Just in Time Bacteria Testing

There’s little as heartbreaking as learning that a patient’s death was a result of bacterially contaminated platelets, but it’s the second most common cause of fatalities in transfusion.

According to the CDC, bacterial contamination of platelets is the greatest transfusion-transmitted infectious risk in the U.S. and is significantly higher than the risk of transfusion-transmitted viral infection. Approximately 1 in 1,000-3,000 platelet units may be contaminated with bacteria. Transfusion-transmitted sepsis has been recognized and culture-confirmed in at least 1 of 100,000 recipients, and has led to immediate fatal outcome in 1 in 500,000 recipients. The actual risk of transfusion-associated sepsis is likely higher, as infections due to contaminated blood products are under-reported.

“Patients requiring platelet transfusion are the sickest of the sick,” said Richard Pinkowitz, PhD, vice president of Immunetics. “Patients who’ve suffered a severe trauma, surgery or cancer are already immune compromised. They’re already undergoing severe treatment. To potentially infuse bacterially contaminated platelets exacerbates the risks.”

There’s no test on the market that can guarantee detection of contaminated platelets, but Immunetics just released its newest version, which promises to capture the information as close to the transfusion as possible and hopefully halt a fatal problem in its tracks. The goal is to interdict contaminated platelet units from transfusion.

Early Detection
The BacTx Analyzer, intended for use with Immunetics’ BacTx rapid test for bacteria in whole-blood derived and apheresis platelets offers automated interpretation, tracking, and documentation — features that not only increase transfusion patient safety, but also integrate seamlessly with the laboratory workplace.

The BacTx assay gives hospitals and blood banks a practical tool for assuring the safety of their platelets. The colorimetric assay can detect aerobic, anaerobic, Gram-negative and Gram-positive bacteria in a single test. The test is designed to enable testing closer to time of transfusion, to reduce the risk of transfusing contaminated platelets.

“We’ve taken advantage of the fact that bacteria will be growing,” said Pinkowitz. “Rather than testing platelets early in the cycle with a sensitive culture, we test just prior to the transfusion where the actual count will be measured. BacTx gives real-time results on bacterial presence — which the culture which doesn’t. BacTx is more representative of what’s actually being transfused.”

Complete assay results and analysis are delivered within 30 minutes. Control and standard assay capabilities allow for testing flexibility. A positive or negative result is determined via a color change. If bacteria are present, a color forms, indicating that the platelet unit should be removed from transfusion.

One display shows the immediate as well as final results.

The FDA allows results to hold for 24 hours. Traditionally, bacterial cultures started the day after platelet collection are apparent within 8-24 hours for rapid growers and 3-5 days for slow growers. But most research says the culture method is less than 40% effective.

Features of the updated BacTx Analyzer include:

  • Objective, automated assay reading and result interpretation
  • Permanent electronic record of test result matched to platelet unit tested that can be downloaded for documentation purposes
  • Efficient sample preparation;
  • Bar code scanning capturing patient identification numbers, donor number, and type of material captured in a 16-code format;
  • Random access testing that allows multiple assays to be run at different times;
  • LED touch screen to simplify operation;
  • Logical workflow to accelerate users’ learning curves;
  • Passcode and user ID entry that adds security during testing;
  • Visual confirmation on both the analyzer and touch screen for best-practice quality control (QC), tracking, and platelet management;
  • Automated tracking of tests, trends, and QC;
  • USB port for quick and easy download of data
  • Small footprint for crowded, cramped lab space.

The BacTx system utilizes a patented, highly specific, universal bacterial detection reagent that has been shown to detect wild and cultured bacterial strains. The assay meets AABB standard and can be used for quality-control testing of:

  • Leukocyte-reduced apheresis platelets (LRAP) following testing with an FDA-cleared growth-based bacterial detection device.
  • Pools of up to six units of leukocyte-reduced whole-blood derived platelets that are pooled within 4 hours of transfusion.

Users, typically at high volume cancer centers or tertiary care centers and blood banks, undergo a half day proficiency program where they test blinded samples before certifying as a specialist.

“Hospitals may be transfusing platelets on Day 4 and 5 and the only contamination data they have is from Day 1. Understandably, there’s a lack of confidence. Hospitals now have ability to test prior to transfusion on day 4 or 5 and this offers greater assurance that they’ve not created a risk for patients,” concluded Pinkowitz.

Robin Hocevar is on staff at ADVANCE. Contact her at rhocevar@advanceweb.com

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