Table of Contents

Summary of Findings..................................................................................................................... 1

Preface..........................................................................................................................................3

Overview.......................................................................................................................................4

Attention Deficit Disorder (ADD)/Attention Deficit Hyperactivity Disorder (ADHD)

Diagnosis....................................................................................................................... 4

Epidemiology................................................................................................................. 6

Treatment...................................................................................................................... 7

Continuous Performance Tests............................................................................................... 8

T.O.V.A....................................................................................................................... 8

Reliability and Validity of CPTs...................................................................................... 9

Role of the CPT in diagnosis of ADHD......................................................................... 10

Competing/Complementary Technologies.............................................................................. 10

Patient Populations................................................................................................................ 11

Safety Issues......................................................................................................................... 11

Care Setting.......................................................................................................................... 11

Analysis of the Currently Available Evidence.................................................................................. 11

Key Questions...................................................................................................................... 11

Evidence Base...................................................................................................................... 12

Identification of Clinical Studies..................................................................................... 12

Reimbursement Information........................................................................................... 13

Hand Searches of Journal and Nonjournal Literature...................................................... 13

Study Selection............................................................................................................. 13

Study Characteristics.................................................................................................... 14

Key Outcomes..................................................................................................................... 18

Synthesis of Results............................................................................................................... 20

Question 1: Does the peer reviewed published literature establish the reliability

and validity of CPTs for the purpose of diagnosing ADHD?........................................... 20

Question 2: Does the peer reviewed published literature establish the reliability

and validity of CPTs for the purpose of titrating pharmacotherapy levels in

treating patients with ADHD?........................................................................................ 26

Question 3: Do the published reports of national professional medical associations,

national medical policy organization positions, or reports of national expert

opinion organizations demonstrate consensus in the medical community that the

safety and efficacy of CPTs are accepted for the purpose of diagnosing ADHD?............ 27

Question 4: Do the published reports of national professional medical associations,

national medical policy organization positions, or reports of national expert

opinion organizations demonstrate consensus in the medical community that

the safety and efficacy of CPTs are accepted for the purpose of titrating

pharmacotherapy levels in treating patients with ADHD?............................................... 29

Economic and Regulatory Issues................................................................................................... 29

Manufacturers and Costs...................................................................................................... 29

FDA Status.......................................................................................................................... 30

Medicaid Coverage Policy.................................................................................................... 30

Third Party Payer Coverage.................................................................................................. 31

Conclusions................................................................................................................................... 31

Bibliography.................................................................................................................................. 33

Appendix A: Diagnostic criteria for Conduct Disorder (312.8)...................................................... 38

Appendix B: Diagnostic criteria for Oppositional Defiant Disorder (313.81).................................. 39

Appendix C: Diagnostic Criteria for Learning Disorders................................................................ 40

Appendix D: Names and Curricula Vitae of Those Involved in the Preparation

of This Assessment....................................................................................................................... 41

ECRI Personnel............................................................................................................................ 41

External Reviewers....................................................................................................................... 44

Summary of Findings

This assessment evaluates the efficacy of continuous performance tests (CPTs) in the diagnosis of attention-deficit hyperactivity disorder (ADHD) and its potential use in titrating pharmacotherapy for this disorder.

ADHD is the most commonly diagnosed behavioral disorder of childhood, and is characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity in multiple settings including home, school, and peer relationships. Without identification and proper treatment, ADHD can have serious consequences, including school failure, depression, conduct disorder, failed relationships, and substance abuse. The diagnosis of ADHD typically involves obtaining information from multiple sources including parent and teacher ratings of the child’s behavior, clinical interviews of the parents and child, the clinician’s observations, and neuropsychologcial testing.

The CPT is used frequently in research on attention deficits in children and adults. This computer-based test involves the rapid presentation of stimuli (typically numbers, letters or number/letter sequences) for up to 30 minutes. Children taking the CPT are instructed to respond to the “target” stimulus by pressing a button and to refrain from responding to “non-target” stimuli. Children’s responses, in particular, the types of errors made, are thought to indicate the level of inattention or distractibility. CPT performance measures include correct responses, omission errors, commission errors and reaction time.

This assessment addresses four questions about the efficacy of CPTs in diagnosing ADHD and in titrating pharmacotherapy. Answers to two of these questions employ scientific evidence from the published, peer-reviewed literature. Answers to two other questions require the use of reports, position statements and clinical guidelines by published national professional medical organizations to determine whether there is consensus on the use of CPTs in diagnosis and titration of therapy. The questions are:

1) Does the peer-reviewed published literature establish the reliability and validity of continuous performance tests (CPTs) for the purpose of diagnosing attention deficit disorder (ADD)/attention deficit hyperactivity disorder (ADHD)?

