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False postives on rapid strep test?


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17 replies to this topic

#1 amyslp

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Posted 12 April 2010 - 06:34 PM

My daughter had a rapid strep test 2 weeks ago today. Positive on the rapid (the line was very faint, but the ped. said a line is a line, just like a pregnancy test). Here's the ironic part. HE expected the rapid to be negative, so while we waited a few minutes for the results of the rapid he prepared the other swab to be sent for culture. He sent for the culture anyhow (despite the positive rapid) b/c all the info was filled out. He tells me today that the culture was negative. Now my daughter just finished clindmycin this weekend and ironically began to present with scarletina rash on chest last night. It had been huge welt-like hives that triggered the strep test 2 weeks ago. She has had some mild PANDAS symptoms that she had last year at time of dx.

Anyone ever experience this. My ped wants me to ask on this forum. He says it is not typical to send a positive rapid out for culture b/c they are supposed to be accurate. Now he's questioning if all the rapids my daughter tested positive on last year would have been the same on culture. And if so, what does that mean? He's perplexed and is asking me to call the specialist about this. I know I always get my best info. here. So what do you think? Any similiar experiences?
Thanks,
Amy
Allison, age 8, dx. PANDAS at age 4 after 6 months of chronic strep infection and EBV
Jillian, age 5, dx. PANDAS at age 3 initially after impetigo.
Myself, my sisters, my father and my paternal grandmother all with symtoms consistent with PANDAS/OCD


#2 vickie

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Posted 12 April 2010 - 06:39 PM

Maybe he didn't get a good swab on the second swab for the culture. I'd trust the rapid.

Did her PANDAS behaviors improve at all while on the antibiotics?

#3 amyslp

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Posted 12 April 2010 - 06:50 PM

Maybe he didn't get a good swab on the second swab for the culture. I'd trust the rapid.

Did her PANDAS behaviors improve at all while on the antibiotics?



yes, PANDAS symptoms are gone. THe only thing is the new onset of the scarletina rash.
Allison, age 8, dx. PANDAS at age 4 after 6 months of chronic strep infection and EBV
Jillian, age 5, dx. PANDAS at age 3 initially after impetigo.
Myself, my sisters, my father and my paternal grandmother all with symtoms consistent with PANDAS/OCD

#4 peglem

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Posted 12 April 2010 - 06:55 PM

My guess would be that the swab was not done well enough, too.

-Peggy, mom to 19yo PANDAS daughter w/ onset probably in infancy. Manifests w/ severe autism symptoms and currently nonverbal.


#5 amyslp

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Posted 12 April 2010 - 07:07 PM

My guess would be that the swab was not done well enough, too.


So simple...it's probably that he didn't get a good swab. It's not like she sits there and just opens her mouth. After minutes of screaming, crying, covering her mouth with two hands, we lay her down on the table and he struggles to get the swabbing-I think she even kicked him. I wonder if that is why the rapid test appeared so faintly.
Allison, age 8, dx. PANDAS at age 4 after 6 months of chronic strep infection and EBV
Jillian, age 5, dx. PANDAS at age 3 initially after impetigo.
Myself, my sisters, my father and my paternal grandmother all with symtoms consistent with PANDAS/OCD

#6 vickie

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Posted 12 April 2010 - 07:28 PM

My son does the same. Screaming, kicking, where do they find the strength? One time it took something like 3 or 4 nurses AND my husband to hold him down to get a swab.

Edited by Vickie, 12 April 2010 - 07:28 PM.


