Clinical performance of a new lateral flow immunoassay for xylazine detection.

OBJECTIVES: Xylazine is a potent sedative used in veterinary medicine. Recently, recreational drugs such as fentanyl have been found to contain xylazine, increasing the risk of respiratory depression and death. Despite a similar presentation to opioid overdose, patients who ingest xylazine do not respond to treatment with Narcan. Therefore, rapid detection of xylazine could improve patient management and prevent adverse outcomes. METHODS: We evaluated the XYL500 one-step xylazine drug of abuse test for its ability to detect xylazine in 152 urine samples from patients on chronic opioid therapy for pain management or in treatment for substance use disorder. Results were compared to LC-MS/MS as the reference method. Precision, cross-reactivity, interference and stability studies were performed. RESULTS: Pooled patient samples were consistently negative or positive when tested five times on the same day and over three days of testing. The diagnostic sensitivity, specificity and accuracy of the XYL500 assay were 74, 98, and 82 % respectively, as compared with LC-MS/MS. XYL500 detected 77 of the 104 LC-MS/MS positive samples identified in our initial evaluation, including some that contained low levels of xylazine (n=8), <10 ng/mL. Minimal cross-reactivity with other opioid analgesics and commonly encountered drugs was seen with only one false positive result. Interferences by common urine contaminants were negligible. Specimens were stable up to 160 days refrigerated and up to 80 days at room temperature. CONCLUSIONS: XYL500 allows for rapid detection of xylazine, illustrating its utility in monitoring patients who ingested recreational drugs containing the additive, xylazine, and its potential to improve patient management.

Severe Acute Respiratory Syndrome Coronavirus 2 Messenger RNA Vaccines in Allogeneic Hematopoietic Stem Cell Transplant Recipients: Immunogenicity and Reactogenicity.

The severe acute respiratory syndrome coronavirus 2 messenger RNA vaccine-induced humoral response and reactogenicity profile are described in allogeneic hematopoietic stem cell transplant (HSCT) recipients. Findings showed that 75.0% (by Simoa assay) or 80.0% (by Roche assay) of the HSCT cohort had a positive antibody response on series completion, compared with 100% in the healthy cohort.

Precision and reliability of 5 platelet function tests in healthy volunteers and donors on daily antiplatelet agent therapy.

BACKGROUND: Anticoagulation protocols used during mechanical circulatory support call for titration of antiplatelet agents. We compared the precision and reliability of 5 platelet function tests in healthy volunteers and donors on daily antiplatelet therapy to distinguish their efficacy for titrating antiplatelet therapy. METHODS: We assessed arachidonic acid-induced platelet function by light transmission aggregometry (LTA), Multiplate impedance aggregometry, VerifyNow, and platelet mapping by thromboelastography (TEG PM). We assessed ADP-induced platelet function by the same methods and flow cytometry. Forty healthy volunteers and 10-13 volunteers on daily aspirin and/or clopidogrel therapy were evaluated. We compared tests for intraassay precision, interassay precision (samples from 2 separate blood draws), and reliability coefficient. RESULTS: For arachidonic acid-induced platelet aggregation in healthy volunteers, intra- and interassay CVs were ≤ 10% for all methods. Intra- and interassay precision among donors on daily aspirin was ≤ 30% for all methods except LTA (38% interassay CV) and TEG PM (95% intraassay and 104% interassay CV). For ADP-induced platelet function, intra- and interassay precision was ≤ 10% and ≤ 30% for all methods. Only Multiplate demonstrated moderate or greater (R > 0.40) reliability coefficients for arachidonic acid-induced platelet function among all subjects. All methods of ADP-induced platelet function, except TEG PM, demonstrated substantial or greater (R > 0.60) reliability among all subjects. CONCLUSIONS: TEG PM is least suited to monitor effects of antiplatelet agents. Multiplate impedance aggregometry was the only method to demonstrate an acceptable reliability coefficient among healthy volunteers and donors on both aspirin and clopidogrel therapy.

Impact of COVID-19 on Drug Positivity Rates in the Emergency Departments in Boston and Surrounding Areas.

