Welcome to Noozhawk Asks, a feature in which you ask the questions, you help decide what Noozhawk investigates, and you work with us to find the answers.
Question: With a current restriction on testing to people with coronavirus symptoms, doesn’t that skew the positive test rate upward, hence the jump to 17-plus percent? Is there no remedy to this because of testing equipment and lab shortages?
— Katey O’Neill, Santa Barbara
The testing positivity rate refers to how many of the people tested for the coronavirus get a positive result.
The number of daily test results fluctuates because of laboratory delays and other factors, and Santa Barbara County tracks the positivity rate as a rolling seven-day average.
The countywide test positivity rate was high in the early days of the pandemic, when testing was mostly limited to severely ill people in emergency rooms.
It dropped in April and May, when there was less community transmission and more widespread testing, which captured more healthy, uninfected people.
Limiting testing to people with symptoms can cause a higher positive test rate, as reader Katey O’Neill suggested, and so does increased community transmission. Both of those are happening in Santa Barbara County, according to the Public Health Department.
Long laboratory delays and ongoing shortages in testing supplies prompted county leaders to ask people to seek testing only if they had COVID-19 symptoms or a known exposure to a person who tested positive. That was a reversal from previous months, when public health officials encouraged everyone to get tested, regardless of symptoms, at the state-run community testing sites.
Expanding testing to people with mild symptoms or no symptoms can capture more uninfected people. That and decreasing the spread of the virus in the community are ways to lower the positivity rate, generally.
The Santa Barbara County Public Health Department has posted articles helping people evaluate the exposure risk for different activities, and in general advises everyone to avoid all gatherings with people outside their household, stay at least 6 feet away from other people, wear a face covering when in public, and frequently wash hands and sanitize surfaces.
Tracking Novel Coronavirus Test Positivity Rate Over Time at Sansum Clinic
Sansum Clinic, which operates primary and specialty care clinics in southern Santa Barbara County, has been consistently testing 400 to 500 patients per week during the pandemic response.
It’s a small sample size, but it’s consistent in the number of patients and the kind of patients, said Dr. Kurt Ransohoff, chief executive officer and chief medical officer for Sansum Clinic.
Sansum Clinic staff use drive-through appointments to test pre-operative patients and people with COVID-19 symptoms who were referred to a test by their doctor. The symptomatic patients have a higher positivity rate than the pre-op patients, who have no symptoms.
“The positivity rate is really useful because it gets rid of this notion that we’re just testing more people,” Ransohoff said. “If we’re just testing more people, then the positivity rate should be the same.”
If the rate increases, “we’re either testing different kinds of people or there’s just more of it,” he added. “When things were pretty good and we thought things were under control, like April and early May, we were kind of running at a 1 percent positive rate.”
By the end of June, it had skyrocketed to 9 percent.
It’s difficult to compare positivity rates between organizations without knowing who is being tested. It’s easier to look at the relative changes — tracking one dataset over time, like the county’s number or Sansum Clinic’s, Ransohoff said.
The Santa Barbara County positivity rate (which excludes testing at the Lompoc federal prison complex) represents how many positive cases are reported out of all test results reported in the county, from testing at hospitals, primary care providers, clinics and skilled nursing facilities.
Both Cottage Health and Sansum Clinic have reported internal testing positivity rates in the 3- to 4-percent range for recent weeks, but the countywide positivity rate has been above 8 percent (the state’s reopening metric) for weeks.
It’s important to note that Cottage Health and Sansum Clinic facilities are on the South Coast, while the majority of COVID-19 cases and hospitalizations have been in North County, especially Santa Maria.
“It’s as if we’re giving a weather report by looking out our window. We feel pretty good looking at the weather out of our window; (the county’s number) is more like a satellite,” Ransohoff said.
Santa Barbara County’s Public Health Department reported a 3.5 percent weekly average positivity rate in a May 19 report to the Board of Supervisors, and a 3 percent rate on June 2.
There was a large increase in the positivity rate countywide through late June and early July. In the two-week period between June 23 and July 6, the seven-day average positivity rate rose to 8.3 percent from 4.1 percent.
This week’s numbers show a drop in the countywide rate, but the county has a disclaimer on its website saying the number of positive cases being reported right now is a definite undercount related to state database reporting errors. The state data problems have been reported for more than a week, so recent local trends are difficult to track based on the numbers currently reported.
— Noozhawk managing editor Giana Magnoli can be reached at firstname.lastname@example.org. Follow Noozhawk on Twitter: @noozhawk, @NoozhawkNews and @NoozhawkBiz. Connect with Noozhawk on Facebook.