title: Preliminary validation of a patient-based self-assessment measure of severity of illness in type 2 diabetes: results from the pilot phase of the Veterans Health Study.
abstract: Measures of case mix are needed to control for patients' clinical status in studies assessing the process and outcomes of care. The Veterans Health Study (VHS) is a longitudinal study of determinants of health outcomes in ambulatory veterans. This study assessed the validity of a case-mix measure developed to quantify severity of illness in ambulatory type 2 diabetic patients. As part of the pilot phase of the VHS, 245 veterans using 4 primary care clinics in Boston were screened for diabetes and 5 other chronic illnesses when they presented for care. Subjects screening positive for diabetes returned to complete severity of illness and outcome measures. The variables for the diabetes case-mix module were chosen based upon the principles of parsimony, duration of follow-up, and clinical validity and credibility. Variables were selected to predict function, as measured by the Medical Outcomes Study Short-Form 36 (SF-36). The diabetic patients in this study had a heavy burden of chronic illness, with an average of 3.9 comorbid conditions and a mean general health perceptions score of 48 on the SF-36 (scored from 0 to 100, with 100 indicating best health). A summary variable called DMSEV was created for "diabetes severity". This included atherosclerotic complications(stroke, transient ischemic attack or myocardial infarction; chest pain frequency; and claudication), plus any history of eye, foot, or neuropathic symptoms. DMSEV correlated with all 8 outcome scales of the SF-36, and in particular was highly associated with physical function (r=0.49, P=.0001). Least squares linear regression analysis controlling for age and comorbidity confirmed the association of DMSEV with all 8 SF-36 scales. The correlation with physical function remained highly significant (P<.0001), with an R of 0.31. This patient-based self-assessment questionnaire and the summary variable DMSEV appear to be valid measures of severity of illness in ambulatory diabetic veterans with multiple comorbidities. After further testing, this case-mix measure may be suitable for controlling for severity of illness in ambulatory-based studies of diabetic patients with multiple chronic illnesses.
authors.affiliation: Department of Medicine, University of Wisconsin School of Medicine, Madison, WI 53705, USA. mxl@medicine.wisc.edu
authors.forename: Mark
authors.initials: M
authors.lastname: Linzer
authors.forename: Catherine
authors.initials: C
authors.lastname: Pierce
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Lincoln
authors.forename: Donald R
authors.initials: DR
authors.lastname: Miller
authors.forename: Susan M
authors.initials: SM
authors.lastname: Payne
authors.forename: Jack A
authors.initials: JA
authors.lastname: Clark
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Skinner
authors.forename: Sheldon
authors.initials: S
authors.lastname: Greenfield
authors.forename: Sherrie
authors.initials: S
authors.lastname: Kaplan
authors.forename: Colleen A
authors.initials: CA
authors.lastname: McHorney
authors.forename: Austin
authors.initials: A
authors.lastname: Lee
authors.forename: Lewis E
authors.initials: LE
authors.lastname: Kazis
mesh_terms: D000368:Aged; D001900:Boston; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D010865:Pilot Projects; D011788:Quality of Life; D012720:Severity of Illness Index; D014728:Veterans