JRSSEM 2022, Vol. 01, No. 7, 938 – 946
E-ISSN: 2807 - 6311, P-ISSN: 2807 - 6494
DOI : 10.36418/jrssem.v1i7.106
PERFORMANCE OF RAPID ANTIBODY TEST AND RT-PCR
AS FRONTLINE TEST FOR COVID-19 DIAGNOSIS IN
PREGNANCY: AN EXPERIENCE IN INDONESIA
Evert S. Pangkahila1*
Ryan S. Mulyana1
Hariyasa Sanjaya2
Mulyantari K3
Daniel H. Susanto4
1Department of Obstetrics and Gynecology, Maternal Fetal Medicine Division, Udayana University
Hospital-Bali
2Department of Obstetrics and Gynecology, Maternal Fetal Medicine Division, Sanglah Hospital-
Bali
3Department of Clinical Pathology, Udayana University Hospital & SanglahHospital,Bali
4Registrar Department of Obstetrics and Gynecology, Maternal Fetal Medicine Division, Sanglah
Hospital-Bali
e-mail: evertpangkahi[email protected]1, ryanmul83@gmail.com1, sanjayahariyasa@gmail.com2,
melyan79@yahoo.co.id3, daniel_susanto@live.com4
*Correspondence: evertpangkahila@gmail.com
Submitted: 29 January 2022, Revised: 10 February 2022, Accepted: 20 February 2022
Abstract. Ensuring an accurate diagnosis is critical for limiting the spread of SARS-CoV-2 and for
the clinical management of COVID-19, especially in pregnant women. For now real-time reverse
transcription polymerase chain reaction (RT-qPCR) is the currently recommended laboratory
method for the diagnosis of acute SARS-CoV-2 infection. More recently, several easy-to-perform
rapid antigen detection tests have been developed and are recommended as first-line screening
test in several countries. The purpose of this study was to evaluate the comparative performance
of a rapid antibody test and RT-PCR for the detection of SARS-CoV-2 infection, as a front-line test
for the diagnosis of COVID-19 in pregnancy. This research method is a descriptive study to describe
comparation of sensitivity and specificity between rapid SARS-CoV-2 antibody test to the gold
standard nasopharyngeal RT-PCR swab test. Of the 271 samples, only 257 were eligible and
fourteen cases were excluded from the study due to a lack of rapid antibody test and RT-PCR
results. The results of this study showed that the rapid SARS-CoV-2 antibody test sensitivity was
80.95%, and the specificity was 90.68%, the NPV (negative predictive value) and the PPV (positive
prognosis value) were 98.17% and 43.59%, respectively. Based only on the results of IgM and IgG,
IgM and IgG sensitivity were 33.33% (7/21) and 71.43% (15/21), respectively, and the specificity
was 91.1% (215/236, 21 false positive) and 91.53% (216/236, 20 false positive), respectively. The
use of rapid antibody tests during pregnancy is a screening tool and is not currently applicable for
diagnostic tool. To minimize false positives and negatives results, the use of rapid antibody tests
should be combined with the RT-PCR test results.
Keywords: COVID-19; rapid antibody detection test; SARS-CoV-2; RT-PCR; pregnancy.
Evert S. Pangkahila, Ryan S. Mulyana, Hariyasa Sanjaya, Mulyantari K, Daniel H. Susanto | 939
DOI : 10.36418/jrssem.v1i7.106
INTRODUCTION
The COVID-19 virus is spreading rapidly
from person to person in China, and the
World Health Organization (WHO) has
reported an outbreak of COVID-19 is now
spreading globally (Almaghaslah et al.,
2020). Highly sensitive and specific tests are
critical for the diagnosis and treatment of
COVID-19 patients (Scohy et al., 2020)
This was announced by the Centers for
Disease Control and Prevention (CDC),
pregnant women appear to be at the same
risk as non-pregnant adults, with data on
pregnancy status available for 91,412
(28.0%) women with laboratory-confirmed
infection; of these, 8,207 (9.0%) were
pregnant (Berghella, et al., 2020). The
reliable laboratory testing is necessary
because the number of suspected cases
increases. RT-PCR testing of asymptomatic
or mildly symptomatic individuals may be
considered when evaluating people who
have been in close contact with a confirmed
case of COVID-19 (Scohy et al., 2020);
WHO, 2020).
