Latent information in fluency lists predicts functional decline in persons at risk for Alzheimer disease

OBJECTIVE

We constructed random forest classifiers employing either the traditional method of scoring semantic fluency word lists or new methods. These classifiers were then compared in terms of their ability to diagnose Alzheimer disease (AD) or to prognosticate among individuals along the continuum from cognitively normal (CN) through mild cognitive impairment (MCI) to AD.

METHOD

Semantic fluency lists from 44 cognitively normal elderly individuals, 80 MCI patients, and 41 AD patients were transcribed into electronic text files and scored by four methods: traditional raw scores, clustering and switching scores, "generalized" versions of clustering and switching, and a method based on independent components analysis (ICA). Random forest classifiers based on raw scores were compared to "augmented" classifiers that incorporated newer scoring methods. Outcome variables included AD diagnosis at baseline, MCI conversion, increase in Clinical Dementia Rating-Sum of Boxes (CDR-SOB) score, or decrease in Financial Capacity Instrument (FCI) score. Receiver operating characteristic (ROC) curves were constructed for each classifier and the area under the curve (AUC) was calculated. We compared AUC between raw and augmented classifiers using Delong's test and assessed validity and reliability of the augmented classifier.

RESULTS

Augmented classifiers outperformed classifiers based on raw scores for the outcome measures AD diagnosis (AUC .97 vs. .95), MCI conversion (AUC .91 vs. .77), CDR-SOB increase (AUC .90 vs. .79), and FCI decrease (AUC .89 vs. .72). Measures of validity and stability over time support the use of the method.

CONCLUSION

Latent information in semantic fluency word lists is useful for predicting cognitive and functional decline among elderly individuals at increased risk for developing AD. Modern machine learning methods may incorporate latent information to enhance the diagnostic value of semantic fluency raw scores. These methods could yield information valuable for patient care and clinical trial design with a relatively small investment of time and money.

Malaria-induced IL-10 contributes to the systemic burden of non-typhoidal Salmonella (164.10)

Non-typhoidal Salmonella serotypes (NTS) in pediatric patients with severe malaria can develop a life threatening bacteremia, a major source of child mortality in Sub-Saharan Africa. Here, we use a mouse model, mimicking severe anemia seen in humans, to address mechanisms by which an underlying malaria infection contributes to the increased risk of NTS bacteremia. Plasmodium yoelli infected red blood cells were administered i.p. in CBA or B6 mice. At peak parasitemia, Salmonella Typhimurium was administered by g.g. in a streptomycin-induced colitis model. Characterization of inflammation to NTS in the cecum was assessed by histopathology, microarray and qRT-PCR. Bacterial loads in systemic tissues were followed up to 4 days post inoculation. Our results indicate that the malaria parasite infection causes a global suppression of proinflammatory responses in the intestine, blunts intestinal neutrophil influx and increases the bacterial burden at systemic sites. Blunting of intestinal inflammatory responses was independent of antibody-induced anemia, but required induction of the immunoregulatory cytokine IL-10. Blocking IL-10 activity reduced systemic NTS in coinfected mice and administration of exogenous IL-10 was sufficient to increase the systemic burden of NTS in the absence of parasite infection. However, an increase in circulating NTS required both anemia and IL-10. Thus, we have identified two factors that synergize to increase bacteremia using a murine model.

The effect of importance level, delay, and rate of forgetting on prose recall in multiple sclerosis

Memory deficits are frequently seen in patients with multiple sclerosis (MS). The focus of this study was to examine semantic encoding and the rate of forgetting in MS patients. The prose passages of the Wechsler Memory Scale Logical Memory subtest were used to examine MS patients' semantic sensitivity to the idea units of a story. The stories were divided into high, medium, and low idea units, reflecting their overall importance to the meaning of the story. MS patients recalled fewer idea units than controls, but both groups favored the main ideas relative to the nonessential details at both the immediate and delayed recall of the passages. Likewise, MS patients forgot information at a much faster rate than controls. Implications of this faster forgetting rate in MS patients are discussed from an applied setting.