IDEXX SARS-CoV-2 (COVID-19) RealPCR Test

Validation and cross-specificity studies

IDEXX Reference Laboratories developed a novel real-time PCR test to detect SARS-CoV-2 (COVID-19) based on a unique alignment to the published genetic sequences of the virus from the human outbreak. The IDEXX SARS-CoV-2 (COVID-19) RealPCR Test met all analytic and clinical validation requirements. Specificity studies showed no cross-reactivity with the new PCR test against common veterinary coronaviruses affecting companion animals. Likewise, currently available RealPCR tests for these veterinary coronaviruses were demonstrated to not detect synthetic COVID-19 nucleic acid. Clinical validation included successful completion of proficiency testing, resulting in external quality-control assurance certification through the European group, INSTAND e.V. The IDEXX test demonstrated 100% sensitivity and specificity on the specimens included in the proficiency testing. IDEXX RealPCR tests are designed on a standarized real-time PCR platform. Initial validation was performed in the West Sacramento, California, molecular diagnostics (PCR) laboratory. Canine, feline, and equine specimens were screened with the new IDEXX SARS-CoV-2 (COVID-19) RealPCR Test. Over 3,500 patient specimens were submitted over a four-week period from February 14–March 12, 2020. The specimens used for test development and validation were obtained from specimens submitted to IDEXX Reference Laboratories for respiratory PCR panels. The specimens originated from the United States and South Korea, and included specimens from regions, such as the Seattle area, that were experiencing significant human COVID-19 cases. Specimens were also tested in parallel with three assays from the Centers for Disease Control and Prevention (CDC). In mid-March, IDEXX expanded monitoring to Canada and European countries, including areas with high rates of COVID-19 in the human population. By mid-April, over 6,000 specimens had been tested for the SARS-CoV-2 virus. All specimens tested negative.

Screening methodology

Specimens were selected at random from specimens submitted to IDEXX Reference Laboratories for IDEXX RealPCR canine respiratory, feline respiratory, canine diarrhea, and equine diarrhea panels. Initial specimens used for screening included swabs (majority were deep pharyngeal [throat] and conjunctival [eye] swabs) and feces. Of the more than 3,500 specimens screened from February 14 to March 12:

• Specimens screened were from all 50 states and from South Korea.
• 55% of the specimens were from canine, 41% were from feline, 4% were from equine.
• 77% were respiratory, 23% were fecal.

In mid-March, IDEXX expanded monitoring to Canada and European countries, including areas with high rates of COVID-19 in the human population. By mid-April, over 6,000 specimens had been tested for the SARS-CoV-2 virus. All specimens tested negative. Surveillance was discontinued on April 17, 2020.

Quality controls

The following controls ran during the real-time PCR validation phase and screening:

• Negative extraction control (NEC): all negative extraction controls scored negative by PCR.
• Preanalytical specimen quality control using a real-time TaqMan® PCR assay for an endogenous control gene. All specimens, regardless of negative or positive character, passed the specimen quality control.
• PCR negative controls: all PCR-negative controls scored negative.
• PCR positive controls: all PCR-positive controls (synthetic-positive control) tested positive.
• Environmental contamination monitoring: all specimens from different location within the PCR laboratory tested negative on the contamination monitoring.