If you ever test positive for CF is that a guarantee?

[Jeana]

<P>When I was tested for CF as an infant at two days old, I tested positive.  Then, two weeks later they retested and it was negative.  They said that you can have a false positive that young.  Then, when I was 16 months old, a sweat test confirmed it and I was finally diagnosed with CF.  Also, that doctor told my parents that there is never a false positive for CF.</P>
<P> </P>
<P>Roll the clock forward 33 years, and I have a friend whose daughter is having breathing/digestive issues.  Her daughter was tested for CF (PKU) and was positive.  A couple of weeks later, she was tested and it was negative.  </P>
<P> </P>
<P>So, here's my question.  Are there false positives when being tested for CF?</P>

 

[Jeana]

<P>When I was tested for CF as an infant at two days old, I tested positive. Then, two weeks later they retested and it was negative. They said that you can have a false positive that young. Then, when I was 16 months old, a sweat test confirmed it and I was finally diagnosed with CF. Also, that doctor told my parents that there is never a false positive for CF.</P>
<P></P>
<P>Roll the clock forward 33 years, and I have a friend whose daughter is having breathing/digestive issues. Her daughter was tested for CF (PKU) and was positive. A couple of weeks later, she was tested and it was negative. </P>
<P></P>
<P>So, here's my question. Are there false positives when being tested for CF?</P>

 

[Jeana]

<P>When I was tested for CF as an infant at two days old, I tested positive. Then, two weeks later they retested and it was negative. They said that you can have a false positive that young. Then, when I was 16 months old, a sweat test confirmed it and I was finally diagnosed with CF. Also, that doctor told my parents that there is never a false positive for CF.</P>
<P></P>
<P>Roll the clock forward 33 years, and I have a friend whose daughter is having breathing/digestive issues. Her daughter was tested for CF (PKU) and was positive. A couple of weeks later, she was tested and it was negative. </P>
<P></P>
<P>So, here's my question. Are there false positives when being tested for CF?<BR></P>

 

[Printer]

<P>Hi:</P>
<P> </P>
<P>About 8 years ago, Massachusetts passed a law requiring all newborns to he tested for CF (and several other diseases.  The CF Doctor that I had at that time (MGH CF Clinic),  said "the problem with the CF screening is that there are too many false posivites".  That is pretty much a direct quote as I remember it.</P>
<P> </P>
<P>Bill</P>

 

[Printer]

<P>Hi:</P>
<P></P>
<P>About 8 years ago, Massachusetts passed a law requiring all newborns to he tested for CF (and several other diseases. The CF Doctor that I had at that time (MGHCF Clinic), said"the problem with the CF screening is that there are too many false posivites". That is pretty much a direct quote as I remember it.</P>
<P></P>
<P>Bill</P>

 

[Printer]

<P><BR>Hi:</P>
<P></P>
<P>About 8 years ago, Massachusetts passed a law requiring all newborns to he tested for CF (and several other diseases. The CF Doctor that I had at that time (MGHCF Clinic), said"the problem with the CF screening is that there are too many false posivites". That is pretty much a direct quote as I remember it.</P>
<P></P>
<P>Bill</P>

 

[hmw]

It depends on what kind of test. The test done as part of the newborn screen- IRT levels- often has false positive and can also have false negative results. The majority of elevated IRT's are false positives, so sweat tests and genetic testing must be done on all elevated results to further rule cf in or out. Most elevated results turn out to be due to the baby being a carrier or having jaundice, although in some cases they never figure out why.
<br>
<br>Elevated IRT + elevated sweat test (30 for a baby) is rarely a false positive, although genetic testing is done next.
<br>Elevated IRT + genetic results showing 2 mutations is of course diagnostic, although sweat test is often done too.
<br>
<br>Elevated IRT + 1 found mutation on a panel is up for debate, since some newborn screens do IRT/DNA panel routinely. Before assuming the baby is merely a carrier they need a sweat test. If it's elevated they of course need something like Ambry testing. The question comes into play- do they need Ambry testing anyway even if sweat test is negative or is the assumption made that the test was elevated due to being a carrier? Do they wait for symptoms to show up before doing genetic sequencing? There doesn't seem to be a good consensus on that one.<br><br>efa> all 50 states now require CF testing to be part of the newborn screen. This does result in false positives, but has caught MANY babies that would otherwise go a long time without essential treatment, so it is a good, good thing.<br>

 

[hmw]

It depends on what kind of test. The test done as part of the newborn screen- IRT levels- often has false positive and can also have false negative results. The majority of elevated IRT's are false positives, so sweat tests and genetic testing must be done on all elevated results to further rule cf in or out. Most elevated results turn out to be due to the baby being a carrier or having jaundice, although in some cases they never figure out why.
<br>
<br>Elevated IRT + elevated sweat test (30 for a baby) is rarely a false positive, although genetic testing is done next.
<br>Elevated IRT + genetic results showing 2 mutations is of course diagnostic, although sweat test is often done too.
<br>
<br>Elevated IRT + 1 found mutation on a panel is up for debate, since some newborn screens do IRT/DNA panel routinely. Before assuming the baby is merely a carrier they need a sweat test. If it's elevated they of course need something like Ambry testing. The question comes into play- do they need Ambry testing anyway even if sweat test is negative or is the assumption made that the test was elevated due to being a carrier? Do they wait for symptoms to show up before doing genetic sequencing? There doesn't seem to be a good consensus on that one.<br><br>efa> all 50 states now require CF testing to be part of the newborn screen. This does result in false positives, but has caught MANY babies that would otherwise go a long time without essential treatment, so it is a good, good thing.<br>

