TR2-5 ESTIMATING UTILITIES FOR CHRONIC KIDNEY DISEASE IN PATIENTS WITH TYPE 2 DIABETES USING TRANSFORMED SF-36 AND SF-12 RESPONSES: CHALLENGES IN A VETERAN POPULATION

Monday, October 24, 2011: 11:42 AM
Grand Ballroom CD (Hyatt Regency Chicago)
(ESP) Applied Health Economics, Services, and Policy Research

Mangala Rajan, MBA1, Chin-Lin Tseng, DrPH1, Alfredo Selim, MD, MPH2, Shirley Qian, MS2, Lewis Kazis, ScD2, Leonard Pogach, MD, MBA1 and Anushua Sinha, MD, MPH3, (1)East Orange Veterans Administration Medical Center, East Orange, NJ, (2)Boston University, Boston, MA, (3)University of Medicine and Dentistry of New Jersey - New Jersey Medical School, Newark, NJ

Purpose: To compare four previously-published methods of transforming Short Form 36 and 12 Item Health Surveys (SF-36 /SF-12) data into utilities, using survey responses from veterans with diabetes (DM) and chronic kidney disease (CKD); to determine if these transformations are valid for discriminating utility losses (disutilities) as CKD severity increases; and to estimate the disutility associated with progressive CKD.

Methods: Veterans with DM were selected who responded to the Large Veterans Health Survey in 1999 and divided into those with recent-onset DM (duration of ≤3 years) and prevalent DM (duration >3 years). Surveys were merged with data from the Diabetes Epidemiology Cohort, a well-established longitudinal cohort of veterans with diabetes. ICD-9 and procedure codes determined if respondents were on dialysis or had end-stage renal disease (ESRD). If subjects did not have ESRD/dialysis, serum creatinines were used to stage CKD.  Four previously-published SF-36 /SF-12-to-utility transformations (A = SF-12 to SF-6D, B = SF-36 to SF-6D, C = SF-36 to HUI2, D= SF-12 to VR-6D) were used to estimate utilities (U) for each respondent. Generalized linear regression models estimated the disutility associated with each CKD stage, after adjustment for demographics, socio-economics, and co-morbidities.

Results: Of 67,694 diabetic patients, 22,273 had recent-onset and 45,691 patients had prevalent DM. The figure gives mean utilities by each method for recent-onset DM patients; results were similar for prevalent DM.  Method A did not discriminate utility by CKD stage, among either recent-onset or prevalent diabetics. The remaining three methods showed a stepwise decline in utility as CKD stage increased. The rank order was consistently U(A)>U(C)>U(B)>U(D). In recent-onset DM, mean disutilities associated with increasing CKD stage differed significantly by transformation method (p<0.0001) and ranged between 0.0017 - 0.0042, -0.0067 - -0.0019, -0.0256 - -0.0041, and -0.0116 - -0.0091 for CKD stages 2, 3, 4/5, and ESRD/dialysis respectively; results were similar for prevalent DM.

Conclusions: In a cross-sectional analysis of diabetic veterans, systematic differences were found in utilities estimated using four transformations of SF-36 /SF-12 data. In particular, method A may not capture all available SF-36 information, resulting in inconsistent utility estimates relative to other methods. CKD-associated disutility values differed significantly between methods at each CKD stage, suggesting that selection of transformation method requires careful consideration of potential floor and ceiling problems.