BACKGROUND: The COVID-19 pandemic reportedly had a significant impact on drug and alcohol use. In this article, we determine positivity rates for urine drugs of abuse and blood alcohol in 5 emergency departments (ED) in the greater Boston metropolitan area over a 4-year period (pre-, during, and post-COVID-19 pandemic). METHODS: Positivity rates for the urine drug screening (UDS) panel and blood alcohol concentration (>80 mg/dL; over the legal limit in MA) were calculated in patients presenting to one of the 5 ED (2 academic hospitals in Boston, MA and 3 community hospitals outside Boston, MA) during each of the 4 different time periods: pre-COVID (January 1, 2019 to December 31, 2019), stay-at-home (March 24, 2020 to May 18, 2020), during COVID (May 19, 2020 to March 28, 2021), and post-COVID (May 12, 2023 to August 31, 2023). Trend analysis was performed. Additionally, positivity rates during and post-COVID were compared to pre-COVID to determine any significant changes in drug positivity. RESULTS: Stimulant (amphetamines and cocaine), cannabinoid, and methadone positivity increased during the pandemic and cocaine, cannabinoid, and methadone positivity remains elevated. By contrast, benzodiazepine and opioid (opiates, fentanyl, oxycodone) positivity decreased and remains lower post-COVID compared to pre-COVID. Patients in the ED with blood alcohol over the legal limit decreased both during and post-COVID. CONCLUSION: Our study showed that the COVID-19 pandemic significantly affected drug and alcohol positivity rates in patients presenting to the ED in greater Boston area. We encourage other institutions to perform similar analyses to help determine local drug use patterns and appropriate composition of UDS panels.

Performance of a Norfentanyl Immunoassay in Specimens with Low Concentrations of Fentanyl and/or Norfentanyl.

BACKGROUND: Many fentanyl immunoassays are limited in their ability to detect norfentanyl. Urine specimens collected from individuals who have been exposed to fentanyl frequently have detectable concentrations of norfentanyl (≥2 ng/mL) but low concentrations of fentanyl (<2 ng/mL) by LC-MS/MS. The Lin-Zhi Fentanyl II Immunoassay (Lin-Zhi) claims 100% cross-reactivity with norfentanyl and therefore may detect exposure missed by other assays. METHODS: In addition to verifying the manufacturer's analytical sensitivity claims, we selected 92 urine specimens with low-positive Lin-Zhi results (1-99 absorbance units, lowest 10%) for analysis by the Immunalysis Health Equity Impact Assessment and ARK II fentanyl methods. The accuracy of the 3 immunoassays was compared to LC-MS/MS as the reference method. RESULTS: Spiking studies using purified fentanyl and norfentanyl and a set of 100 consecutive specimens confirmed the manufacturer's claims of limit of detection for fentanyl (3.8 ng/mL) and norfentanyl (5.0 ng/mL). However, the 92 low-positive patient specimens demonstrated concentrations of norfentanyl and fentanyl below 2.0 ng/mL by LC-MS/MS, with 47 (51%) having only norfentanyl detected. When comparing Lin-Zhi to the Immunalysis and ARK II immunoassays, only 27 (29%) of the 92 specimens were concordant. Fifty-two (57%) of the specimens were positive by LC-MS/MS and Lin-Zhi but false negative by one or both other immunoassays. Seven specimens (8%) were positive by Lin-Zhi but negative by the other immunoassays and had undetectable concentrations (<2 ng/mL) of fentanyl and norfentanyl by LC-MS/MS. CONCLUSIONS: The clinical sensitivity of the Lin-Zhi exceeds the manufacturer's claims, providing results comparable to LC-MS/MS methods.

Despite the improved clinical sensitivity of the Roche benzodiazepines II assay it cannot replace mass spectrometry in all patient populations.

