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Background/Aims Rheumatology is a complex specialty covering many conditions of varying severity, from muscle pain through inflammatory arthritis such as Rheumatoid arthritis (RA) and connective tissue diseases. Most of the conditions can be managed in an outpatient/day case setting. However, acutely ill patients require safe and prompt inpatient management including specific intravenous infusions. This need to be done urgently and cannot wait to be accommodated through the Infusion unit at our hospital. Historically Medicine Acute Admission Unit has been the route to bring in these patients. However, operational bed pressures faced challenges leading to instances of delayed treatment with complications including fatality. This led to creating a direct inpatient admission pathway to the specialist ward. Methods Ward Matron designed the following robust pathway for direct patient admission to our specialist Rheumatology ward, Jevington ward. This was implemented in February 2022 after discussion and agreement with Clinical Lead consultant, pharmacist, clinical site managers and other colleagues. Rheumatology team and nurses covered the ward during working hours and by the on-call team out of hours. The overall responsibility remained with the rheumatology team. The referrals accepted only after completing appropriate paperwork. Patients carried out Lateral Flow Test (LFT) at home prior to admission. We ensured negative results and followed the Trust COVID 19 screening protocols. Subsequent screenings were done according to the updated guidelines. The planned assessment and treatments were carried out by the ward team complying with BSR/ EULAR Guidelines, infusion protocols such as standard and continuous Iloprost Infusion Protocols of the Trust. Results We assessed the delay in patient's admission, length of stay, patient outcome and experience after implementing the pathway. The significant change has been in the time to admit;from two weeks in 2018 & 19 to two days this year. This is reflected in the patient feedback. All our acutely ill patients were assessed, treated and discharged promptly on this specialist ward. Conclusion This pathway allowed safe and prompt treatment, prognosis and excellent experience for acutely ill patients with rheumatological disorders. This additionally enabled reduced length of stay supporting financial sustainability of the Trust. (Table Presented).
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Background: Antibody testing for COVID-19 may represent an interesting tool to document past SARS-CoV- 2 infections, both in individual patients with suspected COVID-19 symptoms or late-stage complications who had no (conclusive) PCR test. In addition, measuring SARS-CoV- 2 antibodies may offer a prognostic value and convey information on protective immunity in vaccination trials. The objective of the study is the evaluation of a rapid test for the quantitative interpretation of Anti-SARS- CoV- 2 IgG compared with other in-vitro methods. Method(s): The Anti-SARS- CoV- 2 LFA (Lateral Flow Assay) is a rapid test for the quantitative measurement of IgG antibodies to SARS-CoV- 2 in human serum, plasma and whole blood within 20 minutes. The complexes of Anti-SARS- CoV- 2 antibodies from patient's sample and coloured conjugate are retained at the test line by the complete SARS-CoV- 2 Spike Protein. The use of a special scanner system provides the opportunity of quantitative interpretation of the results, by using calibration curve established with "First WHO International Standard for anti-SARS- CoV- 2 immunoglobulin (human)". Result(s): Serum samples were taken from the serum bank at Dr. Fooke Laboratorien GmbH and tested for Anti-SARS- CoV- 2 IgG by the newly developed LFA (Dr. Fooke Laboratorien GmbH). The results were compared with established assay methods like Anti-SARS- CoV- 2 ELISA IgG (Dr. Fooke Laboratorien GmbH and Euroimmun). Good agreements were observed. Sensitivity and specificity between the newly developed LFA and Anti-SARS- CoV- 2 ELISA IgG of Dr. Fooke / Euroimmun were found at 0.95/0.88 and 1.00/0.93, respectively. The calibration curve established with "First WHO International Standard for anti-SARS- CoV- 2 immunoglobulin (human)" shows a reproducibility of > 90%. Conclusion(s): The Anti-SARS- CoV- 2 LFA shows comparable results to the ELISA systems of Dr. Fooke Laboratorien and Euroimmun. By the use of small amounts of serum, plasma or whole blood (10muL) the patients receive a fast and reliable result. A calibration curve, established with "First WHO International Standard for anti-SARS- CoV- 2 immunoglobulin (human)" offers the comparability to quantitative ELISA systems.
