Dr. Tristan Timbrook, PharmD, Global Medical Scientist, BioFire Diagnostics

Bloodstream infections: The impact of syndromic testing on patient care and antimicrobial stewardship

The BioFire^® Blood Culture Identification 2 (BCID2) Panel tests for a comprehensive set of 43 targets associated with bloodstream infections, including gram-positive bacteria, gram-negative bacteria, yeast, and antibiotic resistance genes. Dr. Tristan Timbrook, lead author of a systematic review and meta-analysis on the impact of using such molecular rapid diagnostic tests, details the important role syndromic panels can play in antimicrobial stewardship programs.

Why should molecular rapid diagnostic tests (mRDTs) be the standard of care for patients with bloodstream infections?

Ultimately, it’s the right thing to do for patient care. Diagnostic tests improve clinical decision-making by giving a more informed clinical picture of the patient. Better-informed decisions translate into improved clinical outcomes. Rapid diagnostics are particularly helpful because they make that extra information available much faster—24 to 72 hours earlier.

An excellent example of the BioFire® FilmArray^® Blood Culture Identification (BCID) Panel’s ability to rapidly identify organisms and their resistance characteristics is in the detection of vancomycin-resistant enterococci (VRE). I worked on a meta-analysis that found a huge impact in time to effective therapy—it was greater than 24 hours difference in time to effective therapy for VRE cases with mRDTs versus conventional testing. Rapid diagnostic tests really impact that because it’s not something that we typically empirically cover for.

We also saw a two-and-a-half-day decrease in length of stay based on the use of rapid diagnostics. In the US, there’s an average $2,000 bed-day cost, so that’s $5,000 per patient. If you’re able to get somebody on effective therapy more quickly, you’re able to get them clinically stable sooner, which leads to them being able to get out of the hospital and get well sooner.

What are important considerations when implementing a rapid diagnostic test, and why might this lead to choosing a syndromic panel?

Patient population is huge when you’re considering implementing a rapid diagnostic test. To use the same example, in a population with increased incidence of VRE, you’ll definitely see more of a clinical impact because you are able to get patients on effective therapy so much sooner, and in an ICU that really makes a larger difference, because immune systems are so fragile.

Lab capability and lab hours are also important. Not all microbiology labs run 24 hours, particularly in smaller facilities. The BioFire BCID Panel is straightforward enough that often you don’t need somebody trained in microbiology. The chemistry portion of the lab department can run those overnight if they don’t have a 24-hour lab. With other methods you can’t do that unless you have somebody that’s trained to run that technology. That definitely impacts decision-making around implementation strategies, and it can save money over time.

How does the comprehensive, syndromic approach of the BioFire BCID Panel over a Gram stain-directed approach impact clinical operations?

As a clinician doing antimicrobial stewardship and patient care, you start to develop a healthy appreciation that Gram stains are helpful, but they’re not foolproof. There’s a lot of variability when you do repeat Gram stains. It’s an art, and with that, if you have direct detection of genes and organisms, it doesn’t really make sense to direct your panel based off of a Gram stain.

It’s not just a conceptual thing. We’ve actually seen this. During my residency training, I ran across this within a week of starting with the BioFire product. We only saw gram-positive cocci in clusters on the Gram stain, but the BioFire BCID Panel detected six organisms and multiple resistance mechanisms. This was a cystic fibrosis patient that had a central line, was in the ICU and was very sick, and we were able to really streamline their therapy because of what the panel found.

Then using the panel as a guide for a second review of the Gram stain with high-power fields, we were actually able to see yeast elements and gram-positive cocci in chains. With further workup of that culture, we were able to isolate all of those organisms and phenotypically confirm the resistance markers that we saw on the BioFire BCID Panel as well. That really speaks to the fact that Gram stain-directed approaches for syndromic assays for bloodstream infections aren’t really optimal, because you’ll have situations with critically ill patients where you do inappropriate therapy for an extended period of time, probably 48 hours, before you actually find out that you made the wrong decision based off of a Gram stain. These technologies are game changers.

Bloodstream infections: The impact of syndromic testing on patient care and antimicrobial stewardship

Why should molecular rapid diagnostic tests (mRDTs) be the standard of care for patients with bloodstream infections?

What are important considerations when implementing a rapid diagnostic test, and why might this lead to choosing a syndromic panel?

How does the comprehensive, syndromic approach of the BioFire BCID Panel over a Gram stain-directed approach impact clinical operations?

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