[R] Fw: Logistic regresion - Interpreting (SENS) and (SPEC)

[Frank E Harrell Jr]

cryan at binghamton.edu wrote:
> I recall a concept of Snout:  sensitivity that is high enough to essentially rule out the presence of disease.  And Spin:  specificity that is high enough to essentially rule in the presence of disease.
> 
> So perhaps the below is backwards?  The higher the sensitivity, the greater the NPV?  And the higher the specificity, the 
greater the PPV?
> 

Why should we care when we can directly estimate Prob(disease | test 
results and risk factors)?  Am I the only person who likes logistic 
regression models this week?

Frank

> http://www.musc.edu/dc/icrebm/diagnostictests.html
> 
> --Chris Ryan
> 
> ---- Original message ----
>> Date: Mon, 13 Oct 2008 18:14:39 -0400
>> From: "John Sorkin" <jsorkin at grecc.umaryland.edu>  
>> Subject: Re: [R] Fw:  Logistic regresion - Interpreting	(SENS)	and	(SPEC)  
>> To: "Ph.D. Robert W. Baer" <rbaer at atsu.edu>, "Frank E Harrell Jr" <f.harrell at vanderbilt.edu>
>> Cc: r-help at r-project.org, dieter.menne at menne-biomed.de, p.dalgaard at biostat.ku.dk
> 
> . . . . .
>> Further, PPV is a function of sensitivity (for a given specificity in a population with a given disease prevalence), the higher the sensitivity almost always the greater the PPV (it can by unchanged, but I don't believe it can be lower) and as
>>              NPV is a function of specificity (for a given sensitivity in a population with a given disease prevelance), the higher the specificity almost always the greater the NPV (it can by unchanged, but I don't believe it can be lower) . . . .
> 
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-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University