Screening-tests are commonly used to detect early stage chronic medical conditions before they become disabling. Devices used to perform screening-tests include blood pressure meters, which detect signs of early stage cardiovascular disease, and eye pressure tests, which detect signs of early stage glaucoma. To be cost-effective, screening-tests must be sensitive to physiological changes. Screening-tests must also be accurate, accessible, easily administered to a large number of individuals, and relatively inexpensive to manufacture. When these criteria are met, the cost of screening a large number of individuals may be offset by the savings achieved through reduction in the incidence and/or severity of disabling chronic diseases.
Newly recognized chronic medical problems occurring primarily (but not exclusively) in the elderly population involve falling and fall-related injuries. Such fall-related injuries often lead to the restriction of activities involved in daily living and loss of independent mobility. Recent epidemiological studies have found that restriction of activities, and injuries related to falling, are major causes of impairment to functional independence in the over sixty-five year old population. Because people are living longer today, the prevalence of these chronic problems is projected to increase substantially in years to come.
Recent research studies have demonstrated that the risk of fall related restriction of activities and fall related injuries can be identified before disability occurs. If the risk is identified early and treated, the incidence of injury and loss of functional independence can be reduced. According to other recent studies, balance is one of the most important factors influencing fall risk. An American Medical Association review of an article titled “Preventable Medical Injuries in Older Patients” published in the Archives of Physical Medicine provides a succinct summary of this problem.
In the current state of the art, both subjective observational and objective technology-based means are available for quantifying an individual's balance function. One well-known example of an observational test with documented ability to detect fall risk is the Berg Balance test. The Berg test requires a clinically trained individual to observe and numerically rate an individual's ability to perform a series of standardized balance and movement tasks. This test has the advantage of requiring no specialized equipment. However, the test requires considerable time to administer, and the results are dependent on the observational skills and experience of a clinically trained administrator.
Effective screening-tests for hearing, vision, and blood pressure abnormalities are currently offered to the general public in uncontrolled, non-medical environments such as drug stores and shopping malls. These types of screening-tests are administered by individuals without specialized medical training. Compared to medical tests administered by highly trained individuals in controlled medical environments, the potential for errors in administration and interpretation of the tests is substantially higher. These screening errors can result in needless worry on the part of the subject if one or more of the errors places a normal subject in an at-risk category. Additionally, if an error in the administration of a test occurs, and the administer fails to detect that the subject is at risk, an opportunity may be lost to help the at-risk individual.
In screening-tests administered in non-medical environments, data transmission applications are often employed. Many of these data transmission applications require that high volumes of information be transferred from one site to another as rapidly as possible with a minimum of errors. Two devices used to transfer high volumes of information rapidly include the high-speed modem, for transmission of digital data over a phone line; and relatively low-powered transmitters on space vehicles (such as satellites), for radio frequency transmission of data over great distances of space. To maximize the efficiency of data transmission, these and many other applications use data compression means. Transmission of high volumes of compressed data, however, increases the risk of errors.