Longitudinal characterization of the IgM and IgG humoral response in symptomatic COVID-19 patients using the Abbott Architect.
ABSTRACT: BACKGROUND:Antibody testing has recently emerged as an option to assist with determining exposure to SARS-CoV-2, the causative agent of COVID-19. Elucidation of the kinetics and duration of the humoral response is important for clinical management and interpreting results from serological surveys. OBJECTIVES:Here we evaluated the clinical performance of Abbott SARS-CoV-2 IgM and IgG assays, as well as the longitudinal dynamics of the antibody response in symptomatic COVID-19 patients. STUDY DESIGN AND RESULTS:The diagnostic specificity was 100 % for IgM and 99.67 % for IgG using 300 pre-COVID-19 serum specimens. Using 1349 sequential serum samples collected up to 168 days post symptom onset from 427 PCR-confirmed individuals, clinical test sensitivity of the SARS-CoV-2 IgM assay was 24.6 % at ?7 days, 75.3 % at 8-14 days, 95.0 % at 15-21 days, and 96.0 % at 4-5 weeks (peak test sensitivity). The median duration of time for IgM seroconversion was 10 days. IgM levels declined steadily 4-5 weeks after symptom onset, and the positive rate dropped to 30.8 % at >3 months. The diagnostic sensitivity for the SARS-CoV-2 IgG assay post symptom onset was 23.2 % at ?7 days, 69.5 % at 8-14 days, 93.6 % at 15-21 days, and 99.6 % at 4-5 weeks (peak test sensitivity). The median duration of time for IgG seroconversion was 11.5 days. During the convalescent phase of the infection, a decline in the IgG level was observed in patients who were followed for >100 days. Despite that decline, 92.3 % of the patient cohort remained IgG positive 3-6 months following symptom onset. CONCLUSIONS:This study demonstrates the Abbott IgM assay against SARS-CoV-2 is detected slightly earlier compared to IgG, with both tests exhibiting excellent overall sensitivity and specificity. In symptomatic patients who test negative by PCR for a SARS-CoV-2 infection, assessing IgM and IgG antibodies can aid in supporting a diagnosis of COVID-19.
Project description:This multicenter, retrospective study included 346 serum samples from 74 patients with coronavirus disease 2019 (COVID-19) and 194 serum samples from non-COVID-19 patients to evaluate the performance of five anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody tests, i.e. two chemiluminescence immunoassays (CLIAs): Roche Elecsys® Anti-SARS-CoV-2 Test (Roche Test) and Abbott SARS-CoV-2 IgG (Abbott Test), and three lateral flow immunoassays (LFIAs): Wondfo SARS-CoV-2 Antibody Test (Wondfo Test), ASK COVID-19 IgG/IgM Rapid Test (ASK Test), and Dynamiker 2019-nCoV IgG/IgM Rapid Test (Dynamiker Test). We found high diagnostic sensitivities (%, 95% confidence interval [CI]) for the Roche Test (97.4%, 93.4-99.0%), Abbott Test (94.0%, 89.1-96.8%), Wondfo Test (91.4%, 85.8-94.9%), ASK Test (97.4%, 93.4-99.0%), and Dynamiker Test (90.1%, 84.3-94.0%) after >21 days of symptom onset. Meanwhile, the diagnostic specificity was 99.0% (95% CI, 96.3-99.7%) for the Roche Test, 97.9% (95% CI, 94.8-99.2%) for the Abbott Test, and 100.0% (95% CI, 98.1-100.0%) for the three LFIAs. Cross-reactivity was observed in sera containing anti-cytomegalovirus (CMV) IgG/IgM antibodies and autoantibodies. No difference was observed in the time to seroconversion detection of the five serological tests. Specimens from patients with COVID-19 pneumonia demonstrated a shorter seroconversion time and higher chemiluminescent signal than those without pneumonia. Our data suggested that understanding the dynamic antibody response after COVID-19 infection and performance characteristics of different serological test are crucial for the appropriate interpretation of serological test result for the diagnosis and risk assessment of patient with COVID-19 infection.
