Talk:Positive and negative predictive values

message: request merge of "negative predictive value" "positive predictive value" and "Sensitivity and specificity".
these terms are intimiately related, and should be in one place, possibly with a discussion of ROC.
Further, suggest modeling on <http://www.musc.edu/dc/icrebm/sensitivity.html>> this is a great expostion of this complicated stuff.Cinnamon colbert (talk) 22:25, 16 November 2008 (UTC)
thread_title: merge

message: See Talk:Sensitivity (tests) re past wish list for simpler description, setting what it is before launching in mathematical jargon. I have also added a table and in Sensitivity (tests) added a worked example. The table is now consistant in Sensitivity, Specificity, PPV & NPV with relevant row or column for calculation highlighted. David Ruben  Talk  02:45, 11 October 2006 (UTC)
thread_title: Table and edits

message: "Physician's gold standard" seems to be an unhelpful phrase as it is used in this article.
My experience has been that when "gold standard" is used in this context it refers to the reference test against which the accuracy of a test is measured.  As we all know, sensitivity, specificity, PPV, etc., require a "gold standard" test for reference -- otherwise we don't have a basis for claims about % true positives and % true negatives.
Here it seems that "physician's gold standard" means something like "it is the statistical property of a test that is most useful to physicians".
It seems that either the author was confused about the use of "gold standard" in biostatistics or there's another (unfortunate) use of the phrase that I'm not familiar with.  Since I don't know which, I'm not editing the page.  If others agree, perhaps this phrase should be replaced.
--will 02:19, 24 July 2007 (UTC)
replies: text: I agree with 'will' above (24 july 2007) that PPV cannot be seen as a gold standard. I suggest to replace 'It is the physician's .....' by 'It is the most important measure for ruling in disease' Any objections? Michel soete 16:52, 19 October 2007 (UTC)
replies: text: Agree "physician's gold standard" is awful and needs rehrasing. Like your suggestion Michel soete... go ahead :-) David Ruben  Talk  20:50, 19 October 2007 (UTC)
thread_title:  "Physician's Gold Standard"  Remove? 

message: Let's consider following tabel (Grant Innes, 2006, CJEM. Clinical utility of novel cardiac markers: let the byer beware.)
Table 3. Diagnostic performance of ischemia modified albumin (IMA) in a low (5%) prevalence population.
  
 ACS   Yes No Total Sensitivity (true-positive rate) = 35/50 = 70% 
 IMA + 35 722  757 Specificity (true-negative rate) = 228/950 = 24% 
 IMA – 15 228  243 Positive predictive value = 35/757 = 4.6% 
       50 950 1000 Negative predictive value = 228/243 = 94% 
The positive predictive value is smaller than the prevalence. We must conclude that a positive test result decreases the probability of disease or in other words that the post-test probability of disease, given a positive result, is smaller than the pre-test probability (prevalence): very strange and unusual conclusion. 
From a statistical point of view this very strange conclusion can be avoided by interchanging the rows of thet table: IMA- becomes a positive test result. This operation results in a predictive value of 6.17%. The conclusion is that a positive test result, if the test is of any value at all, increases the post-test probability as it is expected to do and in no case decreases this value. 
This example illustrates the need for an unequivocal definition of a positive test result. If a positive test result is unequivocally defined, the positive predictive value is mathematically unequivocally defined. A text providing such an unequivocal definition was removed by someone who called it 'garble'.
I intend to put the text back, any objections?  —Preceding unsigned comment added by Michel soete (talk • contribs) 18:57, 22 September 2007 (UTC)
thread_title:  the need for an unequivocal definition of positive predictive value 

message: The article uses a lot of language very specific to the field of medicine.  Even the very definition uses terms like "patients" and "diagnosed."  Unless I am mistaken, I believe that this is not a term specific for medicine but rather for any binary classification scheme.  I think there are a lot of ambiguities/inconsistencies throughout related articles about this and about multiple terms for the same concept (see precision and recall framed differently).  It seems that the articles should be a lot clearer on whether this term is just the specific term used in medicine for a concept with other names in other fields, or is the term truly domain agnostic as I believe it is.  I posted something along these lines in the statistics project page but have yet to receive a response.  What am I missing? Mickeyg13 (talk) 15:29, 24 May 2010 (UTC)
thread_title:  Specific to Medicine? 

message: Surely it's absurd to say "a negative result is very good at reassuring that a patient does not have cancer (NPV = 99.5%) given that this is only marginally better than pointing to a random person and declaring they don't have cancer (probability 98.5%)"
Also, the sooner this and Positive predictive value are merged, the better, IMO - the articles are essentially identical. Jmc200 (talk) 16:58, 3 June 2010 (UTC)
thread_title:  Negative result "very good"?? 

message: A merge has been proposed for 1 1/2 years with no objections, and in addition there are three statements of support (on in 2008, one above, and one on the Negative Predictive value talk page. In this light, I have done my best to merge these two articles, however I feel this article would benefit from a significant copyedit. --LT910001 (talk) 08:09, 22 December 2013 (UTC)
thread_title:  Merge 

message: Hello all,
I was nervous to make the edit myself, but there is a big problem with the beginning of this article.  It says NPV and NPA are the same and cites an FDA article.  The article says they are not the same.  There is an important difference.  NPA is TN/(FP + TN) and NPV = TN/(FN + TN).  This actually caused me a lot of trouble as I believe the text in Wikipedia and made a determination about how to trust a rapid COVID test that listed a 100 percent NPA.  The NPV may be more relevant and much worse, because I got a conflicting positive result days later after I had already resumed some activity.  — Preceding unsigned comment added by 2601:249:8D80:3120:A586:2211:DEF8:5C1B (talk) 19:55, 22 August 2020 (UTC)
replies: text: The stated claim was not in the referenced article so I removed the sentence and the reference. PeepleLikeYou (talk) 11:47, 23 August 2020 (UTC)
thread_title: big problem with NPV vs NPA