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Objectives: The goal of the present study was to assess the SARS-CoV-2 antigen detection test's performance features and compare them to the real-time reverse transcription polymerase chain reaction (RT-PCR) test, the gold standard test for the diagnosis of COVID-19 cases. Method(s): From October 2020 to May 2021, patients attending the OPD, including those undergoing surgery, at a Tertiary Care Teaching Hospital in Telangana provided 1000 respiratory samples, primarily nasopharyngeal swabs. A skilled technician had collected two nasopharyngeal swabs from each person in a COVID sample collection room while wearing personal protective equipment and following strict infection control procedures. One swab was used for the rapid antigen test given by the standard Q COVID-19 Ag test kit and placed into the extraction buffer tube. Second swab was kept in the viral transport medium and used for AllplexTM 2019-nCoV Assay (Seegene, Korea), which targets envelope gene (E), and RNA dependent RNA polymerase (RdRp) and nucleocapsid (N) genes of SARS CoV-2, was used for SARS-CoV-2 RNA detection according to the manufacturer's instructions. Result(s): Out of 1000 samples tested for COVID-19, 623 (63.7%) were males and 377 (36.3%) were females. Out of 1000 samples, 347 samples were RT-PCR positive and 653 were RT-PCR negative. Out of 347 RT-PCR samples positive, 341 were Rapid antigen test positive samples and six were negative. Overall sensitivity and specificity are 98.27% and 99.85%, respectively. Conclusion(s): The real-time RT-PCR assay's sensitivity and specificity were comparable to those of the rapid assay for SARS-CoV-2 antigen detection. It can be utilized for contact tracing measures to control the COVID-19 pandemic in places such as border crossings, airports, interregional bus and train stations, and mass testing campaigns needing quick findings. This is especially true in areas with a high prevalence of the disease.Copyright © 2023 The Authors. Published by Innovare Academic Sciences Pvt Ltd.
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Rationale: To establish a novel SARS-CoV-2 human challenge model enabling controlled investigation of pathogenesis, correlates of protection and efficacy testing of interventions. Method(s): Thirty-six healthy 18-29-year-old subjects, without evidence of previous infection or vaccination, received 10 TCID50 of a wild-type virus (SARS-CoV-2/human/GBR/484861/2020) intranasally. Following inoculation, subjects resided in a high-containment quarantine, with 24-hour medical monitoring. The study's main objectives were to identify a virus dose that induced well-tolerated infection in >50% of subjects and assess virus and symptoms over time. AEs and longitudinal disease profiles are presented. Result(s): Eighteen of thirty-four evaluable (~53%) subjects became infected and developed serum antibodies. Viral load rose steeply and peaked ~5 days post-inoculation (PI). Virus was first detected in the throat but rose to significantly higher levels in the nose, peaking at ~8.87 log10 copies/ml (median, 95% CI [8.41,9.53]). Viable virus was recoverable from the nose up to ~10 days PI, on average. Mild-to-moderate symptoms were reported by 16 (89%) infected subjects, beginning 2-4 days PI. Anosmia or dysosmia developed in 15 (83%) subjects. Results from lateral flow tests were associated with viable virus and modelling showed that twice-weekly rapid antigen tests could diagnose infection before 70-80% of viable virus had been generated. There were no overt lung function changes, CT abnormalities, or SAEs. Conclusion(s): This novel SARS-CoV-2 challenge of 18-29-year-olds was considered safe. Viral kinetics over the course of primary infection was established, with implications for public health recommendations and strategies to impact transmission.
