Discussion:
In this 3-week COVID-19 antibody screening test, 12 staff out of 310
screened (3.8%) had been exposed to the COVID-19 infection without
being aware of it. This serology surveillance reflected the actual rate
of asymptomatic and non-PUI infection among the SHC healthcare worker.
Many of these infections were not detected earlier because the PUI
criteria were not met. Some HCW who had close contact (low-medium
risk)31 with confirmed cases did not receive the PCR
testing during the early days of pandemic. This is likely due to scarce
resources leading to prioritization protocol as suggested by many
sources.18,32
WHO estimated a 2%-3% of the world’s population tested positive for
antibody response towards COVID-19.33 Applying this
projected percentage to our total HCW in SHC (686 clinical staff), the
estimated number of staff with IgG antibody would be 13.7. Our
surveillance result showed a higher percentage of the previous infection
compared to this estimation (3.8% vs. 2%). However, this comparison is
a lot lower compared to the findings of a multicentre RT-PCR
surveillance study conducted on mildly symptomatic HCW in the
Netherlands (COVID centres)13,3.8% vs. 9.5%.
We postulated a few reasons for the discrepancy of our staff’s infection
rate with the WHO and European data. Comparing to the public population,
HCW have a higher risk of being exposed to infection while delivering
medical care in the frontline. While the public are expected to observe
a more controlled social distancing manoeuvres during the public
movement restriction orders, HCW are required to travel, and hence a
higher potential risk of exposure to infection. Lower rate of infection
compared to the Netherlands data may be explained by the work
environment, where lower staff exposure is anticipated in a non-COVID
medical facility. Shorter timing of exposure to COVID-19 patients may
also explain the lower risk and rate of
infection.31,34 A lower prevalence of COVID-19 cases
in Kuching-Samarahan in compared to Netherlands could also be the reason
for less possibility of community-acquired
infections.7,35 Total HCW infection from
China12 or the Netherlands13 may be
higher than what were reported by the two countries if their positive
PCR results had been combined with positive IgG tests in asymptomatic
HCW.
Statistical analysis of our study showed a significant association of
IgG status with the clinical symptoms, potential exposure at the cluster
area, and place of work within the cardiology department. This finding
agreed with the criteria used by WHO36 and our
Ministry of Health28 to consider screening persons at
higher risk when they developed respiratory symptoms or had close
contact with to confirmed COVID patients or cluster areas. While testing
capacity is generally not meeting the needs, this finding could guide
the hospital occupational safety team to prioritize screening of HCW
with higher risk in the future. Another interesting observation from our
study is the significant number of staff, 7(2.7%), who tested positive
with IgG but reported no symptoms at all. Asymptomatic cases remained a
challenge to the COVID-19 management.37 More work is
needed to study other potential clinical or epidemiological factors to
risk stratify this group of patient.38
Our study had two false-positive IgM results. This observation explained
the importance of interpreting lateral flow immunochromatographic assay
as positive, only when the result line is clearly demarcated. A false
positive result can also occur due to the cross reactivity to the other
coronavirus infection.21 All 14 staff from our survey
were quarantined until two sets of RT-PCR tests returned negative. These
positive findings in our survey highlighted the need for post antibody
serological testing plan if non-COVID medical facilities wishes to
conduct an antibody serology survey. The capacity to carry out RT-PCR
testing with support from the relevant authority such as the ID team,
needs to be established for confirmation of viral status. It is
necessary to adjust staff duty roster and pre-inform all sections of a
possibility of staff shortage if quarantine orders are issued once
antibody screening results are positive. Staff should also ensure that
proper quarantine place is available before attempting the screening
test.
Our centre’s lower IgG prevalence during the peak of the pandemic in our
country may be the result of effective in-hospital infection control
measures. Our COVID-19 taskforce team produced a temporary infection
control protocol to reduce staff’s exposure to the infection within the
hospital. Elective invasive cardiology procedures, i.e., diagnostic
angiogram, transcatheter aortic valve replacement, and transoesophageal
echocardiography, were postponed. Patients with clinic appointments were
contacted via telephone and given options to either defer their clinic
consultation with auto-renewal of prescriptions or to continue clinic
consultation. To prepare for potential admission and emergency
catheterization of cardiac diseases with concomitant COVID-19 infection,
we redesigned ward and established a dedicated cardiac catheterization
laboratory team. Medical personnel who attended to patients were
directed to don level II personal protective equipment (PPE) and level
III PPE, in normal wards and isolation rooms, respectively. If aerosol
producing procedures were unavoidable, i.e., intubation, level III PPE
were to be used. Screening of cardiac cases with respiratory symptoms
were done in a temporary tent as the holding bay. Suspected PUI cases
were not admitted but were referred to a COVID designated hospital.
Cases expressing respiratory symptoms without epidemiological links were
also discussed with infectious disease specialists to risk stratify them
before admission into the wards. These patients who did not fulfill the
PUI criteria but with respiratory symptoms were admitted to the
temporarily designated ward where level 2 PPE were imposed for every
healthcare staff who manage the patients. Patients with respiratory
symptoms who needed intensive coronary care were admitted to the
coronary care unit’s isolation room with negative pressure.
Lower IgG prevalence also reflects the limited potential immunity among
SHC healthcare workers towards COVID-19. The in-hospital infection
control measurements should be continued and constantly reviewed to suit
the latest trend of pandemic control. It is still uncertain whether the
presence of IgG antibodies confers long-term immunity to the individual.
If so, it will have several implications such as the deployment of these
“immune” staff to work in high risk areas, and the prioritization of
staff for immunization32 once a vaccine becomes
available.