The FDA continues to authorize new tests and more efficient methods to diagnose COVID-19, but as the pandemic reignites across multiple states, the lack of swabs, reagents and staff to process tests is creating time lags that could make it difficult to contain the outbreak and stymie some reopening efforts, including those envisioned by employers, schools and universities.
On July 2, the FDA granted an Emergency Use Authorization (EUA) to the third test that can detect SARS-CoV-2 and influenza viruses. In advance of flu season in the fall, “with just one swab or sample, combination tests can be used to get answers to Americans faster,” FDA Commissioner Stephen Hahn said.
To further increase the speed and efficiency of COVID-19 diagnostic tests, the FDA also updated its molecular diagnostic templates with more recommendations for the validation of assays used for pooling patient samples. The process allows the lab to mix several samples together in a batch and then test the pooled sample. The pooling or batch strategy, especially useful in areas with low prevalence of the virus, allows labs to quickly rule out groups of people if the pooled sample comes back negative (if the pooled sample comes back positive, the lab would then run the group’s samples individually).
While pooling samples runs the risk of missing cases if the test returns a false negative, researchers at the Renal Research Institute and the Icahn School of Medicine developed a model to estimate the risk of false negatives and found that pooled sampling was more efficient than individual testing in scenarios where the prevalence of the disease is less than 30%.
Pooled testing has been considered by some to be an efficient surveillance tool to test millions of individuals at businesses and universities as they reopen, quickly identifying and isolating individuals who may be infected.
As of Monday, the FDA had granted EUAs to 175 tests, including 145 molecular tests, 28 antibody tests and two antigen tests. This is a far cry from the handful of tests available in March as the pandemic forced stay-at-home orders across the country. However, new reports are emerging about shortages of ancillary supplies and staff to rapidly conduct the test and report the result, causing significant delays.
Two national testing companies have reported a surge in demand (see here and here), resulting in longer turnaround times of four to seven days or more for non-priority patients. The spike in demand is due to the spread of the virus in the South, West and Southwest, as well as in facilities such as prisons, nursing homes and hospitals.
The lag in obtaining results could blunt surveillance efforts. Researchers at the University of Colorado Boulder and Harvard University found that effective surveillance depends “largely on frequency of testing and the speed of reporting, and is only marginally improved by high test sensitivity.”
On July 8, a group of regional, community, academic, hospital and public health laboratory professionals sent a letter to Vice President Mike Pence requesting “visibility” around the allocation of testing supplies, such as swabs, transport media and personal protective equipment (PPE), as well as the names and contact information of individuals in each state who are overseeing the allocation of supplies. They wrote that for planning purposes, laboratories need information in real time on availability of resources, reagents and supplies.
While pooled testing of samples can save on some of these supplies, it doesn’t eliminate the demand for others, such as swabs.
In May, the FDA held a virtual town hall to provide information and answer questions about 3D-printed swabs for COVID-19 diagnostic tests. A 3D-printed swab is also in clinical testing, with the company having the capability to produce 1,500 swabs in eight hours from one printer.