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Introduction: Covid-19 results in a wide spectrum of illness ranging from asymptomatic, mild to severe respiratory disease and multi-organ involvement. Transplant recipients are at increased risk of severe Covid-19. The risk of transmission from a Covid-19 positive donor to recipient in kidney transplantation is unknown. National Health Service Blood and Transplant, UK recommended respiratory polymerase chain reaction (PCR) testing for all donors for Covid-19 and advice against organ donation if positive within the last 28 days. However, a recent amendment of guideline (www.odt.nhs.uk, POL304/3) supports organ donation from selected donors with positive or indeterminate SARS-CoV-2 PCR results. Method(s): We report two cases of kidney transplantation including one unvaccinated recipient where donors had tested SARS-CoV-2 PCR positive. Result(s): 1: Mrs A is a 38-year old Caucasian with end-stage kidney disease (ESKD) secondary to reflux nephropathy, established on haemodialysis (HD). She had declined Covid-19 vaccinations. The donor died of traumatic brain injury and he had a positive lateral flow test 3 weeks prior. The PCR test was positive. Decision was made to proceed with deceased donor kidney transplantation. She was high immunological risk with a HLA antibody calculated reaction frequency (CRF) of 79%, donor specific antibody negative. She was given Basiliximab induction followed by Tacrolimus, Mycophenolate Mofetil and steroids. Graft function was immediate and at 3 week post-transplant, she is well with excellent graft function and no evidence of Covid-19. 2: Mrs B is a 63-year old Asian with ESKD secondary to diabetes and hypertension. She was established on HD and fully vaccinated (three doses of Pfizer-BNT162b2 mRNA vaccine). The donor died of subarchnoid haemorrhage. He had a positive lateral flow test 15 days prior with flu-like symptoms. Respiratory PCR for SARS-CoV-2 was positive. The decision was to proceed with deceased donor transplantation. She was low immunological risk with a HLA antibody CRF of 0%. There were no peri-operative complications and she had immediate graft function. She had Basiliximab induction and was discharged on Tacrolimus and Mycophenolate mofetil with prednisolone withdrawn on day 7 (our low immunological risk protocol). At 3 week post-transplant, she is well with no evidence of Covid-19 and excellent graft function. Conclusion(s): We report 2 cases of kidney transplantation from Covid-19 positive donors in whom the cause of death was not Covid-19 pneumonia. Covid-19 status of the donor was discussed with the patients who both consented. Neither recipient developed Covid-19 in the early post-transplant period, despite being heavily immunosuppressed. Although there remains a theoretical risk, there are no reports of transmission of Covid-19 to kidney transplant recipients from positive donors. Prophylactic antivirals or monoclonal antibodies for the recipient post-transplant or spike antibody test to guide decision making are not currently recommended. We used clinical details of the donor and virology advice which accounts for PCR cycle threshold value to make a decision to transplant. The outcomes of 2 patients reported along with similar experience from other centres is encouraging and supports use of kidneys from selected SARS-CoV-2 positive deceased donors after obtaining virological advice and appropriate consent. No conflict of interestCopyright © 2023
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Lateral flow assays are low-cost devices suitable for point-of-care testing, particularly in low-resource settings. However, some of the lateral flow assays exhibit limited diagnostic utility because the assays can only sample <100uL specimen and the biomarker concentration is significantly lower than the assay detection limit, which compromise the sensitivity. To address the challenge, we have developed the osmoprocessor that statically and spontaneously concentrated biomarkers via osmosis. The specimen in the device interfaces with the aqueous polymer solution via a dialysis membrane. The polymer solution induces an osmotic pressure difference that extracts water from the specimen, while the membrane retains the biomarkers. The evaluation demonstrated that osmosis induced by various water-soluble polymers efficiently extracted water, ca. 15 mL/hr. The water transport kinetics can be adjusted by varying polymer molecular weights and mass concentrations. The osmoprocessor concentrated the specimens to improve the lateral flow assays' detection limits for the model analytes-human chorionic gonadotropin and SARS-CoV-2 nucleocapsid protein. The device processed a 10 mL specimen into a 100uL concentrated sample. Then, the lateral flow assays detected the corresponding biomarkers in the concentrated specimens. The test band intensities of the assays with the concentrated specimens were very similar to the reference assays with 100-fold concentrations. The mass spectrometry analysis estimated the SARSCoV- nucleocapsid protein concentration increased ca. 200-fold after the osmosis. With its simplicity and flexibility, this device demonstrates a great potential to be utilized in conjunction with the existing lateral flow assays for enabling highly sensitive detection of dilute target analytes.
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Introduction: since the scarce diagnostic accuracy of specific circulating antibodies for SARS-CoV-2, we aimed to assess the clinical utility of IgM detection in SARS-CoV-2 using the Big Data analysis. Methods: this is a retrospective study;all the blood samples collected between March and September 2020 were processed using a lateral flow immunoassay (LFIA) kit for IgG and IgM antybody testing. Positives results were tested again using a chemiluminescent method. Subjects confirmed with a positive result were contacted for a molecular test. Results: more than 69 000 serological tests (from 42 911 subjects) were performed. 94.5% (40 559/42 911) of subjects had negative results for both IgG and IgM. 1.5% (n = 640) subjects had both IgG and IgM positive results, and viral RNA research confirmed positivity in 16% (85/533). Among subjects with IgG negative and IgM positive results (n=271), a positivity was confirmed in 1% (4/270). Conversely, in subjects with IgG positive and IgM negative results, a positivity was confirmed in 8% (97/1 215). Therefore, the analysis suggests that up to 98% of serological test results of IgM positivity and IgG negativity are false positive. Discussion: the study, based on Big Data analysis application, proved the scarce clinical utility of IgM detection in COVID-19 management, and underlines the responsibility of laboratory professionals in highlighting the limitations of the serological tests also due to uncertainty in their interpretation.
