Discrepancy in coronavirus case counting due to statistical change

The discrepancy between the number of new confirmed cases of novel coronavirus in Wuhan and that of the Hubei province released on Thursday is due to a change in statistical methodology, expert said on Thursday.

The Chinese mainland reported its biggest drop in new novel coronavirus infections in almost a month, with only 394 new confirmed cases on Wednesday.

Hubei province reported 349 new confirmed cases in the period, but Wuhan, the provincial capital, recorded 615 such cases. This caused some confusion among the media and the public regarding the statistics.

Wang Guiqiang, the director of infectious diseases at the Peking University First Hospital, explained that the difference was due to the latest edition of the treatment and diagnosis plan published by the National Health Commission on Wednesday, which removed counting clinically diagnosed patients as confirmed patients.

Clinically diagnosed patients were suspected patients who were identified as having the disease based on symptoms, medical history and computerized tomography, or CT scans, and do not require testing positive for the virus using lab kits.

In early February, the previous treatment plan required Hubei province to count clinically diagnosed patients as confirmed cases so that more suspected patients can receive the same standard of treatment as confirmed ones, thus reducing the possible spread of the virus and improving the treatment success rate.

"This was a temporary measure because we didn't have enough test kits at that time to satisfy our clinical needs, and we had patients who needed immediate treatment but couldn't wait for their conclusive test results," Wang said at a press briefing.

"Now we have enough test kits, and we have ways to produce results faster, so experts decided to lift that requirement and allow Hubei province to be treated as equal with rest of the nation," he said.

Due to the change, medical workers have reexamined some confirmed cases in Hubei province and ruled out the ones that tested negative for the virus. The number of misdiagnosed patients turned out to be 279 on Wednesday.

Moreover, only 13 new confirmed cases were found in Hubei cities other than Wuhan. So the total number of new cases in Hubei on Wednesday should combine the number from Wuhan and that outside of Wuhan, leading to a total number of 628.

Subtracting the total number with the misdiagnosed number leads to Hubei reporting 349 new confirmed cases on Wednesday.