Breaking down the testing related to COVID-19
As testing for COVID-19 becomes more available, patients are asking their doctors whether or not they should get tested.
Back In March, when testing capacity was extremely limited, we were only able to test patients who had symptoms and were at risk for severe outcomes. More recently, as national labs have ramped up capacity, we are able to test a broader range of patients.
In fact, Gov. Steve Bullock recently set an ambitious goal of doing 60,000 tests per month in Montana for patients without symptoms.
Broadly speaking, there are two ways to look for current or past infection by COVID-19 — PCR tests and serologic tests. PCR stands for “polymerase chain reaction” and is a test that detects fragments of virus RNA in a sample taken from your nasal passage. Serologic tests detect antibodies to the virus in a sample of your blood. Each kind of test has a role, and each has its limitations.
PCR tests are positive when someone is actively infected and for some time afterwards. PCR tests do not tell us who may have been infected with COVID-19 before, or if they are immune to the virus now. As your body responds to the infection, your immune system produces antibodies which initially help fight the infection, then can remain in circulation and may provide future immunity.
We are still learning whether antibodies to COVID-19 will provide long term immunity. For some infections — like measles — antibodies provide immunity that lasts a lifetime. For other diseases — including many coronaviruses — immunity is short-lived, just weeks. Unfortunately, there are some diseases — such as Dengue — where antibodies can actually make symptoms from a second infection worse due to a process called antibody-dependent enhancement.
As our understanding of COVID-19 grows, serologic testing may help us understand disease resistance in a community, or demonstrate whether a new vaccine is effective. But, for now, given the many questions that remain around serologic testing (including how accurate they are), there is really no reason for a patient without symptoms to request antibody testing.
PCR testing to monitor statewide disease activity, on the other hand, does serve an important public health goal. As part of our efforts to support the statewide effort to do 60,000 tests per month, we will be asking patients to get tested when they come to the emergency department or to one of our clinics. The test is voluntary, but your participation helps us in our mission to protect both patients and healthcare workers. Together, we can continue to keep Montana the safest place in the nation during this pandemic.
Dr. Jason Cohen is the Chief Medical Officer at North Valley Hospital.
Editor’s Note: Over the coming months, different senior leaders of North Valley Hospital will share their perspectives on healthcare in the community.