Molecular methods for diagnosing infectious diseases have become part of routine testing algorithms in clinical laboratories of all sizes. Laboratory and clinical personnel are enthusiastic about this because molecular testing provides higher sensitivity and specificity and, in most cases, a shorter turnaround time than traditional methodologies, wrote Elizabeth Palavecino, MD, in the April issue of CLN.

For example, while conventional culture and susceptibility testing may require 72 hours to produce results, multiplex PCR assays can do so in 1 to 3 hours after the blood culture is flagged as positive by the blood culture instrument. Benefits from this rapid testing will be realized if therapeutic decisions are made as soon as results are available; therefore, support from an antimicrobial stewardship team is paramount to achieve the goals of cost-effective testing and improved patient outcomes.

Based on the increased acceptance of these tests in clinical practice, manufacturers have developed a wide variety of options—both instruments and assays—from which laboratories can choose. The technology has evolved from manual to fully automated, closed systems that provide sample-to-result automation. To date, there are two Food and Drug Administration-cleared molecular blood culture panels: The FilmArray Blood Culture Identification panel manufactured by Biofire Diagnostics, and the Verigene blood culture test manufactured by Nanosphere. A sample from a positive blood culture bottle is tested on the corresponding system and all three reactions—sample preparation, amplification, and detection—are performed automatically by the instrument. The FilmArray assay is offered as a panel that detects gram negative, gram positive, and yeasts. The Verigene assay uses a separate detection panel for gram positive and gram negative, with the panel selected based on Gram stain results.

Evaluation of both of these panels has shown that they accurately identify most leading causes of bloodstream infections and provide results significantly faster than traditional methodologies, enabling clinicians to prescribe appropriate therapy much earlier.

Pick up the April issue of CLN to learn more about advantages and limitations of multiplex PCR assays.