Antibody tests had amounted to less than 9 percent of the state’s overall screening for the coronavirus. Removing them from the total slightly increases the percentage of positive tests among the overall number of tests given, to 15 percent from 14 percent.
The Health Department said that uptick does not alter the overall trend of a decline in the percentage of positive tests, one of the fundamental metrics Northam said he is weighing as he begins to roll back some restrictions on businesses.
Phase 1 reopening is expected to begin Friday for most of the state, although hard-hit Northern Virginia will remain under full restrictions for at least two more weeks.
Because they are less accurate than the genetic tests conducted by swabbing a patient’s nose, the antibody — or serologic — tests were not used to confirm positive cases reported by the state.
But by inflating the overall number of tests given, they slightly held down the apparent percentage of positive infections.
Health experts have cautioned against relying on the results of antibody testing, which can show the presence of antibodies in the blood that suggest someone has been exposed to the virus. The results have been plagued with false positives and false negatives.
“We don’t have enough information about the performance of these tests to know ideally how to use them,” Angela M. Caliendo, secretary of the Infectious Diseases Society of America board of directors and a vice chair in the medicine department at Brown University’s Alpert Medical School, said earlier this month.
Virginia has faced criticism for lagging most other states in its per capita testing. Earlier this month, the state changed the way it counts tests, slightly improving its standing.
That change involved counting tests administered instead of individuals tested; since people are often given a second test before they can go back to work, the change boosted the state’s numbers.
On Monday, Northam chief of staff Clark Mercer seemed to suggest that including the antibody tests in the count was another way to improve the state’s standing.
“If another state is including serological tests and they’re ranked above Virginia and we are not, and we are getting criticized for that, you can’t win either way,” Mercer said during a public news briefing. “Now we are including them, and our ranking will be better, and we’re being criticized.”
The remarks led to an article in the Atlantic saying that Virginia had “juked” its data to try to look better, and they amplified criticism from state Republicans.
“Doctor Northam and his team are committing malpractice with Virginia’s testing program,” House Minority Leader Todd Gilbert (R-Shenandoah) said in a statement, referring to Northam’s career as a pediatric neurologist.
But officials said Thursday that Virginia had been including the serological tests all along and did not add them as a way to pump up the numbers.
State epidemiologist Lilian Peake said in an interview that the state’s data system was designed from the beginning of the outbreak to gather all kinds of tests being administered in the field.
“So when we set up this data feed very early on, when all of the tests were still being developed, we weren’t sure how the antibody tests were going to be used for counting cases,” Peake said. Lacking guidance from the federal government, she said, the department’s information technology staffers included them along with the more reliable genetic tests.
At the start, she said, very few antibody tests were being used. It was not until about three weeks ago that the numbers climbed to a point that caught the attention of health officials, she said.
According to data released Thursday, only a handful of antibody tests were part of the state’s initial data set. The week of April 5, for instance, the state reported 18,417 tests, and only 10 of those were serological.
The big jump came the week ending April 19, when serological tests accounted for 1,375 of the overall 24,837 tests reported by the state. The number inched upward in each of the following weeks.
By Thursday, the state had reported 184,444 total tests administered since February, and just over 15,000 of those were for antibodies.
While the antibody tests are getting better and will have value for understanding how far the disease has spread, Peake said, officials became concerned that they were polluting the overall presentation of the scope of the disease in Virginia.
Northam has pledged to get the state to a capacity of 10,000 tests per day as part of his effort to safely begin rolling back some restrictions, and Peake said adding the antibody tests was never intended as a way to get closer to reaching that goal.
She said that she consulted with epidemiologists in a handful of other states to see how they were handling the data and that they told her they were counting only the genetic tests. Once the issue came to light — partly because of reports in the news media, including the Richmond Times Dispatch — officials decided to remove those tests from the rest of the data.
“When I found out recently that data from all types of tests were being combined, I immediately directed that the diagnostic tests be separated out,” Northam said Thursday via tweet.
Officials said it took several days to bring the change about.
“Because we had automated our reports, it required going back into our IT system and changing the code,” Peake said.