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The timely and accurate diagnosis of porcine epidemic diarrhea virus (PEDV) infection is crucial to reduce the risk of viral transmission. Therefore, the objective of this review was to evaluate the overall diagnostic accuracy of rapid point-of-care tests (POCTs) for PEDV. Studies published before 7 January 2022 were identified by searching PubMed, EMBASE, Springer Link, and Web of Science databases, using subject headings or keywords related to point of care and rapid test diagnostic for PEDV and PED. Two investigators independently extracted data, rated risk of bias, and assessed the quality using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. The bivariate model and the hierarchical summary receiver operating characteristic (HSROC) model were used for performing the meta-analysis. Threshold effect, subgroup analysis, and meta-regression were applied to explore heterogeneity. Of the 2908 records identified, 24 eligible studies involving 3264 specimens were enrolled in the meta-analysis, including 11 studies on evaluation of lateral flow immunochromatography assay (ICA)-based, and 13 on nucleic acid isothermal amplification (NAIA)-based POCTs. The overall pooled sensitivity, specificity and diagnostic odds ratio (DOR) were 0.95 (95% CI: 0.92-0.97), 0.96 (95% CI 0.88-0.99) and 480 (95% CI 111-2074), respectively; for ICA-based POCTs and the corresponding values for NAIA-based, POCTs were 0.97 (95% CI 0.94-0.99), 0.98 (95% CI 0.91-0.99) and 1517 (95% CI 290-7943), respectively. The two tests showed highly comparable and satisfactory diagnostic performance in clinical utility. These results support current recommendations for the use of rapid POC tests when PEDV is suspected.
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Porcine epidemic diarrhea virus , Animals , Point-of-Care Systems , Point-of-Care Testing , ROC Curve , Sensitivity and Specificity , SwineABSTRACT
Background Rapid antigen detection tests of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) play a crucial role in the control of the current coronavirus disease 2019 (COVID-19) pandemic. Data about the real diagnostic performance of such tests is still insufficient and hence their evaluation is of high priority. Objectives The aim of this study was to evaluate the diagnostic performance of BIOCREDIT COVID-19 antigen test alone and in combination with either C-reactive protein (CRP) or neutrophil/lymphocyte ratio (NLR) in comparison to real-time quantitative polymerase chain reaction (RT-qPCR). Additionally, we investigated the selection criteria of the suspect for best performance of the antigen test. Materials and Methods Paired nasopharyngeal (NP) swabs were collected from 200 suspected COVID-19 subjects for SARS-CoV-2 RNA by RT-qPCR and for antigen detection by BIOCREDIT test. Simultaneously, for all suspect, clinical presentations were recorded as well as CRP level and NLR were determined. Results Among 200 tested NP swabs, 125 (62.5%) were RT-PCR positive. Overall sensitivity, specificity and accuracy of BIOCREDIT test were 34.4, 98.7, and 58.5%, respectively. Sensitivity of the BIOCREDIT test was higher in COVID-19 suspect, with high viral load (100%), severely ill (56.2%), with fever alone (40%), elevated CRP (41.1%), and high NLR (36.2%). In combination with NLR or CRP, sensitivity of BIOCREDIT test increased to 89.4 and 81.6%, respectively, while its specificity decreased to 67 and 59%, respectively. Conclusion The overall low sensitivity of BIOCREDIT/COVID-19 antigen test does not permit its use as a single diagnostic test for COVID-19. However, its use should be restricted only if it is combined with either CRP or NLR in suspect with certain criteria.
