"In addition, some Slovak officials questioned the reliability of the quick coronavirus test kits purchased from China. According to the preliminary conclusion, the Slovak medical workers used these antigen test kits incorrectly with a preceding method applicable to nucleic acid testing, which led to the inaccurate results. China's embassy in Slovakia then issued a reminder on the correct use of different testing methods.

"Ninety percent plus of the millions of pieces of face masks and protective gear and test kits that are going out to the world from China are perfectly great, but they're writing articles about the small percentage that happened to be defective," Mario Cavolo, an Italian American writer living in China, told media.

http://www.xinhuanet.com/english/2020-04/09/c_138961792.htm