Analysis of Waiting-Time Data in Health Services Research

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Springer Science & Business Media, Jan 3, 2008 - Medical - 214 pages
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In health care systems that provide universal access to care, efforts to contain costs for standby hospital capacity usually result in wait lists for surgical procedures. When access to health care is rationed by such wait lists, the length of time that patients are required to wait is usually uncertain. This uncertainty is a natural product of stochastic variation in service time and in the percentage of urgent cases in any queuing system. However, in a queue for elective (nonemergency) procedures, waiting-time uncertainty has many additionalcauses. Forinstance,decisionsofbothpatientsandcareprovidersmayoverrideaqueuediscipline. Alternatively, the lack of a hospital resource, such as beds in the intensive care unit, may change queuing practices in favor of services that would not require the resource. Waiting time is often compared between regions, hospitals, periods, or surgical services to evaluate p- icy and performance. However, surprisingly little attention has been given to the variation in times spent in a single queue. Why some patients wait longer than others remains an important question in health services - search. Itisunclear,forexample, whether timetoservicevariesmorethanwouldbeexpected throughchance alone after differences in clinical condition are taken into account. Another important issue is preferential allocation of hospital resources. It also remains unclear whether patients of low priority are admitted directly as a way to circumvent long wait lists or to substitute for cancellations on the operating room schedule.
 

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Contents

Variation and access probabilities
75
53 What is the probability of undergoing surgery within a certain time?
82
532 Elective coronary artery bypass grafting
85
Factors influencing waiting times
87
622 Elective coronary artery bypass grafting
91
63 Does registration period affect waiting times?
94
64 Does the type of procedure affect waiting times?
100
65 Does waitlist size at registration affect time to surgery?
102

1711 What is the risk of unplanned emergency surgery among patients waiting for surgery?
11
1712 What is the relation between length of the wait list and chances of death while on the wait list?
12
18 Types of inferences
13
192 Truncated samples
15
195 Competing risks
16
Waitingtime data used in this book
17
22 Access to coronary artery bypass grafting surgery
18
222 Other data sources
20
224 Patient population
22
23 Access to elective vascular surgery
24
233 Priority groups
27
242 Patient population
28
Waits and outcomes What should be reported?
30
322 Proportions and odds Definition
32
323 Hazard and rates Definition
33
324 Probabilities of access Definition
36
325 Cumulative incidence functions Definition
39
326 Conditional probability functions Definition
44
33 Methods of comparison
47
334 Comparison of probabilities of access Logrank test
50
335 Comparison of cumulative incidence functions
51
336 Comparison of conditional probability functions
53
34 Regression models
54
343 Cox regression
57
344 Poisson loglinear regression
60
345 Discretetime regression
61
346 Regression for pseudovalues of cumulative incidence functions
65
Waitingtime Studies
68
Overview of waiting times and other variables
69
423 Waitlist size
72
442 Waiting outcomes
73
652 Elective coronary artery bypass grafting
106
Surgery after target access time
111
73 What is the relation between weekly number of emergency referrals and elective admissions within the target time?
114
Adverse events while waiting
117
83 What is the risk of unplanned emergency surgery among patients waiting for surgery?
124
832 Elective coronary artery bypass grafting
128
84 What is the relation between length of the wait list at registration for coronary artery bypass grafting and chances of death while on the wait list?
132
85 What is the relation between length of the wait list at registration for coronary artery bypass grafting and chances of unplanned emergency surgery?
136
86 What is the risk of death associated with delayed surgical treatment of coronary artery disease?
139
Intermediate events
141
93 What is the effect of registration period in the presence of delays?
149
Survival benefit of coronary artery bypass grafting 101 Introduction
153
Appendices
162
Data dictionaries
165
A2 Data dictionary for vascular
167
A3 Data dictionary for cholecystectomy
169
SAS code
170
B12 Preparing data set on access to coronary artery bypass grafting surgery
176
B13 Preparing data set on access to cholecystectomy surgery
181
B2 Estimating summary measures
183
B22 Macro to estimate event rates by group
184
B3 Creating new variables and reformatting records
187
B32 DATA step for creating patient by week data for access to surgery
189
B33 DATA step for creating patient by week data for ontime surgery
190
B34 DATA step for expansion to pseudovalues data
191
Matlab code
193
C2 Estimating the conditional probability function
195
C3 Comparing conditional probability functions in two groups
197
References
201
Index
208
Copyright

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Page 207 - Yusuf S, Zucker D, Peduzzi P, et al: Effect of coronary artery bypass graft surgery on survival: overview of 10-year results from randomised trials by the Coronary Artery Bypass Graft Surgery Trialists Collaboration.
Page 205 - Romano PS. Roos LL. Jollis JG. Adapting a clinical comorbidity index for use with ICD,9,CM administrative data: differing perspectives.
Page 205 - Effect of coronary artery diameter in patients undergoing coronary bypass surgery. Northern New England Cardiovascular Disease Study Group. Circulation 1996; 93:652.

About the author (2008)

Boris Sobolev is Associate Professor in the Department of Health Care and Epidemiology at the University of British Columbia.

Lisa Kuramoto is a Statistical Analyst with the Vancouver Coastal Health Services Research Institute.

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