The latest bottleneck to rolling out diagnostic testing for COVID-19 has been a shortage of tools and equipment needed to collect and transport samples. Manufacturers of swabs and transport media say that this is likely to be a short-lived shortage, however, as they have already ramped up manufacturing.
Although lowly nasopharyngeal swabs are rarely in the spotlight, they became a hot topic this week when some hospitals began reporting back orders from their primary suppliers. Likewise, specially designed commercial transport media was reportedly becoming hard to procure.
The market for NP swabs and transport media is dominated by Becton Dickinson, Copan Diagnostics, Puritan Medical Products, and Thermo Fisher Scientific. Other companies, like Lucence and Longhorn Vaccines and Diagnostics, also make special sample collection media that could potentially be used in the COVID-19 crisis.
NP swabs are not the ordinary Q-tip. They have extra-long, flexible, thin shafts, to reach far into the nose, and they are manufactured in a such a way to reduce the likelihood of contaminating nucleic acids that might interfere with testing.
There are now seven molecular diagnostic tests for COVID-19 and they have varying requirements for swabs and transport media.
For example, DiaSorin's product information for its EUA Simplexa COVID-19 Direct Test specifies that the acceptable specimen type is nasopharyngeal swabs in approximately 3 mL of Copan Universal Transport Media (UTM) or BD Viral Transport Media (VTM), "or equivalent." In terms of swabs, the information does not specify a manufacturer, only that swabs have a synthetic tip, for example, made with Dacron, nylon, or rayon, as well as an aluminum or plastic shaft. The instructions note that calcium alginate swabs—which are typically used to obtain samples for bacterial culture—may contain substances that inhibit PCR testing and should not be used.
Hologic's instructions for the Panther Fusion test recommend a polyester-, rayon-, or nylon-tipped swab, and state that the test has been verified with Copan UTM, BD VTM, and also certain formulations of a transport media from Remel MicroTest.
Roche's Cobas test meanwhile specifies nasopharyngeal and oropharyngeal swab samples collected in a Copan UTM-RT System (UTM-RT) or BD Universal Viral Transport System (UVT), which are essentially kits that contain the transport media in a tube as well as the swab.
The Quidel Lyra assay does not constrain the swab manufacturer, but requires viral transport media to be certain formulations of Remel MicroTest or Copan's UTM.
The test information for the Abbott RealTime test directs users to Centers for Disease Control and Prevention guidelines for specimen collection, which were updated to adjust for the shortages. The CDC guidelines now say that an oropharyngeal swab is an acceptable specimen type if NP swabs are not available. They also note that standard operating procedure for public health labs is to create their own viral transport media in accordance with CDC's protocols.
Quest Diagnostics, meanwhile, guides users of its lab-based testing to use its "V-C-M transport medium or other comparable transport medium," as well as CDC-guided sample collection methods.