The term "aphasia" describes a disturbance, often caused by damage to the brain, in the ability to comprehend or produce speech. Aphasia can be divided into two specific types: expressive aphasia and receptive aphasia. A speech language pathologist (SLP) is trained to identify the types of aphasia with which the patient presents and to assess the condition using one of several techniques. Among the different types of aphasia assessment are the Halstead Screening Test, the Token Test, the Porch Index of Communicative Ability (PICA) and the Minnesota Test for Differential Diagnosis of Aphasia (MTDDA). Other types of aphasia assessment are the Boston Diagnostic Aphasia Examination and the Communicative Abilities in Daily Living (CADL) screening test.
The initial aphasia assessment test generally is a screening to detect the type of aphasia present and to call attention to specific characteristics. Screening tests do not require specialized training on the part of the assessor. They should, however, be conducted by a competent healthcare provider. Using the available aphasia assessment tools, a speech language pathologist will tailor therapy to the patient, planning a program to optimize speech for the most successful outcome achievable.
The two most common screening tests for aphasia assessment are the Halstead Screening Test and the Token Test. The Halstead Screening Test, developed in 1984, requires that the subject perform a series of tasks such as spelling common words, naming common objects and identifying numbers and letters. The patient might also be asked to read, write and understand spoken language to identify the severity of both receptive and expressive aphasia. The Token Test, revised in 1978, is an easy-to-administer test that requires 20 tokens varying in shape, size and color. The patient will be asked to identify more than 60 combinations, such as being asked to “touch the red square” or “place the green rectangle on top of the blue circle.”
More comprehensive aphasia assessments do require the assessor to have extensive training in conducting aphasia examinations. The Minnesota Test for Differential Diagnosis of Aphasia provides an assessment of the patient’s strengths and weaknesses in all language modalities. It is the most comprehensive of tests, requiring two to six hours to administer. The MTDDA consists of more than 40 subtests divided into five sections, such as auditory disturbances, visual disturbances and speech/language disturbances.
The Boston Diagnostic Aphasia Examination, developed in 1972, contains more than two dozen subtests that diagnose the presence of aphasia, measure the level of performance over a wide range and assess the severity of the deficits in all areas of language. A patient is given a score that objectively describes the level of aphasia displayed.
The Porch Index of Communicative Ability consists is used primarily as an objective measure of the degree of language deficit. It also is an indicator of the patient’s prognosis for recovery. The subtests require the patient to participate in object manipulation, visual matching and copying abstract forms.
The Communicative Abilities in Daily Living is a more recently developed aphasia assessment. The patient is engaged in a role-playing exercise that simulates normal activities such as being in a doctor’s office or at the grocery store. Patients are asked to respond to more than 60 specific questions, and each response is graded on a three-point scale according to how effective the patient communicated his or her thoughts.