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The COVID-19 pandemic resulted in a rapid requirement for a safe and effective vaccination programme. Currently, three types of vaccines exist: mRNA (Pfizer), adenoviral vector (AstraZeneca) and inactivated whole-virus vaccines (Sinofarm). These all have reported cutaneous side-effects, including papulovesicular, pityriasis rosea-like and papulosquamous eruptions (McMahon DE, Kovarik CL, Damsky W et al. Clinical and pathologic correlation of cutaneous COVID-19 vaccine reactions including V-REPP: a registry-based study. J Am Acad Dermatol 2021;86: 113-21). We present a case of delayed type III hypersensitivity reaction clinically resembling urticarial vasculitis (UV) in a 66-year-old woman following AstraZeneca vaccine. She initially reported urticarial lesions on the hands after the first vaccination;these settled spontaneously. On subsequent vaccination she developed a florid rash 4 days later, presenting to Accident & Emergency with angio-oedema, malaise and urticaria. The eruption was presumed viral given the mildly elevated C-reactive protein, and negative lateral flow test for COVID-19. She was given fexofenadine 180 mg QDS for 6 weeks;however, the rash persisted and became more widespread over the following 4 weeks. The initial urticated wheals persisted >24 h, becoming bruise-like and painful. Skin biopsy confirmed UV. ANA, complement, ANCA and COVID-19 polymerase chain reaction were nonsignificant. We believe this is the first documented case of UV triggered by the AstraZeneca vaccine and the third case of UV following a Sars-CoV-2 vaccine reported in English literature. The two other cases were secondary to Pfizer and whole-virus vaccine, respectively. From the literature it is believed UV is potentially caused by the coronavirus particles rather than vaccine additives, as the Sars-CoV-2 nucleocapsid has been demonstrated in skin lesions of asymptomatic COVID-19 patients with UV (Criado PR, Criado RFJ, Gianotti R et al. Urticarial vasculitis revealing immunolabelled nucleocapsid protein of SARS-CoV-2 in two Brazilian asymptomatic patients: the tip of the COVID-19 hidden iceberg? J Eur Acad Dermatol Venereol 2021;35: e563-6). Thus, although rare, clinicians should be aware of this entity.
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OBJECTIVE: To evaluate the accuracy of a modified bedside test in ruling out an ectopic pregnancy. The test is based on a lateral flow immunoassay for alpha-fetoprotein (AFP). It has been shown that a high AFP level in vaginal blood indicates the passage of fetal tissue, suggestive of a miscarriage [1].We hypothesized that high AFP levels in sampled intrauterine tissue, assuming non-heterotopic pregnancy, rules out the presence of an ectopic pregnancy. MATERIALS AND METHODS: This is a prospective cohort study. The study included pregnant women undergoing a dilation and curettage (D&C) for pregnancy loss or termination, women with pregnancy loss or an ectopic pregnancy presenting with vaginal bleeding, and non-pregnant women with vaginal bleeding. Vaginal blood was collected on gauzes, sanitary pads, and cotton swabs. Samples were then tested for AFP levels using a commercial kit (ROMplus, Laborie, USA) originally designed to detect leakage of amniotic fluid. This kit contains a lateral flow immunoassay strip capable of detecting the presence of AFP. Positive samples for AFP were retested at a later date (after 3 to 20 days) to ascertain the stability of AFP and reliability of the test. Official sonograms, pregnancy tests, and final pathology results were obtained to confirm pregnancy status as well as the presence or absence of fetal tissue in the vaginal blood. A sensitivity and specificity analysis was performed against these final results to validate the accuracy of the test strip in ruling out an ectopic pregnancy. RESULTS: A total of 30 vaginal blood samples were tested for AFP. All pregnant women who had a miscarriage or D&C had detectible AFP in their vaginal blood (n=13). On retesting the samples 3 to 20 days later, these results remained the same (positive test strip). The remaining 17 vaginal blood samples were from 4 women with ectopic pregnancies and from 13 non-pregnant women with vaginal bleeding. All 4 ectopic pregnancies had no AFP detected in the vaginal blood and only 1 out of 13 non-pregnant patient samples had AFP detected. The ROMplus test strip correctly detected AFP in all samples tested containing fetal tissue (n=13) resulting in a test sensitivity of 100%. ROMplus correctly identified the absence of AFP in 16 out of the 17 samples lacking fetal tissue, a 94% test specificity. CONCLUSIONS: ROMplus has the potential to accurately and reliably detect the presence of AFP, and hence fetal tissue, in vaginal blood samples. This could be a vital non-invasive aid in ruling out an ectopic pregnancy at the bedside (currently off-label use). Furthermore, it could limit the amount of invasive testing and visits needed in cases of pregnancies of unknown location. IMPACT STATEMENT: In light of the recent COVID-19 pandemic, a simple non-invasive bedside test to rule out an ectopic pregnancy is highly desired given its potential for reducing the number of visits, investigations performed, and personnel involved in the workup of a pregnancy of unknown location.
