The Preclinical Alzheimer's Cognitive Composite (PACC) is a baseline standardized composite of
pacc(dd, keepComponents = FALSE)
data frame to score with variables ADASQ4, LDELTOTAL, DIGITSCOR, MMSE, TRABSCOR, DX.bl, and VISCODE
should components and z scores be returned? Defaults to FALSE so that just the composite scores are returned.
data.frame with appended columns for
Free and Cued Selective Reminding Test (FCSRT)
Logical Memory IIa Delayed Recall (LM)
Digit Symbol Substitituion Test (DSST)
Mini-Mental State Examination (MMSE)
This function generates two modified versions of PACC scores based on ADNI data. FCSRT is not used in ADNI, so we use the
Delayed Recall portion of the Alzheimer's Disease Assessment Scale (ADAS) as a proxy. Score
mPACCdigit uses the
DSST when available (ADNI1).
mPACCtrailsB uses (log transformed) Trails B as a proxy for DSST. Raw component scores
standardized according to the mean and standard deviation of baseline scores of ADNI subjects with normal cognition
Z scores for each component
(Z=(raw - mean(raw.bl))/sd(raw.bl)).
The Z scores are reoriented if necessary so that greater scores reflect better performance.
The composite is the sum of these Z scores.
Missing components: At least two components must be present to produce a score. If more than two components are missing,
the PACC will be
Donohue MC, et al. The Preclinical Alzheimer Cognitive Composite: Measuring Amyloid-Related Decline. JAMA Neurol. 2014;71(8):961–970. doi:10.1001/jamaneurol.2014.803 http://dx.doi.org/10.1001/jamaneurol.2014.803
Donohue MC, Sperling RA, Petersen R, Sun C, Weiner MW, Aisen PS, for the Alzheimer’s Disease Neuroimaging Initiative. Association Between Elevated Brain Amyloid and Subsequent Cognitive Decline Among Cognitively Normal Persons. JAMA. 2017;317(22):2305–2316. http://dx.doi.org/10.1001/jama.2017.6669