To evaluate the utility of CPTs in diagnosing ADHD, we calculated measures of sensitivity, specificity, positive predictive value and negative predictive value from eight studies that addressed this question. Our analysis revealed low to moderate measures of sensitivity (range = 9% to 88%). Measures of specificity ranged from 23% to 100%; however, the studies with higher specificities (100% and 94%) had low sensitivities (13% and 62%, respectively). Thus, the utility of the CPT as a stand-alone diagnostic tool is not high. Even so, we would not expect the diagnostic utility of any test or behavioral rating scale to be high when it is used as the sole instrument for diagnosis. Comparing the performance of the CPT to the performance of any other diagnostic test for ADHD would require a full assessment of the other test.

It is possible that CPTs may be useful in measuring some isolated symptoms of ADHD; however, we did not consider this use in this assessment because it is not clear how these symptoms would relate to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) or to diagnostic judgements of clinicians. Furthermore, there is little research addressing how or whether the CPT, or any other test, could be used in conjunction with other assessments as part of a clinical algorithm for diagnosing ADHD.

2) Does the peer-reviewed published literature establish the reliability and validity of continuous performance tests (CPTs) for the purpose of titrating pharmacotherapy levels in treating patients with attention deficit disorder (ADD)/attention deficit hyperactivity disorder (ADHD)?

We were unable to demonstrate a strong correspondence between CPTs and ADHD as measured by the DSM-IV or clinical judgment. Thus, the only type of study that can answer Question 2 would be one that correlated measures of drug dosage, CPT scores, and DSM-IV evaluation (or a reference standard validated by the DSM). We found no suitable studies of this type. Thus, we were unable to find literature that either supports or does not support the use of CPTs for titration of medications.

Although there is clinical evidence indicating that the dose of methylphenidate given to a child affects CPT performance, these trials did not validate the CPT by correlating its results to diagnosis of ADHD or to individual treatment related outcomes such as school performance. Associations between drug dose and such treatment related outcomes were not covered by the key questions in this assessment. If other evidence establishing an association between CPT scores and ADHD diagnosis or school performance is available, it may be possible to establish the validity of the CPT in titrating methylphenidate dose.

3) Do the published reports of national professional medical associations, national medical policy organization positions, or reports of national expert opinion organizations demonstrate consensus in the medical community that the safety and efficacy of continuous performance tests (CPTs) are accepted for the purpose of diagnosing attention deficit disorder (ADD)/attention deficit hyperactivity disorder (ADHD)?

All of the guidelines we retrieved advised against use of CPT scores alone for diagnosis of ADHD. Although some guidelines recognized some usefulness of the CPT during diagnosis and management, none specified any particular purpose for CPTs other than research.

4) Do the published reports of national professional medical associations, national medical policy organization positions, or reports of national expert opinion organizations demonstrate consensus in the medical community that the safety and efficacy of continuous performance tests (CPTs) are accepted for the purpose of titrating pharmacotherapy levels in treating patients with attention deficit disorder (ADD)/attention deficit hyperactivity disorder (ADHD)?

We identified only one guideline that addressed the issue of CPTs and medication for ADHD. The guideline questioned whether the behaviors measured by CPT tests were representative of behaviors likely to be expressed by children in more natural settings (e.g., home or school). The guideline concluded that the applicability of CPTs to monitor treatment for ADHD is “unproven or even absent.”

Preface

This assessment is organized into three major sections: 1) Overview, 2) Analysis of the Currently Available Evidence, and 3) Economic and Regulatory Issues. In the Overview section, we provide background information related to the particular health condition or illness under evaluation, including details about the epidemiology, diagnosis and treatment of the condition or illness. We provide background information on the specific instrument(s) often used for diagnosing the condition or illness, and some details on competing or complementary diagnostic technologies. The final part of the Overview section addresses issues relating to patient populations under study, patient safety and care setting.

The Analysis of the Currently Available Evidence section details the methods we used to evaluate currently available data. We detail the strategies employed for our searches of the literature, which includes an exhaustive list of the electronic databases searched and the protocol for hand-searches of the non-journal literature. We describe the inclusion and exclusion criteria used to identify, retrieve and analyze studies. When appropriate, we provide details of the characteristics of those studies included, and we list and define the key outcomes for analysis. We also describe any statistical methods that we employed. Finally, for each of the key questions addressed in the assessment, the synthesis of results is presented and discussed.

