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The SNAP-IV is a questionnaire developed in the US, initially to the standards of the DSM III, to screen for Attention Deficit Hyperactive Disorder, Oppositional Defiance Disorder, as well as overlapping symptoms of all other psychiatric disorders of childhood. It has a short and longer, more comprehensive form, which contains 90 items and includes all of the previously mentioned constructs. The short form, referred to as the MTA version, has 26 items and measures the core ADHD symptoms of impulsivity, hyperactivity, inattention, and a few ODD symptoms. While either can be used in both the clinical and research setting, the MTA version seems to be more commonly used because of its brevity and its ability to measure the core aspects of ADHD. It is designed to be filled out by either the parent or teacher of an elementary school aged child.
The most recent study on the SNAP-IV (MTA version) re-evaluated the psychometric properties of the scale. Factor analysis indicated that the SNAP-IV loads on 3 factors. This matches the framework guiding its construction. Two factors for ADHD emerged – impulsivity/hyperactivity and inattention, while the third one was for ODD. The authors compared the results of the scale with the Diagnostic Interview Schedule for Children, Parent Version (DISC-IV-P), which bases its diagnosis on the DSM-IV and explores functioning in both the home and at school. There is suitable predictive validity support for the SNAP-IV when screening for ADHD.
As for reliability, the study demonstrated that it had acceptable reliability figures. They computed for the reliability figures for the parent and teacher ratings separately, as well as producing subdomain alphas for each factor. The coefficient alpha for overall parent ratings was .94, with alphas of .90, .79, and .89 for the inattention, hyperactivity/impulsivity, and ODD subdomains, respectively. The reliability of the teacher ratings was slightly better at .97 for the overall scale, .96 for inattention, .92 for hyperactivity/impulsivity, and .96 for ODD. The report also produced Pearson correlations for the inter-rater reliability between the parent and teacher ratings for each factor. The correlations are as follows: .49 for inattention, .43 for hyperactivity/impulsivity, and .47 for ODD, and all were statistically significant (p < .001)
While the psychometrics of the SNAP-IV may be quite good, it is important to note the limitations of its norms. The researchers may have used sizable samples for their parent (n = 1,613) and teacher (n = 1,205) ratings, as well as for their validation sample (n = 266), but the norms are far more limited. They sampled in just one school district in North Florida with high poverty rates and limited diversity. Additionally, they only included white and African American children in the assessment. Interestingly, there is a Japanese and a Chinese version of the SNAP-IV, each with its own corresponding norms.
There may be valid reasons to take a conservative approach to interpreting the results of the SNAP-IV, but it still functions effectively as a relatively quick and easy screener to use.
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Gau, S. S., Lin, C. H., Hu, F. C., Shang, C. Y., Swanson, J. M., Liu, Y. C., & Liu, S. K. (2009). Psychometric properties of the Chinese version of the Swanson, Nolan, and Pelham, Version IV Scale-Teacher Form. Journal of Pediatric Psychology, 34(8), 850-861. doi:10.1093/jpepsy/jsn133
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