Real-time reverse transcription
polymerase chain reaction (RT-qPCR) is the
currently recommended method for the
diagnosis of acute SARS-CoV-2 infection.
However, several factors such as
specialized equipment and skilled
personnel limit the use of this method
(Scohy, et al., 2020).
Higher viral load linked to better
antigen detection rates and antibody
formation in blood (Scohy, et al., 2020;
WHO, 2020). Seroconversion may not occur
1-3 weeks after onset of the symptoms, so
this test method may be of limited use in
diagnosing acute infections. However,
detection of anti-SARS-CoV-2 antibodies in
serum can be used to determine the
transmission chains, which may be useful
for contact tracing investigation (Berghella,
et al., 2020).
Currently, all government and private
hospitals in Bali use rapid antibody tests as
to screening all pregnant women who are
going to have obstetric procedure.
However, many of the cases detected using
the SARS-CoV-2 rapid antibody test had
negative swab results. In this study, we
present the results of two diagnostic
methods: a serum total antibody assay
against SARS-COV-2 and RT-PCR for
detection of SARS-COV-2 infection in
pregnant women.
The purpose of this study was to
compare the performance of a rapid
antibody test as a front-line test and RT-
PCR for the diagnosis of COVID-19 in
pregnancy.
METHODS
This research method is a descriptive
study to describe comparation of sensitivity
and specificity between rapid SARS-CoV-2
antibody test to the gold standard
nasopharyngeal RT-PCR swab test.
Test
The COVID-19 RT-PCR test is a real-
time reverse transcriptase polymerase
chain reaction (RT-PCR) test for the
qualitative detection of SARS-CoV-2
nucleic acid in upper and lower respiratory
tract samples (such as nasopharyngeal or
oropharyngeal swabs, sputum, lower
respiratory tract aspirate, bronchoalveolar
lavage and nasopharyngeal lavage/
aspirate). Laboratory diagnosis of COVID-
940 | Performance of Rapid Antibody Test and RT-PCR as Frontline Test for COVID-19
Diagnosis in Pregnancy: an Experience in Indonesia
19 at Udayana Hospital and Sanglah
Hospital relies on RNA extracts to detect
viral RNA by targeting the RNA-dependent
RNA polymerase (RdRp) gene (De Kauwe et
al., 2020). Amplification was performed on
a LightCycler 480 instrument (Roche
Diagnostics, Mannheim, Germany)
according to the manufacturer's
recommendations. Samples with a SARS-
CoV-2 RT-qPCR cycle threshold (Ct) below
40 were considered positive.
The Autobio Anti-SARS-CoV-2 Rapid
Test is based on a one-step detection
method. The cassette contains membranes
pre-coated with two mouse anti-human
monoclonal antibodies (anti-IgG and anti-
IgM) on two separate assay lines. SARS-
CoV-2 recombinant spike protein antigen
reagents capable of specific binding to
SARS-CoV-2 antibodies (IgM and/or IgG)
were bound to colloidal gold and sprayed
onto the conjugate pad. When the sample
is applied to the test well, a complex of
antibody and labeled antigen are formed
and migrates to the top of the strip. Gold-
labeled colorimetric reagents are used to
form visible red/pink lines.
Statistics
This research used sensitivity and
specificity as criteria to assess the
performance of SARS-CoV-2 rapid
antibody test. RT-PCR is considered the
gold standard for this evaluation, so
positive and negative samples detected by
RT-PCR are considered true positives and
true negatives.
