Sensitivity and specificity of the animal fluency test for predicting postoperative delirium

Abstract

Background Preoperative cognitive impairment is a major risk factor for postoperative delirium. We therefore investigated the prognostic significance and feasibility of administering a brief cognitive screen before surgery. Methods Patients [ 65 yr of age undergoing hip, knee, or spine surgery were enrolled. A 60-sec cognitive screen, the animal fluency test (AFT), was administered preoperatively. Postoperative delirium was measured using a chart-based tool previously validated using criteria from the Confusion Assessment Method. Results Of the 362 patients satisfying the inclusion/ exclusion criteria, 199 (55%) underwent the AFT. Among them, 57 patients (29%) had an AFT score \ 15, and 38 patients (19%, 95% confidence interval [CI]: 14 to 25%) developed postoperative delirium as measured by chart review. Patients with scores of \ 15 were more likely to develop postoperative delirium than those who scored C 15 (54% vs 5%, P \ 0.01). A multiple logistic regression, with postoperative delirium as the dependent variable, identified an AFT score of \ 15 (odds ratio 20.1, 95% CI: 7.9 to 51.4) and high American Society of Anesthesiologists classification (odds ratio 3.5, 95% CI: 1.3 to 9.2) as independent predictors. Conclusions The AFT is a potentially useful brief cognitive screen for identifying patients at risk of developing postoperative delirium. Limited participation by eligible participants in this study, however, raises questions about how useful and feasible systematic administration of the test is. Large studies using prospective measurement of postoperative delirium are indicated to validate our results. Résumé

Poor Performance on a Preoperative Cognitive Screening Test Predicts Postoperative Complications in Older Orthopedic Surgical Patients

“…14 Category fluency has also been used as a cognitive screening test in this setting with similar results in terms of prevalence of probable cognitive impairment preoperatively and association with delirium postoperatively but selection bias is possible since about half of eligible patients were not screened. 43 It is important to emphasize in this context that no single cognitive test, administered at a single time, can diagnose MCI or dementia. Therefore, by itself, a low preoperative MiniCog score is not enough to diagnose or label a patient as having a memory disorder.…”

Preoperative Cognitive Stratification of Older Elective Surgical Patients: A Cross-Sectional Study

“…Still, we cannot exclude the possibility that other brief instruments could work as well or better in the presurgical setting. (14,26,27,44–47) As screening instruments, the Mini-Cog and CIB will inevitably yield false positives and negatives. Someone falsely labeled as impaired may elect to forgo elective surgery for fear of having cognitive impairment afterward but those who proceed will likely just receive increased vigilance (e.g., geriatric consultation, more careful monitoring during anesthesia, joint discharge instructions), and those with undetected impairment will be no worse off than our patients are currently.…”

Brief Preoperative Screening for Frailty and Cognitive Impairment Predicts Delirium after Spine Surgery

“…There are myriad reasons for this, but one is the perception that such screening is unduly burdensome and time-consuming for a surgical setting. 8,[11][12][13] This has been addressed to some degree in the case of preoperative cognitive screening, with work by several groups, including us, demonstrating that brief instruments such as the Mini-Cog and Animal Verbal Fluency can identify patients at risk for poor surgical outcomes. 10,11,14,15 Similarly, there are numerous validated tools to assess frailty, but little consensus about which are best suited to the preoperative setting.…”

“…8,[11][12][13] This has been addressed to some degree in the case of preoperative cognitive screening, with work by several groups, including us, demonstrating that brief instruments such as the Mini-Cog and Animal Verbal Fluency can identify patients at risk for poor surgical outcomes. 10,11,14,15 Similarly, there are numerous validated tools to assess frailty, but little consensus about which are best suited to the preoperative setting. Thus far, investigations of the relationship between frailty and adverse surgical outcomes have largely relied on instruments such as the Frailty Index or the Frailty Phenotype which, are relatively time consuming and labor intensive and therefore unlikely to be widely accepted or adopted in a high throughput preoperative setting.…”