Multiplex Fragment Analysis for Flexible Detection of All SARS-CoV-2 Variants of Concern.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants continue to emerge, and effective tracking requires rapid return of results. Surveillance of variants is typically performed by whole genome sequencing (WGS), which can be financially prohibitive and requires specialized equipment and bioinformatic expertise. Genotyping approaches are rapid methods for monitoring SARS-CoV-2 variants but require continuous adaptation. Fragment analysis may represent an approach for improved SARS-CoV-2 variant detection. METHODS: A multiplex fragment analysis approach (CoVarScan) was validated using PCR targeting variants by size and fluorescent color. Eight SARS-CoV-2 mutational hot spots in variants of concern (VOCs) were targeted. Three primer pairs (recurrently deleted region [RDR] 1, RDR2, and RDR3-4) flank RDRs in the S-gene. Three allele-specific primers target recurrent spike receptor binding domain mutants. Lastly, 2 primer pairs target recurrent deletions or insertions in ORF1A and ORF8. Fragments were resolved and analyzed by capillary electrophoresis (ABI 3730XL), and mutational signatures were compared to WGS results. RESULTS: We validated CoVarScan using 3544 clinical respiratory specimens. The assay exhibited 96% sensitivity and 99% specificity compared to WGS. The limit of detection for the core targets (RDR1, RDR2, and ORF1A) was 5 copies/reaction. Variants were identified in 95% of samples with cycle threshold (CT) <30 and 75% of samples with a CT 34 to 35. Assay design was frozen April 2021, but all subsequent VOCs have been detected including Delta (n = 2820), Mu, (n = 6), Lambda (n = 6), and Omicron (n = 309). Genotyping results are available in as little as 4 h. CONCLUSIONS: Multiplex fragment analysis is adaptable and rapid and has similar accuracy to WGS to classify SARS-CoV-2 variants.

Clinical Evaluation of the Abbott Alinity SARS-CoV-2 Spike-Specific Quantitative IgG and IgM Assays among Infected, Recovered, and Vaccinated Groups.

The coronavirus disease 19 (COVID-19) pandemic continues to impose a significant burden on global health infrastructure. While identification and containment of new cases remain important, laboratories must now pivot and consider an assessment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunity in the setting of the recent availability of multiple COVID-19 vaccines. Here, we have utilized the latest Abbott Alinity semiquantitative IgM and quantitative IgG spike protein (SP) serology assays (IgMSP and IgGSP) in combination with Abbott Alinity IgG nucleocapsid (NC) antibody test (IgGNC) to assess antibody responses in a cohort of 1,236 unique participants comprised of naive, SARS-CoV-2-infected, and vaccinated (including both naive and recovered) individuals. The IgMSP and IgGSP assays were highly specific (100%) with no cross-reactivity to archived samples collected prior to the emergence of SARS-CoV-2, including those from individuals with seasonal coronavirus infections. Clinical sensitivity was 96% after 15 days for both IgMSP and IgGSP assays individually. When considered together, the sensitivity was 100%. A combination of NC- and SP-specific serologic assays clearly differentiated naive, SARS-CoV-2-infected, and vaccine-related immune responses. Vaccination resulted in a significant increase in IgGSP and IgMSP values, with a major rise in IgGSP following the booster (second) dose in the naive group. In contrast, SARS-CoV-2-recovered individuals had several-fold higher IgGSP responses than naive following the primary dose, with a comparatively dampened response following the booster. This work illustrates the strong clinical performance of these new serological assays and their utility in evaluating and distinguishing serological responses to infection and vaccination.

Crossroads between Autoimmunity and COVID-19 in Lung Transplant Recipients.

