Sequential battery of COVID-19 testing to maximize negative predictive value before surgeries

SARS-CoV-2 is a novel virus which has proven to be highly contagious. Specific viral dynamics and immune response to the virus are yet to be fully defined and determining the sensitivity and specificity of the available testing methods is still a work in progress. This study examines the published information on the testing methods, and finds that yield of COVID-19 tests changes with specimen types and with time through course of illness. We propose a sequential battery of testing consisting of an epidemiologic survey, RT-PCR tests, serologic tests and chest CT on surgical candidates which may increase the negative predictive value, and facilitate surgical procedures.

Severity has been seen mostly in the elderly population and patients with underlying diseases such as diabetes, hypertension, and pulmonary conditions, but fatalities have also been reported in young patients 7,8 .  18,19 .

Transmission routes
The incubation period of an infectious disease is defined as the elapsed time from the moment a person is exposed to an infective agent and the appearance of signs and symptoms. For COVID-19, the incubation period is thought to extend up to 14 days, with a median of 4-5 days from exposure to symptomatic onset 9,20,21 .
Several small cluster studies have suggested viral transmission from asymptomatic patients by conducting epidemiologic studies on this population 9-10,13, 22-26 . One of the patients that contracted the infection from an asymptomatic patient in Germany had a high sputum viral load after symptoms disappeared, also raising concerns patients 33 .
Higher viral loads have been detected in the nose and saliva compared to throat samples 27  3.9% conversion rate, which is highly concerning, since asymptomatic patients are usually not detected early 28 . The fact that asymptomatic and recovered patients may spread the virus is worrisome, not only for the epidemiologists trying to implement measures to avoid the spread, but for health care workers evaluating their patients without personal protective equipment 29 .

Viral shedding Pattern
The actual shedding pattern of COVID-19 is yet to be determined. However, real time RT-PCR is being used to detect viral presence in patients. The viral load can peak as early as one day before symptom onset or 5-6 days after, with a median viral load of 5.2 log10 copies/ mLl at presentation, and then start declining 38 . This suggested shedding pattern seems similar to the one of influenza virus which is more contagious than SARS-CoV that usually peaks around day 10 of symptom onset 27,30 .
One study determined that the median duration of SARS-CoV-2 viral shedding was 12.0 days, the shortest being

COVID-19 and elective operations
The rapidly changing situation of COVID-19, the fact that the understanding about the virus is evolving, and that it might be contagious on the incubation and convalescence phases, raises concerns when planning a surgery. Furthermore, the fact that surgery decreases cellmediated immunity, an important mechanism to mitigate viral damage, might deter surgeons from performing the procedure. One retrospective study conducted in

Proposed battery testing
At this stage of the pandemic, multiple things remain uncertain. It is too early to fully understand the incidence, prevalence and fatality rate of the infection.  (Table 1).
If at any step of the sequential battery of tests, COVID-19 is diagnosed, the sequential battery is terminated, and the standard of care is to be followed for confirmed COVID-19 patients.

Pre-surgical evaluation
When considering patients for surgery, we suggest that more tests be performed at different stages to increase negative predictive value. 1) To evaluate the pre-test probability of infection, an epidemiologic questionnaire can be conducted ( Table 2)

Post-surgery testing
Testing should not stop after surgery is performed.
The fact that during the incubation stage patients might be should also be performed to increase the sensitivity at the weekly post-surgical evaluations.

Donor transplant evaluation
As stated above, little is known about the possible transmission of SARS-CoV-2 through transplanted organs.
However, preventing the use of an organ from an infected donor would be imperative. Kumar  Regarding transplant recipients, the battery of testing stated on Table 1 should also be performed.