Reliable Digit Span: Does it Adequately Measure Suboptimal Effort in an Adult Epilepsy Population?

Area of Science:

• Neuropsychology
• Clinical Neuroscience

Background:

• Performance validity assessment is crucial in neuropsychological evaluations.
• Previous research suggests Reliable Digit Span (RDS) cutoffs of ≤6 or ≤7 detect suboptimal effort in adults.
• These cutoffs lack validation in adult epilepsy populations.

Purpose of the Study:

• To determine if established RDS cutoff scores (≤6 or ≤7) can detect suboptimal effort in adults with epilepsy.
• To investigate alternative RDS cutoff scores for this specific clinical group.

Main Methods:

• Sixty-three adult epilepsy patients underwent the Digit Span subtest (WAIS-III/IV).
• Most participants (98%) passed the Test of Memory Malingering (TOMM) Trial 2 (≥45), indicating generally valid effort.
• Statistical analyses examined RDS performance validity and its relation to cognitive factors.

Main Results:

• Established RDS cutoffs of ≤6 and ≤7 showed suboptimal specificity (85% and 77%, respectively) in this epilepsy cohort.
• RDS scores correlated positively with attention and intellectual functioning.
• A preliminary RDS cutoff score of ≤4 appears more appropriate for adults with epilepsy, particularly those with lower average IQs.

Conclusions:

• The standard RDS cutoffs of ≤6 and ≤7 are not recommended for assessing performance validity in adults with epilepsy.
• Lowering the RDS cutoff score to ≤4 may improve the detection of suboptimal effort in this population, especially for individuals with below-average intellectual functioning.