Clinical Performance of Two Methods for Detecting Anti SARS-CoV-2 Antibodies

Abstract

Evaluating the clinical performance of available methods to detect antibodies against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has become a primordial issue in clinical laboratories. The aim of this study was to evaluate the clinical performance of two methods for SARS-CoV-2 antibodies detection, an automated Chemiluminescent Immunoassay (CLIA) and an immunochromatographic Lateral-Flow Assay (LFA) in patients with positive reverse transcription polymerase chain reaction (RT-PCR). Performance for CLIA method was Positive Agreement (PA) 56.6% and Negative Agreement (NA) 96,6% for IgM and PA 85.8%/NA 90,2% for IgG. Performance for LFA method was PA 56.2% and NA 100% for IgM and PA 95.5% and NA 100 % for IgG. LFA general agreement IgG was better than CLIA. In both methods, significant differences in Kappa index are observed when IgG and IgM are compared. When evaluating the data from a clinical perspective, we found that both method performance for IgM detection may not meet the expected requirements for their clinical utility and could lead to an inappropriate medical decision. The findings of this study show that both immunoassay methods might be reliable for assessing immunological response in COVID-19 patients. Our results also confirm that IgG measurement could be helpful, especially for epidemiological studies in our population. These results provide evidence to justify epidemiological studies in our population.

Keywords: Anti SARS CoV-2 antibodies; Clinical performance; Immunoassay

Introduction

In the last decades, there is a trend of laboratories incorporating automated methodology, which is partly due to the need of searching for a better analytical and clinical performances than manual or semiquantitative methods such as immunochromatographic methods. Nowadays, in times of pandemic, evaluating the clinical performance of available methods to detect antibodies against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has become a primordial issue in clinical laboratories since the contribution of these evaluations has influenced the action plan followed by health authorities to define adequate health policies in different areas.

Currently, antibody response in SARS-CoV-2 infected patients continues being investigated and the clinical utility of commercially available tests for antibodies detection is under discussion. Several authors have observed heterogeneity in the sensitivity of different antibodies tests during the course of infection [1] but most of these investigations evaluated the tests performance in North American, European or Asian population. The performance is still uncertain in our environment. The aim of this study was to evaluate the clinical performance of two methods for SARS-CoV-2 antibodies detection, an automated Chemiluminescent Immunoassay (CLIA) (Maglumi^TM 2019-nCov IgM/IgG) (Shenzhen New Industries Biomedical Engineering (SNIBE) Co., Ltd., Shenzhen, China) and an immunochromatographic Lateral-Flow Assay (LFA) (Lungene^® SARS-CoV-2 Virus IgG/IgM rapid test) (Hangzhou Clongene Biotech Co., Ltd., Hangzhou, China), in patients with positive Reverse Transcription Polymerase Chain Reaction (RT-PCR) for SARS-CoV-2 target ORF1ab in nasopharyngeal swab samples, and in health workers from Hospital de Clinicas “José de San Martín” in the city of Buenos Aires, Argentina. All RT-PCR analysis were performed at BIOGENAR laboratories.

Materials and Methods

MAGLUMI 2019-nCoV IgM CLIA method uses magnetic microbeads coated with anti-human IgM monoclonal antibody and SARS-CoV-2 recombinant antigen labeled with N-(4-Aminobutyl)- N-ethylisoluminol (ABEI). And for IgG detection it uses magnetic microbeads coated with SARS-CoV-2 recombinant antigen and ABEI labeled anti-human IgG antibody. Claimed clinical sensitivity and specificity for IgM are 78.6% and 98.5%, and for IgG are 91.2% and 95.6%, respectively. The manufacturer report that there is no cross reactivity with antibodies generated by other respiratory diseases such as respiratory syncytial virus, adenovirus, parainfluenza, influenza A and B. Lungene SARS-CoV-2 LFA method uses the principle of immunochromatography and presents two capture zones with mouse anti-human IgM and anti-human IgG antibodies. After adding the sample, the reaction ends with the addition of recombinant envelope antigens SARS-CoV-2 conjugated with colloidal gold. The claimed clinical sensitivity and specificity for IgM are 87.0% and 98.9% respectively, and for IgG it is only claimed a clinical sensitivity of 97.4%. It is reported that it does not present cross reactivity with other antibodies produced by HIV, Hepatitis A, B and C, Syphilis, HTLV, respiratory syncytial virus, Influenza A and B.

Eighty-nine sera from patients with positive RT-PCR for SARSCoV- 2 in nasopharyngeal swab and 48 sera from negative RT-PCR individuals were analyzed in order to evaluate LFA method. On the other hand, 106 positive and 61 negative RT-PCR individuals were included for evaluating CLIA method. Procedure and analysis were performed according to EP-12 A2 CLSI guideline [2]. The differences between Kappa index, used to estimate general agreement between the analyzed methodologies and RT-PCR, were evaluated according to the Chi-square test. Obtained data from both methodologies and RT-PCR are shown in table (Table 1).

  

    
Statistics
    
MaglumiTM2019-nCoV IgM/lgG (CLIA)
    
Lungene® SARS-CoV-2 IgG/lgM
  
  

    

    
lgM
    
IgG
    
IgM + IgG
    
IgM
    
IgG
    
IgM + IgG
  
  

    
Positive agreement %
    
56.6
    
85.8
    
86.8
    
56.2
    
95.5
    
96.6
  
  

    
with RT-PCR (95% CI)
    
(47.1-65.6)
    
(78.0-91.2)
    
(79.0-92.0)
    
(45.8-66.0)
    
(89.0-98.2)
    
(90.6-98.8)
  
  

    
Negative agreement %
    
96.6
    
90.2
    
86.2
    
100.0
    
100.0
    
100.0
  
  

    
with RT-PCR (95% CI)
    
(88.3-99.1)
    
(80.2-95.4)
    
(75.1-92.8)
    
(92.6 -100.0)
    
(92.6-100.0)
    
(92.6-100.0)
  
  

    
Kappa index
    
0.454
    
0.737
    
0.713
    
0.473
    
0.937
    
0.953
  
  

    
(95% CI)
    
(0.341- 0.566)
    
(0.633-0.841)
    
(0.602-0.824)
    
(0.354-0.592)
    
(0.876-0.998)
    
(0.899-1.006)
  
  

    
Chi-square test
    

    
p=0.0003 vs lgM
    
NS vs IgG    p=0.0013 vs lgM
    

    
p<0.0001 vs lgM
    
NS vs IgG    p<0.0001 vs lgM
  
  

    
*NS: Non Significative. 
  

Table 1: Clinical performance results.

  

    
Statistics
    
lgM
    
lgG
  
  

    
Positive agreement % (95% CI)
    
77.5 (62.5-87.7)
    
96 (88.9-98.6)
  
  

    
Negative agreement % (95% CI)
    
58.2 (45.0-70.3)
    
95 (76.4-99.1)
  
  

    
Kappa index (95% CI)
    
0.341 (0.116-0.520)
    
0.878(0.761-0.995)
  
  

    
Chi-square test
    

    
p<0.0001 vs IgM
  

Table 2: Agreement evaluation of antibodies detection between CLIA and LFA
methods.

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Citation: Jacobsen D, Gonzalez D, Jamardo J, Ibar C, Pugliese L, Fortuna F, et al. Clinical Performance of Two Methods for Detecting Anti SARS-CoV-2 Antibodies. J Immun Res. 2021; 7(2): 1040.

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