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The American Journal of Managed Care July 2016
Enhanced Risk Prediction Model for Emergency Department Use and Hospitalizations in Patients in a Primary Care Medical Home
Paul Y. Takahashi, MD; Herbert C. Heien, MS; Lindsey R. Sangaralingham, MPH; Nilay D. Shah, PhD; and James M. Naessens, ScD
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Shelly P. Smith, DNP, APRN-BC, and Beth L. Elias, PhD, MS
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Economic and Clinical Impact of Routine Weekend Catheterization Services
Kirsten Hall Long, PhD; James P. Moriarty, MSc; Jeanine E. Ransom, BA; Ryan J. Lennon, MS; Verghese Mathew, MD; Rajiv Gulati, MD, PhD; Gurpreet S. Sandhu, MD, PhD; and Charanjit S. Rihal, MD, MBA
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Karen M. Kuntz, ScD; Ann G. Zauber, PhD; Amy B. Knudsen, PhD; Carolyn M. Rutter, PhD; Iris Lansdorp-Vogelaar, PhD; Barry M. Berger, MD FCAP; and Bernard Levin, MD, FACP
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Ana Palacio, MD, MPH; Jessica Chen, MD; Leonardo Tamariz, MD, MPH; Sylvia D. Garay, MD; Hua Li, PhD; and Olveen Carrasquillo, MD, MPH
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Seuli Bose-Brill, MD; Matthew Kretovics, MPH; Taylor Ballenger, MD; Gabriella Modan, PhD; Albert Lai, PhD; Lindsay Belanger, MPH; Stephen Koesters, MD; Taylor Pressler-Vydra, MS; Christopher Holloman, PhD; and Celia Wills, PhD, RN

Economic and Clinical Impact of Routine Weekend Catheterization Services

Kirsten Hall Long, PhD; James P. Moriarty, MSc; Jeanine E. Ransom, BA; Ryan J. Lennon, MS; Verghese Mathew, MD; Rajiv Gulati, MD, PhD; Gurpreet S. Sandhu, MD, PhD; and Charanjit S. Rihal, MD, MBA
Weekend cardiac catheterization availability for inpatients reduced length of stay and maintained quality of care (no excess hazard for weekend cases), but costs were similar.
ABSTRACT

Objectives: To assess the impact of weekend cardiac catheterization (cath) services for nonemergent inpatients.

Study Design: Retrospective cohort study of patients undergoing cath before and after Saturday cath service availability (CSA).

Methods: Cohorts included Friday and Saturday admissions with cath (with or without revascularization) on the subsequent Monday from January 1, 2007, to December 31, 2008 (pre-CSA events), and Friday or Saturday admissions undergoing cath the subsequent or same Saturday from January 1, 2009, to December 31, 2010 (post-CSA events). Administrative and registry data provided demographics, comorbidities, percutaneous coronary intervention (PCI) details, adverse events, hospital length of stay (LOS), and inpatient expenditures. We used generalized linear modeling to predict LOS and costs, and logistic regression to estimate the likelihood of adverse events during follow-up.

Results: We identified 331 pre-CSA cases (327 patients) and 244 post-CSA cases (243 patients). Cohorts were similar in age (66 years), sex (59% male), and level of comorbidity. PCI use was higher following CSA (42% vs 26%; P <.001), with procedural success accomplished in 95% and 94% of pre- and post-CSA patients, respectively. Adjusted clinical outcomes were similar (odds ratio [OR] for in-hospital mortality, 0.67 post-CSA vs pre-CSA; P = .55; OR for 30-day revascularization, 1.14; P = .68). Models predict an average LOS reduction of 1.7 days following CSA (5.7 vs 4.0 days; P <.001) yet inpatient costs were similar ($24,817 vs $24,753; 95% CI of difference, –$3611 to $3576).

Conclusions: Weekend CSA for routine inpatients was clinically safe and effective, and reduced hospital LOS. Similar inpatient costs likely reflect a shift in case mix in this nonrandomized study.