In the Economic and Regulatory Issues section, we provide information on the manufacturers of devices or technologies used in the studies analyzed for this assessment. Where available, we also provide cost information for the device, instrument or technology. We include information on whether the technology is regulated by the U.S. Food and Drug Administration (FDA) and if so, the status of the technology in the FDA approval process. Lastly, we provide information on health insurance coverage for the technology under evaluation. This includes discussion of the coverage policies of Medicare, Medicaid and other third party payers.

Overview

Attention Deficit Disorder (ADD)/Attention Deficit Hyperactivity Disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) is the most commonly diagnosed behavioral disorder of childhood and is characterized by a persistent pattern of inattention, impulsivity and hyperactivity. (1,2) Children with ADHD usually have functional impairment across multiple settings including home, school, and peer relationships. ADHD also has been shown to have long-term adverse effects on academic performance, vocational success and social-emotional development. Without identification and proper treatment, ADHD can have serious consequences, including school failure, depression, conduct disorder, failed relationships, and substance abuse. (3)

Diagnosis

There is no laboratory test or set of physiological features that has been identified as an unequivocal marker for ADHD. That is, there is no “gold standard” for diagnosing ADHD. The disorder is behaviorally based; thus, behavioral observations are required to identify and correctly diagnose the disorder. It has been argued that ADHD is not a distinct diagnostic entity, but that it is a “symptom complex” characterized by multiple possible etiologies and a constellation of pathologic behaviors. (4,5) The observed behaviors are interpreted subjectively by parents and teachers who describe these observations to clinicians. Clinicians often observe the child during clinical interviews and psychometric testing. Typically, parent, teacher and clinical observations are incorporated into a diagnostic decision. However, this subjective interpretation can lead to inter-observer differences, and can make ADHD diagnosis difficult. For example, the prevalence of behaviors related to hyperactivity as rated by a teacher can be higher than that rated by a clinician. (6) In contrast, the prevalence of behaviors related to hyperactivity can be lower if these behaviors must be judged to be present by more than one source (e.g., parent and teacher). (7)

Because there is no gold standard for diagnosing ADHD, it is important to make a distinction between how ADHD is defined and how it is diagnosed. The disorder is currently defined by criteria contained in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). (3) The DSM-IV defines ADHD according to two behavioral domains: inattention and hyperactivity-impulsivity. Each domain contains nine possible symptoms; a child must have at least six of the nine symptoms to qualify for a diagnosis of ADHD. If the child has at least six symptoms on the inattention domain, s/he qualifies for the “ADHD-Predominantly Inattentive Type” diagnosis. If the child has at least six symptoms on the hyperactivity-impulsivity domain, s/he qualifies for the “ADHD-Predominantly Hyperactive-Impulsive Type” diagnosis. If the child has at least six symptoms on both inattention and hyperactivity-impulsivity domains, s/he qualifies for the “ADHD-Combined Type” diagnosis. (3)

Additional DSM-IV criteria specify that some inattentive or hyperactive-impulsive symptoms must have been present before the age of seven years, although the diagnosis can be made at older ages. In addition, the symptoms must be present in at least two settings (e.g., home and school) and must cause impairment. That is, there must be evidence of interference with developmentally appropriate social, academic, or occupational functioning. The symptoms should not occur exclusively during the course of a pervasive developmental disorder (e.g., autism), schizophrenia, or other psychotic disorder. Furthermore, the symptoms should not be better accounted for by another mental disorder (e.g., mood, anxiety, dissociative or personality disorders). (3) The DSM‑IV criteria for ADHD are listed in Table 1 .

Table 1. Diagnostic criteria for Attention-Deficit/Hyperactivity Disorder

Either (1) or (2):

1. Six (or more) of the following symptoms of inattention have persisted for at least 6 months to a degree that is maladaptive and inconsistent with developmental level:

Inattention

a. often fails to give close attention to details or makes careless mistakes in schoolwork, work, or other activities

b. often has difficulty sustaining attention in tasks or play activities

c. often does not seem to listen when spoken to directly

d. often does not follow through on instructions and fails to finish schoolwork, chores, or duties in the workplace (not due to oppositional behavior or failure to understand instructions)

e. often has difficulty organizing tasks and activities

f. often avoids, dislikes, or is reluctant to engage in tasks that require sustained mental effort (such as schoolwork or homework)

g. often loses things necessary for tasks or activities (e.g., toys, school assignments, pencils, books, or tools)

h. is often easily distracted by extraneous stimuli

i. is often forgetful in daily activities

2. six (or more) of the following symptoms of hyperactivity-impulsivity have persisted for at least 6 months to a degree that is maladaptive and inconsistent with developmental level:

Hyperactivity

a. often fidgets with hands or feet or squirms in seat

b. often leaves seat in classroom or in other situations in which remaining seated is expected

c. often runs about or climbs excessively in situations in which it is inappropriate (in adolescents or adults, may be limited to subjective feelings of restlessness)

d. often has difficulty playing or engaging in leisure activities quietly

e. is often “on the go” or often acts as if “driven by a motor”

f. often talks excessively

Impulsivity

g. often blurts out answers before questions have been completed

h. often has difficulty awaiting turn

i. often interrupts or intrudes on others (e.g., butts into conversations or games)

Some hyperactive-impulsive or inattentive symptoms that cause impairment were present before age 7 years.

Some impairment from the symptoms is present in two or more settings (e.g., school [or work] and at home).

There must be clear evidence of clinically significant impairment in social, academic, or occupational functioning.

The symptoms do not occur exclusively during the course of a Pervasive Developmental Disorder, Schizophrenia, or other Psychotic Disorder and are not better accounted for by another mental disorder (e.g., Mood Disorder, Anxiety Disorder, Dissociative Disorder, or a Personality Disorder.

(Continued on next page)

Table 1. Diagnostic criteria for Attention-Deficit/Hyperactivity Disorder (cont’d)

Code based on type:

314.01 Attention-Deficit/Hyperactivity Disorder, Combined Type: if both Criteria A1 and A2 are met for the past 6 months

314.00 Attention-Deficit/Hyperactivity Disorder, Predominantly Inattentive Type: if Criterion A1 is met but Criterion A2 is not met for the past 6 months

314.01 Attention-Deficit/Hyperactivity Disorder, Predominantly Hyperactive-Impulsive Type: if Criterion A2 is met but Criterion A1 is not met for the past 6 months

Coding note: For individuals (especially adolescents and adults) who currently have symptoms that no longer meet full criterion, “In Partial Remission” should be specified.

While ADHD is defined by the DSM-IV criteria, the symptom complex is diagnosed by a clinician. In the absence of a gold standard, the “reference standard” is the clinician’s judgment. Ideally, this decision would be based on information gathered from a number of sources (e.g., parent, teacher, observations of the child), and would be reached by consensus. That is, a number of qualified clinicians would confer in making the appropriate diagnosis. Nevertheless, the clinician’s decision is ultimately a subjective one, and this introduces a level of variability that is difficult to control for in evaluating any tool used for diagnosing ADHD. Moreover, the DSM has undergone several iterations over the past two decades (see below), suggesting that ADHD is indeed a “symptom complex” characterized by behaviors that are difficult to agree upon.

The terminology for attention deficit disorder has changed over the past 70 years. Previous terms included “minimal brain dysfunction”, (8,9) “hyperkinetic syndrome”, “attention deficit disorder” (ADD), and “attention deficit disorder with hyperactivity” (ADDH). The DSM-II, published in 1968, (10) referred to the symptom complex as the “hyperkinetic reaction of childhood”, and described it as “characterized by overactivity, restlessness, distractibility, and short attention span, especially in young children; the behavior usually diminishes in adolescence.” (10) In the DSM-III (1980), ADHD was classified among the Disruptive Behavior Disorders and the terminology was changed to Attention Deficit Disorder (ADD). (11) DSM-III differentiated two types of ADD based on the presence or absence of hyperactivity: attention deficit disorder with hyperactivity (ADDH) and attention deficit disorder without hyperactivity (ADDnoH). (11) In DSM-III-R (1987), the distinction between attention deficit disorder with and without hyperactivity was shifted by focusing on a new term: attention deficit hyperactivity disorder (ADHD). (12) Attention deficit disorder without hyperactivity was included in a category referred to as undifferentiated attention deficit disorder (UAD). (12) DSM-IV (1994) reapplied the distinction between attention deficit disorder with and without hyperactivity by including categories and criteria for all three behavioral domains: inattention, hyperactivity and impulsivity (see Table 1). (3)

Because the DSM-IV refers to the disorder as Attention Deficit Hyperactivity Disorder (ADHD), we use the term for this assessment. However, in systematically reviewing the literature, we have identified studies published as early as 1938. Thus, as we discuss the results of individual studies that relied on prior versions of the DSM and its accepted terminology, we apply the terms used by the original investigators.

