Income-Related Disparities in Surgical Outcomes Have Declined, But Some Inequities

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1 Income-Related Disparities in Surgical Outcomes Have Declined, But Some Inequities Persist Considerable effort and attention at the national and locals levels has been given to improving the quality of healthcare and patient safety in recent years. Although there is still much more work to be done, there have been substantial improvements in several inpatient outcomes over the last 20 years. Declines in specific inpatient outcomes such as operative mortality have been realized for a number of high-risk cardiovascular and cancer-related procedures. 1-2 Additionally, health conditions such as acute myocardial infarction, stroke, and pneumonia have also seen declines in mortality. 3 Concurrently, hospital patient safety has improved for select measures such as failure to rescue, postoperative hip fracture, obstetric traumas, iatrogenic pneumothorax, and postoperative wound dehiscence. 4-5 However, multiple measures from different data sources indicate that, despite improvements in care, disparities still exist and are widening for some measures for low-income populations. 6 Low income has been associated with increased waiting times for cardiac care, lower rates of use of cardiac procedures, and underuse of preventive services 7-8 and higher rate of hospitalization for ambulatory care sensitive conditions 9. Surgical outcomes have also been found to be associated with socioeconomic status. For example, low-income populations had significantly increased risks for postoperative complications after neurosurgery, lower survival rates for AAA repair, higher likelihood of death after CABG, and higher rates of adjusted operative mortality across a wide range of surgical procedures This study provides exploratory analysis of post-surgical outcomes for patients residing in low-income areas as compared to those from high-income areas over a 10-year period ( ). It examines two questions: (1) do patients living in the poorest communities have worse post-surgical outcomes than those from the wealthiest communities and (2) has the level of these differences changed over time. Risk-adjusted outcomes (post-operative complications and mortality) are measured using the Agency for Healthcare Research and Quality (AHRQ) Inpatient Quality Indicators and Patient Safety Indicators applied to the Page 1 of 13

2 Nationwide Inpatient Sample (NIS) for each study year to produce all-payer, national estimates for adults in the poorest and highest income communities (measured by the median household income of the patient s zip code). Methods Data Sources The Healthcare Cost and Utilization Project NIS contains summary records for 8 million discharges from 1,000 hospitals with accompanying weights for national estimates. It is based on a 20% stratified random sample of US community hospitals, which in 2009 was drawn from a sampling frame of 95 percent of all inpatient discharges in the United States. Measures Mortality and patient safety measures This study measures in-hospital mortality rates for patients receiving one of eight surgeries: abdominal aortic aneurysm repair, coronary artery bypass graft, carotid endarterectomy, craniotomy, esophageal resection for cancer, hip replacement, pancreatic resection for cancer, and percutaneous transluminal coronary angioplasty. The AHRQ Inpatient Quality Indicators (IQI) software (IQI Version 4.1) was used for this analysis. 16 The IQI software identified the study population to include discharges with one of the study surgical conditions based on ICD-9-CM diagnosis codes. For patients transferred from one hospital to another, the software includes the record for the final hospital in which the patient was treated, but not the record for the initial hospitalization. The software excludes obstetrics discharges and includes discharges for those age 18 years and older, with the exception of the CABG and PTCA patients (40 years and older). As required for the AHRQ mortality IQIs, All-Patient Refined-DRG (APR-DRG) software was applied to the data to obtain the APR-DRG and Risk of Mortality subclass for use in risk adjustment. The APR-DRG classification expands the CMS DRG classification (used for Medicare reimbursement) to be Page 2 of 13

3 applicable to non-medicare populations and for uses beyond those related to resource consumption. The APR-DRG software classifies each discharge into a single APR-DRG and assigns a Risk of Mortality subclass within the APR-DRG: minor, moderate, major, and extreme. The AHRQ Patient Safety Indicators (PSI) software (PSI Version 4.1) was used for the postoperative patient safety measures. 17 The PSIs are the mostly widely used measure set in research studies published on patient safety using routinely collected hospital data. 18 In addition, almost all of the PSIs examined in this study are endorsed by the National Quality Forum for measuring hospital patient safety events and are used by the Centers for Medicare and Medicaid in their reporting on hospital-level patient safety in Hospital Compare The PSIs included in the analysis are: deaths among surgical patients with serious treatable complications, postoperative hemorrhage or hematoma, postoperative respiratory failure, postoperative sepsis, and postoperative wound dehiscence. Two post-operative PSIs-- postoperative hip fracture, and postoperative pulmonary embolus and deep vein thrombosis-- were not included in the analysis because prior research indicates they have a high rate of cases in which the condition is present on admission (POA), thus not a complication of the current hospitalization. 21 Most states contributing data for the NIS did not have an all-payer POA indicator reporting during the time periods of the study. One PSI, postoperative sepsis, was not included in trend analyses due to ICD-9-CM coding changes during the period under study. However, the postoperative sepsis rates for 2008 and 2009 are included. Both PSI and IQI risk adjustment variables include age, gender, age-gender interaction and Major Diagnostic Category. The PSI risk adjustment further includes Diagnosis-Related Group and comorbidities and the IQI risk adjustment additionally includes APR-DRG and the Risk of Mortality subclass applicable to each surgical condition. Additional information on the regression-based standardization of risk-adjustment models is available Two data elements (POA and day of procedure) used in some of the PSI and IQI algorithms were not used because the NIS does not include these for records from some states. Missing Page 3 of 13

