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#215543 - 02/26/12 06:23 PM Re: Max/hemangio...he's gone [Re: Woodreb]
MaxaLisa Offline

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Registered: 01/26/10
Posts: 19428
Loc: Northern CA
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Thanks Johanna, I wanted to make sure that I was understanding.

I've sent another email off to Steve at VDI. Not very well-worded, but I'm hoping he'll respond with some more info.
_________________________
MaxaL (aka LisaT)

Jazmine, mini-mix, 10/18/2011
Max-n-Indy
Max, 5/2001-2/2012, RIP my partner, my Regal Boy
Indy, 5/1997-10/2010, RIP my friend, my teacher

Health Index
K9 TBD info and Tick List Links
http://www.rabieschallengefund.org/

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#215584 - 02/26/12 09:01 PM Re: Max/hemangio...he's gone [Re: Woodreb]
Mary Jane Offline
Carpal Tunnel

Registered: 02/16/10
Posts: 2658
Likes: 118
Lisa,

I read the terminology like you do, but I'll read more. I don't know what'sensitivity' means or 'specificity'. Positive and negative predictive values are like they sound, I think, but I don't know how bad it can be before you discount it.

Mostly, the test is supposed to tell us something about our dog's health or illness and it's just not so clear.

awful,
MJ

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#215853 - 02/28/12 02:01 AM Re: Max/hemangio...he's gone [Re: Mary Jane]
MaxaLisa Offline

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Registered: 01/26/10
Posts: 19428
Loc: Northern CA
Likes: 254
Originally Posted By: Mary Jane
Mostly, the test is supposed to tell us something about our dog's health or illness and it's just not so clear.

awful,
MJ


Absolutely.

...I was walking to lunch on campus today and ran into an old student. He said that he had heard about Max and offered his condolences.

The day before I ran into two students that had long graduated and were back visiting. Of course they asked me how Indy was doing.

It brings comfort to me that they are so warmly remembered.
_________________________
MaxaL (aka LisaT)

Jazmine, mini-mix, 10/18/2011
Max-n-Indy
Max, 5/2001-2/2012, RIP my partner, my Regal Boy
Indy, 5/1997-10/2010, RIP my friend, my teacher

Health Index
K9 TBD info and Tick List Links
http://www.rabieschallengefund.org/

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#215854 - 02/28/12 03:34 AM Re: Max/hemangio...he's gone [Re: MaxaLisa]
bianca Offline
Carpal Tunnel

Registered: 05/14/10
Posts: 8875
Loc: Queensland. Australia
Likes: 149
hugging
_________________________
Molly Moo (aka The Piranha, 4 legged mouth) GSD (31/10/09)
Cooper GSD (The Gremlin) 19/10/11
Texas - Tabby cat (Feb 1996-2013) Run free sweet Teppie
Paris - Tabby cat (Feb 1996-2013) Run free my beautiful girl.

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#215931 - 02/28/12 11:26 AM Re: Max/hemangio...he's gone [Re: bianca]
Mary Jane Offline
Carpal Tunnel

Registered: 02/16/10
Posts: 2658
Likes: 118
I hate statistics. Sensitivity is the fraction of true positives called positive in the test, specificity is the fraction of true negatives called negative. They are calculated differently than positive and negative predictive value-and I don't know how any of it is calculated.

This is a figure from the paper I cited showing that a ton of dogs who actually had hemangiosarcoma had TK values similar to unaffected dogs; particularly dogs with benign splenic masses for some reason.

OK, we're all nauseated now. An essay in the NY Times today by a physician questions the value of a lot of disease prevention by screening.

I just don't know.

Mary Jane

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#215937 - 02/28/12 12:48 PM Re: Max/hemangio...he's gone [Re: Mary Jane]
Woodreb Offline
Carpal Tunnel

Registered: 02/18/10
Posts: 5375
Loc: New Milford, CT
Likes: 135
Originally Posted By: Mary Jane
I hate statistics. Sensitivity is the fraction of true positives called positive in the test, specificity is the fraction of true negatives called negative. They are calculated differently than positive and negative predictive value-and I don't know how any of it is calculated.

This is a figure from the paper I cited showing that a ton of dogs who actually had hemangiosarcoma had TK values similar to unaffected dogs; particularly dogs with benign splenic masses for some reason.

OK, we're all nauseated now. An essay in the NY Times today by a physician questions the value of a lot of disease prevention by screening.

I just don't know.

Mary Jane


I'm not too fond of statistics either.
As far as the TK values being similar to unaffected dogs, with benign splenic masses, since TK is involved in DNA production, I'm guessing it would be elevated regardless of if the tumor were benign or malignant. To me it says you need something elsse to make it more discriminating in the evaluation.

I think what bothers me the most is that this is already a marketed product, with all these questions about how valid it actually is - at least here in our forum world.

Got a meeting to go to. blush
_________________________
Johanna

Caleb (aka Caleb-Moose)
Ciara(aka Ciara Belle, Black Devil)

RIP Aodhán, Rica, Max, Kelly - gone but never forgotten - forever in my heart

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#216039 - 02/28/12 08:29 PM Re: Max/hemangio...he's gone [Re: MaxaLisa]
Tara Offline
Pooh-Bah

Registered: 02/24/10
Posts: 2161
Loc: Virginia
Likes: 85
Originally Posted By: MaxaLisa

Serum TK1 activity was significantly higher in dogs with hemangiosarcoma (HSA) than in normal dogs (mean ± SEM = 17.0 ± 5.0 and 2.01 ± 0.6, respectively), but not dogs with benign disease (mean ± SEM = 10.0 ± 3.3).
Okay, Max's was 18.5, yes, right above the average.