Epidemiology

The prevalence of ADHD has been investigated in the school, community, and clinic settings. One systematic review of the literature found that school-based studies reported prevalence rates for ADHD ranging from 4% to 26%; community-based studies reported prevalence rates between 4.5% and 12%. (1) Multiple logistic regression revealed that gender, setting and diagnostic definition (i.e., different versions of the DSM) were significant contributors to the variability in the prevalence of ADHD. (1) In the Ontario Child Health Study, ADHD prevalence rates also varied widely, ranging from 1% to 14%. (13) These findings are consistent with the notion that the diagnosis of ADHD is made in the absence of an appropriate reference standard. The prevalence of ADHD diagnoses is substantially higher in boys than it is in girls. Prevalence ratios in boys and girls range from 2:1 to 5:1. (2,13) The prevalence of ADHD appears to decline during adolescence for both boys and girls. (13,14)

ADHD can occur in individuals with considerable and varied comorbidity. (15,16) Systematic reviews of the literature examining the comorbidity of ADHD with other disorders, have reported prevalence rates for ADHD with conduct disorder (CD), oppositional defiant disorder (ODD), mood and anxiety disorders, and learning disabilities (LD). (1,15) For externalizing disorders (disruptive behavior disorders), ADHD and CD reportedly occur together in 26% to 50% of all cases studied in community and clinical samples, respectively. The comorbidity of ADHD and ODD in children is at least 35%, either for ODD alone or combined with CD in cases studied. (1,15) For internalizing disorders (mood and anxiety disorders), ADHD and mood disorders reportedly occur together in 15% to 75% of cases from community and clinical samples. (15) For anxiety disorders, ADHD co-occurs in approximately 25% of cases surveyed. (1,15) The proportion of ADHD children with multiple comorbidities was 28%. (1) The co-occurrence of ADHD and LD has been consistently reported in the literature, (15) but the reported rates of co-occurrence are variable, ranging from as low as 10% to as high as 92%. (16) The prevalence of LD in children with ADHD was about 9%-10% in hyperactive boys (17) and 8% in a sample of Connecticut school children. (18) Lambert and Sandoval (1980) found that 43% of hyperactive children met objective criteria for LD. (19)

To evaluate the efficacy of the CPT in diagnosing ADHD, it is important to consider ADHD children with comorbidities. That is, in the clinical setting children are likely to have ADHD as well as CD, ODD or LD. (3,20,21) It is not enough to differentiate ADHD from normal children (non-specific diagnosis), but one must distinguish among disorders that tend to occur together (differential diagnosis). Because ADHD frequently co-occurs with CD, ODD and LD, the DSM-IV criteria for these disorders have been appended (Appendices A, B and C).

Treatment

The most common treatment for ADHD is pharmacological intervention. It has been estimated that 2-3% of all elementary school-age children in North America receive some form of pharmacotherapy for hyperactivity. (22) While a variety of medications for ADHD have been used, including anti-depressants and neuroleptics, by far the most widely prescribed and extensively studied are the psychostimulants, especially Ritalin (methylphenidate). Other common stimulant medications include Adderall, Dexedrine, and Cylert (pemoline). These are considered the “first line” of pharmacotherapy for ADHD. (23)

More recently, psychosocial treatments have been examined as potential treatment strategies, either alone or in combination with stimulant medication. Such psychosocial treatments include classroom-based behavior modification, social skills and cognitive training, parent training and home-based interventions, and intensive summer treatment programs.

Overall, there appears to be a trend towards a multimodal approach to ADHD treatment. With this approach, clinicians are using multiple treatment strategies in combination. That is, stimulant medication is combined with cognitive and/or behavioral modification programs. Such programs may be individualized or designed to involve the child, his or her family and relevant school personnel. (24,25)