Introduction: Benzodiazepines are frequently prescribed and misused therefore urine drug screening (UDS) is performed in many patient populations. Most current benzodiazepine immunoassays have poor sensitivity, particularly for detecting the metabolites of newer benzodiazepines such as lorazepam in urine. Objectives: We aimed to verify the clinical performance of the new qualitative Roche Benzodiazepines II (BNZ2) immunoassay, as well as compare its performance to the Roche Benzodiazepines Plus (BENZ) assay in two patient populations: UDS in the emergency department (ED) and compliance monitoring. Methods: An initial verification study was performed, selecting for samples containing clonazepam and lorazepam metabolites. Performance of the BNZ2 and BENZ assays was compared to liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the reference method. Sensitivity, specificity, false positive rate (FPR) and false negative rate (FNR) were determined. Results: We verified the performance claims in the initial verification and demonstrated similar precision, with coefficient of variations (CVs) of 12.8% and 7.7% for negative and positive controls, respectively. Furthermore, we observed higher clinical sensitivity and lower FNR with the BNZ2 assay in both the ED and compliance monitoring populations due to improved cross-reactivity for lorazepam and clonazepam metabolites. Despite these improvements, the BNZ2 assay was unable to detect 27% of specimens positive by LC-MS/MS, including specimens from patients using benzodiazepines without prescription. Discussion: Due to its improved performance and rapid turnaround time, the BNZ2 assay should be implemented for UDS in the ED. However, the assay should not replace LC-MS/MS testing for compliance monitoring, as unsuspected benzodiazepine use may go undetected.

Consensus Considerations and Good Practice Points for Use of Continuous Glucose Monitoring Systems in Hospital Settings.

Continuous glucose monitoring (CGM) systems provide frequent glucose measurements in interstitial fluid and have been used widely in ambulatory settings for diabetes management. During the coronavirus disease 2019 (COVID-19) pandemic, regulators in the U.S. and Canada temporarily allowed for CGM systems to be used in hospitals with the aim of reducing health care professional COVID-19 exposure and limiting use of personal protective equipment. As such, studies on hospital CGM system use have been possible. With improved sensor accuracy, there is increased interest in CGM usage for diabetes management in hospitals. Laboratorians and health care professionals must determine how to integrate CGM usage into practice. The aim of this consensus guidance document is to provide an update on the application of CGM systems in hospital, with insights and opinions from laboratory medicine, endocrinology, and nursing.

Correctly Establishing and Interpreting Oxygenation Status in Sickle Cell Disease.

BACKGROUND: As hypoxemia and hypoxia are central elements of disease pathophysiology and disease-related morbidity and mortality in individuals affected by sickle cell disease (SCD), clinical management aims to optimize oxygenation. CONTENT: Hypoxemia is primarily screened for with pulse oximetry. However, in SCD pulse oximetry can inaccurately reflect arterial saturation, posing the risk of undetected (occult) hypoxemia. Solely relying on pulse oximetry might therefore lead to misdiagnosis or mismanagement, with devastating effects on tissue oxygenation. The interpretation of oxygenation status is multifaceted, and "oxygen saturation" is often used as an umbrella term to refer to distinctly different measured quantities-estimated oxygen saturation (O2Sat), hemoglobin oxygen saturation (SO2) by either pulse oximetry or co-oximetry, and fractional oxyhemoglobin (FO2Hb). While in many clinical situations this ambiguous use is of little consequence, O2Sat, SO2, and FO2Hb cannot be used interchangeably in the setting of SCD, as dyshemoglobins, anemia, cardiopulmonary comorbidities, concomitant medications, and frequent transfusions need to be accounted for. This article describes the parameters that determine blood and tissue oxygen concentration, discusses laboratory method performance characteristics and the correct interpretation of currently available clinical laboratory testing, and reviews the literature on noninvasive vs invasive oxygenation measurements in SCD. SUMMARY: By correctly establishing and interpreting oxygenation parameters, clinical and laboratory teams can ensure high-quality, equitable healthcare, counteracting systemic exacerbations of health disparities frequently experienced by individuals with SCD.

Estimated GFR With Cystatin C and Creatinine in Clinical Practice: A Retrospective Cohort Study.

Rationale & Objective: Estimation of glomerular filtration rate (eGFR) and staging of chronic kidney disease (CKD) are essential to guide management. Although creatinine is routinely used, a recent national task force recommended the use of cystatin C for confirmation. The objective of this study was to examine the following parameters: (1) how cystatin C correlates with creatinine eGFR; (2) how it indicates differences in CKD staging; and (3) how it may affect kidney care delivery. Study Design: Retrospective observational cohort study. Setting & Participants: 1,783 inpatients and outpatients who had cystatin C and creatinine levels drawn within 24 hours at Brigham Health-affiliated clinical laboratories. Predictors: Serum creatinine levels, basic clinical/sociodemographic variables, and reasons for ordering cystatin C from a structured partial chart review. Analytical Approach: Univariate and multivariable linear and logistic regression. Results: Cystatin C-based eGFR was very strongly correlated with creatinine-based eGFR (Spearman correlation ρ = 0.83). Cystatin C eGFR resulted in a change to a later CKD stage in 27%, an earlier stage in 7%, and no change in 66% of patients. Black race was associated with a lower likelihood of change to a later stage (OR, 0.53; 95% CI [0.36, 0.75]; P < 0.001), whereas age (OR per year OR, 1.03; 95% CI [1.02, 1.04]; P < 0.001) and Elixhauser score (OR per point OR, 1.22; 95% CI [1.10, 1.36]; P < 0.001) were associated with a higher likelihood of change to a later stage. Limitations: Single center, no direct measurement of clearance for comparison, and inconsistent self-identification of race/ethnicity. Conclusions: Cystatin C eGFR correlates strongly with creatinine eGFR but can have a substantial effect on CKD staging. As cystatin C is adopted, clinicians must be informed on this impact.