The presence of a certain group of auto-antibodies (AAbs) is known to correlate with the severity of COVID-19. It is, however, unknown if such AAbs are prevalent and impact COVID-19-related outcomes in lung transplant recipients (LTRs) who are immunosuppressed. We performed a retrospective study of LTRs with COVID-19 and analyzed samples before and after COVID-19 for IgG AAbs. AAbs analysis was carried out using autoimmune and coronavirus microarray and the resulting cross-sectional differences in Ab-scores and clinical variables were analyzed using Fischer's Exact test for categorical variables and a paired t-test for continuous variables. Linear regression was used to analyze the differences in Ab-scores and COVID-19 severity. LTRs with non-severe [NS gp (n = 10)], and severe [S gp (n = 8)] COVID-19 disease were included. Ferritin and acute respiratory failure were higher in the S group (p = 0.03; p < 0.0001). Among the AAbs analyzed, interferon-related AAbs (IFN-alpha2, IFN-beta, IFN lamba, IFN-epsilon), eight interleukin-related AAbs, and several tissue-related AAbs were also found to be changed significantly from pre- to post-COVID-19 (p < 0.05). IFN-lambda (p = 0.03) and IL-22 (p = 0.002) were significantly associated with COVID-19 severity and remained significant in linear regression analysis while controlling for other variables. AAbs are common in LTRs, and certain groups of antibodies are particularly enhanced in LTRs with severe COVID-19. Preliminary observations of this study need to be confirmed by a larger sample size.

SARS-CoV-2 Vaccination IgG Antibody Responses in Patients with Hematologic Malignancies in a Myeloid Enriched Cohort: A Single Center Observation.

OBJECTIVE: Patients diagnosed with hematologic malignancies are at increased risk for severe SARS-CoV-2 infection. We evaluated the serological IgG response following two doses of the SARS-CoV-2 vaccine in patients with hematologic malignancies. METHODS: Patients treated at UT Southwestern Medical Center with a diagnosis of a myeloid or lymphoid neoplasm were included. SARS-CoV-2 vaccination response was defined as a positive quantifiable spike IgG antibody titer. RESULTS: Sixty patients were included in the study and 60% were diagnosed with a myeloid neoplasm. The majority (85%) of the patients with a myeloid malignancy and 50% of the patients with a lymphoid malignancy mounted a serological response after receiving two doses of the vaccine. CONCLUSION: Vaccination should be offered irrespective of ongoing treatment or active disease. Findings require validation in a larger cohort of patients.

SARS-CoV-2 coinfections with variant genomic lineages identified by multiplex fragment analysis.

Immunocompromised patients can experience prolonged SARS-CoV-2 infections in the setting of a lack of protectivity immunity despite vaccination. As circulating SARS-CoV-2 strains become more heterogeneous, concomitant infection with multiple SARS-CoV-2 variants has become an increasing concern. Immunocompromised patient populations represent potential reservoirs for the emergence of novel SARS-CoV-2 variants through mutagenic change or coinfection followed by recombinatory events. Identification of SARS-CoV-2 coinfections is challenging using traditional next generation sequencing pipelines; however, targeted genotyping approaches can facilitate detection. Here we describe five COVID-19 cases caused by coinfection with different SARS-CoV-2 variants (Delta/Omicron BA.1 and Omicron BA.1/BA.2) as identified by multiplex fragment analysis.

Translation suppression underlies the restrained COVID-19 mRNA vaccine response in the high-risk immunocompromised group.

