Structural magnetic resonance imaging for the early diagnosis of dementia due to Alzheimer's disease in people with mild cognitive impairment.

BACKGROUND: Mild cognitive impairment (MCI) due to Alzheimer's disease is the symptomatic predementia phase of Alzheimer's disease dementia, characterised by cognitive and functional impairment not severe enough to fulfil the criteria for dementia. In clinical samples, people with amnestic MCI are at high risk of developing Alzheimer's disease dementia, with annual rates of progression from MCI to Alzheimer's disease estimated at approximately 10% to 15% compared with the base incidence rates of Alzheimer's disease dementia of 1% to 2% per year. OBJECTIVES: To assess the diagnostic accuracy of structural magnetic resonance imaging (MRI) for the early diagnosis of dementia due to Alzheimer's disease in people with MCI versus the clinical follow-up diagnosis of Alzheimer's disease dementia as a reference standard (delayed verification). To investigate sources of heterogeneity in accuracy, such as the use of qualitative visual assessment or quantitative volumetric measurements, including manual or automatic (MRI) techniques, or the length of follow-up, and age of participants. MRI was evaluated as an add-on test in addition to clinical diagnosis of MCI to improve early diagnosis of dementia due to Alzheimer's disease in people with MCI. SEARCH METHODS: On 29 January 2019 we searched Cochrane Dementia and Cognitive Improvement's Specialised Register and the databases, MEDLINE, Embase, BIOSIS Previews, Science Citation Index, PsycINFO, and LILACS. We also searched the reference lists of all eligible studies identified by the electronic searches. SELECTION CRITERIA: We considered cohort studies of any size that included prospectively recruited people of any age with a diagnosis of MCI. We included studies that compared the diagnostic test accuracy of baseline structural MRI versus the clinical follow-up diagnosis of Alzheimer's disease dementia (delayed verification). We did not exclude studies on the basis of length of follow-up. We included studies that used either qualitative visual assessment or quantitative volumetric measurements of MRI to detect atrophy in the whole brain or in specific brain regions, such as the hippocampus, medial temporal lobe, lateral ventricles, entorhinal cortex, medial temporal gyrus, lateral temporal lobe, amygdala, and cortical grey matter. DATA COLLECTION AND ANALYSIS: Four teams of two review authors each independently reviewed titles and abstracts of articles identified by the search strategy. Two teams of two review authors each independently assessed the selected full-text articles for eligibility, extracted data and solved disagreements by consensus. Two review authors independently assessed the quality of studies using the QUADAS-2 tool. We used the hierarchical summary receiver operating characteristic (HSROC) model to fit summary ROC curves and to obtain overall measures of relative accuracy in subgroup analyses. We also used these models to obtain pooled estimates of sensitivity and specificity when sufficient data sets were available. MAIN RESULTS: We included 33 studies, published from 1999 to 2019, with 3935 participants of whom 1341 (34%) progressed to Alzheimer's disease dementia and 2594 (66%) did not. Of the participants who did not progress to Alzheimer's disease dementia, 2561 (99%) remained stable MCI and 33 (1%) progressed to other types of dementia. The median proportion of women was 53% and the mean age of participants ranged from 63 to 87 years (median 73 years). The mean length of clinical follow-up ranged from 1 to 7.6 years (median 2 years). Most studies were of poor methodological quality due to risk of bias for participant selection or the index test, or both. Most of the included studies reported data on the volume of the total hippocampus (pooled mean sensitivity 0.73 (95% confidence interval (CI) 0.64 to 0.80); pooled mean specificity 0.71 (95% CI 0.65 to 0.77); 22 studies, 2209 participants). This evidence was of low certainty due to risk of bias and inconsistency. Seven studies reported data on the atrophy of the medial temporal lobe (mean sensitivity 0.64 (95% CI 0.53 to 0.73); mean specificity 0.65 (95% CI 0.51 to 0.76); 1077 participants) and five studies on the volume of the lateral ventricles (mean sensitivity 0.57 (95% CI 0.49 to 0.65); mean specificity 0.64 (95% CI 0.59 to 0.70); 1077 participants). This evidence was of moderate certainty due to risk of bias. Four studies with 529 participants analysed the volume of the total entorhinal cortex and four studies with 424 participants analysed the volume of the whole brain. We did not estimate pooled sensitivity and specificity for the volume of these two regions because available data were sparse and heterogeneous. We could not statistically evaluate the volumes of the lateral temporal lobe, amygdala, medial temporal gyrus, or cortical grey matter assessed in small individual studies. We found no evidence of a difference between studies in the accuracy of the total hippocampal volume with regards to duration of follow-up or age of participants, but the manual MRI technique was superior to automatic techniques in mixed (mostly indirect) comparisons. We did not assess the relative accuracy of the volumes of different brain regions measured by MRI because only indirect comparisons were available, studies were heterogeneous, and the overall accuracy of all regions was moderate. AUTHORS' CONCLUSIONS: The volume of hippocampus or medial temporal lobe, the most studied brain regions, showed low sensitivity and specificity and did not qualify structural MRI as a stand-alone add-on test for an early diagnosis of dementia due to Alzheimer's disease in people with MCI. This is consistent with international guidelines, which recommend imaging to exclude non-degenerative or surgical causes of cognitive impairment and not to diagnose dementia due to Alzheimer's disease. In view of the low quality of most of the included studies, the findings of this review should be interpreted with caution. Future research should not focus on a single biomarker, but rather on combinations of biomarkers to improve an early diagnosis of Alzheimer's disease dementia.

