Description

The RAND Medical Outcomes Study [MOS-20] is a brief instrument designed to assess general health status and health-related quality of life. It consists of 20 items covering key aspects of physical, social, and emotional functioning, providing a concise overview of the ways in which health affects an individual’s everyday life.

The MOS-20 can be used in both general and clinical populations, particularly when a relatively brief multidimensional measure of health status is required.

Purpose

The primary purpose of the MOS-20 is to provide a systematic assessment of general health and quality of life, with particular emphasis on the impact of illness and treatment on everyday functioning.

More specifically, the questionnaire may be used to:

  • assess the effects of health status on daily activities,
  • examine physical, social, and emotional dimensions of functioning,
  • monitor changes in health over time,
  • and evaluate outcomes of therapeutic or other health-related interventions.

Main Areas of Assessment

According to the provided material, the MOS-20 examines several major areas:

  • Physical Functioning: the individual’s ability to perform usual daily activities.
  • Social Functioning: the extent to which health affects social activities and interpersonal relationships.
  • Emotional Well-Being: the degree to which emotional difficulties, such as anxiety or depressive mood, affect everyday life.
  • Pain: the intensity of pain and the extent to which it interferes with daily functioning.
  • General Health Perceptions: the individual’s overall subjective assessment of their health status.

This multidimensional approach allows the instrument to assess not only symptoms but also their functional consequences.

Scoring

MOS-20 responses are recorded using graded Likert-type response options, depending on the content of each item.

Individual responses are used to calculate scores for the different health dimensions. The direction and transformation of scores should follow the scoring instructions for the specific version of the instrument being used.

When interpreting results, the individual domains should be considered separately, since the MOS-20 is intended to capture different aspects of functioning and health-related quality of life rather than only a single overall score.

Data Analysis and Use

MOS-20 data may be used to evaluate physical and psychosocial functioning and to monitor changes in health status across different time points.

In research applications, analyses may include:

  • descriptive statistics to summarize scores across health dimensions,
  • reliability analyses to evaluate the internal consistency of subscales,
  • comparisons between groups or across different assessment points,
  • and factor analyses to investigate or confirm the underlying structure of the instrument.

The questionnaire may be particularly useful in longitudinal studies and pre-post intervention designs, where changes in functioning and perceived health status are of interest.

Psychometric Evaluation

When the MOS-20 is administered, it is important to examine its reliability, validity, and structural adequacy within the population being studied.

The internal consistency of individual dimensions may be evaluated using appropriate reliability coefficients, while the structure of the instrument may be investigated through factor-analytic methods.

For translated or culturally adapted versions, cross-cultural validity should also be considered to ensure that scores are meaningful and comparable within the target population.

Applications

The MOS-20 may be used in clinical research, epidemiological studies, quality-of-life research, and health-outcomes assessment.

It may contribute to:

  • evaluating the impact of chronic or acute health conditions,
  • monitoring patients’ health status,
  • assessing treatment outcomes,
  • comparing different clinical or population groups,
  • and investigating factors associated with quality of life.

The instrument is not intended to function as a stand-alone diagnostic tool, but rather as a complementary measure of functioning and perceived health status.

References

Sherbourne, C. D., & Stewart, A. L. (1991). The MOS social support survey. Social Science & Medicine, 32(6), 705–714.

Hays, R. D., Sherbourne, C. D., & Mazel, R. M. (1993). The RAND 36-Item Health Survey 1.0. Health Economics, 2(3), 217–227.

Stewart, A. L., & Ware, J. E. (Eds.). (1992). Measuring Functioning and Well-Being: The Medical Outcomes Study Approach. Duke University Press.