Background: Immunocompromised (IC) patients show diminished immune response to COVID-19 mRNA vaccines (Co-mV). To date, there is no 'empirical' evidence to link the perturbation of translation, a rate-limiting step for mRNA vaccine efficiency (VE), to the dampened response of Co-mV. Materials and methods: Impact of immunosuppressants (ISs), tacrolimus (T), mycophenolate (M), rapamycin/sirolimus (S), and their combinations on Pfizer Co-mV translation were determined by the Spike (Sp) protein expression following Co-mV transfection in HEK293 cells. In vivo impact of ISs on SARS-CoV-2 spike specific antigen (SpAg) and associated antibody levels (IgGSp) in serum were assessed in Balb/c mice after two doses (2D) of the Pfizer vaccine. Spike Ag and IgGSp levels were assessed in 259 IC patients and 50 healthy controls (HC) who received 2D of Pfizer or Moderna Co-mV as well as in 67 immunosuppressed solid organ transplant (SOT) patients and 843 non-transplanted (NT) subjects following three doses (3D) of Co-mV. Higher Co-mV concentrations and transient drug holidays were evaluated. Results: We observed significantly lower IgGSP response in IC patients (p<0.0001) compared to their matched controls in 2D and 3D Co-mV groups. IC patients on M or S showed a profound dampening of IgGSP response relative to those that were not on these drugs. M and S, when used individually or in combination, significantly attenuated the Co-mV-induced Sp expression, whereas T did not exert significant influence. Sirolimus combo pretreatment in vivo significantly attenuated the Co-mV induced IgMSp and IgGSp production, which correlated with a decreasing trend in the early levels (after day 1) of Co-mV induced Sp immunogen levels. Neither higher Co-mV concentrations (6µg) nor withholding S for 1-day could overcome the inhibition of Sp protein levels. Interestingly, 3-days S holiday or using T alone rescued Sp levels in vitro. Conclusions: This is the first study to demonstrate that ISs, sirolimus and mycophenolate inhibited Co-mV-induced Sp protein synthesis via translation repression. Selective use of tacrolimus or drug holiday of sirolimus can be a potential means to rescue translation-dependent Sp protein production. These findings lay a strong foundation for guiding future studies aimed at improving Co-mV responses in high-risk IC patients.

Bone marrow-based homeostatic proliferation of mature T cells in nonhuman primates: implications for AIDS pathogenesis.

Bone marrow (BM) is the key hematopoietic organ in mammals and is involved in the homeostatic proliferation of memory CD8(+) T cells. Here we expanded on our previous observation that BM is a preferential site for T-cell proliferation in simian immunodeficiency virus (SIV)-infected sooty mangabeys (SMs) that do not progress to AIDS despite high viremia. We found high levels of mature T-cell proliferation, involving both naive and memory cells, in healthy SMs and rhesus macaques (RMs). In addition, we observed in both species that lineage-specific, BM-based T-cell proliferation follows antibody-mediated in vivo CD4(+) or CD8(+) T-cell depletion, thus indicating a role for the BM in maintaining T-cell homeostasis under depleting circumstances. We also observed that, in SIV-infected SMs, but not RMs, the level of proliferation of BM-based CD4(+) T cells is higher than that of circulating CD4(+) T cells. Interestingly, limited BM-based CD4(+) T-cell proliferation was found in SIV-infected SMs with low CD4(+) T-cell counts, suggesting a regenerative failure in these animals. Collectively, these results indicate that BM is involved in maintaining T-cell homeostasis in primates and suggest a role for BM-based CD4(+) T-cell proliferation in determining the benign nature of natural SIV infection of SMs.

Silent SARS-CoV-2 Infections, Waning Immunity, Serology Testing, and COVID-19 Vaccination: A Perspective.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus causes a spectrum of clinical manifestations, ranging from asymptomatic to mild, moderate, or severe illness with multi-organ failure and death. Using a new machine learning algorithm developed by us, we have reported a significantly higher number of predicted COVID-19 cases than the documented counts across the world. The sole reliance on confirmed symptomatic cases overlooking the symptomless COVID-19 infections and the dynamics of waning immunity may not provide 'true' spectrum of infection proportion, a key element for an effective planning and implementation of protection and prevention strategies. We and others have previously shown that strategic orthogonal testing and leveraging systematic data-driven modeling approach to account for asymptomatics and waning cases may situationally have a compelling role in informing efficient vaccination strategies beyond prevalence reporting. However, currently Centers for Disease Control and Prevention (CDC) does not recommend serological testing either before or after vaccination to assess immune status. Given the 27% occurrence of breakthrough infections in fully vaccinated (FV) group with many being asymptomatics and still a larger fraction of the general mass remaining unvaccinated, the relaxed mask mandate and distancing by CDC can drive resurgence. Thus, we believe it is a key time to focus on asymptomatics (no symptoms) and oligosymptomatics (so mild that the symptoms remain unrecognized) as they can be silent reservoirs to propagate the infection. This perspective thus highlights the need for proactive efforts to reevaluate the current variables/strategies in accounting for symptomless and waning fractions.

