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 Subject : How should we screen patients coming to the ASC? Very lengthy answer i.. 04/22/2020 10:46:14 AM 
Leopoldo Rodriguez, MD, MBA, FAAAP, FASA, SAMBA-F
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Subject :How should we screen patients coming to the ASC? Very lengthy answer included in text:

ANSWER:
In order to screen patients, we have to rely on:
A. Questionnaires that will tell us if patients are symptomatic: fever, flu-like symptoms (cough, sore throat, runny nose, sneezing, malaise, myalgias), gastrointestinal symptoms (nausea, vomiting, diarrhea).
B. Temperature check upon arrival.

Screening questionnaire:
Patient with positive symptoms: don’t do the procedure in ASC. If medically necessary, do in Hospital , if not urgent: wait until the patient is symptom free for 14-days or has tested negative at least twice separated by 24-hrs and is symptom free.

Patient without symptoms: If the patient has no symptoms, they are allowed to come to the facility, upon entrance, if available and feasible ( especially in areas with a high prevalence of infection ( hot spot)), they should be tested for COVID-19 (see 3.b.). Then proceed to surgery. However, when tests are not available, and/or very low infection rate infection, may proceed with infection mitigation measures.

3.Testing:
Up to 80% of patients testing positive for COVID-19 can be asymptomatic. It appears the true asymptomatic rate is closer to 30-50 %.4 We recommend that health care providers read the FAQs on Diagnostic Testing for SARS-CoV-2.5

VERY IMPORTANT: the prevalence within a given population must be considered when applying tests

Two types of tests are used to detect COVID-19:
1. Nucleic acid amplification test (viral detection): tests are molecular tests that detect the virus's genetic material in a sample that typically comes from a patient's respiratory system.
2. Serology or antibody test (antibody) measures the number of antibodies present in the blood when the body is responding to a specific infection, like COVID-19.

Viral detection vs. antibody?

At this point there is no evidence that a positive antibody test confers immunity from COVID-19.
When we refer to testing, we refer to Viral detection in the patient’s airway. The FDA has published a list Test Kit Manufacturers and Commercial Laboratories Table.5

Viral detection: Reverse transcription-polymerase chain reaction (RT-PCR) assays are used to test patients and key workers for infection with the causative SARS-CoV-2 virus. Testing throat and nasal swabs by RT-PCR is not guaranteed to yield a positive result for SARS-CoV-2 infection and this probability decreases with time since the onset of symptoms. RT-PCR tests are highly specific and the probability of false positives is low, but false negatives can occur if the sample contains insufficient quantities of the virus to be successfully amplified and detected, the longer the time to the onset of symptoms the more likely it will be falsely negative.6
False negative rates of testing up to 50% have been reported. Even in the best of traditional laboratory settings, institutions like Mayo Clinic have recently reported a 10% false-negative rate.7
Thus, we cannot be sure even if we test all patients and providers that we are truly “safe” to allow those with negative tests to interact with others without maintaining. Universal precautions

Antibody testing: A patient may have a negative result early in infection even when they are symptomatic or asymptomatic but actively shedding the virus. Since IgM antibodies may not develop early or at all in infected patients, this type of antibody test is not used to rule out SARS-CoV-2 in an individual. We also do not know how long IgM or IgG antibodies to SARS-CoV-2 will remain present in the body after the infection has been cleared.

The FDA issued a policy explaining that FDA does not intend to object when developers of serological tests market or use their tests without prior FDA review where:
The tests are validated by the developer to determine that they are accurate and reliable,
Notification of the developer’s validation is provided to FDA, and
The tests are labeled appropriately, including that they are not to be used as a sole basis for diagnosis.

The policy does apply to tests that can be performed in patient care settings. Laboratories could validate tests they receive from commercial manufacturers and determine if they should be used in their facilities. Some laboratories have already done so or have developed their own serological tests.
The bottom line is that the FDA still expects tests to be validated even under our revised policy for tests. However, the EUA process or evaluation by NIH supports greater confidence in test performance.

What to do with results?
Viral detection test positive: patient should not have surgery at an outpatient surgery center. If the procedure is medically necessary, it should be done at a hospital, or it can be rescheduled until the patient has tested negative at least twice, separated by a 24-hr period.

Viral detection test negative or test unavailable/not feasible: patient can have the procedure at an outpatient surgery center, however, due to the number of false-negative results, we should still consider the patient an asymptomatic carrier of the virus, and thus, we should proceed with the planned surgery and infection mitigations strategies such as the patient should wear a level 3 mask while in clinical areas, staff should take precautions by wearing appropriate masks during aerosolizing procedures such as intubation, extubation, ENT surgery, upper GI endoscopy, and bronchoscopy. Avoid noninvasive ventilation.

CMS on 4/19/2020 published “When an adequate testing capability is established, patients should be screened by laboratory testing before care, and staff working in these facilities should be regularly screened by laboratory test as well.”1

I believe that the test will be more effective in areas with high incidence of COVID-19.
Because of what we learned during the last webinar, in patients that test positive, it is better to delay surgery, because if patients become symptomatic, the morbidity and mortality is high. Plus, we would be exposing staff and other patients to the virus.

As stated before, a negative viral RT-PCR, can be considered a False Negative in a high incidence area, and thus the patient should be treated as if they were an asymptomatic carrier: mask,( N95 and face shield for an aerosolizing procedure).

References:
4. https://www.cebm.net/covid-19/covid-19-what-proportion-are-asymptomatic/
5. FAQs on Diagnostic Testing for SARS-CoV-2: https://www.fda.gov/medical-devices/emergency-situations-medical-devices/faqs-diagnostic-testing-sars-cov-2 (last visited 4/20/20)
6. Emergency use authorization: https://www.fda.gov/medical-devices/emergency-situations-medical-devices/emergency-use-authorizations#covid19ivd (last visited 4/20/2020)
7. https://www.sciencedaily.com/releases/2020/04/200409144805.htm.
8. Wikramaratna,P; Paton, RS; Ghafari, M., and Lourenco, J. Estimating false-negative detection rate of SARS-CoV-2 by RT-PCR. https://www.medrxiv.org/content/10.1101/2020.04.05.20053355v2.full.pdf (last visited 4/20/20).
 
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