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Background: Reliable serologic assays are needed to accurately measure prevalence of prior exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, several countries in Africa have reported apparent SARS-CoV-2 assay cross-reactivity with other non-coronavirus pathogens. We used 3 SARS-CoV-2 serologic assays to assess positivity in archived serum specimens collected in Zambia prior to the COVID-19 pandemic and explored seropositivity associations with participant characteristics. Methods: SARS-CoV-2 antibody seropositivity was measured using serum specimens collected from pregnant women aged 15-49 years enrolled in an HIV and syphilis sentinel surveillance study in 26 sites across Zambia during 2017-2018. Of 9,508 participants with archived specimens, 1,500 (16%) were selected using stratified random sampling (by study site). SARS-CoV-2 antibody seroprevalence was measured using the Panbio IgM/IgG lateral flow assay, Euroimmun spike IgG enzyme-linked immunosorbent assay (ELISA), and the Wantai pan-Ig ELISA. HIV and syphilis testing followed the national testing algorithms. We compared age group and HIV and syphilis status with SARS-CoV-2 antibody seropositivity using chi-square test. Results: Among the 1,500 female participants, 1,297 (86%) had specimens available for testing. Participants' median age was 25 years (interquartile range: 21-30 years). HIV and syphilis prevalence were 16% and 6%, respectively. SARS-CoV-2 antibody seropositivity was 14% on the Panbio assay, 7% on the Euroimmun assay, and 2% on the Wantai assay. There was no concordance of positive results between the 3 assays, and no association between SARS-CoV-2 antibody seropositivity and age group, HIV status, or syphilis status on all 3 assays (p>0.05 for all comparisons). Conclusion: Three SARS-CoV-2 serologic assays showed antibody positivity in pre-pandemic specimens, possibly indicating cross-reactivity with antibodies to other coronaviruses or other non-coronavirus pathogens. Panbio and Euroimmun assays yielded more false positives than would be expected based on manufacturer-reported specificities. Although there was no association of SARS-CoV-2 antibody seropositivity with HIV or syphilis, testing for other pathogens could provide information about the identities of cross-reacting antibodies with these assays. Assessing for virus neutralizing capability of cross-reacting antibodies in SARS-Cov-2 antibody positive specimens could provide information about possible pre-existing SARS-CoV-2 immunity.
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Background: Seroprevalence studies of antibodies to SARS-CoV-2 are important for public health surveillance. Recent studies have shown that antibodies to SARS-CoV-2, both from natural infection and vaccination, decrease with time from exposure. Variation in the performance of antibody assays will impact the estimates of SARS-CoV-2 exposure and vaccination levels in a population. Using standardized serial dilutions, we evaluated 17 SARS-CoV-2 assays to establish an approximate limit of detection for each assay. Methods: The evaluated assays consisted of three chemiluminescent immunoassays (CLIAs), eight standard enzyme-linked immunosorbent assays (ELISAs), and six lateral flow assays (LFAs). All assays either evaluated IgG antibodies or total antibodies to SARS-CoV-2. The target antigen of 14 assays was the spike protein (S) or receptor binding domain (RBD);three assays evaluated antibodies to the nucleocapsid protein (N). A human SARS-CoV-2 serology standard with a WHO SARS-CoV-2 Serology International Standard binding antibody units (BAU) value of 764 BAU/mL to spike IgG and 681 BAU/mL to nucleocapsid IgG was obtained from the Frederick National Laboratory for Cancer Research. Half-logarithmic serial dilutions of the standard were then run in triplicate on each assay. Results: The MSD V-Plex chemiluminescent immunoassays (CLIAs) were the most sensitive by three logs, with positive results at a dilution greater than 1:106 (Figure). Standard ELISAs were less sensitive, with limits of detection ranging from dilutions of 1:20 (Euroimmun NeutraLISA) to 1:1620 (Euroimmun SARS-CoV-2 IgG and Euroimmun QuantiVac). Lateral flow assays (LFAs) were the least sensitive, with only one assay (Wondfo Colloidal Gold) having at least one positive result with a dilution greater than 1:180. Conclusion: As population seroprevalence to SARS-CoV-2 continues to rise, tests with a high limit of detection will be crucial for surveillance studies. As antibody levels decline after vaccination or infection, our data indicate that CLIAs like the MSD assay may provide the best opportunity to capture asymptomatic cases and individuals with low antibody titers.