Variable Creatinine Levels in Critical Care Patients: A Concerning Knowledge Gap.

An accurate creatinine (Cr) estimate is pivotal for the assessment of renal function. Both patient- and practice-spawned factors palliate the test accuracy of serum creatinine (sCr) and can erratically represent actual kidney function. This study evaluated the caregivers' awareness of enzymatic serum creatinine (E-sCr) assay interfering in dopamine/dobutamine (DD)-infused patient samples and the frequency of such interference in a critical care setting. We conducted an sCr awareness survey among UT Southwestern physicians, nurses, and pharmacists. We then performed a cross-sectional E-sCr comparison against the kinetic Jaffe method using the DD-infused patient samples collected from central venous catheters (CVC), peripherally inserted central catheter (PICC) lines, and the peripheral vein (PV). We retrospectively compared the longitudinal E-sCr results of the CVC/PICC draws with the corresponding blood urea nitrogen (BUN) levels. The survey results show a significant lack of awareness among caregivers about the negative interference of DD infusions on E-sCr. Cross-sectional E-sCr assessment relative to the Jaffe method displayed a negative interference in 12% of CVC/PICC line samples (7/57 DD-infused patients) compared to none in the PV draws. A longitudinal assessment of E-sCr, BUN, and potassium (K) levels from CVC/PICC line samples further confirmed a spurious decrease for E-sCr in about 12/50 (24%) patients who did not show a concurrent BUN or K decrease. The results suggest that a direct PV sampling accompanied by clinical laboratory-directed proactive discussion/activities can foster awareness among caregivers and eschew the false E-sCr estimates in DD-infused patients.

Serological Response in Lung Transplant Recipients after Two Doses of SARS-CoV-2 mRNA Vaccines.

BACKGROUND: Lung-transplant (LT) recipients are at high risk for COVID-19 due to immunosuppression and respiratory tropism of SARS-CoV-2. The information on the effect of COVID-19 mRNA vaccines to elicit immunogenic responses after a two-dose (2D) regimen in LT recipients is sparse. Thus, we assessed the effect of Pfizer-BioNTech and Moderna mRNA vaccines' 2D regimen on anti-spike responses in immunocompromised LT recipients. METHODS: We utilized serum samples from LT recipients vaccinated for SARS-CoV-2 with 2D of either the Pfizer-BioNTech or Moderna vaccines and 2D-vaccinated naïve (non-transplanted and non-exposed to COVID-19) group. Antibody responses were assessed using the FDA-approved SARS-CoV-2 anti-nucleocapsid protein IgG assay (IgGNC), the SARS-CoV-2 anti-spike protein IgM assay (IgMSP), and the SARS-CoV-2 anti-spike protein IgG II assay (IgGSP). CD4+ T-cell activity was assessed as a marker of immune competence using the ImmuKnow® assay. RESULTS: About 25% (18/73) of SARS-CoV-2 uninfected-LT patients generated a positive spike-IgG response following 2D of vaccines, with 36% (9/25) in the Moderna cohort and only 19% (9/48) in the Pfizer cohort. 2D in LT patients elicited a significantly lesser median IgGSP response (1.7 AU/mL, 95% CI: 0.6-7.5 AU/mL) compared to non-transplanted, uninfected naïve subjects (14,209 AU/mL, 95% CI: 11,261-18,836 AU/mL; p < 0.0001). In LT patients, the Moderna-evoked seropositivity trend was higher than Pfizer. CONCLUSION: 2D COVID-19 vaccination elicits a dampened serological response in LT patients. Whether assessing other arms of host immunity combined with a higher vaccine dose can better capture and elicit improved immunogenicity in this immunocompromised population warrants investigation.

Expanding COVID-19 Vaccine Availability: Role for Combined Orthogonal Serology Testing (COST).

