Molecular Diagnostics Laboratory
The University of Denver Molecular Diagnostics Laboratory (MDL) provides high-quality, highly specific and highly accurate public health laboratory services for the University, the City and County of Denver, and the State of Colorado.
Under the leadership of Professor Phil Danielson and Lead Scientist Vicente Contreras, the MDL has developed saliva-based testing capabilities for every strain and variant of SARS-CoV-2 as well as a host of other viral communicable diseases including influenza. Since January 2021, the MDL has processed more than half a million saliva samples, with an average turnaround time of less than 24 hours.
The MDL is proud to be accredited by the College of American Pathologists, which demonstrates that we meet their high standards for laboratories and rank among the top laboratories nationwide.
The MDL began by examining samples using a method called "direct from saliva." The saliva sample is placed directly into a polymerase chain reaction (PCR) and within hours you know the results of the test. However, when working with real-world samples — some containing things like leftover food and blood — many of the samples were failing, meaning they were unable to recover sufficient viral RNA that could then be tested. The MDL then began using an extraction-based approach where saliva is run through an automated process that neutralizes the chemicals that attack the RNA in saliva. We are now able to separate the “garbage” from the RNA in the samples providing a more accurate result.
Our data suggests that SARS-CoV-2 is detectable in extracted saliva PCR samples days before it is detectable in nasopharyngeal PCR samples. The overall concordance of the Spit Test to the comparator nasopharyngeal PCR test is 99.7% measured within 7,520 paired saliva and nasopharyngeal samples. Sensitivity of spit to nasopharyngeal was 94.4% and specificity of spit to nasopharyngeal sample was 99.8%. Our comparator test was the National Jewish Health RT-PCR nasopharyngeal evaluation for SARS-CoV-2. The MDL utilizes the TaqPath Combo Kit with a salivary sample instead of a nasopharyngeal sample and utilization of a Beckman Coulter extraction machine and RNAdvance for extraction. The Spit Test demonstrated 96.7% sensitivity, a specificity of ≈100%, and 98.3% total agreement. It provides for an improved limit of detection compared to similar tests.