NIH toolbox cognition tests following traumatic brain injury: Frequency of low scores.
James A Holdnack, Grant L Iverson, Noah D Silverberg and 2 others
PMID 29265868WHAT IT FOUND
After TBI, one low NIH Toolbox cognition score is common even without TBI.
Clinicians should look at several low scores together and compare them with estimated premorbid ability before calling cognitive impairment.
Key findings
01One or more low NIH Toolbox fluid scores at or below the 16th percentile is not strong evidence of TBI, because 46% of the normative sample had that pattern.
02Having three fluid scores at or below the 16th percentile was 2.8 times more likely in the complicated mild/moderate TBI group and 4.5 times more likely in the severe TBI group than in the normative sample.
03Low-score criteria can be stratified by estimated pre-injury ability, with algorithms designed to keep the false positive rate below 15%.
STILL TO COME
How it was doneWhat they foundWhat it means for OTs
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What it does not show
All participants were assessed at one time point, so the results do not show how these low-score patterns change during recovery after TBI. The study did not include people with the mildest forms of TBI, such as those discharged from an emergency department without inpatient rehabilitation. The comparison group was a general normative sample rather than people with non-head traumatic injuries, so pre-injury differences between groups may remain. The analysed TBI sample was smaller than the sample administered the battery: 182 people were tested, but 158 were analysed because complete data on all seven tests were required. The Crystallized composite was used as a stand-in for pre-injury ability, but severe TBI can lower that score, so some people may have been placed in the wrong ability group. For people near the edge of an ability group, the algorithms may under-estimate how many actually have cognitive impairment.
Declared interests
The authors declared no financial interest in the NIH Toolbox.
The easy way to misread this
Do not treat one low NIH Toolbox fluid score as proof of TBI-related cognitive impairment. A single score at or below the 16th percentile was only 1.3 times more likely in the complicated mild/moderate TBI group and 1.6 times more likely in the severe TBI group than in the normative sample, and the paper says this is not significantly associated with TBI.