Measurement in veterans affairs health services research: veterans as a special population

Health Services Research, Oct, 2005 by Robert O. Morgan, Cayla R. Teal, Siddharta G. Reddy, Marvella E. Ford, Carol M. Ashton

ICD codes are now used in many applications, including research, reimbursement, identification of medical errors, and denoting causes of death on death certificates. Because ICD 9 CM and ICD-10-CM codes are widely applied to "measure" diagnoses, their accuracy is of considerable interest. Understanding sources of error in the application of these codes is critical to the evaluation of their usefulness and limitations. In the third article, "Measuring Diagnoses: ICD Code Accuracy," O'Malley, Cook, Price, Raiford Wildes, Hurdle, and Ashton conceptualize diagnostic coding as a measurement problem. The authors summarize the process for assigning diagnostic codes, identify sources of errors in the process, summarize research related to code accuracy, and review methods for quantifying the accuracy of diagnostic codes. By understanding potential sources of errors in the process of assigning diagnostic codes, code users (i.e., researchers, clinicians, payers, etc.) can make better decisions about the usefulness of the codes in various applications.

Identifying Populations of Interest and Appreciating Measurement Challenges Associated with these Populations

The next two articles address issues involved in identifying populations of interest. The fourth manuscript, "Measurement Issues in Health Disparities Research," by Ramirez, Ford, Stewart, and Teresi provides an overview of measurement instruments in diverse populations. Members of minority groups have higher rates of morbidity and mortality than their nonminority counterparts for almost all categories of disease. Racial and ethnic health disparities may be because of comorbidity, access to care, attitudes and perceptions, or disease etiology. However, in order to conduct comparative studies in a meaningful manner, investigators must face the challenge of addressing cross-cultural measurement equivalence, including issues of validity and reliability.

In turn, valid and reliable measures of race and ethnicity are needed to ensure accurate assessment of disease prevalence and incidence, and accounts of appropriate health services utilization, in different population groups. Thus, the purpose of the fifth manuscript, "Conceptualizing and Categorizing Race and Ethnicity in Health Services Research," by Ford and Kelly, is threefold. First, this manuscript provides an overview of different methods currently employed to assess the constructs of race and ethnicity. Second, the authors illustrate consistent standards for measuring these constructs. The authors conclude with suggestions for measurement methods that would improve future research.

Consideration of Alternative Methodologies to Measure the Same Construct

The final set of articles examines the properties and use of two important measurement methodologies. In "Proxies and Other External Raters: Methodological Considerations," Snow, Cook, Lin, Morgan, and Magaziner review past research on proxy reports and examine ways to increase the reliability and validity of these types of reports. Many of the constructs health services researchers attempt to measure are those that have no single objective gold standard (e.g., quality of life, pain). Thus, the accrual of validity evidence for a health services research assessment instrument is often a daunting task. The difficulty of this task is increased further when it is not possible to obtain a self-report from the patient, or when the self report is suspect. Thus, the use of reports from external raters (e.g., family members, clinicians) is a necessary strategy for establishing evidence of validity. The authors differentiate between external rater reports gathered for the purpose of substituting for self-report and those gathered to supplement the self-report. The authors explain why appropriate use of externally rated data requires careful consideration of the nature of the data and how it will be analyzed and interpreted.