Saccharomyces boulardii for the prevention of antibiotic-associated diarrhea in adult hospitalized patients: a single-center, randomized, double-blind, placebo-controlled trial.

OBJECTIVES: Antibiotic-associated diarrhea (AAD) and Clostridium difficile-associated diarrhea (CDAD) are common complications of antibiotic use. Probiotics were effective in preventing AAD and CDAD in several randomized controlled trials. This study was aimed at testing the effect of Saccharomyces boulardii on the occurrence of AAD and CDAD in hospitalized patients. METHODS: A single-center, randomized, double-blind, placebo-controlled, parallel-group trial was performed. Patients being prescribed antibiotics or on antibiotic therapy for <48 h were eligible. Exclusion criteria were ongoing diarrhea, recent assumption of probiotics, lack of informed consent, inability to ingest capsules, and severe pancreatitis. Patients received a capsule containing S. boulardii or an indistinguishable placebo twice daily within 48 h of beginning antibiotic therapy, continued treatment for 7 days after antibiotic withdrawal, and were followed for 12 weeks after ending antibiotic treatment. RESULTS: Of 562 consecutive eligible patients, 275 patients aged 79.2 ± 9.8 years (134 on placebo) were randomized and 204 aged 78.4 ± 10.0 years (98 on placebo) completed the follow-up. AAD developed in 13.3% (13/98) of the patients receiving placebo and in 15.1% (16/106) of those receiving S. boulardii (odds ratio for S. boulardii vs. placebo, 1.16; 95% confidence interval (CI), 0.53-2.56). Five cases of CDAD occurred, 2 in the placebo group (2.0%) and 3 in the probiotic group (2.8%; odds ratio for S. boulardii vs. placebo, 1.40; 95% CI, 0.23-8.55). There was no difference in mortality rates (12.7% vs. 15.6%, P=0.60). CONCLUSIONS: In elderly hospitalized patients, S. boulardii was not effective in preventing the development of AAD.

Homocysteine, MTHFR C677T gene polymorphism, folic acid and vitamin B 12 in patients with retinal vein occlusion.

BACKGROUND: Many available data have suggested that hyperhomocysteinaemia, an established independent risk factor for thrombosis (arterial and venous), may be associated with an increased risk of retinal vein occlusion (RVO). AIM OF THE STUDY: To evaluate homocysteine metabolism in consecutive caucasian patients affected by RVO from Northern Italy. PATIENTS AND METHODS: 69 consecutive patients from Northern Italy (mean age 64.1 +/- 14.6 yy) with recent RVO, were tested for plasma levels of homocysteine (tHcy: fasting and after loading with methionine), cyanocobalamine and folic acid levels (CMIA-Abbot) and looking for MTHFR C677T mutation (Light Cycler-Roche) and compared to 50 volunteers, enrolled as a control group. RESULTS: Fasting levels of tHcy were significantly higher in patients than in controls: mean value 14.7 +/- 7.7 vs 10.2 +/- 8 nmol/ml. Post load levels were also significantly higher: mean value 42.7 +/- 23.7 vs 30.4 +/- 13.3 nmol/ml; Total homocysteine increase was also evaluated (i.e. Delta-tHcy) after methionine load and was also significantly higher in patients compared to control subjects: mean Delta-tHcy 27.8 +/- 21.5 vs 21.0 +/- 16 nmol/ml (normal value < 25 nmol/ml). Furthermore, patients affected by RVO show low folic acid and/or vitamin B12 levels, although differences with control group did not reach statistical significance. Heterozygous and homozygous MTHFR mutation were respectively in study group 46% and 29% vs control group 56% and 4%. CONCLUSION: our data confirm that hyperhomocysteinaemia is a risk factor for RVO, and also that TT genotype of MTHFR C677T is more frequently associated with RVO: if the mutation per se is a risk factor for RVO remains an open question to be confirmed because another study from US did not reveal this aspect. Hyperomocysteinemia is modifiable risk factor for thrombotic diseases. Therefore, a screening for tHcy plasma levels in patients with recent retinal vein occlusion could allow to identify patients who might benefit from supplementation with vitamins and normalization of homocysteine levels, in fasting and after methionine load.