Three other options were considered but not adopted to identify people with potentially disabling chronic conditions for the Private Payers Study. These included the method used by the Social Security Administration (SSA) to define disability, the International Classification of Impairments, Disabilities, and Handicaps (World Health Organization, 1980), and a method used in earlier research by Altman and Barnett (1996). These methods were not used either because ICD-9-CM mappings could not be made or because the method could not be applied to all ICD-9-CM codes. These methods might be relevant in the future for other studies, however, so we describe them briefly below.
1. The Social Security Administration Approach
Another option which does not rely on survey data is the list of medical problems used by the SSA to identify those with disabling conditions (SSA, 1995). This condition list--approximately 150 pages long--is divided into separate sections for each body system--patients with any of these conditions meet SSA requirements regarding the disabling nature of their medical problems. One problem with this list is that SSA has not assigned ICD-9-CM diagnosis codes to the condition on the list. Furthermore, many of the SSA criteria are much more specific than the ICD-9-CM coding system, making a one-to-one translation impossible. Therefore it is not possible to replicate the SSA approach with the data contributed by the two employers who took part in the Private Payers Study.
2. The International Classification of Impairments, Disabilities, and Handicaps
The International Classification of Impairments, Disabilities, and Handicaps (ICIDH) was developed in the 1970s and released by the World Health Organization in 1980. The ICIDH was developed to classify patients according to the consequences of their diseases or conditions (World Health Organization, 1980). Clinicians who use the ICIDH must ask probing questions about the nature of patients' problems and how those problems limit social and functional status. Thus, the ICIDH holds some potential as a means of bridging the gap between the type of information available from ICD-9-CM diagnosis codes and the information requested on many disability surveys.
Unfortunately for the Private Payers Study, the ICIDH is still considered a work in progress. It is in the process of being updated to better address the potential for negative consequences associated with the use of the term handicap, and it is not in widespread use by clinicians in the United States. Because it was not used by providers affiliated with the employers who contributed data for the Private Payers Study, the ICICH could not be used to identify potentially disabled people for this study.
3. The Altman and Barnett (1996) Approach
Another example of methods that may be used to identify those with potentially disabling chronic conditions was described recently by Altman and Barnett (1996). Altman and Barnett developed a list of life-threatening conditions, chronic conditions, mental health conditions, impairments, and conditions with severe pain, and then related these conditions to variations in employment status. Altman and Barnett provided a list of ICD-9-CM diagnosis codes to define these types of disabling conditions. They also defined other types of disabling conditions that require the use of survey data. Their work showed a high degree of variation in employment history according to the definition of disability chosen. Altman and Barnett did not recommend a single best way to define disability status, and implicit in their work is the message that a variety of ways should be tested to determine the sensitivity of results according to the definitions chosen.
The Altman and Barnett approach is attractive because of its recognition that the various types of disabilities they define are likely to influence health care service use differently. Their approach is also helpful in that they found a useful way to group a wide variety of chronic conditions for analysis. Applying the Altman and Barnett approach for the Private Payers Study would require additional work, however, because their approach was based only on the diagnoses found in the National Medical Expenditure Survey; other diagnoses not defined by the National Medical Expenditure Survey respondents were not covered. Depending upon the scope of diagnoses identifiable in the National Medical Expenditure Survey, a substantial amount of clinical input may be required to make their approach more comprehensive. For our study, however, we considered the added value of that effort to be limited, since MEDSTAT clinical staff had already reviewed the entire ICD-9-CM manual to identify disabling conditions.