TANGO false positive results due to carry-over

[Susan Betler]

Has anyone, using the TANGO, experienced "carry-over" to another patient from strong positive antibody screen?

Today, we have 2 patient samples running consecutively on the TANGO. Both samples gave similar results with the antibody screen---Screen I and II positive (3-4+), Screen III-negative. First sample tested is 92yo female who is O Negative. The second patient is 19yo pregnant female who is O Positive. The 92yo female's antibody ID panel (I-8) appears to be anti-D + anti-C. The 19 year old was just at another facility on 7/30/15 and results were O Rh Positive with a negative antibody screen using gel.

We purposely run our solidscreen controls to detect carry-over and have never had false positive results with the controls? I have looked at the troubleshooting guide......

Any comments??

Thanks

[tbostock]

Yes, we have seen sporadic carryover, but only with a very strong Anti-D.

[SCinSC]

We've had it happen 4 times in the last 2 years.  Always with a strong Rh system antibody.  One of the samples was a CAP PT sample.  Haven't figured out why it happens now when it didn't happen the first 4-5 yrs we used the instrument.

[BankerGirl]

When I was looking at the new and improved Tango Optimo, the rep told me that the current Tango "has a known problem with carryover..." and they have fixed it with the new one.  Funny how they didn't mention that when they were trying to sell me the current analyzer.

[SMW]

This phenomenon has also been reported with infectious disease testing instruments, e.g. Hamilton automated pipetor.  In those cases it is also associated with a high titer/load of the previous sample, e.g., Hepatitis B carrier, and the pipetting device is “inoculating” the next sample with Hep B surface antigen.  It may also depend on how many “inoculations” the second sample receives and the order of sampling before testing positive.  As for the first 4-5 years, it may just be the right (or wrong!) sampling order and strength of the antibody, e.g. if weaker antibody in first sample you may just see nebulous reactions in the second sample rather than an identified antibody and not identified or recognized it as a potential carry-over issue. 

[Avid1234]

We have had our Tango for about 5 years and have seen this issue a few times. It is a known issue and the FDA approved the instrument without making them fix it. First time was with a CAP sample. We have made it a policy that when we get back to back positive antibody screens on the same strip, we have to rerun the second patient. We had a case where the specimen of the second position patient was actually contaminated with antibody from the first patient and carried over into the third patient. The first patient had 3 antibodies and an anti-D titer of 8092! We know the second specimen was contaminated because when repeated it was still positive. When we tested the CBC specimen it was negative. The third patient was negative on the repeat.

And I still love my Tango.

 

JL

[tbostock]

I still love my Tango too!