BACKGROUND: The persisting Coronavirus disease 2019 (COVID-19) pandemic and limited vaccine supply has led to a shift in global health priorities to expand vaccine coverage. Relying on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) molecular testing alone cannot reveal the infection proportion, which could play a critical role in vaccination prioritization. We evaluated the utility of a combination orthogonal serological testing (COST) algorithm alongside RT-PCR to quantify prevalence with the aim of identifying candidate patient clusters to receive single and/or delayed vaccination. METHODS: We utilized 108,505 patients with suspected COVID-19 in a retrospective analysis of SARS-CoV-2 RT-PCR vs. IgG-nucleocapsid (IgGNC) antibody testing coverage in routine practice for the estimation of prevalence. Prospectively, an independent cohort of 21,388 subjects was simultaneously tested by SARS-CoV-2 RT-PCR and IgGNC to determine the prevalence. We used 614 prospective study subjects to assess the utility of COST (IgGNC, IgM-spike (IgMSP), and IgG-spike (IgGSP)) in establishing the infection proportion to identify a single-dose vaccination cohort. RESULTS: Retrospectively, we observed a 6.3% (6871/108,505) positivity for SARS-CoV-2 RT-PCR, and only 2.3% (2533/108,505) of cases had paired IgGNC serology performed. Prospectively, IgGNC serology identified twice the number of COVID-positive cases in relation to RT-PCR alone. COST further increased the number of detected positive cases: IgGNC+ or IgMSP+ (18.0%); IgGNC+ or IgGSP+ (23.5%); IgMSP+ or IgGSP+ (23.8%); and IgGNC+ or IgMSP+ or IgGSP+ (141/584 = 24.1%). CONCLUSION: COST may be an effective tool for the evaluation of infection proportion and thus could define a cohort for a single dose and/or delayed vaccination.

Comparison of Methods to Estimate Low-Density Lipoprotein Cholesterol in Patients With High Triglyceride Levels.

Importance: Low-density lipoprotein cholesterol (LDL-C) is typically estimated with the Friedewald or Martin/Hopkins equation; however, if triglyceride levels are 400 mg/dL or greater, laboratories reflexively perform direct LDL-C (dLDL-C) measurement. The use of direct chemical LDL-C assays and estimation of LDL-C via the National Institutes of Health Sampson equation are not well validated, and data on the accuracy of LDL-C estimation at higher triglyceride levels are limited. Objective: To compare an extended Martin/Hopkins equation for triglyceride values of 400 to 799 mg/dL with the Friedewald and Sampson equations. Design, Setting, and Participants: This cross-sectional study evaluated consecutive patients at clinical sites across the US with patient lipid distributions representative of the US population in the Very Large Database of Lipids from January 1, 2006, to December 31, 2015, with triglyceride levels of 400 to 799 mg/dL. Data analysis was performed from November 9, 2020, to March 23, 2021. Main Outcomes and Measures: Accuracy in LDL-C classification according to guideline-based categories and absolute errors between estimated LDL-C and dLDL-C levels. Patients were randomly assigned 2:1 to derivation and validation data sets. Levels of dLDL-C were measured by vertical spin-density gradient ultracentrifugation. The LDL-C levels were estimated using the Friedewald method, with a fixed ratio of triglycerides to very low-density lipoprotein cholesterol (VLDL-C ratio of 5:1), extended Martin/Hopkins equation with a flexible ratio, and Sampson equation with VLDL-C estimation by multiple least-squares regression. Results: A total of 111 939 patients (mean [SD] age, 52 [13] years; 65.0% male) with triglyceride levels of 400 to 799 mg/dL were included, representing 2.2% of 5 081 680 patients in the database. Across all individual guideline LDL-C classes (<40, 40-69, 70-99, 100-129, 130-159, 160-189, and ≥190), estimation of LDL-C by the extended Martin/Hopkins equation was most accurate (62.1%) compared with the Friedewald (19.3%) and Sampson (40.4%) equations. In classifying LDL-C levels less than 70 mg/dL across all triglyceride strata, the extended Martin/Hopkins equation was most accurate (67.3%) compared with Friedewald (5.1%) and Sampson (26.4%) equations. In addition, for classifying LDL-C levels less than 40 mg/dL across all triglyceride strata, the extended Martin/Hopkins equation was most accurate (57.2%) compared with the Friedewald (4.3%) and Sampson (14.4%) equations. However, considerable underclassification of LDL-C occurred. The magnitude of error between the Martin/Hopkins equation estimation and dLDL-C was also smaller: at LDL-C levels less than 40 mg/dL, 2.7% of patients had 30 mg/dL or greater differences between dLDL-C and estimated LDL-C using the Martin/Hopkins equation compared with the Friedewald (92.5%) and Sampson (38.7%) equations. Conclusions and Relevance: In this cross-sectional study, the extended Martin/Hopkins equation offered greater LDL-C accuracy compared with the Friedewald and Sampson equations in patients with triglyceride levels of 400 to 799 mg/dL. However, regardless of method used, caution is advised with LDL-C estimation in this triglyceride range.

