Stephen P Gulley, Elizabeth K Rasch, Christina D Bethell, Adam C Carle, Benjamin G Druss, Amy J Houtrow, Amanda Reichard, Leighton Chan

There is a concerted effort underway to evaluate and reform our nation's approach to the health of people with ongoing or elevated needs for care, particularly persons with chronic conditions and/or disabilities. This literature review characterizes the current state of knowledge on the measurement of chronic disease and disability in population-based health services research on working age adults (age 18-64). Scoping review methods were used to scan the health services research literature published since the year 2000, including medline, psycINFO and manual searches. The guiding question was: "How are chronic conditions and disability defined and measured in studies of healthcare access, quality, utilization or cost?" Fifty-five studies met the stated inclusion criteria. Chronic conditions were variously defined by brief lists of conditions, broader criteria-based lists, two or more (multiple) chronic conditions, or other constructs. Disability was generally assessed through ADLs/IADLs, functional limitations, activity limitations or program eligibility. A smaller subset of studies used information from both domains to identify a study population or to stratify it by subgroup. There remains a divide in this literature between studies that rely upon diagnostically-oriented measures and studies that instead rely on functional, activity or other constructs of disability to identify the population of interest. This leads to wide ranging differences in population prevalence and outcome estimates. However, there is also a growing effort to develop methods that account for the overlap between chronic disease and disability and to "segment" this heterogeneous population into policy or practice relevant subgroups.