Performance profile of an updated safety measure rapid assay for bacteria in platelets

Abstract

Background: The Verax PGD rapid test for bacteria in platelets (PLTs) has been updated to simplify workflow and improve specificity and sensitivity by employing a novel sequential format. The performance of this updated version, called PGDprime, was evaluated to determine its suitability for use as an FDAcleared "safety measure" to supplant the current PGD test. Study design and methods: Three consecutive cGMP-manufactured lots of PGDprime were evaluated for specificity (at three separate sites), sensitivity, reproducibility, interfering substances, assay robustness, and detection in analytical growth and ultralow-inoculum growth studies. PGDprime's performance was compared to that of PGD. Results: Specificity studies yielded no false-positive results among 3802 individual indate PLTs of seven different types (observed specificity, 100%). PGDprime detected all 10 PGD claim bacteria at the same limit of detection or better. Wildtype Gram-negative bacteria growing in PLTs were detected at earlier elapsed times than PGD by 12 to 30 hours. In growth studies, PGDprime detected bacteria growing in PLTs within the same 12-hour interval as PGD or 12 to 48 hours earlier. Assay reproducibility was not affected by operator, day of test, or manufacturing lot. PGDprime tolerated a wide variation in volume transfers, timing, temperature, and relative humidity and was not affected by 15 of 16 potential interferents found in samples at extremely high or low levels. Conclusion: The PGD test has been successfully updated to PGDprime with an innovative sequential assay format to deliver a robust simplified workflow and improved specificity and sensitivity.

Evaluation of an improved rapid bacterial assay with untreated and pathogen‐reduced platelets: Detection of Acinetobacter strains

“…Separate studies not covered in this report show that the very high level of specificity of PGD prime 12 (no repeat reactive or false positive result in 3800 confirmed negative non‐PR platelet units of various types) has not been compromised by the inclusion of the new antibody. In new specificity studies of the updated test with the Acinetobacter antibody, no repeat reactive (false positive) results were observed in 1100 non‐PR platelet units.…”

Supplemental findings of the 2019 National Blood Collection and Utilization Survey

“…These findings suggest that additional adoption of bacterial risk mitigation methods may further prevent morbidity and mortality among transfusion recipients in the United States. Some recent encouraging steps have occurred including the introduction of a more sensitive and efficient rapid immunoassay and planned expanded adoption of PRT for apheresis PLT in the United States 38–41 …”

Bacterial Contamination of Platelet Products

“…In an earlier study using the original PGD Test, the test detected bacterial contamination in 9 of 27,620 platelet doses (326 per million) released as negative by primary culture [ 37 ]. The specificity of the PGD prime Test in a study of 3800 platelet components of all US platelet product types (except pathogen-reduced) showed no false-positives (100% specificity, with a lower 1-sided 95% confidence limit of 99.9%) [ 38 ]. Use of the test to extend storage from 5 to 7 days has been demonstrated to significantly reduce outdating, with more than 1.4 million PGD devices shipped to users to date without any fatal septic reactions resulting from the transfusion of a PGD-negative platelet product.…”