Preliminary Validation of a Patient-based Self-assessment Measure of Severity of Illness in Type 2 Diabetes

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.

Disease severity is associated with the use of complementary medicine to treat or manage type-2 diabetes: data from the 2002 and 2007 National Health Interview Survey

“…The three diabetes complications counted were: 1) weak or failing kidneys; 2) severe vision problems; and 3) coronary heart disease. The items chosen for the count were based on the literature where measures of diabetes severity routinely included use of diabetes prescription drugs [25], time since diagnosis [25], and major complications of diabetes (even if self-reported) including kidney disease [25-27], retinal diseases [25-27] and coronary heart disease [25-27], but not co-morbid diseases that are not considered complications of diabetes.…”

“…Also included in some of the published studies examining diabetes severity were diabetes-related functional limitations [27,28]. In the present study, the measure of functional limitation for diabetes was based on the following sequential questions from the NHIS core: “The next questions ask about difficulties you may have doing certain activities because of a HEALTH PROBLEM.…”

Medication effectiveness studies in the United States Veterans Administration health care system: a model for large integrated delivery systems

“…These were selected because they were easily identifiable upon screening, prevalent in the population, variable in severity and thus responsible for varied impacts on function, and susceptible to a range of treatments that could affect outcomes differently . The screening questionnaire for case identification of other chronic illnesses was written according to expert physicians and other scientists in each of the chronic disease areas Felson et al, 2001;Fincke et al, 2005;Gage et al, 2003;Hankin et al, 1999Hankin et al, , 2006Linzer et al, 2005;Mansell et al 2005a,b;Ren et al, 2006;Selim et al, 1997Selim et al, , 1998Selim et al, , 2000Selim et al, , 2001Selim et al, , 2002aSkinner et al, 2005;Spiro et al, 2006].…”

“…Individual validation studies of illness severity were conducted to develop diseasespecific measures of patient-based severity for osteoarthritis of the knee ], chronic lung disease [Ren et al, 2006;Selim et al, 1997], diabetes Linzer et al, 2005], hypertension Kazis et al, 2000], alcohol-related disorders [Mansell et al, 2005a,b], and chronic lowback pain [Selim et al, , 2000. These patient-centered measures focused on symptoms of illness and gave the patient's perspective about illness severity.…”

“…This library includes general and disease-specific measures of HRQoL including the VR-36 as one of the centerpieces of functional status assessment [Kazis et al, 2004a-c;Clark et al, 2005]. Other assessments include measures of comorbidity for medical and mental health conditions [Selim et al, 2002a[Selim et al, ,b, 2004a and a number of illness-specific severity measures including osteoarthritis [Felson et al, 2001], hypertension and diabetes Linzer et al, 2005], Parkinson's disease [Gage et al, 2003], depression [Hankin et al, 1999, alcohol-related disorders [Mansell et al, 2005a,b], chronic lung disease [Ren et al, 2006;Selim et al, 1997], chronic low back pain [Selim et al, , 2000, and post-traumatic stress disorder . These VHS assessments provide a range of general and disease-specific measures with a prior history of psychometric testing for future application in patient populations.…”