Two Approaches to Identif

Identif

Non‐Surgical Controls fo

Bariatric Surgery Evaluati

M tt a M i j ki Maciejewski, PhD
Acknowledgements

• Co

‐Investigators

• Leila Kahwati, Valerie Smith: Durham VA

• Edward Livingston: Livingston: UT

‐Southwestern Southwestern

• William Henderson: University of Colorado• David Arterburn: Arterburn: Group Health Cooperative Cooperative

• HSR&D Funding

• IIR 05

‐201, SHP 08

‐137

• RCS 10

‐391
Outline

• P ir or aims and results

• Reaction to this work and scientific refl

to reaction

• Cohort identification analysis analysis• Implications for evidence base?
Evidence and Demand for Bar

Surgery

• Most effective effective treatment treatment for weight los

comorbidity reduction, and improved Q

• Low mortality mortality (30‐day: 0 28% . , 1 yr: 1%

250000

1300

150000200000

71733

102739

121055

1300

100000150000

9409 12295 13368 22638

30438

54557

71733

0

50000

1996 1997 1998 1999 2000 2001 2002 2003 2004 200

Davis, Slish, 2006; Encinosa, Bernard, 2005; Santry, Gillen, Lauderdale, 2005; Thom
Prior Research Question

IIR 05‐201• Specific Aim 1: Compare survival rates of morbidly obese veterans who had bariatric surgery from 200

cohort of morbidly obese veterans who did not have surgery

– JAMA June 2011

• Specific Specific Aim 2: Compare Compare the health care use and expenditures expenditures of morbidly morbidly obese veterans veterans who had bar

bar

a cohort of morbidly obese veterans who did not have surgery

– Under review at Medical Care

• Secondary Aim 1: Compare the preoperative and postoperative health care use and expenditures for m

who had bariatric surgery in VA medical centers from 2000 to 2005

– Medical Care Nov 2010

• Secondary Aim 2: Identify patient‐level predictors of survival and adverse events among morbidly obes

bariatric surgery in VA medical centers from 2000 to 2005

– Archives of Surgery Oct 2009

SHP 08‐137• S ifi pec c Aim 1: For obese veterans who h da b i ti ar a ric surgery in 2000‐2006, how much did th i e r wei ht g 

months after surgery? Did these changes persist over time?

– Under review at Obesity Research & Clinical Practice

• Specific Aim 2: Compared to non‐surgical controls, how much did weight and BMI of obese veterans w

2000‐2006 change in the months after surgery?

– Not done

• Specific Aim 3: Among obese veterans with diabetes or dyslipidemia who had bariatric surgery in 2000

were able to discontinue their oral hypoglycemic agents or statins in the months after surgery?

– SOARD Nov/Dec 2010
Study Design of

Case Analyses

• Retrospective cohort• Veterans who had bariatric surgery in one o

f l aci ities ( ) N=850

• Identified by CPT codes in 2000‐2006

• S iti it Sensitivity: 99 2%. , S ifi it Specificity: 99 9%.
Source for Cases: VA Surgical Q

I t mprovement Program

• VA I iti ti nitiative to M it on or, Compare and I

Surgical Quality

• Founded in 1994

• Trained surgical clinical nurses extract d

major surgical surgical procedures procedures using standa

standa

protocol

• Demographics, pre‐op comorb di ities & l ba s

• 30‐day post‐op complications & mortality
Sample Flow of Surgical Ca

All patients who had bariatric surgery in twelve VA bariatric 

centers from 2000 to 2006

Revisio

pro

centers from 2000 to 2006

N = 892

Patients who had their first bariatric surgery in one of twelve 

VA bariatric centers from 2000 to 2006

N = 888

Died prior t

s

Patients alive for surgery

N = 884

Patients w

BMI data 

s

Patients with eligible start date BMI data

N = 875

Surgical cases in unmatched analytic sample

N = 850

Patients w

DC

N = 850 N 
Survival Analysis of Case

Hazard Ratio 95% Confidence Interva

Age (continuous) 1.02 (0.98, 1.05) Male 1.26 ( ) 0.58, 2.75) Non-Caucasian Race** 0.71 (0.28, 2.36) Unknown Race** 1.51 (, ) 0.85, 2.66) BMI ≥ 50 1.77 (1.01, 3.09) ASA class 3*** 2.13 (0.50, 9.12) ASA class 4*** 4.65 (0.95, 22.84) DCG score ≥ 2**** 3.40 (1.79, 6.48) Smoker 1.24 (0.61, 2.53) Diabetes (oral/insulin) 1.08 (0.62, 1.90) L id aparoscopic procedure 0 10 . (0 01 0 74) (0.01, 0.74) 

Arterburn 2009 Arch Surg
Study Design of

Case‐Control Comparison

• Retrospective cohort w/ non‐equivalent co• 850 veterans who had bariatric surgery