#7 worriedmommy

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Posted 12 April 2010 - 09:22 PM

This exact same thing happened to my daughter last September. I had strep, and a week later my dd started showing signs of peri-anal strep. Her bottom was cultured and it came back positive. Before starting antibiotics they had me bring her back in to swab her throat b/c they were concerned she may be a carrier due to her recurrent peri-anal strep. They swabbed her throat with 2 swabs. Did one as a rapid, and sent the other out for culture. Unexpectedly, her rapid came up positive. This shocked all of us b/c she had no signs of strep throat. It is unclear why the other swab was sent for culture, as they don't do this when a rapid is positive, but it got sent for some reason. Two days later I got a call that the culture was negative. I asked how that could be since the rapid was positive, and the nurse could not explain it. At the time I didn't make a big deal about it since her peri-anal swab had been positive, so we had to finish the full course of antibiotics regardless of her throat.

I did a little bit of researh and could not find any information on rapid false positives. I even asked another specialist, and they said the only explanation would be that they mistakenly thought they saw a line. Doesn't make sense to me. Like the others that have posted, I think it's more likely that they didn't get a good swab on the one that was sent to culture. My dd HATES throat swabs, and that particular time I had to pry her mouth open, during which time she bit me so hard that my thumb bled!!!




Her peri-anal swab came bac

My daughter had a rapid strep test 2 weeks ago today. Positive on the rapid (the line was very faint, but the ped. said a line is a line, just like a pregnancy test). Here's the ironic part. HE expected the rapid to be negative, so while we waited a few minutes for the results of the rapid he prepared the other swab to be sent for culture. He sent for the culture anyhow (despite the positive rapid) b/c all the info was filled out. He tells me today that the culture was negative. Now my daughter just finished clindmycin this weekend and ironically began to present with scarletina rash on chest last night. It had been huge welt-like hives that triggered the strep test 2 weeks ago. She has had some mild PANDAS symptoms that she had last year at time of dx.

Anyone ever experience this. My ped wants me to ask on this forum. He says it is not typical to send a positive rapid out for culture b/c they are supposed to be accurate. Now he's questioning if all the rapids my daughter tested positive on last year would have been the same on culture. And if so, what does that mean? He's perplexed and is asking me to call the specialist about this. I know I always get my best info. here. So what do you think? Any similiar experiences?
Thanks,
Amy



#8 peglem

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Posted 12 April 2010 - 09:28 PM

Before starting antibiotics they had me bring her back in to swab her throat b/c they were concerned she may be a carrier due to her recurrent peri-anal strep.


I'm wondering how they would use that to determine if she was a carrier? And, what did they decide about carrier status for her?

-Peggy, mom to 19yo PANDAS daughter w/ onset probably in infancy. Manifests w/ severe autism symptoms and currently nonverbal.


#9 worriedmommy

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Posted 12 April 2010 - 09:41 PM

Before starting antibiotics they had me bring her back in to swab her throat b/c they were concerned she may be a carrier due to her recurrent peri-anal strep.


I'm wondering how they would use that to determine if she was a carrier? And, what did they decide about carrier status for her?


The doctor told me that if dd was a strep carrier that she would ALWAYS come out positive on a throat culture. Since dd kept getting peri-anal strep, I kept getting strep throat and my son had just had his 3rd case of strep throat (by age 3) and twice didn't show symptoms, they figured someone in the family was a carrier.

My husband, son, daughter and I were all swabbed at the time, and only dd's rapid came up positive. Then when her culture came up negative, they couldn't figure out what happened. They decided to swab both her throat and bottom again after the course of abx, and both were negative...so they told us that she was not a carrier.

Recently I've seen posts saying that ASO and DNase-B tests are the best way to determine a carrier, and I'm seriously considering brining everyone in for that.

#10 peglem

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Posted 12 April 2010 - 10:03 PM

Before starting antibiotics they had me bring her back in to swab her throat b/c they were concerned she may be a carrier due to her recurrent peri-anal strep.


I'm wondering how they would use that to determine if she was a carrier? And, what did they decide about carrier status for her?


The doctor told me that if dd was a strep carrier that she would ALWAYS come out positive on a throat culture. Since dd kept getting peri-anal strep, I kept getting strep throat and my son had just had his 3rd case of strep throat (by age 3) and twice didn't show symptoms, they figured someone in the family was a carrier.

