Citywide serosurveillance of the initial SARS-CoV-2 outbreak in San Francisco using electronic health records.

Serosurveillance provides a unique opportunity to quantify the proportion of the population that has been exposed to pathogens. Here, we developed and piloted Serosurveillance for Continuous, ActionabLe Epidemiologic Intelligence of Transmission (SCALE-IT), a platform through which we systematically tested remnant samples from routine blood draws in two major hospital networks in San Francisco for SARS-CoV-2 antibodies during the early months of the pandemic. Importantly, SCALE-IT allows for algorithmic sample selection and rich data on covariates by leveraging electronic health record data. We estimated overall seroprevalence at 4.2%, corresponding to a case ascertainment rate of only 4.9%, and identified important heterogeneities by neighborhood, homelessness status, and race/ethnicity. Neighborhood seroprevalence estimates from SCALE-IT were comparable to local community-based surveys, while providing results encompassing the entire city that have been previously unavailable. Leveraging this hybrid serosurveillance approach has strong potential for application beyond this local context and for diseases other than SARS-CoV-2.

Citywide serosurveillance of the initial SARS-CoV-2 outbreak in San Francisco.

Serosurveillance provides a unique opportunity to quantify the proportion of the population that has been exposed to pathogens. Here, we developed and piloted Serosurveillance for Continuous, ActionabLe Epidemiologic Intelligence of Transmission (SCALE-IT), a platform through which we systematically tested remnant samples from routine blood draws in two major hospital networks in San Francisco for SARS-CoV-2 antibodies during the early months of the pandemic. Importantly, SCALE-IT allows for algorithmic sample selection and rich data on covariates by leveraging electronic medical record data. We estimated overall seroprevalence at 4.2%, corresponding to a case ascertainment rate of only 4.9%, and identified important heterogeneities by neighborhood, homelessness status, and race/ethnicity. Neighborhood seroprevalence estimates from SCALE-IT were comparable to local community-based surveys, while providing results encompassing the entire city that have been previously unavailable. Leveraging this hybrid serosurveillance approach has strong potential for application beyond this local context and for diseases other than SARS-CoV-2.

SARS-CoV-2 seroprevalence and neutralizing activity in donor and patient blood.

Given the limited availability of serological testing to date, the seroprevalence of SARS-CoV-2-specific antibodies in different populations has remained unclear. Here, we report very low SARS-CoV-2 seroprevalence in two San Francisco Bay Area populations. Seroreactivity was 0.26% in 387 hospitalized patients admitted for non-respiratory indications and 0.1% in 1,000 blood donors in early April 2020. We additionally describe the longitudinal dynamics of immunoglobulin-G (IgG), immunoglobulin-M (IgM), and in vitro neutralizing antibody titers in COVID-19 patients. The median time to seroconversion ranged from 10.3-11.0 days for these 3 assays. Neutralizing antibodies rose in tandem with immunoglobulin titers following symptom onset, and positive percent agreement between detection of IgG and neutralizing titers was >93%. These findings emphasize the importance of using highly accurate tests for surveillance studies in low-prevalence populations, and provide evidence that seroreactivity using SARS-CoV-2 anti-nucleocapsid protein IgG and anti-spike IgM assays are generally predictive of in vitro neutralizing capacity.

SARS-CoV-2 seroprevalence and neutralizing activity in donor and patient blood from the San Francisco Bay Area.

We report very low SARS-CoV-2 seroprevalence in two San Francisco Bay Area populations. Seropositivity was 0.26% in 387 hospitalized patients admitted for non-respiratory indications and 0.1% in 1,000 blood donors. We additionally describe the longitudinal dynamics of immunoglobulin-G, immunoglobulin-M, and in vitro neutralizing antibody titers in COVID-19 patients. Neutralizing antibodies rise in tandem with immunoglobulin levels following symptom onset, exhibiting median time to seroconversion within one day of each other, and there is >93% positive percent agreement between detection of immunoglobulin-G and neutralizing titers.

Development and validation of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay to quantify serum voriconazole.

BACKGROUND: Voriconazole is an azole antifungal drug indicated for use in the treatment of invasive aspergillosis. Due to the large intra- and interindividual variation seen in voriconazole pharmacokinetics along with a high probability of drug-drug interactions, therapeutic drug monitoring is of considerable clinical value. As such, we developed and validated a LC-MS/MS assay to quantify serum voriconazole to improve turnaround time and decrease costs. METHODS: After protein precipitation with D3-voriconazole (deuterated internal standard) in acetonitrile was performed, samples were separated by gradient elution and injected into the mass spectrometer with a total run-time of 4 min per sample. Multiple reaction monitoring was employed using Q1/Q3 transitions of 350/127 and 350/281 for voriconazole and 353/284 and 353/127 for D3-voriconazole. RESULTS: Sample preparation took 30 min for 6 patient samples. The limit of quantitation was 0.1 µg/mL and the linearity ranged from 0.1 µg/mL to 10.0 µg/mL. Extraction recovery was ∼69% and ion suppression ∼13%. Intra- and inter-assay imprecision (%CV) was <5% at the limit of quantitation and <4% through the rest of the linear range. Method comparisons between our assay and two reference laboratory methods, HPLC-UV and LC-MS/MS, revealed mean biases of 11% and 4%, respectively. CONCLUSIONS: We have developed an accurate, rapid, and sensitive LC-MS/MS assay for quantification of human serum voriconazole. Our assay reduces current specimen volume requirements, decreases result turnaround time, and saves institutional funds.

Development and validation of a liquid chromatography-tandem mass spectrometry assay to quantify plasma busulfan.

BACKGROUND: Busulfan is an anti-leukemic, DNA alkylating agent that is used in conditioning regimens for patients undergoing hematopoietic stem cell transplantation. Because of the large intraindividual and interindividual variations seen in busulfan pharmacokinetics, therapeutic drug monitoring is necessary. Currently at the authors' institution, plasma busulfan in adults is measured by gas chromatography-mass spectrometry (GC-MS) at a reference laboratory, whereas pediatric specimens are sent to a different reference laboratory also for GC-MS analysis. As the result turnaround time is not optimal and this practice is of significant cost, a liquid chromatography-tandem mass spectrometry assay to quantify plasma busulfan was developed. METHODS: Protein precipitation with D8-busulfan (deuterated internal standard) in acetonitrile was carried out on 50 µL of heparinized plasma. Gradient elution with ammonium acetate, formic acid, water, and methanol at 0.6 mL/min had a 4-minute run time. Multiple reaction monitoring was employed using Q1/Q3 transitions of 264/151 and 264/55 for busulfan and 272/159 and 272/62 for D8-busulfan. RESULTS: Sample preparation took ∼30 minutes for 6 patient samples. Six calibrators were used (0-2000 ng/mL) with 3 quality controls (means of 12, 356, and 1535 ng/mL). The limits of detection and quantitation were 1 and 6 ng/mL, respectively. Extraction recovery was ∼77% and ion suppression ∼5%. Within-run and between-run precision studies yielded <15% coefficient of variation at the limit of quantitation and <6% coefficient of variation through the rest of the linear range. Method comparisons between this assay and 2 GC-MS assays revealed mean biases of 7% and 1%. CONCLUSIONS: An accurate, rapid, and sensitive liquid chromatography-tandem mass spectrometry assay for quantification of plasma busulfan was developed. This assay reduces current specimen volume requirements, reduces result turnaround time for patients and clinicians, and additionally saves institutional funds.