Product Manual

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Sofia SARS Antigen FIA Page 17 of 22
Reference Extracted RT-PCR assay
95% CI
POS
NEG
Total
PPA
96.7%
83.3%
99.4%
Sofia SARS Antigen
FIA Assay
POS
29
0
29
NPA
100.0%
97.9%
100.0%
NEG
1
179
180
PPV
100.0%
88.3%
100.0%
Total
30
179
209
NPV
99.4%
96.9%
99.9%
Prevalence
14.4%
10.2%
19.8%
The performance of this test has not yet been clinically validated for use in patients without signs and
symptoms of respiratory infection or for serial screening applications, and performance may differ in these
populations.
ANALYTICAL PERFORMANCE
Limit of Detection
a) Limit of Detection (LoD):
The Limit of Detection (LoD) of the Sofia SARS Antigen FIA was determined using limiting dilutions of
heat-inactivated SARS-CoV-2 (bei Resources NR-52286). The NR-52286 is a preparation of SARS-Related
Coronavirus 2 (SARS-CoV-2), isolate USA-WA1/2020, that has been inactivated by heating at 65°C for
30-minutes. The material was supplied frozen at a concentration of TCID
50
of 3.40 x10
5
per mL.
The study to determine the Sofia SARS Antigen FIA LoD was designed to reflect the assay when using
direct swabs. In this study a NP swab was spiked with approximately 50-µL of the virus dilution in
saline. The spiked swab was added to the Sofia SARS Antigen FIA extractant concurrently to a NP swab
containing NP matrix. The swabs were processed concurrently according to the package insert.
The LoD was determined in three steps:
1. LoD Screening
10-fold dilutions of the heat inactivated virus were made in saline and processed for each
study as described above. These dilutions were tested in triplicate. The concentration
demonstrating 3 of 3 positives was chosen for LoD range finding.
Based on this testing, the concentration chosen was TCID
50
of 3.40 x10
2
per mL.
2. LoD Range Finding
Five (5) doubling dilutions were made of the TCID
50
of 3.40 x10
2
per mL concentration in saline
processed for the study as described above. These dilutions were tested in triplicate. The
concentration demonstrating 3 of 3 positives was chosen for LoD confirmation.
Based on this testing the concentration chosen was TCID
50
of 1.13 x10
2
per mL.
3. LoD Confirmation
The concentration TCID
50
of 1.13 x10
2
per mL dilution was tested an additional seventeen (17)
times, for a total of twenty (20) results. Twenty (20) of twenty (20) results were positive.
Based on this testing the concentration was confirmed as:
Swab LoD: TCID
50
1.13 x10
2
per mL