Project description:OBJECTIVES:Several serological SARS-CoV-2 immunoassays have been developed recently but require external validation before widespread use. This study aims at assessing the analytical and clinical performance of the iFlash® anti-SARS-CoV-2 chemiluminescence assay for the detection of both IgM and IgG antibodies. The kinetics of the antibody response was also evaluated. DESIGN & METHODS:The precision, carry-over, linearity, limit of blank, detection and quantification were assessed. Sensitivity analysis was performed by using 178 sera collected from 154 RT-PCR confirmed COVID-19 patients. The specificity analysis was performed from 75 selected non-SARS-CoV-2 sera with a potential cross-reaction to the SARS-CoV-2 immunoassay. RESULTS:This iFlash® SARS-CoV-2 assay showed excellent analytical performance. After 2 weeks since symptom onset, the sensitivities for IgM and IgG were 62.2% (95% CI: 52.3-71.2%) and 92.9%% (95% CI: 85.7-96.7%), respectively by using the cut-off provided by the manufacturer. After cut-off optimization (i.e. >2.81 for IgM and >4.86 for IgG), the sensitivity for IgM and IgG were 81.6 (95% CI: 72.7-88.1%) and 95.9% (95% CI: 89.4-98.7%), respectively. Optimized cut-off for IgG improved the sensitivity to reach 100% (95%CI: 87.6-100) from 28 days since symptom onset. CONCLUSIONS:This study shows that the iFlash® SARS-CoV-2 assay from YHLO biotechnology, has satisfactory analytical performance. Nevertheless, the sensitivity of the IgM is limited for a proper clinical use compared to IgG. The determination of anti-SARS-CoV-2 IgG antibodies from 28 days since symptom onset was associated with high sensitivity, especially using optimized cut-offs (i.e. 100%).
Project description:BACKGROUND:Besides SARS-CoV-2 RT-PCR testing, serological testing is emerging as additional option in COVID-19 diagnostics. Aim of this study was to evaluate novel immunoassays for detection of SARS-CoV-2 antibodies in human plasma. METHODS:Using EDITM Novel Coronavirus COVID-19 Enzyme Linked Immunosorbent Assays (ELISAs), we measured SARS-CoV-2 IgM and IgG antibodies in 64 SARS-CoV-2 RT-PCR confirmed COVID-19 patients with serial blood samples (n = 104) collected at different time points from symptom onset. Blood samples from 200 healthy blood donors and 256 intensive care unit (ICU) patients collected before the COVID-19 outbreak were also used. RESULTS:The positivity rates in the COVID-19 patients were 5.9% for IgM and 2.9% for IgG ? 5 days after symptom onset; Between day 5 and day 10 the positivity rates were 37.1% for IgM and 37.1% for IgG and rose to 76.4% for IgM and 82.4% for IgG after > 10-15 days. After 15-22 days the "true" positivity rates were 94.4% for IgM and 100% for IgG. The "false" positivity rates were 0.5% for IgM and 1.0% for IgG in the healthy blood donors, 1.6% for IgM and 1.2% for IgG in ICU patients. CONCLUSIONS:This study shows high "true" vs. low "false" positivity rates for the EDITM SARS-CoV-2 IgM and IgG ELISAs.
Project description:OBJECTIVES:SARS-CoV-2 infection diagnosis is challenging in patients from 2 to 3 weeks after the onset of symptoms, due to the low positivity rate of the PCR. Serologic tests could be complementary to PCR in these situations. The aim of our study was to analyze the diagnostic performance of one serologic rapid test in COVID-19 patients. METHODS:We evaluated a lateral flow immunoassay (AllTest COVID-19 IgG/IgM) which detects IgG and IgM antibodies. We validated the serologic test using serum samples from 100 negative patients (group 1) and 90 patients with COVID-19 confirmed by PCR (group 2). Then, we prospectively evaluated the test in 61 patients with clinical diagnosis of pneumonia of unknown etiology that were negative for SARS-CoV-2 by PCR (group 3). RESULTS:All 100 patients from group 1 were negative for the serologic test (specificity = 100 %). Regarding group 2 (PCR-positive), the median time from their symptom onset until testing was 17 days. For these 90 group-2 patients, the test was positive for either IgM or IgG in 58 (overall sensitivity = 64.4 %), and in patients tested 14 days or more after the onset of symptoms, the sensitivity was 88.0 %. Regarding the 61 group-3 patients, median time after symptom onset was also 17 days, and the test was positive in 54 (88.5 % positivity). CONCLUSIONS:Our study shows that Alltest lateral flow immunoassay is reliable as a complement of PCR to diagnose SARS-CoV-2 infection after 14 days from the onset of symptoms and in patients with pneumonia and negative PCR for SARS-CoV-2.
