Outcome measurement is a central concept of quality of care has both conceptual appeal and limitations as a practical assessment tool. The degree to which Outcome Measurements can be directly related to processes of care continues to be especially problematic in the healthcare industry and beyond. There has been a continued debate about whether processes or outcomes are the preferable measures of quality as fundamentally unproductive because both are needed. In order to have a better understanding of all types of outcome measures in ascertaining quality of care,it is better to first understand the four key areas that outcome measurements are best represented: more definitive evidence of process and outcome linkages; stronger relationships between technology assessment and quality assessment; improved reliability and validity of outcome measures as screening tools; and continued development of health status measures.
An outcome measure is the result of a test that is used to objectively determine the baseline function of a patient at the beginning of treatment. Once treatment has commenced, the same instrument can be used to determine progress and treatment efficacy. In recent times, there has been a forward move towards evidence-based practice and evidence-based care. The move towards Evidence Based Practice (EBP) and evidence-based care in the health sciences, objective measures of outcome are important to provide credible and reliable justification for treatment. For example, the instrument should also be convenient to apply for the therapist or doctor and comfortable for the patient.
The Properties of Outcome Measurement
The properties of outcome measurements that are an integral part of a healthcare investigator’s evaluation and selection of appropriate measures include reliability, validity, and variability. Reliability is the degree to which a score or other measure remains unchanged upon test and retest when no change is expected, or across different interviewers or assessors. It is measured by statistics. Validity, broadly speaking, is the degree to which a measure assesses what it is intended to measure, and types of validity include face validity (this is the degree to which users or experts perceive that a measure is assessing what it is intended to measure), content validity (this is the extent to which a measure accurately and comprehensively measures what it is intended to measure), and construct validity (this is the degree to which an instrument accurately measures a nonphysical attribute or construct such as depression or anxiety, which is itself a means of summarizing or explaining different aspects of the entity being measured). Variability usually refers to the distribution of values associated with an outcome measure in the population of interest, with a broader distribution or range of values said to show more variability. Responsiveness is another property usually discussed in the context of patient-reported outcomes (PROs) but extendable to other measures, representing the ability of a measure to detect a change in an individual over time.
These measurement properties may affect the degree of measurement error or misclassification that an outcome measure is subject to, with the consideration that the properties themselves are specific to the population and setting in which the measures are used. Issues of misclassification and considerations in reducing this type of error are discussed further in the section on avoidance of bias in study design.
In discussing the importance of outcome measurement, it is important to note in every discuss the fact that process measures are equally important. Achieving outcomes is important, but the process by which health systems achieve outcomes is equally important. Process measures capture provider productivity and adherence to standards of recommended care. For example, if a health system wants to reduce the incidence of skin breakdown, then it might implement the process measure of performing a risk assessment using the Barden Scale for reducing pressure ulcer risk in all the appropriate units in the hospital. If health systems are too focused on an outcome, then they lose sight of the process. Hence the importance of always adding process measures to every discuss.