Positive rapid strep. negative culture

[peglem]

Allie's culture for strep (from Saturday's positive rapid) came back negative for strep. The only reason it was sent in was because they wanted a sensitivity test.

I know there was somebody here awhile ago who continually got rapid positives w/ negative cultures. Looking back, Allie has NEVER had a positive culture, even when she's been PANDAS symptomatic. The only time culture was ordered was when rapid was neg.

Her pediatrician suggested that it may be something cross reacting with the strep test (something has the same or a similar antigen that the tests looks for). So in researching, it seems that colonization w/ staph aureus may cause false positives on the rapid. I was wondering if the other person who was plagued with positive rapids/negative cultures ever got it figured out?

[Kayanne]

I'm going by memory, but I think it was nojo. I tried to pull up her content but for some reason I got an error.

 

Can they culture for that type of staph?

[peglem]

I'm going by memory, but I think it was nojo. I tried to pull up her content but for some reason I got an error.

 

Can they culture for that type of staph?

I think they can culture for a staph infection. Kinda funny, because all along, her pediatrician has been saying it looks like her skin is colonized by staph (underlayers- not on top). I'll try looking at nojo, maybe I can find something.

[Stephanie2]

I had this happen once with my 3yo, back in Sept. The rapid was a faint line. It was apparent by his sudden-onset, thought, that he definitely had something and Augmentin did a good job of pulling him out.

 

Our ped later explained why she felt that this happened but I can't remember what she said. Something about the strep being "dead cells" meaning that since he had been exposed to azith that week (his usual prophylactic dose), whatever grew back from that was only able to show up on the rapid. I know I am butchering this and I meant to post this on the forum that day to let people know.

 

The other thing is that we did once get staph aureus show up on my 6yo's culture. I am sorry, I don't know what type of culture was ordered but it was ordered a year ago by the local allergist. My 3yo had a staph infection of the skin at the same time. Also, my 3yo's culture came back with enterobacter species of some sort. What a mixed bag that was!

 

All this to say that I do indeed think you should consider this positive for strep. I'm not sure, though, how you will get the sensitivity test. Our recent sensitivitiy report indicated resistence to erythromycin, and they assumed resistence to azith based on that (same class), which would be a correct inference since azith had failed earlier that week.

[MIAS_MOM]

My dd's last rapid was positive, I requested it cultured just for documentation paper work since we are getting our Medical Records ready for review in another state, and the culture came back negitive ! I took her to the peds because she had very, very, painful sore throat, it was puss filled and swollen, had fever and all the clasic syptoms of strep, plus PANDAS flare up, I was shocked with the neg culture, the ped said to discontinue the antibiotic, HA, NO WAY !

[nojo]

Hi, that was our family, and no we never got that figured out. I kind of gave up on this issue, and I did consider us positive. The read on I considered my daughter positive is that she would sometimes test negative, so I do not consider her a carrier. We started culturing every positive rapid, and the culture was always negative. Most people do not culture positive rapid tests, so I've wondered if there are more with this problem.

 

Currently, we finished our 3rd ivig, and will be back for number 4 in about 2 weeks. She has not had a positive tests since we started in November, but I am not sure she has had a test. This is a record for us. She is now homeschooled to help keep her away from germs. She does have immune deffiency, and has a tendency to get really sick, so the ivig has really helped. She also was positive for Lyme. What bad luck, we had kept the tick and I remember when she got bitten. I personally think she started with immune deffiency, has the tendency for auto-immune issues from family history, and the constant bombardment of germs at school and then the tick bite, she couldn't fight anything. It is really rare to have a false positive on the rapid, but again, I don't think it was false, or carrier, she did have symptoms every time I took her in, albeit not typical symptoms. One other thought we had was she was not yet a full blown infection at that point, but colonized and so sensitive we could tell. When we first met with Dr. B. He told us that he had not heard of positive rapid/neg culture. That was back in September, and as you all know, we are all still trying to figure this out. What I can say for certain is that we have had this happen numerous times, I would have to look at my notes for the number of times. It was not an isolated fluke.

 

Let me know if you find out more. I have never been able to figure this out, and I think it is important. I will also asked Dr. B again during next ivig.

 

Noelle

[peglem]

Thanks. I'm so baffled right now! I'll let you know if we figure anything out.

[amyjoy]

I also wonder more and more about the accuracy of cultures. Cultures need extremely controlled environments to grow and incredibly controlled innoculation of perfectly stored media. I hate to say it but I see more and more issues in our office with lab test errors and, problems with cultures. For example one of the GI tests i like to use is by Metametrix and includes DNA screening to look at microbes that are growing, and if bact or fungus is detected they will then do a culture and sensitivity. At least half the time the sensitivity comes back blank with some thing about failure to detect growth on the medium. I called a couple of times and got a huge story about growing stuff on media how there has to be foolproof technique that is difficult. Not sure but if its always been difficult then why am I seeing more and more problems? Is it the level of employee they are trusting to run the tests? How do we know??

 

I also hate to say it but we get a number of oddities in Quest test results every week and i do question the competency of Quest specifically more and more, they have a strange corporate culture where the only people really dedicated to customer are the sales reps that come to our office. A number of times I've had patients leave Quest lab stations in tears after someone was rude. I don't know but it sure does make it more difficult to trust their results.