Am J Manag Care. 2016;22(7):e233-e240
Take-Away Points
 
We assessed the economic and clinical impact of increased weekend catheterization service availability (CSA) for nonemergent inpatients.
  • Weekend CSA for inpatient use significantly reduced length of stay and maintained excellent clinical outcomes with no signal of an excess hazard for weekend cases, but total costs of care were similar due to offsetting utilization. 
  • These data suggest that weekend CSA for routine inpatients can improve patient access and efficiency of care, while maintaining clinical quality.
High operating costs can force hospitals to reduce staffing and the availability of elective services on weekends. This “weekend phenomenon” typically provides capacity for acute treatment and maintains staff satisfaction with traditional work-day hours, but can delay patient access to elective testing and procedures.1,2 For some conditions, weekend admissions have resulted in delayed hospital discharge, which, if not fully reimbursed, brings into question the overall economic efficiency of this staffing model.3-5

Weekend admissions may also correlate with an increased risk of adverse events compared with weekday admissions, although whether this is a result of unmeasured patient risk factors or hospital processes remains uncertain.6-15 Much of this research focused on clinical outcomes for higher-risk cardiovascular admissions; for example, acute myocardial infarction (MI) or ischemic stroke, where timeliness of therapy is critical.6,8,9,11-15 Research on whether “weekend effects” persist for elective admissions is limited for nonemergent cardiac patients, such as those presenting with chest pain, unstable angina, or non-ST segment elevation myocardial infarction (NSTEMI), where timely catheterization laboratory (cath lab) availability may impact patient care processes and outcomes.16

Mayo Clinic Rochester has a long history of providing emergency cath and revascularization services 24/7 for patients presenting with acute cardiac conditions, such as STEMI. In January 2009, cardiac catheterization service availability (CSA) was expanded to Saturdays for inpatients who previously would have waited until a weekday for a cath procedure.  This clinical practice change had a goal of timely access with improved efficiency of care; no other cardiovascular services changed at this time. We assessed the economic and clinical impact of this increased weekend CSA for nonemergent inpatients.

METHODS

Study Setting and Population

Mayo Clinic is a high-volume integrated healthcare delivery system. Physicians are salaried and, with administrative leaders, are accountable for both professional and technical costs. The Division of Cardiovascular Diseases has a long-standing tradition of physician-led continuous quality improvement focused on improving the value of service delivery through evidence-based clinical pathways and ongoing cost-containment strategies.17 

The study population consisted of pre-CSA and post-CSA cohorts of hospitalized patients aged at least 18 years, undergoing diagnostic cath (with or without

revascularization for a non-STEMI indication) between January 1, 2007, to December 31, 2008, and January 1, 2009, to December 31, 2010, respectively. Pre-CSA episodes included Friday and Saturday admissions with cath procedures on the subsequent Monday, whereas post-CSA episodes included Friday or Saturday admissions undergoing cath procedures the subsequent or same Saturday.

To gain the best perspective on the impact of this expanded model of care on the overall nonemergent practice, no additional patient subsets (other than STEMI indications) were excluded. We included multiple qualifying procedures per patient; however, for procedures with percutaneous coronary intervention (PCI), target vessel revascularization was considered a complication of initial PCI and not an index event. We obtained institutional review board approval and excluded all patients who did not authorize use of their records for research.

Data Sources

Clinical, administrative, and research databases were accessed to obtain the data needed to complete study aims. A clinical scheduling tool was used to identify relevant cath cases and service days, associated demographic and clinical characteristics, and whether adjunctive revascularization was performed. We cross-referenced the pre- and post-CSA cohorts with the local STEMI database to exclude patients undergoing procedure for a suspected or acute STEMI indication.18 For PCI-treated patients, we linked to the institutional PCI Registry for more detailed clinical, procedural, angiographic, and outcome data. 

Since 1979, all PCI patients have been followed prospectively according to a well-established and validated protocol.19 Angiographic and procedural characteristics are determined and documented by the PCI operator. A blinded team of registered nurses and data coordinators collects and enters all pre- and postprocedural data, including any adverse clinical events; patients are interviewed in person or by telephone at 6 and 12 months after PCI and yearly thereafter. Medical records for local care and at other institutions are obtained for review with the patient’s written informed release.

Administrative data provided additional information on comorbid conditions, discharge disposition, and adverse events (revascularization and MI) during follow-up. Claims also tracked medical resource utilization, related expenditures, and length of stay (LOS) measured in days for these inpatient cath episodes. Same-day patient admission and discharges were considered a 1-day hospital LOS. Further, because of well-known discrepancies between billed charges and true resource use, utilization was valued using the Medicare Part A and Part B classification. Part A billed charges (hospital-billed services and procedures) were adjusted using hospital cost-to-charge ratios at the departmental level and wage indexes and Medicare Part B items (primarily physician-billed services) were valued using national average Medicare reimbursement rates by Current Procedural Terminology (CPT-4) code.