• Identified by CPT codes in 2000‐2006

• Sensitivity: 99.2%, Specificity: 99.9%

• Veterans who did not have surgery

• Identified Identified from NCP registry registry made in 2000
Control Cohort

C

N

CO
Descriptive Statistics

Surgical Pts

N=850

Controls

N=41,244

Age (Mean, (SD)) 49.5 (8.3) 54.7 (10.2) 

Age ≥ 65 years (%) 18 (2.1) 8,534 (20.7) 

Male (%) 628 (73.9) 37,840 (91.7) 

Caucasian (%) 662 (77.9) 27,967 (67.8) 

Non‐Caucasian (%) 136 (16.0) 7,977 (19.3) Married (%) 443 (52.1) 23,808 (57.7) Previously Married (%) 258 (30.4) 11,259 (27.3) Never Married (%) 139 (16.4) 5,700 (13.8) 

BMI (Mean, SD) 47.4 (7.8) 42.0 (5.0) 

Super Obese (BMI ≥ 50) (%) 266 (31.3) 2,905 (7.0) 

Diagnostic Cost Group (DCG) score 0.60 (0.92) 0.47 (0.75) 

DCG score ≥ 2 (%) 42 (4.9) 1,633 (4.0) 

Fiscal year of start time: 2000 339 (39.9) 34,908 (84.6) 

Fiscal year of start time: 2001 104 (12.2) 4,921 (11.9) 

Fiscal year of start time: 2002 110 (12.9) 468 (1.1) 

Fiscal year of start time: 2003 94 (11.1) 342 (0.8) 

Fi l sca year of start time: 2004 87 (10 2) . 216 (0 5) . Fiscal year of start time: 2005 69 (8.1) 212 (0.5) 

Fiscal year of start time: 2006 47 (5.5) 177 (0.4) 
Covariate Imbalance Improved w

Propensity Matching

Unmatched M

Age (Mean, (SD)) ‐55.92 

Age ≥ 65 years (%) ‐61.20 

Male ( ) % ‐48.54 Caucasian (%) 22.86 

Non‐Caucasian (%) ‐8.66 

Married (%) ‐11.27 

Previously Married (%) 6.85 Never Married (%) 7.00 BMI (Mean, SD) 82.43 

Super Obese (BMI ≥ 50) (%) 64.93 

Diagnostic Cost Group (DCG) score 15.49 Fiscal year of start time: 2000 ‐104.24 

Fi l sca year of start time: 2001 0 92 . Fiscal year of start time: 2002 47.21 Fiscal year of start time: 2003 44.61 Fiscal year of start time: 2004 44 14 . Fiscal year of start time: 2005 38.14 

Fiscal year of start time: 2006 30.49 
Matched & Unmatched Surv

Outcomes

Unmatched

Covariate

Matc

Y

Unadjusted Adjusted Unadjusted 

Bariatricsurgery

0.638 0.795 0.833 

0.511 - 0.797 0.634 - 0.995 0.607 - 1.144 

Sample size 42,094 1,6

Maciejewski 2011 JAMA
Reaction To These Resul

• Survival results can’t possibly be right

– SOS, Utah studies (2007 NEJM) & systema

show protective effect against death (Patt

& Wolfe JAMA 9/28/11)

• Absence of evidence isn’t evidence of a• Explained Explained by volume‐outcome outcome relation

relation
Reflection in

Response to Reaction

• Initial response

– Compare demographics– Compare follow‐up time– Compare analytic methods
Prior Mortality Comparison

Author

Journal,

Patients Survival

Results

,

Year Cases Controls

MacDonald 154 with 78 with 9% v. 28% at 6 J Gastro’97 diabetes diabetes years Christou

‘

1035 pts in‘

5746 0.68% vs. 6.2% 

AnnSurg‘04 ‘86‐02 patients at 5 yrs 

Flum

JACS ’04

3328 pts in’87 01

62,781

ti t

HR=0.67 (0.54‐0 85)

JACS ’04 ’87‐01 patients 0.85) SOSNEJM ‘07

2010 pts in

‘87 01

2037patients

HR=0.76 (0.59‐0 99)

NEJM 07 87‐01 patients 0.99) AdamsNEJM ‘07

7925 ptsin ’84 02

7925patients

HR=0.60 (0.45‐0 67)

NEJM 07 in 84‐02 patients 0.67) 
Evidence about Survival associate

Bari i atr c Surgery

Patient Characteristics

Mean Age Male Follow‐Up

In Years

Years 

Flum 2004 43 19% 4.4 Adams 2007 40 16% 7.1 SOS 2007 47 29% 10.9 Maciejewski2011

49 74% 6.7 
Three Possibilities

• We are ri hg t and they are ri hg t

– Non‐VA: Surgery good for 40‐50 yr old wom– VA: N t o as good for 50‐60 yr old men

