Re: st: Cut-off point for ROC curve using parametric and non-parametric method

["Roger B. Newson" <r.newson@imperial.ac.uk>]

If your aim is to estimate the Youden index, then you can use the 
-somersd- package, which you can download from SSC. The Youden index is 
an alternative name for Somers' D between 2 binary variables. The 
-somersd- package can also be used, together with -lincom-, to calculate 
the difference between 2 Youden indices for 2 diagnostic tests for the 
same disease.

I hope this helps.

Best wishes

Roger

Roger B Newson BSc MSc DPhil
Lecturer in Medical Statistics
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton Campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: r.newson@imperial.ac.uk
Web page: http://www.imperial.ac.uk/nhli/r.newson/
Departmental Web page:
http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/

Opinions expressed are those of the author, not of the institution.

On 19/01/2013 03:38, Pham Ngoc Minh wrote:
> Dear Statalist,
>
> I want to construct age-adjusted (age is a continuous variable) optimal
> cut-off points for body mass index (bmi)  and waist circumference (wc) in
> determining metabolic syndrome (metabo) for a large study. My question is
> how can I calculate sensitivity and specificity for bmi and wc with
> adjustment for age, based on which I can calculate Youden index. For
> non-parametric method, I know only about using command: roctab metabo bmi,
> detail or senspec metabo bmi, se(varname1) spe(varname2)  (without
> covariate adjustment). Moreover, how can I calculate age-adjusted
> sensitivity and specificity using parametric ROC analysis. It is because
>   using non-parametric method showed P less than 0.01, although AUC for
> bmi and wc was somewhat similar.
> Thank you for your guidance in advance.
>
> Pham Ngoc Minh
> Thai Nguyen University Faculty of Public Health, Vietnam
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