Lessons learned: A look back at the performance of nine COVID-19 serologic assays and their proposed utility.

BACKGROUND: Serologic assays for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been proposed to assist with the acute diagnosis of infection, support epidemiological studies, identify convalescent plasma donors, and evaluate vaccine response. METHODS: We report an evaluation of nine serologic assays: Abbott (AB) and Epitope (EP) IgG and IgM, EUROIMMUN (EU) IgG and IgA, Roche anti-N (RN TOT) and anti-S (RS TOT) total antibody, and DiaSorin (DS) IgG. We evaluated 291 negative controls (NEG CTRL), 91 PCR positive (PCR POS) patients (179 samples), 126 convalescent plasma donors (CPD), 27 healthy vaccinated donors (VD), and 20 allogeneic hematopoietic stem cell transplant (HSCT) recipients (45 samples). RESULTS: We observed good agreement with the method performance claims for specificity (93-100%) in NEG CTRL but only 85% for EU IgA. The sensitivity claims in the first 2 weeks of symptom onset was lower (26-61%) than performance claims based on > 2 weeks since PCR positivity. We observed high sensitivities (94-100%) in CPD except for AB IgM (77%), EP IgM (0%). Significantly higher RS TOT was observed for Moderna vaccine recipients then Pfizer (p-values < 0.0001). A sustained RS TOT response was observed for the five months following vaccination. HSCT recipients demonstrated significantly lower RS TOT than healthy VD (p < 0.0001) at dose 2 and 4 weeks after. CONCLUSIONS: Our data suggests against the use of anti-SARS-CoV-2 assays to aid in acute diagnosis. RN TOT and RS TOT can readily identify past-resolved infection and vaccine response in the absence of native infection. We provide an estimate of expected antibody response in healthy VD over the time course of vaccination for which to compare antibody responses in immunosuppressed patients.

Cannabis positivity rates in 17 emergency departments across the United States with varying degrees of marijuana legalization.

BACKGROUND: Many states in the United States have progressed towards legalization of marijuana including decriminalization, medicinal and/or recreational use. We studied the impact of legalization on cannabis-related emergency department visits in states with varying degrees of legalization. METHODS: Seventeen healthcare institutions in fifteen states (California, Colorado, Connecticut, Florida, Iowa, Kentucky, Maryland, Massachusetts, Missouri, New Hampshire, Oregon, South Carolina, Tennessee, Texas, Washington) participated. Cannabinoid immunoassay results and cannabis-related International Classification of Diseases (ninth and tenth versions) codes were obtained for emergency department visits over a 3- to 8-year period during various stages of legalization: no state laws, decriminalized, medical approval before dispensaries, medical dispensaries available, recreational approval before dispensaries and recreational dispensaries available. Trends and monthly rates of cannabinoid immunoassay and cannabis-related International Classification of Diseases code positivity were determined during these legalization periods. RESULTS: For most states, there was a significant increase in both cannabinoid immunoassay and International Classification of Diseases code positivity as legalization progressed; however, positivity rates differed. The availability of dispensaries may impact positivity in states with medical and/or recreational approval. In most states with no laws, there was a significant but smaller increase in cannabinoid immunoassay positivity rates. CONCLUSIONS: States may experience an increase in cannabis-related emergency department visits with progression toward marijuana legalization. The differences between states, including those in which no impact was seen, are likely multifactorial and include cultural norms, attitudes of local law enforcement, differing patient populations, legalization in surrounding states, availability of dispensaries, various ordering protocols in the emergency department, and the prevalence of non-regulated cannabis products.