Project description:In this study, we evaluated and compared six SARS-CoV-2 serology kits including the Abbott SARS-CoV-2 IgG assay, Beckman Access SARS-CoV-2 IgG assay, OCD Vitros OCD Anti-SARS-CoV-2 Total antibody assay, Roche Elecsys Anti SARS-CoV-2 assay, Siemens SARS-CoV-2 Total assay, and cPass surrogate viral neutralising antibody assay. A total of 336 non-duplicated residual serum samples that were obtained from COVID-19 confirmed patients (n=173) on PCR and negative controls (n=163) obtained pre-December 2019 before the COVID-19 pandemic were used for the study. These were concurrently analysed on the different immunoassay platforms and correlated with clinical characteristics. Our results showed all assays had specificity ranging from 99.3% to 100.0%. Overall sensitivity across all days of symptoms, in descending order were OCD (49.1%, 95% CI 41.8-56.5%), cPass (44.8%, 95% CI 37.5-52.3%), Roche (41.6%, 95% CI 34.5-49.0%), Siemens (39.9%, 95% CI 32.9-47.3%), Abbott (39.8%, 95% CI 32.9-47.3%) and Beckman (39.6%, 95% CI 32.5-47.3%). Testing after at least 14 days from symptom onset is required to achieve AUCs greater than 0.80. OCD and cPass performed the best in terms of sensitivity for >21 days symptoms with 93.3% (95% CI, 73.5-99.2%) and 96.7% (95% CI, 82.8-99.9%), respectively. Both also shared the greatest concordance, kappa 0.963 (95% CI 0.885-1.0), p<0.001, and had the lowest false negative rates. Serology results should be interpreted with caution in certain cases. False negatives were observed in a small number of individuals with COVID-19 on immunosuppressive therapy, pauci-symptomatic or who received antiretroviral therapy. In conclusion, all assays exhibited excellent specificity and total antibody assays with spike protein configurations generally outperformed nucleocapsid configurations and IgG assays in terms of diagnostic sensitivity.
Project description:BACKGROUND:Here, we report on a head-to-head comparison of the fully-automated Elecsys® Anti-SARS-CoV-2 immunoassay with the EDITM enzyme linked immunosorbent assays (ELISA) for the detection of SARS-CoV-2 antibodies in human plasma. METHODS:SARS-CoV-2 antibodies were measured with the Elecsys® assay and the EDITM ELISAs (IgM and IgG) in 64 SARS-CoV-2 RT-PCR confirmed COVID-19 patients with serial blood samples (n = 104) collected at different time points from symptom onset. Blood samples from 200 healthy blood donors and 256 intensive care unit (ICU) patients collected before the COVID-19 outbreak were also used. RESULTS:In COVID-19 patients, the percentage of positive results rose with time from symptom onset, peaking to positivity rates after 15-22 days of 100% for the Elecsys® assay, of 94% for the EDITM IgM-ELISA and of 100% for the EDITM IgG ELISA. In the 104 blood samples, the agreement between positive/negative classifications of the Elecsys® assay and the EDITM ELISAs (IgM or IgG) was 90%. The false positivity rates in the healthy blood donors and the ICU patients were < 1% for the Elecsys® assay and < 3% for the EDITM ELISAs. CONCLUSIONS:Our results indicate a high sensitivity and specificity for the Elecsys® assay and an acceptable agreement with the EDITM ELISAs.
