To the Editor,
From late December 2019, coronavirus infectious disease (COVID‐19) epidemics spread
from Wuhan, China, to all over the world, including Italy.
1
,
2
,
3
To date, real‐time reverse transcription‐polymerase chain reaction (RT‐PCR) in respiratory
samples is the current gold standard method for the diagnosis of COVID‐19.
4
,
5
However, molecular testings are time consuming and require specialized operators,
factors that limit their use in real life when the rapid diagnosis is required for
fast intervention decisions. Recently, an easy to perform serological assay has been
assessed
6
to differentiate COVID‐19 positive patients from negative subjects.
We herein report results of a real‐life study performed in an emergency room department
of a tertiary hospital in Northern Italy to validate VivaDiag COVID‐19 IgM/IgG Rapid
Test lateral flow immunoassay (LFIA) for the rapid diagnosis of COVID‐19.
Overall 110 subjects were tested for COVID‐19‐specific serological assay at Fondazione
IRCCS Policlinico San Matteo. In detail, we enrolled 30 healthy volunteers with documented
negative results for COVID‐19 RT‐PCR in respiratory samples (M 11/F 19; median age,
38.5; range, 25‐69 years). Ten of them (33.3%) had been infected in the past with
one of the common OC43, 229E, HKU1, and NL63 coronavirus. Thirty COVID‐19‐positive
patients (25 M/5 F; median age, 73.5; range, 38‐86 years) admitted to the Infectious
Diseases Department or at the Intensive Care Unit were tested as positive controls.
Finally, the performance of VivaDiag COVID‐19 IgM/IgG Rapid Test LFIA was tested in
50 patients at their first access at emergency room department with fever and respiratory
syndrome (34 M/16 F; median age, 61.50; range, 33‐97 years) in comparison with results
of nasal swab molecular screening.
5
VivaDiag COVID‐19 IgM/IgG from VivaChek was performed according to manufacturer's
instruction by adding 10 µL of serum or whole blood sample into the sample port followed
by adding 2 to 3 drops (70‐100 µL) of dilution buffer.
6
After about 15 minutes, results were read.
Respiratory samples (FLOQSwabs; Copan Italia, Brescia, Italy) were collected from
all the patients. Total nucleic acids (DNA/RNA) were extracted from 200 µL of UTM
using the QIAsymphony instrument with QIAsymphony DSP Virus/Pathogen Midi Kit (complex
400 protocols) according to the manufacturer's instructions (QIAGEN; Qiagen, Hilden,
Germany). Specific real‐time RT‐PCR targeting RNA‐dependent RNA polymerase and E genes
were used to detect the presence of SARS‐CoV‐2 according to the WHO guidelines
7
and Corman et al
5
protocols.
In the cohort of patients admitted to the emergency room department, data from serological
tests were compared to molecular results to define specificity, sensitivity, positive
predictive value (PPV), and negative predictive value (NPV) of the rapid serological
test.
As expected, all 30 COVID‐19 negative volunteers were negative for both immunoglobulin
G (IgG) and immunoglobulin M (IgM) using the VivaDiag COVID‐19 IgM/IgG Rapid Test.
No cross‐reactivity was detected in the 10 subjects with previous coronaviruses infection,
supporting the high specificity of the VivaDiag COVID‐19 IgM/IgG Rapid Test LFIA.
Serum samples were obtained at a median 7 days (interquartile range, 4‐11) after the
first COVID‐19 positive result from 30 hospitalized patients. A total of 19 of 30
(63.3%) were positive for both IgM and IgG, 5 of 30 (16.7%) were negative for both
IgG and IgM, 5 of 30 (16.7%) were weakly positive for both IgM and IgG, and only 1
of 30 (3.3%) was positive for IgM and negative for IgG. Thus, the sensitivity of the
rapid assay was suboptimal (data not are shown). A possible explanation is the low
antibody titers or a delayed humoral response.
6
Focusing on acute patients enrolled from the emergency room department, 12 of 50 (24%)
were negative for COVID‐19 by real‐time RT‐PCR. Of these, 1 (8.3%) showed a positive
results for the VivaDiag COVID‐19 IgM/IgG Rapid Test, while the other 11 of 12 (91.7%)
tested negative. On the other side, 38 patients were positive for COVID‐19 by real‐time
RT‐PCR. Of these, only 7 (18.4%) showed a positive or weak positive serology for IgM
and/or IgG, while the other 31 of 38 (81.6%) tested negative for the rapid serology
assay (Table 1). Thus, the sensitivity of the VivaDiag COVID‐19 IgM/IgG Rapid Test
was 18.4%, specificity was 91.7%, while NPV was 26.2%, and PPV was 87.5% in patients
enrolled from emergency room department. In contrast with the high levels of sensitivity
reported in the previous study,
6
VivaDiag COVID‐19 IgM/IgG Rapid Test revealed a very poor sensitivity (less than 20%).
Indeed, the majority of patients that tested positive for COVID‐19 by real‐time RT‐PCR
would have been identified as negative using only the rapid serological assay, leading
to a misdiagnosis of COVID‐19 disease in the vast majority of patients. On the basis
of our results, VivaDiag COVID‐19 IgM/IgG Rapid Test LFIA is not recommended for triage
of patients with suspected COVID‐19.
