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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 24 th , 2020: • Over 2.7 million COVID-19 cases and over 192,000 deaths have been reported worldwide. As of April 23 rd , 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 on 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 TP TP PPV = Sensitivity = TP + FP TP + FN TN TN NPV = Specificity = TN + FN TN + FP
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 of 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 Prevalence known exposure – Ex. LTCH outbreak • Asymptomatic and no known exposure – Ex. LTCH with no outbreak
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 o 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
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