Medical workers carry a patient from an ambulance to George Washington University Hospital in Washington D.C., the United States, on April 27, 2020. Photo:Xinhua

The U.S. Centers for Disease Control and Prevention (CDC) acknowledged it had mixed together results from COVID-19 viral and antibody tests on its website, according to U.S. media reports.

Eleven states also confirmed mixing viral and antibody test results, CNN reported on Friday.

The CDC said it is planning to separate those numbers in the coming weeks, but experts believe the current method is potentially misleading.

"Initially, when CDC launched its website and its laboratory test reporting, viral testing (tests for current infection) were far more commonly used nationwide than serology testing (tests for past infection)," CDC spokeswoman Kristen Nordlund was quoted by CNN as saying in an email.

"Now that serology testing is more widely available, CDC is working to differentiate those tests from the viral tests and will report this information, differentiated by test type, publicly on our COVID Data Tracker website in the coming weeks," she said.

Antibodies are the body's way of remembering how it responded to an infection, so it can attack again if exposed to the same pathogen.

Different from the molecular test showing whether that person was infected with the virus at the time the test was taken, the antibody test can determine if someone was previously infected and recovered.

The CDC has reported a total of 13,627,379 tests nationwide as of Saturday, with 1,771,749 positive tests, according to data on CDC website. The overall positive rate is 13 percent.

Combining numbers from antibody and viral tests pushes up the total number of tests conducted across the country.

"The CDC's method makes it appear that the U.S. has greater capacity to test than it really does, at least when it comes to identifying current infections," said the CNN report.

The CDC is conflating the results of two different types of coronavirus tests, distorting several important metrics and providing the country with an "inaccurate picture" of the state of the pandemic, according to a report of The Atlantic.

"This is not merely a technical error. States have set quantitative guidelines for reopening their economies based on these flawed data points," said the report.

Across the country, 11 states reported mixing the numbers together, including Colorado, Delaware, Georgia, Maine, Mississippi, Missouri, New Hampshire, Pennsylvania, Texas, Vermont and Virginia, according to CNN report.