Health experts say they now believe nearly one in three patients who are infected are nevertheless getting a negative test result. They caution that only limited data is available, and their estimates are based on their own experience in the absence of hard science.
That picture is troubling, many doctors say, as it casts doubt on the reliability of a wave of new tests developed by manufacturers, lab companies and the U.S. Centers for Disease Control and Prevention. Most of these are operating with minimal regulatory oversight and little time to do robust studies amid a desperate call for wider testing.
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All lab tests have some margin of error, measured in terms of sensitivity— the percent of positive cases a test accurately detects—and specificity, the percent of negative cases it accurately detects.
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The sensitivity of the currently available coronavirus tests seems to be lower than other similar tests, said Mike Lozano, a Tampa, Fla.,-based executive at Envision Healthcare Corp., a medical group that contracts to provide care at hospitals. Dr. Lozano said he estimates that the sensitivity of the tests is in the neighborhood of 70%, meaning nearly one in three positive patients walks away with a reassuring negative result.
