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Loren

yet another doctor's appt. (3rd one and counting)

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I hope this helps, sorry to hear about the tough week you are having...PLEASE NOTE: I have no idea why there are smiley faces in my post and I can't seem to get rid of them!

 

From the NIMH:

 

A. The anti-streptococcal antibody titer determines whether there is immunologic evidence of a previous strep. infection. Two different strep. tests are commercially available: the antistrepolysin O (ASO) titer, which rises 3-6 weeks after a strep. infection, and the antistreptococcal DNAase B (AntiDNAse-:mellow: titer, which rises 6-8 weeks after a strep. infection.

 

Q. What does an elevated anti-streptococcal antibody titer mean? Is this bad for my child?

 

A. An elevated anti-strep. titer (such as ASO or AntiDNAse-:wacko: means the child has had a strep. infection sometime within the past few months, and his body created antibodies to fight the strep. bacteria. Some children create lots of antibodies and have very high titers (up to 2,000), while others have more modest elevations. The height of the titer elevation doesn’t matter. Further, elevated titers are not a bad thing. They are measuring a normal, healthy response – the production of antibodies to fight off an infection. The antibodies stay in the body for some time after the infection is gone, but the amount of time that the antibodies persist varies greatly between different individuals. Some children have "positive" antibody titers for many months after a single infection.

 

Q. When is a strep. titer considered to be abnormal, or "elevated"?

 

A. The lab at NIH considers strep. titers between 0-400 to be normal. Other labs set the upper limit at 150 or 200. Since each lab measures titers in different ways, it is important to know the range used by the laboratory where the test was done – just ask where they draw the line between negative or positive titers.

 

It is important to note that some grade-school aged children have chronically "elevated" titers. These may actually be in the normal range for that child, as there is a lot of individual variability in titer values. Because of this variability, doctors will often draw a titer when the child is sick, or shortly thereafter, [i]and then draw another titer several weeks later to see if the titer is "rising" [/i]– if so, this is strong evidence that the illness was due to strep. (Of course, a less expensive way to make this determination is to take a throat culture at the time that the child is ill.)

 

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http://www.cmaj.ca/cgi/content/full/165/10/1353

 

We recommend evaluation of all children who present with the sudden onset or exacerbation of obsessive–compulsive symptoms, using the approach summarized in Fig. 1. This diagnostic algorithm, which is based on the literature summarized earlier as well as our clinical judgement, begins with a history-taking, mental status examination and focused physical examination. Initial investigations in children with a history suggestive of streptococcal infection or a strong family history of rheumatic fever, or both, should include throat cultures and antistreptolysin O titres. These titres should be repeated after an interval of approximately 3–4 weeks, because a correlation of symptom severity with changes in antibody levels is far more informative than an isolated antistreptolysin O titre. We recommend antistreptolysin O titre, because the other antistreptococcal test reported in the PANDAS literature, namely, antideoxyribonuclease-B (antiDNAse B), is expensive and not widely available in Canada.

 

As stated in this article a single blood test for strep can not rule out or actually dx PANDAS. Whether a level is rising or declining will give much more information. Some children do have chronically elevated strep antibody levels, what matters is the pattern...rising=a more recent infection...declining=recovery.

 

 

BLOOD TESTS

 

Streptozyme: Detection of multiple antibodies to extracellular antigens of streptococcus with streptozyme is of some diagnostic value but should never replace more standard tests such as streptolysin O antibody (ASO) or DNase-B antibody. These antibodies may be detected in patients after streptococcal pharyngitis, rheumatic fever, pyoderma, glomerulonephritis, and other related conditions. In evaluating a patient with suspected acute rheumatic fever or nephritis, determination of ASO, DNAse-B antibody, and streptozyme will likely yield a positive result in 92-98% of cases.

 

Streptolysin O Antibody (ASO): the ASO test is used to provide serologic evidence of previous group A streptococcal infection in patients suspected of having a non-suppurative complication, such as acute glomerulonephritis or acute rheumatic fever. Use of the ASO for diagnosis of an acute group A streptococcal infection is rarely indicated unless the patient has received antibiotics that would render the culture negative. An ASO performed on serum obtained during the presentation of a non-suppurative complication that shows a titer two dilutions above the upper limit of normal is evidence for an antecedent streptococcal infection. It is recommended, however, to use a second test such as the anti-DNase B to confirm antecedent infections. Elevated serum ASO titers are found in about 85% of individuals with rheumatic fever. When both ASO and anti-DNase B are used, the result is over 95%. Skin infections with group A streptococci are often associated with a poor ASO response.

 

Reference Interval:

0-1 year: 0-200 IU/ml

2-12 years: 0-240 IU/ml

>13 years: 0-330 IU/ml

 

DNase-B Antibody: The majority of group A streptococci produce significant quantities of DNase-B, while most other groups of streptococci do not. High levels of neutralizing antibody to DNase-B are commonly found in patients following a group A streptococcal infection. Since it persists longer than other streptococcal antibodies (2-3 months), it is the preferred test in patients with chorea suspected due to rheuamtic fever. Since it is not influenced by the site of infection, DNase-B antibody is more reliable than the ASO test in providing evidence for streptococcal infection in patients with post-impetigo glomerulonephritis. Elevated titers are strongly suggestive of recent or current infection with group A streptococci. Fourfold increases in itier between acute and convalescent samples taken approximately 2 weeks apart are confirmatory.

 

Reference Interval:

 

1-6 years: < 1:60

7-17 years: <1:170

18 years and over: <1:85

 

So these are the "tests" for PANDAS which are not actually tests confirming PANDAS but rather the presence of a streptococci infection in association with the onset of neuropsychiatirc symptoms in a child.

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