Evaluation of SARS-CoV-2 Serological Testing in Patients with Multiple Myeloma and Other Hematologic Malignancies on Monoclonal Antibody Therapies.

BACKGROUND: Patients with hematological malignancies (HM), including multiple myeloma (MM), frequently suffer from immune deficiency-associated infectious complications because of both the disease and the treatment. Alarming results from China and the UK confirm the vulnerability of HM patients to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-driven coronavirus disease 2019 (COVID-19). Given that the immunoassay interference from the endogenous monoclonal immunoglobulin (M paraprotein) and treatment antibodies continually challenges the MM management, it is critical to evaluate the SARS-CoV-2 serology tests for suspected interference/cross-reactivity. METHODS: We compared the degree of interference in three SARS-CoV-2 serology assay platforms in HM patients with and without COVID-19 and on various therapeutic monoclonal antibody (t-mAb) treatments. Further, we confirmed the cross-reactivity in pooled samples from normal and COVID-19 + samples spiked with respective antibodies in vitro. RESULTS: None of the 93 HM patient samples with or without t-MAbs showed cross-reactivity on any of the three serology platforms tested. CONCLUSIONS: The tested three serologic assays for SARS-CoV-2 are specific and do not have cross-reactivity with M-components or t-MAbs indicating that they can be used safely in oncology practice and in research exploring the immunologic response to COVID-19 in patients with HM.

Complete Depletion of Daratumumab Interference in Serum Samples from Plasma Cell Myeloma Patients Improves the Detection of Endogenous M-Proteins in a Preliminary Study.

BACKGROUND: Therapeutic humanized IgG1 kappa monoclonal antibody (t-mAb), daratumumab (DARA) is a Food and Drug Administration approved drug for the treatment of relapsed/refractory plasma cell myeloma (PCM). DARA appears on serum protein electrophoresis (SPEP) and on serum immunofixation (sIFE) as an IgG kappa monoclonal immunoglobulin protein (M-protein), complicating the assessment of the patients' response to therapy. A more ominous threat to patient safety can occur with the misinterpretation of the presence of a small t-mAb spike as being the residual product of the patient's neoplastic clone, presented either as oligoclonality or new clonality, which could result in incorrect interpretation of failure to achieve remission. METHODS: In this report, we describe a novel and cost-effective technique based on biotinylated recombinant CD38 and streptavidin-coated magnetic beads to capture and remove residual DARA present in PCM patient serum samples. The treated samples are then run like regular samples on SPEP and sIFE. We validated this simple technique in DARA-spiked PCM samples and patient samples on DARA treatment. RESULTS: Our simple capture technique completely extracted DARA in all of the tested serum specimens and allowed the assessment of residual M-protein without DARA interference. The results were reproducible and highly specific for DARA, and did not have any impact on endogenous M-protein migration and quantification by SPEP and sIFE. The cost of this technique is much lower and it can be performed in-house with a very short turnaround time compared to the currently available alternative methods. There is a great need for such reflex technologies to avoid interpretation errors. CONCLUSIONS: This method is an effective way to eliminate DARA interference in SPEP and sIFE, and can be easily implemented in any clinical laboratory without any patent restriction. This simple technique can be adopted for other t-mAbs using their respective ligands and will help to reduce additional doses of toxic treatment and further testing in patients on t-mAbs with a false positive M-protein spike.