Clinical Diagnostic Point-of-Care Molecular Assays for SARS-CoV-2.

Laboratories faced many challenges throughout the COVID-19 pandemic. Point-of-care (POC) SARS-CoV-2 nucleic acid amplification tests (NAATs) provided a key solution to the need for rapid turnaround time in select patient populations and were implemented at the POC but also within laboratories to supplement traditional molecular assays. Clinical Laboratory Improvement Amendments-waived rapid POC SARS-CoV-2 NAATs offer the benefit of reduced educational requirements for operators and can be performed by non-laboratory-trained individuals. However, these methods must be validated to ensure the manufacturer's performance specifications are met and they are found to be fit-for-purpose in the clinical workflows they are implemented.

Point-of-care assessment of combined umbilical arterial and venous lactate: A potential screening test for neonatal acidosis.

OBJECTIVE: To examine the relationship between point-of-care (POC) measurement of combined umbilical arterial and venous (CUAV) lactate and umbilical artery (UA) lactate to determine whether POC assessment of this sample could be an alternative screening modality for neonatal acidosis and aid prediction of neonatal morbidity. METHODS: In this cross-sectional pilot study, UA and CUAV cord blood samples were collected from live, singleton neonates delivered between June and August 2019, at a tertiary care center. UA samples were analyzed for pH and lactate using a blood gas analyzer. CUAV lactate was also assessed on a blood gas analyzer and at the POC. Linear regression was used to determine the correlation between these samples. RESULTS: A total of 152 neonates were included. There was a statistically significant correlation between CUAV lactate concentrations and UA lactate concentrations (R2  = 0.744). Additionally, CUAV lactate concentration measured at the POC was significantly correlated with that measured on a traditional blood gas analyzer (R2  = 0.928). CONCLUSION: POC testing of CUAV lactate is reliable and closely correlated with UA lactate concentrations, making POC testing of CUAV lactate a potential screening test for neonatal acidosis. More data are needed to establish standardization of this test relative to its predictive value in clinical neonatal outcomes.

Glucose meter standardization across a large academic hospital system.

BACKGROUND: To select and standardize point-of-care (POC) glucose meters across a multi-hospital system. METHODS: We formed a multidisciplinary POC glucose standardization working group including key stakeholders from each site. A set of selection criteria: usability, clinical and laboratory performance, indications for use, interface connectivity, ease of implementation and ongoing operational costs were used to develop a scoring schemato facilitate a consensus-driven selection process. RESULTS: Method comparison and consensus error grid evaluation against the clinically validated reference methods demonstrated that the analytical performance for all candidate meters was comparable for both the laboratory and clinical evaluation. However, Meter 1 ranked highest in usability evaluations, implementation and streamlined interface connectivity. The meter selection process and implementation were staggered across sites due to complexity of transitioning to a new manufacturer's meter and limitations in vendor support for training and ongoing troubleshooting of interface connectivity. CONCLUSIONS: Standardization of POC glucose meters in a large multi-hospital system is a complex undertaking requiring robust, multidisciplinary organizational structure both system-wide and locally, development of consensus-driven selection tools, usability evaluation by end-users, laboratory and clinical evaluation of the analytical performance, and a strong vendor-laboratory partnership during the implementation process.

Impact of marijuana legalization on cannabis-related visits to the emergency department.

BACKGROUND: Cannabis is widely used in the United States despite federal laws. In US states that have progressed toward legalization, there have been various reported impacts on cannabis-related emergency department (ED) visits. However, studies on the impact of legalization in Massachusetts (MA) EDs are lacking. METHODS: Cannabinoid immunoassay (THC IA) results and cannabis-related ICD-10 codes were obtained for consecutive patient ED visits at two academic medical centers in Boston, MA over the following legalization periods (January 2012-December 2019): decriminalized (DEC), before medical dispensaries (MED BD), medical dispensaries available (MED DISP), before recreational dispensaries (REC BD) and recreational dispensaries available (REC DISP). Trends and monthly positivity rates for THC IA and ICD-10 codes were determined for these legalization periods. RESULTS: There was an increase in both THC IA (p < .0001) and cannabis-related ICD-10 codes (p < .0001) in the ED as legalization progressed at both institutions. Positivity rates significantly increased by 7% for THC IA and 0.4% for ICD-10 codes. Increases in THC IA positivity were seen in females, patients aged 30-39, older adults (>59 years), and those in the highest income tertile. There was an increasing trend in amphetamine positivity and decreasing trend in opiate positivity in patients with positive THC IA. Unlike THC IA, significant trends per patient demographics were not seen with ICD-10 codes. CONCLUSIONS: Legalization of marijuana in MA has led to an increase in cannabis use as indicated by both increasing rates of positive THC IA results, in older adults, as well as increasing cannabis-related ICD-10 codes. Data suggest a steady increase in THC use associated with legalization that was not associated with an increase in opiate, fentanyl, or cocaine use. We recommend using ED THC IA positivity, an objective laboratory measure, to monitor THC use and the impact of state-specific progression in cannabis legalization.

