Date: MONDAY 3 February 2003, 17:00-18:00**
Venue: Euston Centre, room 3.2
Speaker: Prof Sally McClean, University of Ulster, UK

Title: Using Phase-type Distributions to Model the Behaviour of Hospital
Patients
Abstract: Time spent in hospital by patients may be described in terms of
phases, using terms that have been identified by clinicians, such as:
diagnosis, assessment, rehabilitative and long-stay. Phase-type distributions,
which describe the time to absorption of a continuous time Markov chain, are
therefore appropriate to analyse data on lengths of stay of hospital patients.
The phases (or transient states of the Markov chain) can be interpreted in
terms of increasing severity of any illnesses being treated. This leads to an
identification of short-stay, medium-stay and long-stay patients, with the
phase-type distribution interpreted as a mixture of such components.
Differential effects of two covariates, age of patient at admission and year of
admission, are shown on the different phases of the distribution.
Extending this approach we can regard spells in and out of hospital as
interacting phase type behaviour, where patients may move from phases in
hospital to home and phases at home to hospital; death is an absorbing state
for both distributions. We may thus derive probabilities of moving from one
phase to another, along with the mean number of days spent in each phase. Again
these data were analysed to show differential effects of the two covariates:
age of patient at first admission and year of first admission.
Such an approach can be extended to included costs where different phases (e.g.
short-stay, medium-stay, and long-stay) and different situations (e.g. hospital
and home) have differential costs.

Next Talk...
________________________________________________________________________________
Date: TUESDAY 11 March 2003
Speaker: Prof Gary W. Harrison, College of Charleston, USA
Venue: Euston Centre, room tbc
Title: tbc

-----------
Dr. T.J. Chaussalet
University of Westminster
CSCS, Dept of Mathematics
9-18 Euston Centre
London NW1 3ET, UK
Tel: +44(0)207 911 5000 ext 4310
Fax: +44(0)207 915 5438
Email: [log in to unmask]
-----------
PLEASE READ: This e-mail and its attachments are intended for the above
named only and may be confidential. If they have come to you in error you
must not copy or show them to anyone, nor should you take any action based
on them, other than to notify the error by replying to the sender.

Any views expressed in this message are those of the individual sender,
except where the sender specifically states otherwise.