Although the services provided represent local clinical practice patterns, the value of each unit of service has been adjusted to national norms by use of widely accepted valuation techniques providing an estimated economic cost for each line item in the billing record.20 All costs presented here were adjusted to reflect 2010 constant dollars, and economic results are reported in accordance with guidelines for health economic evaluations: the ISPOR Consolidated Health Economic Evaluation Reporting Standards (CHEERS) statement.21

Outcomes

Economic analyses are from the provider perspective and focused on direct medical costs for hospital and physician services associated with the inpatient episode and total hospital LOS. Clinical outcomes included in-hospital mortality and use of revascularization services (PCI and coronary artery bypass graft [CABG] procedures) in the 30 days following diagnostic cath. Revascularization during follow-up was identified in claims based on International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) procedural codes, CPT-4 codes, and Diagnosis-Related Group (DRG) billing codes.

We identified the occurrence of incident MI in the 30 days following discharge in claims based on ICD-9-CM diagnosis codes (initial MI episodes of care: 410.x1). Although likely a cath complication, MIs occurring after cath (without PCI) during the remaining hospital stay were not assessed because we lacked patient data on when an MI occurred within the identified hospitalization. For the patient subset undergoing adjunctive PCI, however, all MIs from cath onwards were assessed and considered adverse events, as captured by the PCI Registry.  Procedural success (defined as ≤20% residual stenosis and without in-hospital death, Q-wave MI, or CABG), as well as composite rates of death, MI, and any revascularization during long-term follow-up, were also assessed for this patient subset.

To account for possible differences in comorbidity burden by CSA cohort, we used the validated systematic method of classifying comorbidity utilizing administrative data (Deyo adaption of the Charlson Comorbidity Index) based on secondary diagnoses assigned as present on hospital admission.22-24 Similarly, validated in-hospital and follow-up Mayo Clinic Risk Scores were assessed using patient and clinical characteristics (recorded in the PCI Registry) to adjust clinical outcomes within the PCI subset.25,26

Statistical Analysis

Continuous data are summarized as mean ± standard deviation. Discrete data are presented as frequency (percentage). Patient characteristics and observed in-hospital clinical outcomes were compared using the t test for continuous data, the Mann-Whitney rank sum test for ordinal data, and Pearson’s χ2 test for categorical data, as appropriate. Kaplan-Meier estimated adverse-event rates during follow-up were compared using the log-rank test for the subset of PCI-treated patients (for whom we had outcomes data in continuous time). For these analyses, only the first PCI per unique patient was included, and follow-up started at index PCI such that in-hospital events were included. Observed costs and LOS were compared using t tests and the 95% CIs for the difference of means calculated using the percentile method for bootstrapping.27,28

Logistic regression modeling estimated the impact of CSA on in-hospital mortality and 30-day MI and revascularization rates. Models adjusted for age, creatinine level, troponin elevation, and use of adjunctive PCI. We employed Cox Proportional Hazard models to estimate the adjusted hazard for adverse events (death or MI) during longer-term follow-up for the PCI patient subset. These follow-up models adjusted risk before discharge with the calculated in-hospital risk score and used the long-term risk score to adjust risk for events after discharge.

We used generalized linear modeling to assess costs and LOS, accounting for the nonnegative and typically skewed nature of these economic end points.29 Cost models assumed a logarithmic link function and a gamma distribution, whereas we assumed a negative binomial distribution function with log link in the model assessing LOS. All economic models adjusted for age, gender, Charlson Comorbidity Index, and adjunctive PCI. All statistical tests were 2-sided, and P values <.05 were considered significant. SAS version 9.3 (SAS Institute, Cary, North Carolina) was used in analyses.

RESULTS
We identified 331 pre-CSA cases (327 patients) and 244 post-CSA cases (243 patients) undergoing diagnostic cath (with or without revascularization) in the years of interest. Baseline clinical and procedural characteristics are shown in Table 1. The 2 cohorts were similar in terms of age (mean = 66 years), sex (59% male), body mass index (30.4), and comorbidity burden. However, a greater proportion of patients treated post-CSA underwent PCI (42% vs 26%; P <.001). Within this PCI subset, clinical characteristics were similar between cohorts, with the exception of a higher proportion of PCI patients having experienced an MI less than 24 hours before procedure post-CSA (32% vs 2%; P <.001).

Clinical Outcomes After CSA

 
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