4 values for admission type (included in the algorithm for some PSIs) were imputed using the method developed by the AHRQ Quality Indicators program. Community Income Community income in the Nationwide Inpatient Sample is assigned based on median household income for patient's ZIP Code from Claritas. Annual cut-offs for quartile designations are determined using ZIP Code demographic data obtained from Claritas. For this analysis we compare patients residing in the poorest communities (lowest quartile) to those from the wealthiest communities (highest quartile). Statistical Analyses Using the methods recommended for variance calculations 24, SAS Proc Survey Means was used to obtain the PSI and mortality rates and standard errors taking into account the clustering of patients within hospitals and the hospital stratification aspects of the sampling design for the NIS. The PSI and in-hospital mortality rates were weighted for national estimates and are presented as risk-adjusted rates per 1000 discharges. Pairwise t-tests were used to test for statistical significance of differences in the rates between patients from low income and high income communities. Results Exhibit 1 (not shown here) provides national estimates for each mortality and patient safety measure by community income category delineating the number of hospital discharges and descriptive statistics associated with the risk adjustors: percentage 65 years and older, percentage female, percentage major or extreme APR-DRG risk of mortality (mortality measures), percentage major or extreme APR-DRG severity of illness (patient safety measures), and average number of comorbidity (as measured by the AHRQ Comorbidity Software 25 ) for 2009 data. The number of discharges, for both the low and high income groups, varied from 20,000 for AAA repair to over 4 million for postoperative hemorrhage and hematoma. The low income group tended to be younger and have a slightly higher average number of comorbidities than the high income group. The percentage of individuals in the major or extreme category of APR-DRG Page 4 of 13

5 risk of mortality was nearly identical for low versus high income groups for all mortality measures. The percentage of individuals in the major or extreme category for APR-DRG severity of illness was slightly higher for low income groups than for high income groups for postoperative hemorrhage, postoperative respiratory failure, postoperative sepsis, and postoperative wound dehiscence. Exhibit 2 (attached) provides risk-adjusted rates of mortality for patients in low and high income communities and compares 2000 to 2009 for each measure. As the risk-adjusted rates show, patients residing in low income communities fare significantly worse for six of the eight mortality measures. In 2009, risk-adjusted rates were still significantly higher for patients from low income areas when compared to those from high income areas for three measures CABG, craniotomy mortality, and esophageal resection for cancer (15 percent,24 percent higher, and 173% higher respectively). Although there were no significant differences between income levels for carotid endarterectomy in 2000, patients residing in low income communities had 25% lower mortality rates in Comparing risk-adjusted rates from 2000 to 2009 we find that all inpatient mortality measures experienced a significant decline for both income levels with the exception of pancreatic resection for cancer for patients residing in high income communities. There was at least a 10 percent decline during the time period for each measure, and as much as a 95 percent decline for risk-adjusted hip replacement mortality for both low income and high income groups. National estimates of risk-adjusted complication rates for 2000 and 2009 for patients residing in low and high income communities are provided in Exhibit 3 (attached). Comparable findings were also observed for patient safety measures in Low income groups had significantly higher risk-adjusted rates for three of the four patient safety measures examined for 2000: death among surgical patient with serious treatable complications, postoperative respiratory failure, and postoperative wound dehiscence. However, in 2009, only one of the five risk-adjusted patient safety events examined was significantly higher for patients from low income compared to high income communities-- postoperative respiratory failure (18 Page 5 of 13