• We are wrong (in a sense) & they are righ

– B fit ene s of surgery t ka es longer to realize for 

our results will converge when we add 4‐5 ye

additional follow‐up in new study

• We are right and they are wrong

– VA results are unbiased, no evidence on wom– Non‐VA results are biased for several reasons

• Poor covariate adjustment and/or no matching• Incorrect control id ifi i identification
Further Reflection in

Response to Reaction

• Initial response

– Compare demographics– Compare f ll o ow‐up time

– Compare analytic methods

• Most recent response

– Examine control selection process– BMI in VA vs. obesity Dx everywhere else
Scientific Objective

• Examine whether patients differ by st

identifying non‐surgical controls

– Demographics– Mortality– Expenditure trends

• Leverage cohort of 34 908 , controls wi 

are eligible based on BMI≥35 in FY00

– Find subset with obesity Dx
Outcomes

• Survival Outcome: Vital status file

• Survival = Date of death or end of study period – 

recorded BMI ≥ 35

• D h eat data from VA, M di e care and S il oc a S i ecur t

• Utilization & expenditures: HERC data

• OP, IP & total expenditures expenditures• 6‐month blocks
Covariates

• Socio‐demographic: Age, gender, race, 

status

• BMI: Corporate Data Warehouse

• Super obese (BMI 50), (BMI>50), binary

• Comorbidity Comorbidity burden: burden: Diagnostic Diagnostic Cost G

(DCG) score

• As predi ti c ve of VA costs (M i j ki (Maciejewski 2005, 200

mortality (Fan, 2006) as other risk measures
Baseline Characteristics

No Morbid Obesity 

Dx

Primary or Secondary 

Dx of Morbid Obesity

(N=32,225) (N=2,683)

Age (Mean, (SD)) 54.4 (10.2) 54.0 (9.5) 

Age ≥ 65 years (%) 20.04 16.40 

Male (%) 91.56 92.69 Caucasian (%) 68.59 70.59 Non-Caucasian (%) 20.11 21.54 U k R (%) Unknown Race (%) 11 30 . 7 86 . Married (%) 57.40 51.73 Previously Married (%) 27.12 30.86 Never Married (%) Never Married (%) 14 25 . 16 73 . Unknown Marital Status (%) 1.23 0.67 BMI (Mean (SD)) BMI (Mean, (SD)) 41 8 (4 7) 41.8 (4.7) 45 9 (6 4) 45.9 (6.4) 

Super Obese (BMI≥50) 5.95% 22.14% 

Diagnostic Cost Group 

(DCG) score (Mean (SD)) 0.48 (0.75) 0.59 (0.96) (DCG) score (Mean,(SD))

DCG score ≥ 2 (%) 4.03 6.08 
Unadjusted Mortality Differe

No Morbid Dx Morbid Dx 

30%

2

20%

p=0.04

12.3%

p=0.35 13.6%

p=0.40

4.7%

10%

2.3% 2.0%

4.3%

0%

One Year Two Year Five Year 
Unadjusted Outpatient Expend

$4 227

$4,500

$5,000

No Morbid Dx Morbid Dx

$3,334

$

$4,227

$3,500$4,000

,

$2,308 $2,374 $2,234

$2,953

$$2,500$3,000

$1,788 $1,769

$1,000$1,500$2,000

$0

$500

$1,000

Year One Year Two Year Three Year Four 
Unadjusted

Inpatient Expenditures

$3 914 $4,027 $4,136

$5,000

$3,023

$3,914 $ ,

$3,414 

$4,000

$2,153

$2,659 $2,673 

$2 000$3,000$1 000$2,000

$0

$1,000

Year One Year Two Year Three Year Four 
Unadjusted Total Expendit

$6 357

$8,363 

$8,000$9,000

$4 981

$6,357 $

$6,288 $6,261 $6,367

$6,000$7,000

$3,942

$4,428

$4,981

$4,000$5,000$2,000$3,000

$0

$1,000

Year One Year Two Year Three Year Four 
Conclusion

• Among controls identified from BMI d

7.7% who had a Dx of morbid obesity

• Veterans with Dx were systematically 

from veterans without without Dx

– Sicker and heavier

• Worse outcomes

– Higher unadjusted mortality mortality rates– Higher unadjusted VA expenditures
Implication for Evidence Bas

Bariatric Surgery?

• Potential issues with control id f enti ica

diagnosis codes

– Smaller sample than BMI identification, 

matching and subgroup analysis

– Sicker and heavier than BMI‐based coho

• If sicker controls are identified but thi

isn’t realized, is evidence base for barsurgery surgery more favorable favorable than it would 

data was used to identify controls?
Questions?