The Relationship of an Anticholinergic Rating Scale With Serum Anticholinergic Activity in Elderly Nursing Home Residents

The purpose of this study was to use serum anticholinergic activity (SAA) to assess the validity of a modified version of the Clinician-Rated Anticholinergic Scale (CR-ACh-mod) in evaluating anticholinergic medication exposure. The CR-ACh-mod scale assigns a value of 0–3 (none to marked anticholinergic effects) to each drug in a subject’s regimen and sums the values to create the CR-ACh-mod score. Subjects were part of a study of delirium in elderly residents of rural long-term care facilities. The 96 subjects had a mean age of 87±7 years (range 68–106), and 82.3% were female. The mean SAA was 0.91±0.51 pmol/0.2 mL atropine equivalents (range 0.09–2.61). The mean CR-ACh-mod score was 2.8±2.3 (range 0–9). CR-ACh-mod scores were significantly associated with SAA using linear regression (t = 2.68, df = 1, P = 0.0087). However, the scores only explained 7.1% of the variance in SAA, suggesting that improvements in the CR-ACh-mod may increase its robustness as a measure of anticholinergic exposure. These findings support the validity of the CR-ACh-mod. However, unexplained variance in SAA suggests that the CR-ACh-mod could benefit from improvements. Future research will evaluate the effect of including factors such as dose and the relative anticholinergic burden from drugs at each rating level. An alternative explanation for the variance, supported by recent research, is that nondrug factors contribute to SAA. Psychopharmacology Bulletin. 2002;36(4):14-19