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The Impact of Volume of Outpatient Surgical Procedures on Quality

Outcomes: 1997-2004

AcademyHealth: June 4, 2007

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Research Team

Askar Chukmaitov, M.D., Ph.D. Nir Menachemi, Ph.D., M.P.H. Steven Brown, M.S. Charles Saunders, Ph.D. Robert Brooks, M.D., M.B.A.

Funding support from the Florida Agency for Health Care Administration (AHCA)

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Inverse relationship between hospital/surgical volume and adverse patient outcomes in inpatient settings

Better outcomes for high-volume hospitals and high-volume surgeons

Lack of research on volume-quality relationship in outpatient surgical settings

Important issue, because:

60-70% of all surgeries are performed now in outpatient settings

Medicare payment for outpatient procedures has doubled over the

last decade

Rationale for the Study

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Methods

Design– Longitudinal analysis of 1997-2004 data

Data– Ambulatory discharge, hospital discharge, vital statistics

Sampling– Colonoscopies (n=2,820,769), Cataracts (n=2,058,090), and

upper gastrointestinal endoscopies (n=1,348,121) in ASCs and HOPDs

Analytical Approach Physician volume and patient outcomes (Model 1) Outpatient facility volume and patient outcomes (Model 2) Combined surgeon and facility volume and patient

outcomes (Model 3) Controls: Patient severity, age, gender, payer type, location

of care, time fixed effects, and clustering of outcomes

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Key Variables

Adverse patient outcomes– 7- and 30-day unexpected hospitalization– 7- and 30-day mortality

Physician and Facility Volume – Ranked providers according to volume tertiles:

low (<34%), medium (34-67%) and high (>67%, the reference group)

Patient Severity/Risk Adjustment – Relative Risk Scores calculated using DCG/HCC

methodology

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Physicians: 2,857 Facilities: 874 (ASC=61.64%) Unexpected Hospitalizations less than 5% Mortality Rates less than 1% Patient demographics

– Age: 65.62 (sd=14.26)– Female: 57.3%– White: 76.79%– Severity risk score: 0.89 (sd=0.82)– Private-pay: 25.92%– Medicare: 54.56%– Medicaid: 1.95% – HMO: 13.42%

Results – Descriptive

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7-day Unexpected Hospitalizations after Colonoscopies

Controlled for patient severity, age, gender, payer type, location of care, time fixed effects, and clustering of outcomes

*p<.05 **p<.01 ***p<.001

Volume Category Odds Ratio (95% CI)

Tertile 3 - High 1.00

Tertile 2 - Medium 1.24 (1.13 – 1.37)*** Model 1:

Physician Volume Only Tertile 1 - Low 1.42 (1.25 – 1.61)***

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7-day Unexpected Hospitalizations after Colonoscopies

Controlled for patient severity, age, gender, payer type, location of care, time fixed effects, and clustering of outcomes

Volume Category Odds Ratio (95% CI)

Tertile 3 - High 1.00

Tertile 2 - Medium 1.24 (1.13 – 1.37)*** Model 1:

Physician Volume Only Tertile 1 - Low 1.42 (1.25 – 1.61)***

Tertile 3 - High 1.00 Tertile 2 - Medium 1.09 (1.01 – 1.17)*

Model 2: Facility

Volume Only Tertile 1 - Low 1.22 (1.19 – 1.32)*** *p<.05 **p<.01 ***p<.001

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7-day Unexpected Hospitalizations after Colonoscopies

Controlled for patient severity, age, gender, payer type, location of care, time fixed effects, and clustering of outcomes

Volume Category Odds Ratio (95% CI) Tertile 3 - High 1.00 Tertile 2 - Medium 1.23 (1.11 – 1.35) ***

Model 3: Physician Volume

Tertile 1 - Low 1.38 (1.21 – 1.57) *** Tertile 3 - High 1.00 Tertile 2 - Medium 1.06 (0.98 – 1.14) Facility Volume Tertile 1 - Low 1.12 (1.02 – 1.23)*

Physician vs. Facility Tertile 2 χ2 = 5.1 *

The Wald Test Physician vs. Facility Tertile 1 χ2 = 5.4 *

*p<.05 **p<.01 ***p<.001

Patterns in 7- and 30-day Mortality Outcomes by Volume Category (1997-2004)

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colonoscopy, 7 day

colonoscopy, 30 day

cataract, 7 day

cataract, 30 day

gastrointestinalendoscopy, 7 day

gastrointestinalendoscopy, 30 day

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Consistent, dose-responsive, inverse relationship between volume and outcomes for unexpected hospitalization

Physician volume demonstrated stronger effects than facility volume

In terms of mortality, a similar pattern was noted. The lack of statistically significant findings may be due to the rarity of deaths

Conclusions

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Significance to Policy

Further research is needed to validate these findings with data from other states, using different outcome measures, risk adjustment techniques, and analytical approaches

Volume of outpatient surgical procedures may indicate improved provider skills and processes of care delivery

Possible development of outpatient standards/guidelines (e.g., Leap Frog)

Volume-based outpatient referrals should be considered by patients, providers, payers, and policy-makers