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COVID-19 Health Care Provider Briefing

Middlesex and London Region April 24, 2020

Welcome

Presenter:

• Dr. Alex Summers

Associate Medical Officer of Health Middlesex-London Health Unit

Surveillance Report

As of April 24th, 2020:

• Over 2.7 million COVID-19 cases and over

192,000 deaths have been reported worldwide. As of April 23rd, 2020:

• 14,068 cases of this illness confirmed in

Ontario, including 806 deaths

• 347 cases confirmed in the Middlesex-London

region, including 26 deaths.

Update from PHOL on COVID-19 Test

• Looked at data for patients tested by

nasopharyngeal and/or throat swab between January 11 and April 14

• Still needs to be validated

Sensitivity

• Based on 569 positive patients who had

more than 1 swab collected and were positive on at least one sample

• 484/569 were positive on first testing

episode

• Suggests sensitivity of 85%

Negative Predictive Value

• Based on 4220 patients who were negative
• n their first swab and retested
• Only 2.5% flipped from negative to positive
• Estimated negative predictive value of the

first test of 97.5%

Let’s Get Boring…

Disease present No disease present Positive test result True positives False positive Negative test result False negatives True negatives

Sensitivity = TP TP + FN Specificity = TN TN + FP PPV = TP TP + FP NPV = TN TN + FN

Sensitivity and Specificity

• Sensitivity = proportion of people with a

disease that have a positive test

• Specificity = the proportion of people

without a disease that have a negative test

• Intrinsic characteristics of the test

PPV and NPV

• PPV = proportion of those with a positive

test that have the disease

• NPV = proportion of those with a negative

test that do not have the disease

• Influenced by the prevalence of disease in a

population

Influence of Prevalence

• Calculating PPV and NPV requires including

individuals with and without the disease

• Therefore, it is affected by the prevalence
• f the disease in question

Influence of Prevalence

• As prevalence increases, PPV increases but

NPV decreases

• Conversely, as prevalence decreases, PPV

decreases but NPV increases

Assumptions of Prevalence

• Symptomatic
• Asymptomatic and

known exposure

– Ex. LTCH outbreak

• Asymptomatic and

no known exposure

– Ex. LTCH with no

• utbreak

Prevalence

What Does That Mean?

• PPV will be higher when testing symptomatic people

than when screening asymptomatic people

• By screening asymptomatic people, we increase the

number of false positives

– Overestimate asymptomatic spread

• There will be very few false negatives

– However, a negative COVID-19 test is only relevant at the period of time in which it is sampled

Testing in LTCH

• One time testing of all residents and all staff in

LTCH

• Will be rolled out over the next two weeks
• REMINDER – Negative test does not change

precautions in a LTCH

• LTCH and RH distribution list for alerts and

newsletters

• Email healthcareproviders@mlhu.on.ca and let us know if

you are part of a LTCH or RH.

Immunizations During the Pandemic

• Providing routine immunizations for

infants and children is an essential service

• Delay or omission in scheduled

immunizations put individuals of all ages at risk for infection.

• Healthcare providers may send completed order forms to

vaccineorders@mlhu.on.ca or fax 519-663-9581

• The Health Unit’s Immunization Clinic remains open. Services

are available by appointment only for individuals who do not have health care coverage (i.e. OHIP) or do not have a primary healthcare provider with some exceptions.

COVID-19 Briefing Webinars

• The MLHU is hosting twice weekly briefing

webinars for healthcare providers.

• Held on Tuesdays and Fridays from 12:00 p.m. to

12:30 p.m.

• Please send your questions to

healthcareproviders@mlhu.on.ca

Questions?

Ask using chat function now, or after the webinar at: healthcareproviders@mlhu.on.ca