Coronavirus cases in the U.S. have skyrocketed in the last several weeks, reaching more than 11 million cases nationwide. As Americans see rising numbers, Fox News contributor Dr. Nicole Saphier broke down the accuracy of available coronavirus testing on "Fox & Friends Weekend." Recently, more patients have reported testing to be inaccurate, including figures from Tesla CEO Elon Musk, who tweeted Friday that after taking four tests for COVID-19, two were negative and two came back positive. Saphier explained these inaccuracies occur mostly from rapid testing – an antigen test screening for virus proteins – since they could have a false negative rate of up to 50%. "It's far more likely to have a false negative of that antigen test than it is to have a false positive," she explained.