Risk-stratified testing at SGH reduced COVID-19 transmission

A risk-stratified testing strategy employed at Singapore General Hospital (SGH) helped minimize disruption to surgical procedures during the COVID-19 pandemic and reduced virus transmission to healthcare workers (HCWs), a recent study showed.

“A risk-stratified approach allowed for early recognition, testing, and isolation of potential COVID-19 infection in surgical patients,” said the researchers.

“As a result of increased vigilance, no HCWs required quarantine, the surgical wards were not locked down, and no onward healthcare-associated transmission was detected on close follow-up for 21 days,” they added.

The study population comprised 8,437 patients who were admitted to the surgical department of SGH between January and April 2020. Of these, 498 (5.9 percent) presented with concurrent respiratory symptoms (32.9 percent), infiltrates on chest imaging (50.8 percent), or suspicious travel or epidemiologic history (36.8 percent). They were admitted to a designated (respiratory surveillance) ward and tested for SARS-CoV-2, with attending HCWs equipped with full personal protective equipment (PPE), including N95 masks, disposable gowns, gloves, and face shields. HCWs attending to these patients donned full PPE until exclusion of COVID-19.

Seventeen surgical inpatients (3.4 percent) tested positive for respiratory viruses compared with 836 (15.1 percent) medical inpatients over this period. In the surgical inpatient group, six of these were SARS-CoV-2 compared with 499 in the medical inpatient group. [Surg Infect (Larchmt) 2020;doi:10.1089/sur.2020.184]

“In all six cases, a risk-stratified testing strategy averted delayed diagnosis,” noted the researchers.

The respiratory virus testing yield in surgical inpatients was lower than that of medical inpatients over the same time frame (odds ratio, 0.20, 95 percent confidence interval, 0.12–0.32; p<0.001).

Three surgeries were conducted in patients with COVID-19, with PPE employed by all healthcare workers. Risk-stratified testing strategy identified six previously unsuspected cases of COVID-19, of which four presented as asymptomatic. There was no evidence of infection to other patients or the 48 HCWs that dealt with these patients.

The 10 patients who required emergency surgery prior to exclusion of COVID-19 were managed as suspected COVID-19 cases using precautions and PPE, though results revealed that none tested positive.

“[A]typical manifestations of COVID-19, such as gastrointestinal symptoms or undifferentiated fever, potentially overlap with common acute surgical presentations [and may lead to] delayed recognition of COVID-19 infection leading to healthcare-associated outbreaks,” noted the researchers. However, universal testing of all surgical inpatients would be a challenge, particularly in asymptomatic or pre-symptomatic cases, not to mention “an inappropriate utilization of a limited resource.”

“Risk-stratification is crucial in ensuring early institution of appropriate infection prevention measures for all potential COVID-19–infected patients requiring operations, to ensure safe delivery of surgical services,” they said.

The researchers recognized that COVID-19–positive patients who were asymptomatic or without risk factors may have been missed. However, those who later developed symptoms could be transferred to the designated ward for further testing. Asymptomatic patients who were scheduled for transfer to community facilities post-surgery were tested for COVID-19 pre-transfer, with none in this study testing positive. Additionally, the two HCWs from the surgical department who developed COVID-19 during the study period were determined to have been infected through community transmission.

“[This demonstrated] the effectiveness of infection control precautions in mitigating patient-to-staff transmission of COVID-19 in our institution,” said the researchers.