## Analysis of Waiting-Time Data in Health Services ResearchIn 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

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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 |

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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 |

208 | |

### Other editions - View all

Analysis of Waiting-Time Data in Health Services Research Boris Sobolev,Lisa Kuramoto No preview available - 2007 |

Analysis of Waiting-Time Data in Health Services Research Boris Sobolev,Lisa Kuramoto No preview available - 2010 |

### Common terms and phrases

100 patient-weeks 52 weeks access to surgery admission rate analysis artery bypass grafting batch CABG chi-square chi-square distribution cholecystectomy comorbidity competing event conditional probability confidence interval coronary artery bypass covariates cumulative incidence function data set DATA step delay in scheduling described in Chapter disease elective coronary artery elective surgery elective vascular surgery emergency admission event of interest event rate hazard ratio indicator variables log-rank test logistic regression nonurgent group null hypothesis number of events number of patients odds ratio operating room patients registered peripheral vascular disease Poisson regression preoperative death primary event priority group probability of undergoing procedures proportion of patients pseudovalues registered for elective registration period registration weeks regression model SAS Code SAS Output scheduling delay semiurgent group surgery rate survival analysis Table target access test statistic time-dependent total number treatment undergoing surgery unplanned emergency surgery urgent wait-list week Wald test weekly rate

### Popular passages

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.