Health authorities in China, the United States and other countries have offered few details on the rates of false positive and false negative results on any coronavirus tests. Experts worry that the rapid tests may be significantly less reliable than the more time-consuming method.

Lower accuracy has been a concern with rapid flu tests. Spanish scientists said the rapid tests for coronavirus they reviewed were less than 30% accurate. The more established lab tests were about 84% accurate.

Those results “would prevent its routine introduction,” according to a report by the Spanish Society of Infectious Disease and Clinical Microbiology that triggered the alarms in Spain and spurred the government’s rejection of the 9,000 antigen tests.

Similar questions swirl around new antibody tests involving blood samples. Some versions have been described as finger-prick tests that can provide important information in minutes.