Using a cut-off of 6.55 U/L, TK activity demonstrated a sensitivity of 0.52, specificity of 0.93
This is a measurement that says it's actually measuring what we think it is, and not something else (like B-12 deficiency, for example?), right?


A sensitivity of 0.52 tells you that 52% of animals that have the disease are going to test positive. That means that false negative tests happen 48% of the time. Sensitivity = #True Positives / (#True Positives + #False Negatives)

A specificity of 0.93 tells you that 93% of animals that do not have the disease test negative, meaning that the false positives happen in 7% of non-diseased animals. Specificity = #True Negatives / (#True Negatives + #False Positives)

Specificity and sensitivity are related directly to the test, itself.

Originally Posted By: MaxaLisa

positive predictive value of 0.94
Is this the measurement that describes the "false positive"? That once you get a positive, the chances that it is false is very low?


This is the percentage of positive test results that have the disease. So in this case, 94% of positive test results actually have the disease and 6% positive test results do not have the disease. So 6% false positives. Positive predictive value = #True Positives / (#True Positives + #False Positives)

Originally Posted By: MaxaLisa

negative predictive value of 0.48 for distinguishing HSA versus normal.
Is this the measurement that describes the "false negative"? That once you get a negative, the chances that there is cancer might still be high?


This is the proportion of negative test results that do not have the disease, in this case 48% of the negative test results actually do not have the disease. This means 52% chance of false negatives. Negative predictive value = #True Negatives / (#False Negatives + #True Negatives)


The difference between sensitivity/specificity and positive predictive values/negative predictive values is that sensitivity/specificity are constant for a particular test whereas the predictive values are dependent on the disease characteristics and the "true prevalence" in a population.

For example a test may have a particular sensitivity/specificity but the predictive values will vary when applied to different populations (e.g. an animal not showing signs of disease (in this case, true prevalence is low) versus animal showing signs/symptoms (true prevalence may be much higher).

Does this make sense? If you want a simple example with numbers, let me know and I can write it up for you.
_________________________
Kristin

Tara NW1 ORT-AC CGC - GSD 2008
Suli - DSH 2006

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#216858 - 03/03/12 04:21 PM Re: Max/hemangio...he's gone [Re: Tara]
MaxaLisa Offline

Global Moderator

Registered: 01/26/10
Posts: 19428
Loc: Northern CA
Likes: 254
I emailed VDI on the 26th about my concerns about the disconnect between what they say about their values and what they write in their letter, and that email I have not yet had a response. I will resend, just in case, and report back on what I learn. I haven't been able to really look at this stuff again, I have to do it at times when I am able.

I have quoted most of the VDI stuff in a new thread here: http://germanshepherdhome.net/forum/ubbthreads.php/topics/216510/Veterinary_Diagnostics_Institu since this may be useful to others down the road.

I have Max's memorial thread here:
http://germanshepherdhome.net/forum/ubbt..._RIP#Post216499

Miss you my boy gsdhalo
_________________________
MaxaL (aka LisaT)

Jazmine, mini-mix, 10/18/2011
Max-n-Indy
Max, 5/2001-2/2012, RIP my partner, my Regal Boy
Indy, 5/1997-10/2010, RIP my friend, my teacher

Health Index
K9 TBD info and Tick List Links
http://www.rabieschallengefund.org/

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#235453 - 06/10/12 11:40 PM Re: ultrasound for the heart?/adrenals? SIBO? [Re: MaxaLisa]
MaxaLisa Offline

Global Moderator

Registered: 01/26/10
Posts: 19428
Loc: Northern CA
Likes: 254
So sad tonight.

Had to take Mom to the ER last night, she had an intestinal blockage. So far, been able to avoid surgery, and she has been admitted to the hospital and will be able to go home if she passes the food test.

She has her own room, because she has a history of ESBL bacteria, namely pathogenic E. Coli. Max's vet thought that the infection that had him was a pathogenic E. coli. I do believe that he had chronic rickettsia that I kept under control by pulsing doxy, but he couldn't handle this other infection, particularly after it had become so systemic. I'm pretty sure I brought it home in 2009 when my mom was so sick, in ICU, the hospital, then rehab, for so long. That seems to be where she picked it up. And shortly after that, Max's fistula, which was infection induced, and then time to disseminate.

Just so sad. It shouldn't have happened that way. He should have had a chance to grow old, instead of sick.

Just miss my boy a lot.
_________________________
MaxaL (aka LisaT)

Jazmine, mini-mix, 10/18/2011
Max-n-Indy
Max, 5/2001-2/2012, RIP my partner, my Regal Boy
Indy, 5/1997-10/2010, RIP my friend, my teacher

Health Index
K9 TBD info and Tick List Links
http://www.rabieschallengefund.org/

Top Likes: 0 
#235464 - 06/11/12 12:03 AM Re: ultrasound for the heart?/adrenals? SIBO? [Re: MaxaLisa]
debbieg Offline
Old Hand

Registered: 02/20/10
Posts: 1041
Loc: CA
Likes: 7
Sorry to hear this Lisa, Praying for your mom. I have been hospitalized three times with blockages and one, because the intestine has kinked into a knot, required surgery that cut two inches from my intestine.

Sorry you miss Max too. This just shows how much love he was. Better a short life full of love than a long one without.
_________________________
Debbie

Benedict GSD 4/13/09 http://www.dogster.com/dogs/1007494
Annie ABPT 4/11/09
Jake Borzoi 12/3/09

Waiting at the Bridge
Eli
Chopper
Raphael

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