A high school student who got mixed test results in the span of about two weeks for the novel coronavirus that causes COVID-19 is highly likely to have had a false positive, the Korea Centers for Disease Control and Prevention said Friday.

The 17-year-old, who is a senior at a high school in Jungnang, northeastern Seoul, tested positive June 7 after a visit to a theme park in the city’s southern district of Jamsil two days prior. Her first test, taken May 25, rendered negative results.

This led to a temporary shutdown of the school as well as the theme park to trace and test all those who may have been exposed. Nearly 800 people who have been identified as contacts tested negative so far, health officials said.

But successive tests conducted on the high school student after she was admitted to the Seoul Medical Center on June 8 contradicted earlier confirmation of COVID-19, yielding negative results. Medics said her symptoms were minimal.

KCDC Director Jung Eun-kyeong said in a press briefing Friday afternoon that such inconsistencies were “extremely rare” and that the agency was still investigating the case for more explanations.

Laboratory medicine specialist Dr. Sung Heung-sup of Seoul’s Asan Medical Center said in a phone interview that the recent case should not serve to undermine the accuracy of COVID-19 testing.

Sung, who is part of the expert committee deliberating the test results with the KCDC scientists, said, “What’s important is that these potential false positives and false negatives are tracked, and then corrected.”

All of the samples used for tests were collected from the upper respiratory tract, he said. The RT-PCR was used as the method of diagnosis.

He added that the conflicting test results were “due to no fault of the test kits.”

Asked how frequent false positives were, he declined to give specific estimates.

By Kim Arin (arin@heraldcorp.com)