My husband, son, daughter and I were all swabbed at the time, and only dd's rapid came up positive. Then when her culture came up negative, they couldn't figure out what happened. They decided to swab both her throat and bottom again after the course of abx, and both were negative...so they told us that she was not a carrier.

Recently I've seen posts saying that ASO and DNase-B tests are the best way to determine a carrier, and I'm seriously considering brining everyone in for that.


Thanks for that! My daughter (who we believe is or was a carrier- I will not take her off abx to find out) tested neg for strep sometimes. All the specialists seemed to think she was a carrier because she tested positive while she was asymptomatic. She never got an "infection" by the time I actually got them to test for strep, but she tested positive whenever she wasn't on abx (and a few times when she was). Titers were always low-

-Peggy, mom to 19yo PANDAS daughter w/ onset probably in infancy. Manifests w/ severe autism symptoms and currently nonverbal.


#11 Stephanie2

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Posted 12 April 2010 - 10:07 PM

My allergist does not do rapid throat cultures in his office for this very reason. He told me that rapid cultures CAN be false positive. I did not believe him as I thought he was trying to be devil's advocate about whether or not my son really had pandas. Anyway, I did a google search and I did read that 5% of the time strep can be false positive on a rapid. I don't remember the reason and I don't remember the site(s) where I read this.

FWIW,
Stephanie
Stephanie
Holistic Healthcare Consultant, specializing in pediatric illness


Currently training to become a Homeopath.

Two boys with formerly severe PANDAS/ASD. Both fully recovered with homeopathic remedies and a handful of supplements.

#12 peglem

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Posted 12 April 2010 - 10:10 PM

My allergist does not do rapid throat cultures in his office for this very reason. He told me that rapid cultures CAN be false positive. I did not believe him as I thought he was trying to be devil's advocate about whether or not my son really had pandas. Anyway, I did a google search and I did read that 5% of the time strep can be false positive on a rapid. I don't remember the reason and I don't remember the site(s) where I read this.

FWIW,
Stephanie

But I wonder if they consider carriers as false positive, since they don't actually have an infection? I just don't see how the test could detect strep that isn't there?

-Peggy, mom to 19yo PANDAS daughter w/ onset probably in infancy. Manifests w/ severe autism symptoms and currently nonverbal.


#13 worriedmommy

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Posted 12 April 2010 - 10:11 PM

My allergist does not do rapid throat cultures in his office for this very reason. He told me that rapid cultures CAN be false positive. I did not believe him as I thought he was trying to be devil's advocate about whether or not my son really had pandas. Anyway, I did a google search and I did read that 5% of the time strep can be false positive on a rapid. I don't remember the reason and I don't remember the site(s) where I read this.

FWIW,
Stephanie


Interesting...I wonder what the cause of the false positive is?

#14 vickie

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Posted 13 April 2010 - 06:54 AM

I was googling about his last night. All I saw for false positives was the suggestion that the person recently had a strep infection that was erradicated and even though the antibiotics killed the strep, there was some left on the back of the throat still and that gave a false +. But then I read somewhere else where that theory was disproven.

#15 colleenrn

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Posted 13 April 2010 - 09:32 AM

This just happened to us. The rapid on my three year old came back positive, but the culture came back negative. The reason it happened in our case is that the nurse took two swabs and swabbed them both at the same time. The culture swab obviously did not get a good sample. Just FYI- it is best if they do each swab separately (not two swabs to do a rapid and a culture) and make sure they get a good sample from both tonsils.

When you get a faint line on a rapid test, it is still positive. It is like with a pregnancy test, if you do it really early in the pregnancy you can get just a very faint line, but still positive. I think that people reading the rapid tests sometimes do not wait long enough or scutinize it enough and if they did they would see a faint line. Years ago I knew my child had strep and the NP belived me. When she read the rapid she saw the faintest line and commented that many nurses would have mistakingly interpreted that as a negative.

Colleen




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