Digit Symbol and Symbol Digit Modalities Tests: Are they directly interchangeable?

45 persons (aged 19–74 yrs) referred for neuropsychological evaluation were administered both the Symbol Digit Modalities Test (SDMT) and the Digit Symbol (DS) subtest of the Wechsler Adult Intelligence Scale (WAIS). SDMT and DS scores correlated very highly (r?=?.91). Relative to the tests' normative populations, however, the SDMT yielded scores for individual Ss that were the equivalent of 4–5 WAIS age-scaled points lower than obtained DS age-scaled scores. Results indicate that SDMT and DS scores cannot be presumed to be directly interchangeable in clinical use and suggest a general need for caution when interpreting interest patterns across measures normed on different populations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)