Introduction

Voice disorders occur in approximately 6% of all adults and in as many as 12% of children. Within the adult group, specific professions report the presence of a voice problem that interferes with their employment. As many as 50% of teachers and 33% of secretaries complain of voice problems that restrict their ability to work or to function in a normal social environment (Smith et al., 1998). The restriction of work, or lifestyle, due to a voice disorder has gone virtually undocumented until recently. While voice scientists and clinicians have focused most of their energy, talent, and time on diagnosing and measuring the severity of voice disorders with various perceptual, acoustic, or physiological instruments, little attention has been given to the effects of a voice disorder on the daily needs of the patient. Over the past few years, interest has increased in determining the functional impact of the voice disorder due to the Internet in using patient-based outcome measures to establish efficacy of treatments and the desire to match treatment needs with patient's needs. This article reviews the evolution of the assessment of functional impact of voice disorders and selected applications of those assessments.

Assessment of the physiological consequences of voice disorders has evolved from a strong interest in the relationship of communication ability to global quality-of-life measurement. Hassan and Weymuller (1993), List et al. (1998), Picarillo (1994), and Murry et al. (1998) have all demonstrated that voice communication is an essential element in patients' perception of their quality of life following treatment for head and neck cancer. Patient-based assessment of voice handicap has been lacking in the area of noncancerous voice disorders. The developments and improvements of software for assessing acoustic objective measures of voice and relating measures of abnormal voices to normal voices have gone on for a number of years. However, objective measures primarily assess specific treatments and do not encompass functional outcomes from the patient's perspective. These measures do not necessarily discriminate the severity of handicap as it relates to specific professions. Objective test batteries are useful to quantify disease severity (Rosen, Lombard, and Murry, 2000), categorize acoustic/physiological profiles of the disease (Hartl et al., 2001), and measure changes that occur as a result of treatment (Dejonckere, 2000). A few objective and subjective measures are correlated with the diagnosis of the voice disorder (Wolfe, Fitch, and Martin, 1997), but until recently, none have been related to the patient's perception of the severity of his or her problem. This latter issue is important in all diseases and disorders when life is not threatened since it is ultimately the patient's perception of disease severity and his or her motivation to seek treatment that dictates the degree of treatment success.

Functional impact relates to the degree of handicap or disability. Accordingly, there are three levels of a disorder: impairment, disability, and handicap (World Health Organization, 1980). Handicap is the impact of the impairment of the disability on the social, environmental, or economic functioning of the individual. Treatment usually relates to the physical well-being of a patient, and it is this physical well-being that generally takes priority when attempting to assess the severity of the handicap. A more comprehensive approach might seek to address the patient's own impression of the severity of the disorder and how the disorder interferes with the individual's professional and personal lifestyle.

Measurement of functional impact is somewhat different from assessment of disease status in that it does not directly address treatment efficacy, but rather addresses the value of a particular treatment for a particular individual. This may be considered treatment effectiveness. Efficacy, on the other hand, looks at whether or not a treatment can produce an expected result based on previous studies. Functional impact relates to the degree of impact a disorder has on an individual patient, not necessarily to the severity of the disease.