6 percent higher). In both 2000 and 2009, the low income community group had significantly lower riskadjusted rates of postoperative hemorrhage and hematoma (5 percent lower). Two of the four risk-adjusted patient safety measures exhibited a significant decline from 2000 to 2009 for both income groups: death among surgical patients with serious treatable complications (25 percent or more decline for both income levels) and postoperative wound dehiscence (15 percent or more decline for both income levels). One patient safety indicator, postoperative respiratory failure, increased significantly from 2000 to 2009 (5-9 percent increase). The only patient safety indicator that exhibited no significant change from 2000 to 2009 for either income group was postoperative hemorrhage and hematoma. Looking at trends over time, we see that although all mortality rates have declined for the 10-year period, the two income groups seemed to reach equity for some measures, whereas differences still exist for others (as noted above). Evident from the graphs is that patients from low income communities had consistently higher mortality than those from high income communities across nearly all years for CABG, Craniotomy, and PTCA. The other five procedures AAA repair, carotid endarterectomy, hip replacement and the two cancer resections-- show a general decline over the ten year period, although the year to year differences are not as clear. The four PSIs for which we have complete data for ten years portray mixed results as noted above: death among surgical patients with serious treatable complications and postoperative wound dehiscence significantly declined, postoperative hemorrhage or hematoma remained unchanged, and postoperative respiratory failure significantly increased from Discussion This study presents national, all-payer estimates of trends in risk-adjusted post-surgical mortality and patient safety outcomes for the adult population during a 10-year period from 2000 to It expands upon previous research, which has typically studied specific populations like Medicare enrollees or specific procedures and conditions such as cancer resection and cardiac procedures. 1-2,13 To the authors Page 6 of 13

7 knowledge, this is the first study to establish national trends in post-surgical patient safety and mortality outcomes by community income level and utilizes the most recent data available. The data presented here show that post-surgical patient safety and mortality outcomes differ based on community income level. In 2000, nine of the twelve risk-adjusted measures were significantly higher for patients residing in low income areas compared with patients residing in high income areas. Consistent with studies of improved operative mortality in the Medicare population 2, we found significant declines in risk-adjusted mortality rates for AAA repair, CABG, craniotomy, and PTCA from 2000 to 2009 for patients from both low and high income areas. Over the time period, the gap in inpatient mortality between patients from low and high income areas was closed for several surgeries -- AAA repair, hip replacement, pancreatic resection for cancer and PTCA, whereas significant differences persisted for CABG, craniotomy and esophageal resection for cancer. Similar findings were observed for the patient safety outcomes. Patients from low income areas had significantly higher risk-adjusted post-surgical patient safety events for three of the four measures in Confirming the finding of a previous study 4, risk-adjusted postoperative wound dehiscence and death among surgical patients with treatable serious complications have declined over time whereas postoperative respiratory failure experienced increases in our study period. By 2009, patients from low income communities experienced significantly higher patient safety events for only one measure-- postoperative respiratory failure. Counter to these findings, in both 2000 and 2009 post-operative hemorrhage and hematoma was lower for patients from low income areas than those from high income areas. This exploratory analysis offers information to help focus quality improvement initiatives and policy interventions for disadvantaged populations. Although trends in hospital safety and inpatient quality showed dramatic improvements from 2000 to 2009 (as much as 95% for one measure), patients from low income Page 7 of 13

8 areas still have worse outcomes in CABG, craniotomy, and esophageal resection mortality rates and postoperative respiratory failure when compared to those from high income areas. Understanding why these disparities in post-surgical outcomes remain is important for developing interventions. We posit that there are two explanations for the disparities observed in surgical outcomes (though not exclusive): 1) characteristics of medical care and 2) patient level characteristics. One study found that the differences in surgical outcomes are largely attributable to where low and high income individuals tend to receive surgical treatment. 13 However, a more recent study suggests that differences in the quality of hospitals treating low income patients do not explain the gap in post-surgical mortality. 14 Patients residing in low-income areas often have problems accessing the care they need either due to cost or transportation, are treated at lower volume hospitals 26 and by lower volume surgeons 27 which are factors that have been associated with poorer outcomes. Patient level characteristics that could help explain disparities in surgical outcomes are that poorer patients are often sicker, are many times admitted urgently, have higher levels of other risk factors associated with general health status (stress, social isolation, perceptions of control and environmental exposures). 28 This study has some limitations. First, we do not adjust for characteristics of medical care such as hospital volume, surgeon volume and surgeon specialty which have been shown to be associated with patient outcomes 29. Second, it is possible that low and high income groups differ in severity of illness levels that were not captured by the administrative data due to limited clinical information. Third, income was derived from information on the income level of the patient's community and is not an individual SES variable, so these results are most generalizable to individuals residing in low and high income communities rather than low and high income people. The study was limited to eight surgical mortality and four other post-operative patient safety outcomes. Future research should examine income disparities Page 8 of 13