Project description:BACKGROUND:To accurately interpret COVID-19 seroprevalence surveys, knowledge of serum-IgG responses to SARS-CoV-2 with a better understanding of patients who do not seroconvert, is imperative. This study aimed to describe serum-IgG responses to SARS-CoV-2 in a cohort of patients with both severe and mild COVID-19, including extended studies of patients who remained seronegative more than 90 days post symptom onset. METHODS:SARS-CoV-2-specific IgG antibody levels were quantified using two clinically validated and widely used commercial serological assays (Architect, Abbott Laboratories and iFlash 1800, YHLO), detecting antibodies against the spike and nucleocapsid proteins. RESULTS:Forty-seven patients (mean age 49 years, 38% female) were included. All (15/15) patients with severe symptoms and 29/32 (90.6%) patients with mild symptoms of COVID-19 developed SARS-CoV-2-specific IgG antibodies in serum. Time to seroconversion was significantly shorter (median 11 vs. 22 days, P = 0.04) in patients with severe compared to mild symptoms. Of the three patients without detectable IgG-responses after >90 days, all had detectable virus-neutralizing antibodies and in two, spike-protein receptor binding domain-specific IgG was detected with an in-house assay. Antibody titers were preserved during follow-up and all patients who seroconverted, irrespective of the severity of symptoms, still had detectable IgG levels >75 days post symptom onset. CONCLUSIONS:Patients with severe COVID-19 both seroconvert earlier and develop higher concentrations of SARS-CoV-2-specific IgG than patients with mild symptoms. Of those patients who not develop detectable IgG antibodies, all have detectable virus-neutralizing antibodies, suggesting immunity. Our results showing that not all COVID-19 patients develop detectable IgG using two validated commercial clinical methods, even over time, are vital for the interpretation of COVID-19 seroprevalence surveys.
Project description:The emerging COVID-19 caused by SARS-CoV-2 infection poses severe challenges to global public health. Serum antibody testing is becoming one of the critical methods for the diagnosis of COVID-19 patients. We investigated IgM and IgG responses against SARS-CoV-2 nucleocapsid (N) and spike (S) protein after symptom onset in the intensive care unit (ICU) and non-ICU patients. 130 blood samples from 38 COVID-19 patients were collected. The levels of IgM and IgG specific to N and S protein were detected by ELISA. A series of blood samples were collected along the disease course from the same patient, including 11 ICU patients and 27 non-ICU patients for longitudinal analysis. N and S specific IgM and IgG (N-IgM, N-IgG, S-IgM, S-IgG) in non-ICU patients increased after symptom onset. N-IgM and S-IgM in some non-ICU patients reached a peak in the second week, while N-IgG and S-IgG continued to increase in the third week. The combined detection of N and S specific IgM and IgG could identify up to 75% of SARS-CoV-2 infected patients in the first week. S-IgG was significantly higher in non-ICU patients than in ICU patients in the third week. In contrast, N-IgG was significantly higher in ICU patients than in non-ICU patients. The increase of S-IgG positively correlated with the decrease of C-reactive protein (CRP) in non-ICU patients. N and S specific IgM and IgG increased gradually after symptom onset and can be used for detection of SARS-CoV-2 infection. Analysis of the dynamics of S-IgG may help to predict prognosis.
Project description: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.
Project description:OBJECTIVES:We aimed to evaluate the role of rapid serological tests in the management of coronavirus disease 2019 (COVID-19) patients. METHODS:This retrospective study enrolled 16 real-time reverse transcription polymerase chain reaction-confirmed symptomatic patients with COVID-19 and 58 COVID-19 negative patients at a medical center in Taiwan over a 3-month period. Serial serum samples were collected and tested for antibody response using four point-of-care (POC) lateral flow immunoassays (LFIA) (ALLTEST 2019-nCoV IgG/IgM Rapid Test, Dynamiker 2019-nCoV IgG/IgM Rapid Test, ASK COVID-19 IgG/IgM Rapid Test, and Wondfo SARS-CoV-2 Antibody Test). Time-dependent detection sensitivity and timeliness of seroconversion were determined and compared between the four POC rapid tests. RESULTS:The overall sensitivity and specificity of the four tests for detecting anti-SARS-CoV-2 antibodies after 3 weeks of symptom onset were 100% and 100%, respectively. There was no significant difference between the rapid tests used for detection of IgM and IgG separately and those used for detection of combined total antibody (mainly IgM/IgG). There was no significant difference between the four POC rapid tests in terms of time required for determining seroconversion of COVID-19. Patients with COVID-19 with pneumonia demonstrated shorter seroconversion time than those without pneumonia. CONCLUSION:Though the POC antibody rapid tests based on LFIA showed reliable performance in the detection of SARS-CoV-2-specific antibodies, the results of these tests should be interpreted and applied appropriately in the context of antibody dynamic of COVID-19 infection. COVID-19 patients complicated with pneumonia exhibited earlier anti-SARS-CoV-2 antibody response than COVID-19 patients without pneumonia.