Continuous Performance Tests

Continuous performance tests (CPTs) are computer-based tests designed to measure inattention and impulsivity. The CPT is one of the most widely used measures of attentional deficits in research on children and adults. (26) . The original version of the CPT, (27) and more recent versions of the test, involve the rapid presentation of a series of visual or auditory stimuli over a period of time, typically from nine (28-30) to 22.5 (31,32) minutes. Specifically, the task requires a subject to respond to “target” stimuli and inhibit responding to “non-target” stimuli that appear on the monitor. In one of the most common CPT formats, the letter “X” is the predetermined target stimulus. For example, during a typical trial, 500 letters will be presented in rapid succession. When the target “X” appears, the child responds as quickly as he or she can by pushing a button on a control panel or computer keyboard. An early modification of the CPT “X” design made this task slightly more difficult by requiring subjects to respond to the letter “X” only when it directly followed the letter “A.” This format is known as the “AX” CPT. Other ways of making the task more difficult include degrading the stimuli by blurring them on the screen or adding adjacent, “distracting” stimuli. Another CPT format is the “identical pairs” CPT. In this test, there is no fixed target; instead, the target is the occurrence of the same stimulus (e.g., playing card) two times in a row. (33,34) This type of CPT is more attentionally demanding and can be associated with more complex stimuli, e.g., 4-digit numbers. (33) The child’s age is generally taken into account when selecting the appropriate CPT format, given that some are more difficult than others.

Stimuli other than letters are also used, including numbers (e.g., “5”), a series of numbers (e.g., a “1” followed by a “9”), geometric forms (e.g., T.O.V.A., see below), and pictures of animals for younger children. While most versions of the CPT are visual, others use an auditory mode (e.g., Auditory Continuous Performance Test (35) ), where numbers, letters or words are spoken and the subject responds to the target stimuli.

Several different performance outcomes are measured during testing. Responding to the designated target is referred to as a correct response, or a hit. Missing a target is referred to as an omission error. Omission errors are thought to measure inattention. (36,37) Responding to any stimulus other than the target is referred to as a commission error, or false alarm. Commission errors are considered to measure impulsivity. (36,37) Other measures of CPT responses include the number of correct responses, reaction time, and variability in reaction time.~~, and activity level~~

T.O.V.A.

The Test of Variables of Attention (T.O.V.A.) is a standardized, visual CPT designed specifically as a clinical tool to screen, assist in the diagnosis and to predict and monitor medication effects in children with attention deficit disorders. (38,39) The T.O.V.A. is a 22.5-minute computerized test that requires no use of language, no right-left discrimination, nor recognition of letters or numerals. Rather, the two visual stimuli are a large box containing a smaller box that is adjacent to the top or bottom edge of the larger box (see Figure 1 ). The stimulus of the inner box adjacent to the top edge is the designated target. The T.O.V.A. presents two 11-minute test conditions that involve frequent and infrequent presentation of targets. These two conditions were designed to measure attention and impulsivity, respectively.

Figure 1. Example of target and non-target stimuli for the T.O.V.A.

Reliability and Validity of CPTs

The reliability of a diagnostic test refers to the extent to which the test results are consistent over time or across conditions. Test-retest reliability is generally expressed as a correlation coefficient, or r. If there is a perfect positive correlation, r equals 1.0; for a perfect negative correlation r equals –1.0. If there is no correlation (i.e., no consistency), r equals 0. A desirable level of reliability for diagnostic tests is .80 or above. (40) For the CPT, the reliability of the test can be assessed by comparing performance scores over time and in different settings.

For the traditional “A-X” CPT, Halperin et al. (1991) demonstrated test-retest reliabilities ranging from 0.65 to 0.74 for hits, misses, hit reaction time and the derived inattention and impulsivity scores. (41) For the T.O.V.A., Greenberg and Waldman (1993) (31) showed test-retest correlations of 0.80 or greater for response times, 0.50 or greater for commission errors, and 0.14 for omission errors. On the SCAT (Seidel Continuous Attention Task) CPT, Seidel and Joschko (1991) found test-retest reliability measures ranging from 0.36 for commission error to 0.82 for reaction time. (42) For the GDS, test-retest reliability for vigilance task total commission errors ranged from 0.52 to 0.94. (43,44)

The validity of a diagnostic test refers to what the test measures and how well it does so. The validity of a test is the most important consideration in test evaluation and must be addressed for three categories: content-related validity, construct-related validity and criterion-related validity. (45) By design, CPT tests measure constructs. That is, the target and non-target letters, numbers or words are aids used to test the constructs of inattention and impulsivity. Two types of evidence are used to demonstrate construct validity: convergent and discriminant. The CPT would have high convergent validity if the results agreed with the results of other tests designed to measure the same constructs. The CPT would have high discriminant validity if the results objectively measured inattention and impulsivity independent of verbal, perceptual and other cognitive processes. (41,42,46)

Klee and Garfinkel (1983)