9 trends in additional types of surgery and additional outcome measures, such as readmissions following surgery and functional status following surgery. In summary, this study found encouraging results in two areas (1) nearly all post-surgical outcomes studied improved for patients from both low and high income communities during the last decade and (2) disparities between patients from low and high income areas have been eliminated for many of the postsurgical mortality and patient safety measures examined. However, patients from low income areas continue to have worse outcomes for four of twelve measures at the end of the 10-year period. The reasons for the remaining disparate outcomes following surgery for low income populations should be examined in future research and interventions developed to reduce these disparities. Perhaps interventions can be developed based on an understanding of what worked for the four outcome measures in which disparities were eliminated during the decade. References 1. Goodney PP, Siewers AE, Stukel TA, Lucas FL, Wennberg DE, Birkmeyer JD. Is surgery getting safer? National trends in operative mortality. J Am Coll Surg Aug;195(2): Finks JF, Osborne NH, Birkmeyer JD. Trends in hospital volume and operative mortality for high-risk surgery. N Engl J Med Jun 2;364(22): Andrews, R. (AHRQ), Russo, C. A. (Thomson Healthcare), and Pancholi, M. (AHRQ). Trends in Hospital Risk-Adjusted Mortality for Select Diagnoses and Procedures, HCUP Statistical Brief #38. October Agency for Healthcare Research and Quality, Rockville, MD. reports/statbriefs/sb38.pdf. 4. Downey JR, Hernandez-Boussard T, Banka G, Morton JM. Is patient safety improving? National trends in patient safety indicators: Health Serv Res Feb;47(1 Pt 2): Friedman B, Berdahl T, Simpson LA, McCormick MC, Owens PL, Andrews R, Romano PS. Annual report on health care for children and youth in the United States: focus on trends in hospital use and quality. Acad Pediatr Jul-Aug;11(4): National Healthcare Quality and Disparities Report, Rockville, MD: Agency for Healthcare Research and Quality. AHRQ Publication No Available at: Accessed July 18, Page 9 of 13

10 7. Alter DA, Naylor CD, Austin P, Tu JV. Effects of socioeconomic status on access to invasive cardiac procedures and on mortality after acute myocardial infarction. N Engl J Med Oct 28;341(18): Woods et al. Vulnerable groups and access to health care: a critical interpretive review. Report for the National Co-ordinating Centre for NHS Service Delivery and Organisation R & D (NCCSDO). April Wier, L. (Thomson Reuters), Merrill, C.T. (Thomson Reuters), and Elixhauser, A. (AHRQ). Hospital Stays among People Living in the Poorest Communities, HCUP Statistical Brief #73. May Agency for Healthcare Research and Quality, Rockville, MD El-Sayed AM, Ziewacz JE, Davis MC, Lau D, Siddiqi HK, Zamora-Berridi GJ, Sullivan SE. Insurance status and inequalities in outcomes after neurosurgery. World Neurosurg Nov;76(5): Dueck AD, Kucey DS, Johnston KW, Alter D, Laupacis A. Survival after ruptured abdominal aortic aneurysm: effect of patient, surgeon, and hospital factors. J Vasc Surg Jun;39(6): Agabiti N, Cesaroni G, Picciotto S, Bisanti L, Caranci N, Costa G, Forastiere F, Marinacci C, Pandolfi P, Russo A, Perucci CA; Italian Study Group on Inequalities in Health Care. The association of socioeconomic disadvantage with postoperative complications after major elective cardiovascular surgery. J Epidemiol Community Health Oct;62(10): Birkmeyer NJ, Gu N, Baser O, Morris AM, Birkmeyer JD. Socioeconomic status and surgical mortality in the elderly. Med Care Sep;46(9): Bennett KM, Scarborough JE, Pappas TN, Kepler TB. Patient socioeconomic status is an independent predictor of operative mortality. Ann Surg Sep;252(3):552-7; discussion Kim C, Diez Roux AV, Hofer TP, Nallamothu BK, Bernstein SJ, Rogers MA. Area socioeconomic status and mortality after coronary artery bypass graft surgery: the role of hospital volume. Am Heart J Aug;154(2): AHRQ. Inpatient Quality Indicators: Software Documentation. Available at Accessed August 3, AHRQ. Patient Safety indicators: Software Documentation Version 4.1. Available at Accessed August 7, Tsang C, Palmer W, Bottle A, Majeed A, Aylin P. A review of patient safety measures based on routinely collected hospital data. Am J Med Qual Mar;27(2): National Quality Forum. NQF-Endorsed Standards. Available at Accessed August 7, Page 10 of 13