RESULTS AND DISCUSSION
We collected 271 pregnancy samples
from referral hospitals (Udayana University
Hospital and Sanglah Hospital) from March
2020 to April 2020, of all cases, only 257
samples were eligible, 14 samples were
excluded from this study due to lack of
rapid SARS-CoV-2 antibody tests and RT-
PCR test results
Evert S. Pangkahila, Ryan S. Mulyana, Hariyasa Sanjaya, Mulyantari K, Daniel H. Susanto | 941
Table 1. Distribution of study population
Variable
f
%
Age
>35 year old
45
17.5
≤ 35 year old
212
82.5
Total
257
100
Gravida
1
80
31.1
2
85
33.1
3
54
21
4
23
8.9
5
11
4.3
6
3
1.2
7
1
0.4
Total
257
100
Parity
0
100
38.9
1
82
31.9
2
53
20.6
3
13
5.1
4
9
3.5
Total
257
100
Trimester
1st trimester
1
0.4
2nd trimester
6
2.3
3rd trimester
250
97.3
Total
257
100
Referral
Referral cases
38
14.8
Not referral cases
219
85.2
Total
257
100
Rapid test reactive
yes
49
19.1
No
208
80.9
Total
257
100
IgM(+),IgG(+)
yes
5
1.9
No
252
98.1
Total
257
100
IgM(+),IgG(-)
yes
13
5.1
No
244
94.9
Total
257
100
IgM(-),IgG(+)
yes
21
8.2
No
236
91.8
Total
257
100
942 | Performance of Rapid Antibody Test and RT-PCR as Frontline Test for COVID-19
Diagnosis in Pregnancy: an Experience in Indonesia
Variable
f
%
IgM(-),IgG(-)
yes
4
1.6
No
253
98.4
Total
257
100
RT-PCR
positive
21
8.2
negative
236
91.8
Total
257
100
Obstetric Management
CS
134
52.2
Vaginal delivery
116
45.1
Conservative management
6
2.3
Curettage
1
0.4
Total
257
100
Symptoms
yes
5
1.9
No
252
98.1
Total
257
100
The above data shows that 82.5%
(212/257) of pregnant women are under 35
years old and 17.5% (45/257) are over 35
years old and most of the samples and
controls are in her second pregnancy 33.1%
(85/257). Most cases are admitted to the
hospital in the third trimester (97.3%,
250/257), 85.2% cases (219/257) were non-
referral cases, and most obstetric
management done in this study was
caesarean section which performed in
52.2% cases (134/257), 116 cases (45.1%)
had vaginal delivery, only 6 cases were
managed conservatively until the RT-PCR
swab test result was negative, and 1 case
had an incomplete abortion and curettage
procedure has been carried out. Of all the
cases and controls, only 5 cases (1.9%) had
clinical symptoms and 252 cases (98.1%)
were asymptomatic.
Table 2. The sensitivity and specificity of SARS-CoV-2 IgG-IgM
combined antibody to the detection of SARS-CoV-2 infection in pregnant women
Clinical Positive sample
Sample Quality
21
IgM-IgG reactive
3
IgM reactive
3
IgG reactive
11
Sensitivity
80,95%
Specificity
Abbreviations: IgG, immunoglobulin G; IgM, immunoglobulin M; SARS‐CoV‐2, severe
acute respiratory syndrome coronavirus 2.
Evert S. Pangkahila, Ryan S. Mulyana, Hariyasa Sanjaya, Mulyantari K, Daniel H. Susanto | 943
DOI : 10.36418/jrssem.v1i7.106
Blood samples were taken from COVID-
19 patients at Udayana University Hospital
and Sanglah Hospital and the data results
were collected from the Clinical Pathology
laboratory of these two hospitals. A total of
257 cases were tested: 21 cases were
confirmed COVID-19 clinically and had
positive RT-PCR results, while the other 236
cases were discarded from COVID-19 and
had negative RT-PCR results. Due to time
constraints, we did not have detailed data
for how long each patient has been
infected or how long they had symptoms
when the blood samples were collected at
Udayana University Hospital and Sanglah
Hospital. Of all the data above, the reactive
results of rapid SARS-CoV-2 antibody test
has 80.95% sensitivity and the specificity
was 90.68%, the NPV (negative predictive
value) and PPV (positive predictive value)
were 98.17% and 43.59%, respectively.
Table 3. Comparisons of IgM and IgG results for 21 cases with RT-PCR positive COVID-19
cases and 236 cases with discarded COVID-19.
RT-PCR
Positive
Negative
IgM
Positive
7
21
Negative
14
215
IgG
Positive
15
20
Negative
6
216
Based on the above results, the study
showed a sensitivity of 33.33% (7/21) and
71.43% (15/21) for IgM and IgG,
respectively. The IgM and IgG overall
specificity was 91.1% (215/236, 21 false
positive) and 91.53% (216/236, 20 false
positives), respectively.
There are three types of tests for
diagnosing viral infections: Reverse
Transcription Quantitative Polymerase
Chain Reaction (RT-PCR), viral antigen
detection tests and serological
immunoassays that detect human response
to virus-specific antibodies (IgM and IgG),
as of serological tests based on antibodies
could be very helpful (Kontou, Braliou,
Dimou, Nikolopoulos, & Bagos, 2020).
