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SUMMARY:Case-Control Studies when Cases are Extreme Values of a Continuous
  Variable - David Steinberg (Tel Aviv University)
DTSTART:20100212T153000Z
DTEND:20100212T163000Z
UID:TALK22579@talks.cam.ac.uk
CONTACT:8047
DESCRIPTION:We typically think of case-control studies as comparing indivi
 duals\nwith a disease to a healthy control group.  However\, sometimes the
 \ncondition that defines a ?case? is an unusual value of a continuous\nout
 come.  For example\, neonates are said to have intra-uterine growth\nrestr
 iction (IUGR) if their weight at birth\, adjusted for gestational\nage\, i
 s below the 10th percentile.  IUGR is associated with a number\nof negativ
 e health effects.  Most research on the etiology of IUGR has\nbeen retrosp
 ective case-control studies in which neonates with IUGR\nare compared to t
 hose above the 10th percentile with respect to\npotential risk factors.\n\
 nThe fact that IUGR is defined by converting a continuous variable\,\n(adj
 usted) weight at birth\, into a dichotomous variable\, suggests that\nmore
  information should be available by making explicit use of weight\nat birt
 h and not just its dichotomous version.  I will present some\nsimple ideas
  that show how to take advantage of the continuous outcome\nitself.  These
  analyses offer much higher power for identifying risk\nfactors.  They eve
 n make it possible to estimate the effect on the\ncontinuous outcome from 
 case-control type sample data and to exploit\ndata from subjects who have 
 not been classified with respect to\nqualitative covariates.  They also su
 ggest how one might choose an\nefficient sampling strategy.\n\nThis resear
 ch was motivated by a large prospective study on\nthrombophilia and pregna
 ncy outcomes conducted by Dr. O. Salomon\,\nProf. U. Seligsohn and Dr. R. 
 Achiron.  Part of the statistical\nresearch was carried out by Ms. Nadya K
 rishtal as part of her M. Sc.\nthesis at Tel-Aviv University.\n\nhttp://ww
 w.math.tau.ac.il/~dms/\n
LOCATION:MR12\, CMS\, Wilberforce Road\, Cambridge\, CB3 0WB
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