Hello,

What is the FALSE POSITIVE rate in your donor center?

Thanks,

Monica

We went a whole year last year with out any positives but some how these last couple of months we've had 2 false positives. We 're not sure if when the heat starts up the vents above us start throwing unwanted contaminates in the air? We're just putting that crazy idea out there. Usually the years before last it averaged maybe one per year. Our draw itsn't too high with about an average of 7 platelet donors a day Monday through Saturday.

Edited October 26, 201014 yr by Gnapplec

We collect about 15,000 SD platelets per year and have approximately one false positive per week. True positives are in the range of 1-2 per year.

What are your procedures to show that it is indeed false positive?

Is it the sub culture? Or the type of organism?

Moreover how do you collect the initial sample for the Bact Alert?

Thanks

When the BacT Alert bottle is positive, we quarantine all of the products from the collection including RBCs and plasma, plate the contents of the bottle AND the platelet product that was positive. If none of the subcultures grow, we consider the initial result falsely positive.

We sample our platelets 24 hours after collection, taking 4 ml for aerobic and an additional 4 ml for anerobic culture. That process came out of the Passport study, designed to see if products could be held for seven rather than five days. (This study was stopped when the number of true positives at 7 days exceeded those positive at 5 day) The products are released 48 hours after collection if all results are negative, but the bottles are held until the expiration date/time of the product.

So you keep your platelets for 5 days?

Also when you sample, do you have the sampling site on your bags?

Thanks

Yes, platelets in the US expire 5 days after collection.

We sterile doc a sampling device to the platelets so they can be entered in a "closed" system.

Thanks, we have a pouch on the Trima or Hemonetics collection bag that we seal off and then have to enter in a sterile way with the needle and syringe. Very dangerous for the tech!!

Can you tell me the brand of the sampling device.

Thank you

I used to work at a large blood center where we used the BacT Alert. We were seeing creeping instrument false positives (IFP) where the bottle was called positive by the instrument but then the subculture from the bottle was negative and the unit in question recultured negative. If you have a copy of the AABB abstract book from Sept. 2009 it is number AP95 starting on the bottom of page 279A. We contacted bio Merieux and talked to a technical specialist who suggested that we look at the drift on the cells at a lowere level than what the instrument looks at in an alarm level. We went from a IFP of 0.16% down to 0.02% after doing this. contact me at caronson@northshore.org if you need more info.

Charter Medical makes the sampling device we sterile doc to our units.

Thank you Colleen A and Thank you Kip.

This is very useful information.

I am thinking of getting the Trima kits with the in-built sampling device, unless it is much more expensive, in that case I shall acquire the devices separately.

We sample at 24-36 hours but more often than not we need to release before. What is your opinion on this?

Thanks.

The goal for this type of sampling would be to interdict 100% of the contaminated units. However, the literature shows us that there are shortcomings with each available procedure for detecting platelet units contaminated with bacteria. There may be advantages to sampling the units twice. We have not detected the release of contaminated products using our procedure for platelet contamination QC though.

There was an article published last month from MD Anderson in which the effect of low level bacteria contamination in platelets was reviewed. Basically the result was that because of the concomitant administration of antibiotics to some recipients of platelets and functioning immune systems in others the effect of low levels of bacteria in products on the outcome of the transfusion was minimal. (I am out of town and cannot grab the reference for you at the moment). I think information like that must be balanced against our compulsive desire to do everything perfectly.

Our procedure has us using the Trima sampling kits that are in-line. A few years ago we would sterile doc on the transfer sets and find it much more effecient using the built-in sampler. We pull 9 mls off after 24-36 hours and incubate the 5 days in aeorbic only. We also did the anaerobic and aerobic 7 day study for a while but went back to 5 day quite a while ago. If a bottle comes up positive we send it and our platelet to a reference lab for a gram stain and culture. Usually there will be GPB species or something similar in the bottle but no organisms seen in the platelet product. When I say false pos. I mean there is actually contaminants in the bottle, just not the product itself. I can't think of an instance that the Bact machine called on positive that didn't have something actually in the bottle. Our SOP also allows us to now release our platelets at 18 hours instead of the old 24 hours. That extra 6 hours reallly helps us with distribution time and work flow. If a platelet did come up positive in that last 6 hours of the 24 the product is usually in transit and can be recalled no problem.

Gnapplec , this was very useful and sounds like ours except that I do store for 7 days. (Always useful when it sounds like mine ) And indeed false positive means that the only the bottle was pos and thus got contaminated during handling and sampling.

Does anyone have the reference that it is now back to 5 days storage?

Thanks