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Background: Live virus micro-neutralization (MN) is the gold standard for quantifying the neutralizing titer (NT) of antibodies to SARS-CoV-2. However, performing MN is labor intensive and requires a biosafety level 3 laboratory. We assessed the performance of 8 immunoassays which measure SARS-CoV-2 NT and compared them to gold standard MN results. Methods: Samples from 269 individuals known to previously be SARS-CoV-2 PCR+ (i.e., convalescent individuals, <10% hospitalized) and 200 pre-pandemic individuals were evaluated on 3 lateral flow immunoassays (LFAs;Wondfo Colloidal Gold, Wondfo Colored Microsphere, Wondfo Finecare) and 5 enzyme-linked immunoassays (ELISAs;ImmunoRank, GenScript, Cusabio, Euroimmun NeutraLISA, Euroimmun QuantiVac). MN was performed on all samples from convalescent individuals;results were classified as undetectable vs any detection of MN NT (NT<20 vs. NT>20), as well as high and low MN NT (NT>80 vs. NT<80). Receiver operating curve analysis was used to assess accuracy for detecting levels of NT. The area under the curve (AUC) was calculated for the manufacturer's cut off and empirically to identify the best discriminatory cut off value. Cohen's kappa statistics were calculated to assess categorical agreement and Spearman's rank statistics were calculated to assess correlations. Results: Of the 269 convalescent plasma samples, 89 (33%) had MN NT values <20 (undetectable) and 117 (43%) >80 (high NT). Using the manufacturer's cutoffs, sensitivity for detection of samples with any NT ranged from 79% to 100%, and the false-positive rate (ie, classifying samples with undetectable NT as positive) was highest for LFAs (72% to 84%) and ranged from 14% to 69% for the ELISAs. For all assays except the ImmunoRank and NeutraLISA ELISAs, discrimination to identify samples with any NT was improved by raising the cut off values (Table). AUCs of ∼0.94 to discriminate high NT samples could be achieved for all quantifiable assays using an adjusted cut off value. Cohen's kappa statistic ranged from 0.20 to 0.69. Spearman's rank correlation between each assay and NT value ranged from 0.73 to 0.86. Using the manufacturer's cutoffs, specificity on pre-pandemic samples was ≥98% for all assays except for Cusabio which was 86%. Conclusion: The performance of immunoassays using manufacturer's cutoff to discriminate samples with any NT was accurate (AUC>0.83 for all assays), but could be improved by changing the cutoff. Identifying samples with high NT could be achieved using an alternative cutoff.
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The presence of neutralizing antibodies (NAbs) against SARS-CoV-2 represent a surrogate marker of immunologic protection in populations at high risk of infection such as healthcare workers caring for hospitalized patients with COVID-19. As recommended by CDC and the European CDC, the use of rapid diagnostic tests during population-based evaluations offers an opportunity to identify individuals with serologic evidence of natural infection or who have undergone vaccination. We carried out a cross-sectional study to assess the presence of neutralizing antibodies against SARS-CoV-2 among medical providers at an intensive care unit of a large referral hospital in Alicante, Spain. In addition, we tested for the presence of neutralizing antibodies compared to serum of uninfected individuals from a Biobank. We were also interested in evaluating the use of a rapid lateral flow immunochromatography (LFIC) test against a surrogate ELISA viral neutralization test (sVNT). This rapid test demonstrated a specificity of 1.000 95% CI (0.91-1.00) and the sensitivity of 0.987 95% CI (0.93-1.00). The negative predictive value was 95%. After six months, this rapid test demonstrated that those immunized with two doses of BioNTech/Pfizer vaccine, maintained optimal levels of neutralizing antibodies. We concluded that all Health Care Workers develop NAbs and the use of this rapid immunochromatographic test represents a potential tool to be used in population-based studies to detect serological antibody responses to vaccination. Vaccination policies could benefit from this tool to assess additional doses of vaccine or boosters among high-risk populations.