimens were analyzed on the Roche cobas 8000 and Optilite analyzers using the Freelite κ and λ assays. Performance was compared using Deming regression. Workflow was compared by assessing turnaround time (TAT) and reagent usage. RESULTS: For cohort A specimens, Deming regression revealed a slope of 1.04 (95% CI, 0.88-1.02) and an intercept of -0.77 (95% CI, -0.57 to 1.85) for sFLCκ and a slope of 0.90 (95% CI, -0.04 to 1.83) and intercept of 1.59 (95% CI, -3.12 to 6.25) for sFLCλ. Regression of the κ/λ ratio revealed a slope of 2.44 (95% CI, 1.47-3.41) and intercept of -8.13 (95% CI, -16.82 to 0.58) with a concordance kappa of 0.80 (95% CI, 0.69-0.92). The proportion of specimens with TAT >60 min was 0.33% and 8% for the Optilite and cobas, respectively (P < 0.001). The Optilite required 49 (P < 0.001) and 12 (P = 0.016) fewer tests for sFLCκ and sFLCλ relative to the cobas. Cohort B specimens showed similar but more dramatic results. CONCLUSIONS: Analytical performance of the Freelite assays was comparable on the Optilite and cobas 8000 analyzers. In our study, the Optilite required less reagent, had a slightly reduced TAT, and eliminated manual dilutions for samples with sFLC concentrations >20 mg/dL.