Overall evidence for the SARS-CoV-2
IgG/ IgM assay reported its sensitivity was
88.66% and its specificity was 90.63% (Li et
al., 2020). Using RT-PCR confirmed case as
true positive, the accuracy if the test was
94.1% (144/153) for IgM and 98.0%
(150/153) for IgG (Hoffman et al., 2020).
The combined IgG-IgM antibody test kit
has 88.66% sensitivity and 90.63 specificity
in his study found a sensitivity of 92.2 %,
95.7 % and 98.6 % for the RT-PCR, the total
antibody test (Li et al., 2020), and the
combined method, respectively, and the
specificity are 100 %, 98.7 %, and 98.7 %,
respectively (Pei Wang, 2020).
This study showed that the SARS-CoV-
2 antibody rapid test has a sensitivity of
80.95%, a specificity of 90.68%, and a NPV
and PPV of 98.17% and 43.59%,
respectively, when compared with RT-PCR
results. When we compared each IgM and
IgG individually, the sensitivity and
specificity of IgM were 33.33% (7/21) and
Evert S. Pangkahila, Ryan S. Mulyana, Hariyasa Sanjaya, Mulyantari K, Daniel H. Susanto | 944
DOI : 10.36418/jrssem.v1i7.106
91.1% (215/236), respectively, and the
sensitivity and specificity of IgG were
71.43% (15/21) and 91.53% (216/236),
respectively. The false negative results may
be mainly due to a low concentration of
antibodies, so the test result will be
negative. Second, differences in antibody
production of individual immune responses
may be responsible for false-negative
results in COVID-19 patients. Third, IgM
antibodies will be disappear after 2 weeks
(Li et al., 2020).
This new combined SARS-CoV-2 IgG-
IgM antibody test kit has several benefits.
Compared to RT-PCR, it is more time
saving, requires no equipment, is easier to
do, and requires minimal training. Serology
antibody testing is essential in patients with
mild to moderate disease who may present
later (2 weeks after symptoms onset).
Serological diagnosis is also important for
tracing COVID-19 contact in community
and for identify immunity status of the
individuals, whether they already had
“protection” from SARS-CoV-2 infection or
not (Sethuraman, Jeremiah, & Ryo, 2020).
Although it is the most sensitive test for
diagnosing COVID-19, RT-PCR still has its
limitations. RT-PCR accuracy requires high-
quality nasopharyngeal swab that contain
sufficient viral RNA and transport medium
and extraction steps. This can vary even in
the same patient, depends on the time of
the test, the onset of infection and/ or the
onset of symptoms. In the absence of
sufficient viral RNA, RT-PCR may provides
false negative test results (Li et al., 2020).
The RNA detection results depend on
sample quality, extracted RNA, RT-PCR
reagents source, and multiple steps in RNA
preparation. In addition, different sample
types gave different positive identification
rates ranging from 1% to 93% (Wenling
Wang et al., 2020).
One study showed that RT-PCR had
high specificity (100%) but relatively low
sensitivity (92.2%) (Pei Wang, 2020). This is
due to its primary design is spesific for the
SARS-CoV-2 genome sequences.
Occasional false positives results can occur
due to technical errors and reagent
contamination (Sethuraman et al., 2020).
The seventh edition guideline for
COVID-19 issued by the National Health
Commision of the People’s Republic of
China recommends serology testing as a
supporting proof for COVID-19, however
virus RNA detection by RT-PCR method has
become the standard diagnostic test for
confirming SARS-CoV-2 infection (Pei
Wang, 2020).
CONCLUSIONS
Based on the above results, this study
showed that IgM and IgG has a sensitivity
of 33.33% and 71.43%, respectively, and a
specificity of 91.1% and 91.53%,
respectively.
The use of rapid antibody tests during
pregnancy is a screening tool and is not
currently applicable for diagnostic tool. To
minimize false positives and negatives
results, the use of rapid antibody tests
should be combined with the RT-PCR test
results.
Evert S. Pangkahila, Ryan S. Mulyana, Hariyasa Sanjaya, Mulyantari K, Daniel H. Susanto | 945
DOI : 10.36418/jrssem.v1i7.106
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