Upload
molly-golden
View
217
Download
2
Tags:
Embed Size (px)
Citation preview
31.5.2005 / AL
National Research and Development Centre for Welfare and Health
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
A propensity score approach to comparing medical costs between hospital districts
Hailuoto workshop 31. 5. 2005
Antti Liski
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The study a part of Reijo Sund’s (STAKES) ”Utilisation of routinely
collected register data in health system performance assessment” –project part of a bigger project led by Pekka Rissanen and funded by the
Academy of Finland
my master’s thesis
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The aim of this study to compare the costs of hip fracture patients between
care districts
there is indication that the prolonged in-hospital operative delay has an effect on mortality (Sund & Liski)
does the prolonged in-hospital operative delay have an effect also on the costs
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
Hip fractures common with older people
lead to lower quality of life
usually surgically operated
the operation is expensive
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The data collected from the Finnish Health Care Register, Finnish
Hospital Discharge Register, Finnish Health and Social Welfare Care Register, the data warehouse of the Finnish Hospital Benchmarking project and the National Causes of Death Register
the final data set consisted of 16881 hip fracture patients in 20 hospital districts in 1998-2001 that hadn’t had a hip fracture during the preceding 10 years
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The data… only surgically operated patients
three types of hip fractures
the costs are based on Diagnosis Related Costs (DRG) classification
every patient has the costs from year 2001
the follow-up period was one year
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
Problems in comparing the costs of hospital districts heterogeneity of patients in different hospital districts
censoring caused by deaths patients who have died quickly after the surgery are ”too cheap”
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The propensity score Rosenbaum & Rubin, Biometrika 1983
e(x)=P(y=1|x), where y = 1 indicates that a patient with observed covariates x will be assigned to a given hospital district (y = 0, a control district)
subclassification on the propensity score will balance x, in the sense that within subclasses that are homogeneous in e(x), the distribution of x is the same for study and control districts
P(x,y|e)=P(x|e)P(y|e)
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
Calculating the propensity score using a logit-model consider the probability π(x) that a patient is assigned to
a given hospital district as a function of covariates x
P(y=1|x) =π(x); compare study district (y=1) vs. control (y=0)
we use the model:
logit[π(x)]=log[π(x)/(1- π(x))]=α+β’x
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
Calculating the propensity score using the logit model… the explanatory variables include: age, sex, days of
care, type of fracture, type of surgery, did the patient come from home, days in care during the preceding 60 days, did the patient die during the follow up, days alive during the follow up and most important comorbidities classified into 13 classes
the predicted values were calculated and used as the propensity score
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The costs the patients were sorted by the propensity score within the
hospital districts
the costs were smoothed over the propensity score using local linear regression with normal weights w and h as the standard deviation of the normal distribution used
the estimator:
nhxxwxxhxs
wherehxshxshxs
yhxxwxxhxshxs
nxm
ir
ir
n
i
iii
/)};()({);(
,);();();(
);()})(;();({1)(
12
102
12
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The costs of hosp. dist. no. 1 (green) and hosp. dist no. 2 (black)
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The costs of hosp. dist. no 1 (green) and hosp. dist. no 3 (black)
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
Calculating the propensity score using a multinomial logit model the estimation can be done using the whole data
all of the cost curves are comparable with each other and not only pairwise as in the case of the binomial logit –model
let πj(xi) denote the probability of response j, j=1,…,J at the ith setting of values of k explanatory variables xi=(1,xi1,…,xik)’.
log[πj(xi) / πJ(xi)]= βj’xi , j=1,…,J-1 , where the last category J is the baseline
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
Calculating the propensity score using a multinomial logit model again the predicted values were calculated and the logit
value corresponding to the probability hospital district 1 (say) is used as the propensity score
now the patients with the same (or almost the same) propensity score should have similar distribution of covariates x within every district
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The costs of hpd. 1(green), 2(blue) and 3(black)
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
Prolonged in-hospital waiting time and costs patients should be operated as soon as possible after
the fracture, provided that their condition is sufficiently good
there is indication that a waiting time over three nights increases mortality
the patients are divided into prolonged (waiting time three nights or longer) and early (waiting time less than three nights) surgery within the hospital districts
the costs were again smoothed inside these subclasses
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The cost of patients with ≥3 nights (green) waiting time and <3 nights (black) waiting time in hpd 1
National Research and Development Centre for Welfare and Health 31.5.2005 / AL
Knowledge for welfare and health A propensity score approach to comparing medical costs between hospital districts
The cost of patients with ≥3 nights (green) waiting time and <3 nights (black) waiting time in hpd 2