Testing various sites could lower false-negatives
Using real-time reverse transcriptase polymerase chain reaction (RT-PCR), investigators detected COVID-19 RNA in lung wash (14 of 15 samples; 93%), sputum (72 of 104; 72%), nasal swabs (5 of 8; 63%), lung biopsy (6 of 13; 46%), throat swabs (126 of 398; 32%), feces (44 of 153; 29%), and blood (3 of 307; 1%). The 72 urine specimens all tested negative.
Twenty patients had two to six specimens collected at the same time. Viral RNA was detected in single specimens from six patients (respiratory specimens, feces, or blood). Seven patients shed live virus in respiratory specimens, 5 in feces (2 of whom did not have diarrhea), and 2 in blood.
"Testing of specimens from multiple sites may improve the sensitivity and reduce false-negative test results," the authors wrote, citing two smaller studies that reported COVID-19 in anal and oral swabs and in blood in 16 patients and viral load throughout disease progression in throat swabs and sputum from 17 infected patients.
The highest viral loads in the JAMA study were found in sputum, the authors note, with moderate loads in nose-throat swabs, the most common way to confirm infection. Four fecal samples had high viral loads.