Deconstructing and Assessing Knowledge and Awareness in Public Health Research

Issues related to the validity and reliability of measurement instruments used in research are reviewed. Key indicators of the quality of a measuring instrument are the reliability and validity of the measures. The process of developing and validating an instrument is in large part focused on reducing error in the measurement process. Reliability estimates evaluate the stability of measures, internal consistency of measurement instruments, and interrater reliability of instrument scores. Validity is the extent to which the interpretations of the results of a test are warranted, which depends on the particular use the test is intended to serve. The responsiveness of the measure to change is of interest in many of the applications in health care where improvement in outcomes as a result of treatment is a primary goal of research. Several issues may affect the accuracy of data collected, such as those related to self-report and secondary data sources. Self-report of patients or subjects is required for many of the measurements conducted in health care, but self-reports of behavior are particularly subject to problems with social desirability biases. Data that were originally gathered for a different purpose are often used to answer a research question, which can affect the applicability to the study at hand. In health care and social science research, many of the variables of interest and outcomes that are important are abstract concepts known as theoretical constructs. Using tests or instruments that are valid and reliable to measure such constructs is a crucial component of research quality.

To explore and explain the different concepts of reliability and validity as they are related to measurement instruments in social science and health care. There are different concepts contained in the terms reliability and validity and these are often explained poorly and there is often confusion between them. To develop some clarity about reliability and validity a conceptual framework was built based on the existing literature. The concepts of reliability, validity and utility are explored and explained. Reliability contains the concepts of internal consistency and stability and equivalence. Validity contains the concepts of content, face, criterion, concurrent, predictive, construct, convergent (and divergent), factorial and discriminant. In addition, for clinical practice and research, it is essential to establish the utility of a measurement instrument. To use measurement instruments appropriately in clinical practice, the extent to which they are reliable, valid and usable must be established.

Improved recognition of the importance of systolic blood pressure (SBP) has been identified as one of the major public health and medical challenges in the prevention and treatment of hypertension (HTN). SBP is a strong independent risk factor for cardiovascular disease but no information is available on whether patients understand the importance of their SBP level. The purpose of this study was to assess HTN knowledge, awareness, and attitudes, especially related to SBP in a hypertensive population. We identified patients with HTN (N=2,264) in the primary care setting of a large midwestern health system using automated claims data (International Classification of Diseases, Ninth Revision [ICD-9] codes 401.0-401.9). We randomly selected 1,250 patients and, after excluding ineligible patients, report the results on 826 completed patient telephone interviews (72% response rate [826/1,151]). Ninety percent of hypertensive patients knew that lowering blood pressure (BP) would improve health and 91% reported that a health care provider had told them that they have HTN or high BP. However, 41% of patients did not know their BP level. Eighty-two percent of all patients correctly identified the meaning of HTN as "high blood pressure." Thirty-four percent of patients correctly identified SBP as the "top" number of their reading; 32% correctly identified diastolic blood pressure (DBP) as the "bottom" number; and, overall, only 30% of patients were able to correctly identify both systolic and diastolic BP measures. Twenty-seven percent of patients with elevated SBP and DBP (as indicated by their medical records) perceived that their BP was high. Twenty-four percent of patients did not know the optimal level for either SBP or DBP. When asked whether the DBP or SBP level was more important in the control and prevention of disease, 41% reported DBP, 13% reported SBP, 30% reported that both were important, and 17% did not know. These results suggest that, although general knowledge and awareness of HTN is adequate, patients do not have a comprehensive understanding of this condition. For instance, patients do not recognize the importance of elevated SBP levels or the current status of their BP control. An opportunity exists to focus patient education programs and interventions on the cardiovascular risk associated with uncontrolled HTN, particularly elevated SBP levels.