August 1, 2015

Since its invention by Kary B. Mullis in 1985, the polymerase chain reaction (PCR) has become well established, even routine, in research laboratories. And now PCR is becoming more common in clinical applications, thanks to advances in genomics and the evolution of more sensitive quantitative PCR methodologies.

Examples of clinical applications of PCR include point-of-care (POC) molecular tests for bacterial and viral detection, as well as mutation detection in liquid or tumor biopsies for patient stratification and treatment monitoring.

Industry leaders recently participated in a CHI conference that was held in San Francisco. This conference—PCR for Molecular Medicine—encompassed research and clinical perspectives and emphasized advanced techniques and tools for effective disease diagnosis.

To kick off the event, speakers shared their views on POC molecular tests. These tests, the speakers insisted, can provide significant value to healthcare only if they support timely decision making.

Clinic-ready PCR platforms need to combine speed, ease of use, and accuracy. One such platform, the cobas Liat (“laboratory in a tube”), is manufactured by Roche Molecular Systems. The system employs nucleic acid purification and state-of-art PCR-based assay chemistry to enable POC sites to rapidly provide lab-quality results.

The cobas Liat Strep A Assay detects Streptococcus pyogenes (group A β-hemolytic streptococcus) DNA by targeting a segment of the S. pyogenes genome. The operator transfers an aliquot of a throat swab sample in Amies medium into a cobas Liat Strep A Assay tube, scans the relevant tube and sample identification barcodes, and then inserts the tube into the analyzer for automated processing and result interpretation. No other operator intervention or interpretation is required. Results are ready in approximately 15 minutes.

According to Shuqi Chen, Ph.D., vp of Point-of-Care R&D at Roche Molecular Systems, clinical studies of the cobas Liat Strep A Assay demonstrated 97.7% sensitivity when the test was used at CLIA-waived, intended-use sites, such as physicians’ offices. In comparison, rapid antigen tests and diagnostic culture have sensitivities of 70% and 81%, respectively (according to a 2009 study Tanz et al. in Pediatrics).

The cobas Liat assay preserved the same ease-of-use and rapid turnaround as the rapid antigen tests. It addition, it provided significantly faster turnaround than the lab-based culture test, which can take 24–48 hours.

A CLIA waiver was announced for the cobas Liat Strep A assay in May 2015. CLIA wavers have been submitted for cobas Liat flu assays, and Roche intends to extend the assay menu.

POC tests are also moving into field applications. Coyote Bioscience has developed a novel method for one-step gene testing without nucleic acid extraction that can be as fast as 10 minutes from blood sample to result. Their portable devices for molecular diagnostics can be used as genetic biosensors to bring complex clinical testing directly to the patient.

“Instead of sequential steps, reactions happen in parallel, significantly reducing analysis time. Buffer, enzyme, and temperature profiles are optimized to maximize sensitivity,” explained Sabrina Li, CEO, Coyote Bioscience. “Both RNA and DNA can be analyzed simultaneously from a drop of blood in the same reaction.”

The first-generation Mini-8 system was used for Ebola detection in Africa where close to 600 samples were tested with 98.8% sensitivity. Recently in China, the Mini-8 system was applied in hospitals and small community clinics for hepatitis B and C and Bunia virus detection. The second-generation InstantGene system is currently being tested internally with clinical samples.