Scale for Measuring Intellectual Impairment and Deterioration [SMIID-40]

Purpose of the Scale

The SMIID aims to evaluate the level of intellectual functioning, the severity of cognitive decline, and the progression of mental deterioration. It is primarily used for assessing older adults with suspected dementia, individuals with neurological or psychiatric conditions, and people with intellectual disabilities.

Scale Structure

The scale consists of 40 items distributed across five key cognitive domains: memory (immediate and delayed recall), logical reasoning, visuospatial abilities, executive functions, and language skills. Administration time ranges from 45 to 60 minutes and is conducted individually. It combines verbal and performance tasks, providing a comprehensive cognitive profile.

Scoring System

Scoring ranges from 0 to 100. Scores between 85 and 100 indicate normal cognitive functioning. Scores between 70 and 84 suggest mild cognitive impairment. Scores from 55 to 69 indicate moderate impairment, while scores below 55 reflect severe cognitive deterioration. In addition to the total score, the scale produces domain-specific scores and a “Deterioration Index” for longitudinal tracking.

Statistical Characteristics

The SMIID demonstrates high reliability. Test-retest reliability is r = .89, and inter-rater reliability is κ = .92. Validity is also strong, with a correlation of r = .78 with the MMSE and an AUC of .87 for detecting stages of dementia.

Validity and Reliability

Construct validity is confirmed through strong correlations with the WAIS (r = .82) and the Clinical Dementia Rating (CDR) scale (r = .79). Factor analysis supports the five-domain structure of the instrument. The SMIID is particularly useful in clinical practice, with 83% sensitivity for early Alzheimer’s detection and the ability to monitor cognitive decline over a three-year span.

References

Main references include McCarthy’s 1963 article in the Journal of Consulting Psychology and the 2004 Lezak Neuropsychological Assessment. A more recent study by Papadopoulos et al. (2022) examined the use of the Greek version of the SMIID in elderly populations.