Suburban diagnostics conducts a research on the pattern of antibodies and antigens present in COVID-19 patients
Observes a falling trend in the COVID-19 positive cases in
Mumbai from June to August 2020
Suburban Diagnostics, in their attempt to objectify their diagnostic and
management strategies, conducted a research on 83 patients with a known history
of COVID-19. These patients were followed up on with serial antibody tests to
study the sero-conversion and the trend of antibody response post infection.
Out of the 83 patients, 64% (53 patients) had symptomatic COVID-19 infection
and 36% (30 patients) had completely asymptomatic infection.
When followed up for 120-150
days post infection, 92% were positive for antibodies and 8% were still
negative. Of the patients who completed 180 days post
diagnosis, 90% were antibody positive. This figure is liable to change once all
the patients being followed up complete 180 days and are tested. On
analysis, it was also found that the peak in antibody levels for the majority
of antibody positive cases happened during the 60-90 day period.
The table below shows that,
from June to October, 2020 there was a rise in the percentage of patients
tested, who developed antibodies. Overall, out of the total 30,884 antibody
tests conducted it was found that 10,840 (35.1%) of the patients had developed
COVID-19 antibodies.
Month |
Number of tests done |
COVID-19 Antibody Positivity Rate |
June |
190 |
27.9% |
July |
6204 |
21.8% |
August |
6234 |
30.6% |
September |
10535 |
36.7% |
October |
7721 |
47.5% |
Total |
30884 |
35.1% |
Another study, conducted on a total of 200
patients by Suburban Diagnostics was to understand the concordance between the
rapid antigen test and the RT-PCR test taking in to consideration, the cycle
threshold (Ct) values of RT-PCR positive patients. In this study, the patients
were simultaneously tested for COVID-19 infection by the rapid antigen method
and the RT-PCR method. The conclusion of the study is that the rapid antigen
test was 100% specific with no false positives found and had a 60% sensitivity compared
to the RT-PCR test. It showed a lower sensitivity of 32% in asymptomatic
patients. In 63% cases, the antigen test had proven negative, but the RT-PCR
test was positive but with borderline Ct values which roughly correspond to low
viral load.
An analysis of
all the RT-PCR samples tested at Suburban Diagnostics revealed that positivity
percentage overall, since March has been 29.3%. Interestingly, a falling trend
of COVID-19 positive percentage has been seen from June till August in the city
of Mumbai, with a slight increase in the month of September, 2020.
Information is provided by Dr. Amar
Dasgupta, Director - Medical Services,Suburban Diagnostics
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