Table 1
Characteristics and VivaDiag COVID‐19 IgM/IgG Rapid Test results of 50 consecutive
patients referred to the emergency room department
Patient
Sex
Age
Result of COVID‐19 real‐time RT‐PCR on NS
VivaDiag COVID‐19 IgM/IgG Rapid Test
IgM
IgG
1
M
33
neg
−
−
2
M
51
pos
−
−
3
M
51
pos
−
−
4
M
38
pos
−
−
5
F
80
pos
−
−
6
F
64
neg
−
−
7
M
81
neg
−
−
8
M
76
pos
+/−
−
9
M
33
pos
−
−
10
M
37
neg
−
−
11
F
45
pos
−
−
12
M
53
pos
−
−
13
M
66
neg
−
−
14
M
78
pos
−
−
15
F
97
pos
−
−
16
M
38
pos
−
−
17
M
72
pos
−
−
18
M
56
pos
−
−
19
M
80
pos
−
+/−
20
M
72
pos
−
−
21
F
55
pos
−
−
22
M
82
pos
−
−
23
M
47
pos
+
+/−
24
F
63
pos
−
−
25
F
80
pos
+/−
−
26
M
59
pos
−
−
27
M
66
pos
−
−
28
M
39
pos
−
−
29
F
78
neg
−
−
30
M
71
neg
−
−
31
F
46
neg
−
−
32
F
51
pos
−
−
33
F
75
pos
−
−
34
F
82
pos
+
+/−
35
F
51
pos
+/−
+/−
36
M
84
pos
−
−
37
M
50
pos
−
−
38
M
50
pos
+
+/−
39
F
72
neg
−
−
40
M
54
neg
−
−
41
F
64
neg
+
−
42
M
64
pos
−
−
43
M
70
pos
−
−
44
M
56
pos
−
−
45
M
68
pos
−
−
46
F
36
pos
−
−
47
M
60
pos
−
−
48
M
66
pos
−
−
49
M
54
neg
−
−
50
M
56
pos
−
−
Abbreviations: −, negative result; +, positive result; +/−, weakly positive result;
COVID‐19, coronavirus infectious disease 2019; IgG, immunoglobulin G; IgM, immunoglobulin
M; NS, nasopharyngeal swab; RT‐PCR, reverse transcription‐polymerase chain reaction.
John Wiley & Sons, Ltd.
This article is being made freely available through PubMed Central as part of the
COVID-19 public health emergency response. It can be used for unrestricted research
re-use and analysis in any form or by any means with acknowledgement of the original
source, for the duration of the public health emergency.
MEMBERS OF THE SAN MATTEO PAVIA COVID‐19 TASK FORCE
R. Bruno, M. Mondelli, E. Brunetti, A. Di Matteo, E. Seminari, L. Maiocchi, V. Zuccaro,
L. Pagnucco, B. Mariani, S. Ludovisi, R. Lissandrin, A. Parisi, P. Sacchi, S. F. A.
Patruno, G. Michelone, R. Gulminetti, D. Zanaboni, S. Novati, R. Maserati, P. Orsolini,
and M. Vecchia (ID Staff); M. Sciarra, E. Asperges, M. Colaneri, A. Di Filippo, M.
Sambo, S. Biscarini, M. Lupi, S. Roda, T. C. Pieri, I. Gallazzi, M. Sachs, and P.
Valsecchi (ID Resident); S. Perlini, C. Alfano, M. Bonzano, F. Briganti, G. Crescenzi,
A. G. Falchi, R. Guarnone, B. Guglielmana, E. Maggi, I. Martino, P. Pettenazza, S.
Pioli di Marco, F. Quaglia, A. Sabena, F. Salinaro, F. Speciale, and I. Zunino (ECU
Staff Emergency Care Unit); M. De Lorenzo, G. Secco, L. Dimitry, G. Cappa, I. Maisak,
B. Chiodi, M. Sciarrini, B. Barcella, F. Resta, L. Moroni, G. Vezzoni, L. Scattaglia,
E. Boscolo, C. Zattera, M. F. Tassi, V. Capozza, D. Vignaroli, and M. Bazzini (ECU
Resident Emergency Care Unit); G. Iotti, F. Mojoli, M. Belliato, L. Perotti, S. Mongodi,
and G. Tavazzi (Intensive Care Unit); G. Marseglia, A. Licari, and I. Brambilla (Pediatric
Unit); D. Barbarini, A. Bruno, P. Cambieri, G. Campanini, G. Comolli, M. Corbella,
R. Daturi, M. Furione, B. Mariani, R. Maserati, E. Monzillo, S. Paolucci, M. Parea,
E. Percivalle, A. Piralla, F. Rovida, A. Sarasini, and M. Zavattoni (Virology Staff);
G. Adzasehoun, L. Bellotti, E. Cabano, G. Casali, L. Dossena, G. Frisco, G. Garbagnoli,
A. Girello, V. Landini, C. Lucchelli, V. Maliardi, S. Pezzaia, and M. Premoli (Virology
Technical staff); A. Bonetti, G. Caneva, I. Cassaniti, A. Corcione, R. Di Martino,
A. Di Napoli, A. Ferrari, G. Ferrari, L. Fiorina, F. Giardina, A. Mercato, F. Novazzi,
G. Ratano, B. Rossi, I. M. Sciabica, M. Tallarita, and E. Vecchio Nepita (Virology
Resident); M. Calvi and M. Tizzoni (Pharmacy Unit); and C. Nicora, A. Triarico, V.
Petronella, C. Marena, A. Muzzi, and P. Lago (Hospital Management).
CONFLICT OF INTERESTS
The authors declare that there are no conflict of interests.
AUTHOR CONTRIBUTIONS
IC, FN, FG, FS, MS, SP, RB, FM, FB, and the other members of the San Matteo Pavia
COVID‐19 Task Force listed reviewed and approved the manuscript. IC and FN discussed
results, data analysis, and wrote the paper. FG, FS, and MS collected the samples.
SP, RB, and FM discussed results. FB conceived the study.