 

If overall there is a documented 2-3% false positive rate with rapid strep compared to throat cultures likely due to s aureas growth, how much more would we see due to just poor lab technique?

[amyjoy]

and p.s. - to really get a good strep culture in a throat swab in a child, you have to get to the area where it is growing. The child should not have eaten or drank anything within some period of time. To do this takes more than the half second that many nurses or medical assistents take because it really aggravates the child and makes them gag. So there is a whole other aspect to false neg cultures - obtaining a true specimen from the child.

Edited April 4, 2011 by amyjoy

[peglem]

Thanks, Amyjoy. It never occurred to me to question the culture being the false result. Its the "gold standard" after all!

 

I've been googling false positive rapid strep antigen tests and came across this abstract that says the test can cross react with streptococcus millieri: http://www.jstor.org/pss/30111175

[nojo]

Thank you both for the information. I am going to forward it to my husband ( he pores over all the medical articles), this has been bugging us for awhile. I think many never culture a positive rapid test. Our pediatrician started culturing all rapid tests because of the frequency that we had strep.

 

I just got out my records, and we have never cultured positive. We started culturing in September 2009 and I have at least 4 dated examples of positive rapid, negative cultures. In between, she would show that she was clear on both the rapid and culture. Every time we took her for a test she was having symptoms. Her main signs are urinary frequency, OCD, and rages when things are really bad. She did not test positive last summer when she had Scarlett fever (101 temp, rash, peeling palms and soles of feet). FYI she was on antibiotics when she got scarlett fever. I don't know if antibiotics can skew the results (it certainly did not work as prophlaxis, even on the full strength dose)

[Kbossman1]

I've been reading these threads.....hate I missed this conversation a couple of months ago...but did anyone ever figure out if they had the staph causing positive rapid, or decide if they had strep? My kids have done the same, positive rapid, negative culture. But then again we've had negative rapid, positive culture!? Who knows. Right now I'm concerned about pandas dd on zithromax and omnicef, with positive rapid. I did the rapid at home, and I can't decide if I take her to the dr...which one to go to, b/c we haven't found 1 dr to help us w/ pandas (in NC anyways)yet. Dr. B says that she is on enough mediation and it should take care of it. This is not the answer that I was expecting, so can I get an update on those who posted with children that had positive rapids on abx? Thanks!

[peglem]

Well, no staph grew out on culture for us. Two weeks ago we had another positive rapid, neg. culture, but the ped asked the lab to try to find out what kinds of bacteria were present in the sample. They said there was normal flora, but some bacteria they couldn't identify as well. So, now, the theory (according to ped) is that there is some other kind of strep that presents the antigen that the rapid test identifies. The rapid test works by identifying an antigen that is highly specific for GABHS, so a positive rapid doesn't happen unless that antigen is present on the swab. So, either there is another bacteria presenting a very similar antigen, or my daughter has constant GABHS that will not grow out in a petri dish.

 

I find it interesting that so many PANDAS kids are experiencing +rap/-cult. Maybe we have some kind of mutant pathogen!

[MojoLuvsAndy]

I found this thread by searching for false postives on the rapid strep tests. I know it has been awhile since this the last post but I thought I would give it a try. My 2 year old dd will be 3 on Aug. 25th, has had three positive rapid strep tests and three negative cultures. Before this discovery, my child had 7 positive rapid strep screens in a years time with no cultures and was placed on antibiotics. I am unaware of what PANDAS is? I have saw where some others have stated their children have Lyme disease. My child has had 3 tick bites in her head and the lymphnodes swelled in the back of her neck/head but she was never tested for Lyme. I didn't didn't know if this was a correlation or what. Just wanting to know what to do for my child. The discussion of surgery with the ENT has stopped with the negative cultures. She continues to get sick with sore throats and has stated that her lower back hurts but her urine tests come back fine. It is so frustrating as a parent. The only other medical history is she had chronic ear infections that stopped after tubes were placed and she had RSV in February of 2012, three days after being diagnosed with strep.

 

All help is appreciated!

**

[peglem]

I found this thread by searching for false postives on the rapid strep tests. I know it has been awhile since this the last post but I thought I would give it a try. My 2 year old dd will be 3 on Aug. 25th, has had three positive rapid strep tests and three negative cultures. Before this discovery, my child had 7 positive rapid strep screens in a years time with no cultures and was placed on antibiotics. I am unaware of what PANDAS is? I have saw where some others have stated their children have Lyme disease. My child has had 3 tick bites in her head and the lymphnodes swelled in the back of her neck/head but she was never tested for Lyme. I didn't didn't know if this was a correlation or what. Just wanting to know what to do for my child. The discussion of surgery with the ENT has stopped with the negative cultures. She continues to get sick with sore throats and has stated that her lower back hurts but her urine tests come back fine. It is so frustrating as a parent. The only other medical history is she had chronic ear infections that stopped after tubes were placed and she had RSV in February of 2012, three days after being diagnosed with strep.

 

All help is appreciated!

**

PANDAS stands for Pediatric Autoimmune Neuropsychiatric Disorder Associated w/ Strep. What that means is that some children make antibodies to strep that cross-react w/ neurons in the brain, producing obsessive compulsive symptoms and movement disorders like tics and chorea. You can find a lot of details/info/FAQs on the Helpful Threads thread pinned at the top of the forum. I would suggest if your child has chronic infections they get checked out by an immunologist.