The Effect of Vaccine Type and SARS-CoV-2 Lineage on Commercial SARS-CoV-2 Serologic and Pseudotype Neutralization Assays in mRNA Vaccine Recipients.

The use of anti-spike (S) serologic assays as surrogate measurements of SARS-CoV-2 vaccine induced immunity will be an important clinical and epidemiological tool. The characteristics of a commercially available anti-S antibody assay (Roche Elecsys anti-SARS-CoV-2 S) were evaluated in a cohort of vaccine recipients. Levels were correlated with pseudotype neutralizing antibodies (NAb) across SARS-CoV-2 variants. We recruited adults receiving a two-dose series of mRNA-1273 or BNT162b2 and collected serum at scheduled intervals up to 8 months post-first vaccination. Anti-S and NAb levels were measured, and correlation was evaluated by (i) vaccine type and (ii) SARS-CoV-2 variant (wild-type, Alpha, Beta, Gamma, and three constructs Day 146*, Day 152*, and RBM-2). Forty-six mRNA vaccine recipients were enrolled. mRNA-1273 vaccine recipients had higher peak anti-S and NAb levels compared with BNT162b2 (P < 0.001 for anti-S levels; P < 0.05 for NAb levels). When anti-S and NAb levels were compared, there was good correlation (all r values ≥ 0.85) in both BNT162b2 and mRNA-1273 vaccine recipients across all evaluated variants; however, these correlations were nonlinear in nature. Lower correlation was identified between anti-S and NAb for the Beta variant (r = 0.88) compared with the wild-type (WT) strain (r = 0.94). Finally, the degree of neutralizing activity at any given anti-S level was lower for each variant compared with that of the WT strain, (P < 0.001). Although the Roche anti-S assay correlates well with NAb levels, this association is affected by vaccine type and SARS-CoV-2 variant. These variables must be considered when interpreting anti-S levels. IMPORTANCE We evaluated anti-spike antibody concentrations in healthy mRNA vaccinated individuals and compared these concentrations to values obtained from pseudotype neutralization assays targeting SARS-CoV-2 variants of concern to determine how well anti-spike antibodies correlate with neutralizing titers, which have been used as a marker of immunity from COVID-19 infection. We found high peak anti-spike concentrations in these individuals, with significantly higher levels seen in mRNA-1273 vaccine recipients. When we compared anti-spike and pseudotype neuralization titers, we identified good correlation; however, this correlation was affected by both vaccine type and variant, illustrating the difficulty of applying a "one size fits all" approach to anti-spike result interpretation. Our results support CDC recommendations to discourage anti-spike antibody testing to assess for immunity after vaccination and cautions providers in their interpretations of these results as a surrogate of protection in COVID-vaccinated individuals.

Structural basis for continued antibody evasion by the SARS-CoV-2 receptor binding domain.

Many studies have examined the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants on neutralizing antibody activity after they have become dominant strains. Here, we evaluate the consequences of further viral evolution. We demonstrate mechanisms through which the SARS-CoV-2 receptor binding domain (RBD) can tolerate large numbers of simultaneous antibody escape mutations and show that pseudotypes containing up to seven mutations, as opposed to the one to three found in previously studied variants of concern, are more resistant to neutralization by therapeutic antibodies and serum from vaccine recipients. We identify an antibody that binds the RBD core to neutralize pseudotypes for all tested variants but show that the RBD can acquire an N-linked glycan to escape neutralization. Our findings portend continued emergence of escape variants as SARS-CoV-2 adapts to humans.