I only knew about the same amount that was posted above, but I did
find one thing in a quick search which seemed promising:<br>
<br>
From wikipedia:<br>
"There are a number of causes of <a href=
"http://en.wikipedia.org/wiki/Hyperphenylalaninemia" title=
"Hyperphenylalaninemia">hyperphenylalaninemia</a>, and less than
10% of the positive results obtained by the screening program are
confirmed as due to phenylketonuria (PKU). There are other
metabolic diseases that can produce hyperphenylalaninemia, but <a
href="http://en.wikipedia.org/wiki/Type_I_and_type_II_errors"
title="Type I and type II errors">false positive</a> results can
also occur due to unexplained mild, transient elevations, <a href=
"http://en.wikipedia.org/wiki/Prematurity" title=
"Prematurity">prematurity</a>, <a href=
"http://en.wikipedia.org/wiki/Parenteral_nutrition" title=
"Parenteral nutrition">parenteral nutrition</a>, or contamination
of the filter paper specimen."<br>
<br>
I found the same thing at webmd with most positives being
false-positives. From a study released this summer based out
of Children's Hospital Boston, they found that "For every true
disorder diagnosed, research suggests there are 12 or more false
positives".<br>
<br>
Ways to get a false positive:<br>
A false positive elevated phe concentration (hyperphenylalaninemia)
may result from:
<ul>
<li>a blood spot that is too thick (when using Guthrie test)</li>
<li>a sample that is improperly prepared</li>
<li>combinations of the following: liver immaturity, protein
overload (in newborns who are fed cow's milk), and heterozygosity
for phenylalanine hydroxylase deficiency.</li>
</ul>
<br>
<br>
In addition to the completely false positives, there are also cases
where the elevated phenylalanine is a product of something other
than PKU.
<br>
<br>
Since the probability of a positive pku gutthrie heel stick being a
true positive is so low, I'm hoping that Abby's
"inconclusive" has even less chance... I did read that an
inconclusive result can just be a product of the child not
digesting and eating well at the time of the test.
REcommended that the infant be at least 72 hours before they
do the test.<br>
<br>
One last thought is that I found an article which provides some
good general explanations and analysis of why false positives
occur: http://www.medscape.com/viewarticle/504722_2 .<br>
<br>
Hope this might help somehow,<br>
<br>
Elizabeth<br>