11 20. The U.S. Department of Health and Human Services. Medicare Hospital Compare Quality of Care. Available at Accessed August 7, Houchens RL, Elixhauser A, Romano PS. How often are potential patient safety events present on admission? Jt Comm J Qual Patient Saf Mar;34(3): AHRQ. AHRQ Quality Indicator: Risk Adjustment Coefficients for the IQI. Available at Accessed October 10, AHRQ. AHRQ Quality Indicator: Risk Adjustment Coefficients for the PSI. Available at a.pdf. Accessed October 10, Houchens R, Elixhauser A. Final Report on Calculating Nationwide Inpatient Sample (NIS) Variances, HCUP Methods Series Report # ONLINE. June 2005 (revised June 6, 2005). U.S. Agency for Healthcare Research and Quality. 25. Elixhauser A, Steiner C, Harris DR, Coffey RM. Comorbidity measures for use with administrative data. Med Care Jan;36(1): Losina E, Barrett J, Baron JA, Levy M, Phillips CB, Katz JN. Utilization of low-volume hospitals for total hip replacement. Arthritis Rheum Oct 15;51(5): Schrag D, Panageas KS, Riedel E, Cramer LD, Guillem JG, Bach PB, Begg CB. Hospital and surgeon procedure volume as predictors of outcome following rectal cancer resection. Ann Surg Nov;236(5): Williams DR. Socioeconomic Differentials in Health: A Review and Redirection. Social Psychology Quarterly Jun; 53(2): Chowdhury MM, Dagash H, Pierro A. A systematic review of the impact of volume of surgery and specialization on patient outcome. Br J Surg Feb;94(2): Page 11 of 13

12 Exhibit 2: Post-Surgical Mortality by Income Level of Patient's Community, Risk-adjusted Rates, National Estimates 2000 and 2009 Surgical Mortality and Income Level of Patient's Community Rate per 1,000 discharges 2000 Adjusted Rate a 2009 Adjusted Rate a Standard error P-value: Lowest vs Highest Income Rate per 1,000 discharges Standard error P-value: Lowest vs Highest Income Page 12 of 13 P-value: 2009 relative to 2000 AAA Repair Mortality Rate Lowest income n.s Highest income Ref Ref CABG Mortality Rate Lowest income Highest income Ref Ref Carotid Endarterectomy Mortality Rate Lowest income n.s Highest income Ref Ref Craniotomy Mortality Rate Lowest income Highest income Ref Ref Esophageal Resection Mortality Rate for Cancer Lowest income n.s Highest income Ref Ref Hip Replacement Mortality Rate Lowest income n.s Highest income Ref Ref Pancreatic Resection Mortality Rate for Cancer Lowest income n.s Highest income Ref Ref n.s. PTCA Mortality Rate Lowest income n.s Highest income Ref Ref Source: Healthcare Cost and Utilization Project, Nationwide Inpatient Sample a Mortality rates are adjusted for age, gender, age-gender interaction, Major Diagnostic Category (MDC), APR-DRG Risk of Mortality. Patient safety rates are adjusted by age, gender, age-gender interactions, co-morbidities, MDC, and Diagnosis Related Group (DRG). Notes: "n.s." is not significant at p<.05 level; "Ref" is reference group; "N/A" is data not available; p value is less than or equal to the value shown

13 Exhibit 3: Post-Surgical Complications by Income Level of Patient's Community, Risk-adjusted Rates, National Estimates 2000 and 2009 Surgical Outcome Complications and Income Level of Patient's Community Rate per 1,000 discharges 2000 Adjusted Rate a 2009 Adjusted Rate a Standard error P-value: Lowest vs Highest Income Rate per 1,000 discharges Standard error P-value: Lowest vs Highest Income P-value: 2009 relative to 2000 Deaths among surgical patients with serious treatable complications Lowest income n.s Highest income Ref Ref Postoperative hemorrhage or hematoma Lowest income n.s. Highest income Ref Ref n.s. Postoperative respiratory failure Lowest income Highest income Ref Ref Postoperative wound dehiscence Lowest income n.s Highest income Ref Ref Postoperative sepsis Lowest income N/A N/A N/A n.s. N/A Highest income N/A N/A N/A Ref N/A Source: Healthcare Cost and Utilization Project, Nationwide Inpatient Sample a Mortality rates are adjusted for age, gender, age-gender interaction, Major Diagnostic Category (MDC), APR-DRG Risk of Mortality. Patient safety rates are adjusted by age, gender, age-gender interactions, co-morbidities, MDC, and Diagnosis Related Group (DRG). Notes: "n.s." is not significant at p<.05 level; "Ref" is reference group; "N/A" is data not available; p value is less than or equal to the value shown Page 13 of 13