SARS-CoV-2 Antibody Responses Do Not Predict COVID-19 Disease Severity.

OBJECTIVES: Initial reports indicate adequate performance of some serology-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) assays. However, additional studies are required to facilitate interpretation of results, including how antibody levels impact immunity and disease course. METHODS: A total of 967 subjects were tested for IgG antibodies reactive to SARS-CoV-2, including 172 suspected cases of SARS-CoV-2, 656 plasma samples from healthy donors, 49 sera from patients with rheumatic disease, and 90 specimens from individuals positive for polymerase chain reaction (PCR)-based respiratory viral panel. A subgroup of SARS-CoV-2 PCR-positive cases was tested for IgM antibodies by proteome array method. RESULTS: All specificity and cross-reactivity specimens were negative for SARS-CoV-2 IgG antibodies (0/795, 0%). Positive agreement of IgG with PCR was 83% of samples confirmed to be more than 14 days from symptom onset, with less than 100% sensitivity attributable to a case with severe immunosuppression. Virus-specific IgM was positive in a higher proportion of cases less than 3 days from symptom onset. No association was observed between mild and severe disease course with respect to IgG and IgM levels. CONCLUSIONS: The studied SARS-CoV-2 IgG assay had 100% specificity and no adverse cross-reactivity. Measures of IgG and IgM antibodies did not predict disease severity in our patient population.

Best practices in mitigating the risk of biotin interference with laboratory testing.

Dietary biotin intake does not typically result in blood biotin concentrations that exceed interference thresholds for in vitro diagnostic tests. However, recent trends of high-dose biotin supplements and clinical trials of very high biotin doses for patients with multiple sclerosis have increased concerns about biotin interference with immunoassays. Estimates of the prevalence of high biotin intake vary, and patients may be unaware that they are taking biotin. Since 2016, 92 cases of suspected biotin interference have been reported to the US Food and Drug Administration. Immunoassays at greatest risk from biotin interference include thyroid and reproductive hormones, cardiac, and immunosuppressive drug tests. Several case studies have highlighted the challenge of biotin interference with thyroid hormone assays and the potential misdiagnosis of Graves' disease. Biotin interference should be suspected when immunoassay test results are inconsistent with clinical information; a clinically relevant biotin interference happens when the blood biotin concentration is high and the assay is sensitive to biotin. We propose a best practice workflow for laboratory scientists to evaluate discrepant immunoassay results, comprising: (1) serial dilution; (2) retesting after biotin clearance and/or repeat testing on an alternate platform; and (3) confirmation of the presence of biotin using depletion protocols or direct measurement of biotin concentrations. Efforts to increase awareness and avoid patient misdiagnosis should focus on improving guidance from manufacturers and educating patients, healthcare professionals, and laboratory staff. Best practice guidance for laboratory staff and healthcare professionals would also provide much-needed information on the prevention, detection, and management of biotin interference.

Susceptibility of Cardiac Troponin Assays to Biotin Interference.

OBJECTIVES: To investigate biotin interference on three cardiac troponin (cTn) assays and demonstrate a method to overcome biotin interference. METHODS: cTn levels were measured in (1) plasma from healthy volunteers on 10-mg daily biotin supplementation mixed with a plasma with known elevated troponin, (2) plasmas with known elevated cTn after mixing in reagent biotin to simulate supplementation, and (3) biotin-spiked plasma specimens pretreated with streptavidin-agarose beads. RESULTS: Daily biotin ingestion (10 mg) and studies simulating daily biotin use resulted in significant interference in the Gen5 cardiac troponin T (cTnT) assay; the contemporary Gen 4 cTnT and high-sensitivity cardiac troponin I (hs-cTnI) assays were unaffected. The biotin interference threshold was 31, 315, and more than 2,000 ng/mL for Gen5 cTnT, cTnT, and hs-cTnI assays, respectively. Streptavidin pretreatment blocked biotin interference in cTn assays. CONCLUSIONS: Biotin interference is possible at plasma concentrations achievable by ingestion of over-the-counter supplements that may lead to delayed or missed diagnosis of myocardial injury with the Gen5 cTnT assay.