When the Long Beach Health Department began collecting data in the early days of the coronavirus pandemic, it hit a snag as some private labs reported the number of positive test results but lagged in reporting negative cases.
The lack of negative test results from some labs made it difficult to accurately calculate the city’s positivity rate, which is the number of positive tests compared to overall tests.
Faced with the choice of how to calculate the numbers, health officials opted to include the positive cases from labs with incomplete data that didn’t include the number of negative tests. As a result, Long Beach’s overall positivity rate for months has been higher than its actual numbers.
Emily Holman, Long Beach’s communicable disease controller, said she felt it was important to count every positive case, even if that meant the positivity rate would be skewed higher.
“We knew there was always a chance that our positivity rates could have been a little higher because we could have been missing negative results,” Holman said Monday. “I just wanted to count every positive. I never wanted to be accused of holding back positive cases.”
Under new guidelines from the state, Long Beach this week switched the California Department of Public Health’s method for calculating the positivity rate. The new calculation method includes only labs that provide both positive and negative results that are entered into the state’s electronic system.
As of Monday, the city’s positivity rate was 5.2% under the new calculation, which puts it closer to Los Angeles County’s rate of 5%.
Long Beach’s rate would have been 7.3% under the old method, Holman said.
The positivity rate has been a key indicator for reopening schools and businesses. Under California’s requirements, a county’s positive test rate must be under 8% before it can be removed from the state’s monitoring list.
Even with the lower positivity rate, Long Beach would not have been a candidate for early reopening as it hasn’t met other indicators, like the overall number of cases per 100,000 residents. Long Beach as of Friday had 158 cases per 100,000 residents. The state requires fewer than 100.
The city on Monday reported a total of 10,524 COVID-19 cases and 216 fatalities, up from 209 on Friday.
Holman said calculating positivity rates is a challenge for many jurisdictions. In July, Florida saw an increase its positivity rate after labs failed to report negative COVID-19 results.
“There has never been one way of calculating positivity rates and every jurisdiction does it the best way they can to get the most accurate numbers,” Holman said.
In Long Beach, one of a handful of California cities with its own health department, 30% of test results come from the city’s drive-through testing sites, while the rest come from private labs through hospitals and other providers.
While many of the larger private labs like Quest Diagnostics provide results to the city through an electronic system, some of the smaller labs send the information manually, Holman said.
Keeping track of numbers through manual reporting has been a headache, she said. Some labs lag in reporting negative test results, while others don’t provide the info, even though it’s required by the state. Holman did not have data on the percentage of labs that report manually.
Long Beach’s positivity rate has typically been higher than neighboring Los Angeles and Orange counties. The city’s highest rate was 17% in April as mostly essential workers and those with symptoms were being tested.
The rate later dropped, but then surged to 15% in July as the state and county eased stay-at-home restrictions. Holman said that percentage may have been slightly higher than the actual numbers, but she believes it is still an accurate indicator as other cities saw surges at the time.
“It was very consistent with what was happening,” she said.
With many new labs signing on for testing, Holman said there is now a statewide push to get all labs to report results electronically.
Either way, the numbers are moving in the right direction as the city and county has seen a drop in positivity rates in recent weeks, she said.
“We are making progress,” she said. “Hopefully we can continue on this trajectory.”
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