- During a peak period of SARS-CoV-2 infection in the Boston area, infectious disease physicians at Massachusetts General Hospital monitored data on 1,985 hospitalized adults who had at least one negative nucleic acid test (NAT) for the virus
- These specialists advised removal of isolation precautions if SARS-CoV-2 infection was deemed unlikely or recommended additional diagnostics if their suspicion for COVID-19 was moderate to high
- After the first negative NAT, 724 patients were considered true negatives based on infectious disease physician review
- The 1,261 remaining patients had two or more nucleic acid tests, and SARS-CoV-2 was detected in only 2.9%
- Only two of the patients who discontinued isolation had a subsequent positive nucleic acid test within seven days
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The sensitivity of a single nucleic acid test (NAT) for SARS-CoV-2, the virus that causes COVID-19, is approximately 70%. Repeat testing increases the sensitivity to 88%.
Accordingly, the Infectious Diseases Society of America recommends repeating a NAT when suspicion of COVID-19 remains moderate or high after the first test.
During a peak period of the COVID-19 pandemic in Boston, Caitlin M. Dugdale, MD, and Emily P. Hyle, MD, MSc, of the Division of Infectious Diseases at Massachusetts General Hospital, and colleagues devised an approach in which infectious disease (ID) physicians provide guidance on which patients should have additional testing. This approach aimed to reduce the need for repeat testing among low suspicion patients while also trying to prevent inappropriate removal of precautions in patients with potential false-negative tests. They describe their experience in Infection Control & Hospital Epidemiology.
The researchers reviewed all 2,736 admissions in which an adult patient under investigation for COVID-19 stayed >24 hours between March 23 and May 18, 2020, and had one or more NAT for SARS-CoV-2.
ID faculty and senior fellows monitored data on each patient with suspected COVID-19 by remote daily chart review and communication with frontline providers. They advised removal of isolation precautions if an infection was deemed unlikely or recommended additional diagnostics if their suspicion for COVID-19 was moderate to high.
- First NAT: 751 (27%) patients tested positive and 1,985 tested negative
- Disposition of the 1,985 negative patients:
- 724 (36%) were considered true negatives based on ID physician review
- 1,261 had a second NAT
- Second NAT: 31 patients (2.5%) tested positive and 1,230 tested negative again
- Additional NATs were suggested for 151 of those 1,230 patients, of whom five (3.3%) tested positive
Thus, only 36 of the 1,261 patients who underwent repeat testing (2.9%) were diagnosed with COVID-19 (31 after the second NAT and five after additional NATs).
Positive Tests After Discontinuing Isolation
Two patients (0.1%) had positive tests within seven days of discontinuing isolation that were prompted by worsened coughing. In both of these cases, the initial negative tests were thought to have been performed in the window period between prehospital exposure and development of infection with viral shedding.
Not Feasible for All Settings
This detailed clinical review process resulted in a low rate of missed COVID-19 diagnoses, and it had the advantage of conserving personal protective equipment. However, it was highly resource-intensive. ID physicians reviewed 80 to 110 patients/day from 6 a.m. to midnight, and on challenging cases they held thrice-daily rounds to establish consensus. This required about 70 physician hours/day and more than 5,000 physician hours over two months.
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Learn more about research in the Division of Infectious Disease