Platelet testing using the verax system

[kim]

Has anyone tested there platelets using the Verax method to detect bacteria? We have just started it and we are encountering alot of false positives? Any suggestions?

[tjohnk1]

The previous hospital I worked at was part of the validation study for Verax. Our procedure was to repeat a false positive. If it was positive again, send it to culture. If it was negative, retest again and culture if positive that 3rd time. So basically, go with 2 out of 3. I don't know if that was from Verax or what our supervisor decided. Good luck!

[Liz]

This sounds discouraging. We use the culture and send them to the BactAlert. Very convenient. The Chair asked me to consider Verax. I believe I just have.

Thanks

Liz

[kim]

We have been having a few false Positives that have been very frustrating. The test is a bit tedious and you really have to keep an eye on your Plt inventory because the test is only good for 24hrs. The test takes about 45min for a batch of 6. I did not know if other hospitals use this testing system and if they did maybe they could shed some insight on getting less false Positives and invalid tests!!!!

[rcollins]

Is Verax FDA approved for randoms or only pheresis? Verax's literature says apheresis but the last CAP survey we got said it was cleared for use with single or pooled whole blood derived platelets. Please shed some light!

[hughes]

Kim,

are you testing every RDP in the pool, or just sampling the pool? Thanks

[mcharapata]

The Verax PGD test was originally cleared only for apheresis and later RDP. We perform the test at issue and typically once the device is loaded, have results within 30 minutes. We use a "mock" humidity chamber (wet papertowels with a plastic cover) because we found during our validation that testing took too long without it. We did have 2 months with a high percentage of false positives in December 2009 & January 2010, but when we switched out lots of the device, the number of reactives went down to the rate we observed prior to November (monthly range of 0.18% to 0.70%). We perform the test on pools (after they have been created) and if positive, test each individual platelet to narrow down which unit is causing the positive result. Positive pools are discarded and a sample of the pool is sent for BacT/Alert. We do not use the device to test apheresis platelets, but rely solely on the BacT/Alert result.

The manufacturer indicates the device should be read within a short time frame after the validity marks change color. We have had some occasions were tests were negative at this point, but when checked 10-15 mins later (against manufacturer instructions/recommendations) appeared positive. Verax was able to explain the reason for this to me, but I don't recall the reason at the moment. Our SOPs are setup with instructions to read and discard immediately to prevent potential mis-interpretation of the result.