 

[hmw]

It depends on what kind of test. The test done as part of the newborn screen- IRT levels- often has false positive and can also have false negative results. The majority of elevated IRT's are false positives, so sweat tests and genetic testing must be done on all elevated results to further rule cf in or out. Most elevated results turn out to be due to the baby being a carrier or having jaundice, although in some cases they never figure out why.
<br>
<br>Elevated IRT + elevated sweat test (30 for a baby) is rarely a false positive, although genetic testing is done next.
<br>Elevated IRT + genetic results showing 2 mutations is of course diagnostic, although sweat test is often done too.
<br>
<br>Elevated IRT + 1 found mutation on a panel is up for debate, since some newborn screens do IRT/DNA panel routinely. Before assuming the baby is merely a carrier they need a sweat test. If it's elevated they of course need something like Ambry testing. The question comes into play- do they need Ambry testing anyway even if sweat test is negative or is the assumption made that the test was elevated due to being a carrier? Do they wait for symptoms to show up before doing genetic sequencing? There doesn't seem to be a good consensus on that one.<br><br>efa> all 50 states now require CF testing to be part of the newborn screen. This does result in false positives, but has caught MANY babies that would otherwise go a long time without essential treatment, so it is a good, good thing.<br>

 

[Jeana]

Thanks, guys!  I will advise my friend that there are false positives, but that I would insist on further tests (sweat or genetic) to be sure.  <img src="i/expressions/face-icon-small-smile.gif" border="0">

 

[Jeana]

Thanks, guys! I will advise my friend that there are false positives, but that I would insist on further tests (sweat or genetic) to be sure. <img src="i/expressions/face-icon-small-smile.gif" border="0">

 

[Jeana]

<BR>Thanks, guys! I will advise my friend that there are false positives, but that I would insist on further tests (sweat or genetic) to be sure. <img src="i/expressions/face-icon-small-smile.gif" border="0">

 

[JennifersHope]

I am the epitomy of a false positive, I lived as a CFer for 10 years, and recently was undiagnosed last November. I have two CF genes, one is not described, Df508 and Q1330E, I have had many positive sweat tests, but also have Addison's disease which can cause false positives. I had a nasal PD in Nov that showed I have a normal working CFTR therefore I was undiagnosed,

I culture PA and Mrsa on and off but not in a few years. I have been on life support numerous numerous times for asthma, laryngeal spasms etc, We don't know exactly what is wrong with me... FUn times

 

[JennifersHope]

I am the epitomy of a false positive, I lived as a CFer for 10 years, and recently was undiagnosed last November. I have two CF genes, one is not described, Df508 and Q1330E, I have had many positive sweat tests, but also have Addison's disease which can cause false positives. I had a nasal PD in Nov that showed I have a normal working CFTR therefore I was undiagnosed,

I culture PA and Mrsa on and off but not in a few years. I have been on life support numerous numerous times for asthma, laryngeal spasms etc, We don't know exactly what is wrong with me... FUn times

 

[JennifersHope]

I am the epitomy of a false positive, I lived as a CFer for 10 years, and recently was undiagnosed last November. I have two CF genes, one is not described, Df508 and Q1330E, I have had many positive sweat tests, but also have Addison's disease which can cause false positives. I had a nasal PD in Nov that showed I have a normal working CFTR therefore I was undiagnosed,
<br />
<br />I culture PA and Mrsa on and off but not in a few years. I have been on life support numerous numerous times for asthma, laryngeal spasms etc, We don't know exactly what is wrong with me... FUn times

 

[ehtansky21]

the initial sweat test for my 7 year old was done at 3 months and it came out negative for CF, because they couldn't get enough sweat. 7 months later, they decided to try it again just to rule it out and then we got 2 definite positives. They say that infants may not sweat enough and thus you cannot get a definite reading.

blessings,
missa

 

[ehtansky21]

the initial sweat test for my 7 year old was done at 3 months and it came out negative for CF, because they couldn't get enough sweat. 7 months later, they decided to try it again just to rule it out and then we got 2 definite positives. They say that infants may not sweat enough and thus you cannot get a definite reading.

blessings,
missa

 

[ehtansky21]

the initial sweat test for my 7 year old was done at 3 months and it came out negative for CF, because they couldn't get enough sweat. 7 months later, they decided to try it again just to rule it out and then we got 2 definite positives. They say that infants may not sweat enough and thus you cannot get a definite reading.
<br />
<br />blessings,
<br />missa