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1.  THE RISK OF THE HEMOLYTIC–UREMIC SYNDROME AFTER ANTIBIOTIC TREATMENT OF ESCHERICHIA COLI O157:H7 INFECTIONS 
The New England journal of medicine  2000;342(26):1930-1936.
Background
Children with gastrointestinal infections caused by Escherichia coli O157:H7 are at risk for the hemolytic–uremic syndrome. Whether antibiotics alter this risk is unknown.
Methods
We conducted a prospective cohort study of 71 children younger than 10 years of age who had diarrhea caused by E. coli O157:H7 to assess whether antibiotic treatment in these children affects the risk of the hemolytic–uremic syndrome and to assess the influence of confounding factors on this outcome. Estimates of relative risks were adjusted for possible confounding effects with the use of logistic-regression analysis.
Results
Among the 71 children, 9 (13 percent) received antibiotics and the hemolytic–uremic syndrome developed in 10 (14 percent). Five of these 10 children had received antibiotics. Factors significantly associated with the hemolytic–uremic syndrome were a higher initial white-cell count (relative risk, 1.3; 95 percent confidence interval, 1.1 to 1.5), evaluation with stool culture soon after the onset of illness (relative risk, 0.3; 95 percent confidence interval, 0.2 to 0.8), and treatment with antibiotics (relative risk, 14.3; 95 percent confidence interval, 2.9 to 70.7). The clinical and laboratory characteristics of the 9 children who received antibiotics and the 62 who did not receive antibiotics were similar. In a multivariate analysis that was adjusted for the initial white-cell count and the day of illness on which stool was obtained for culture, antibiotic administration remained a risk factor for the development of the hemolytic–uremic syndrome (relative risk, 17.3; 95 percent confidence interval, 2.2 to 137).
Conclusions
Antibiotic treatment of children with E. coli O157:H7 infection increases the risk of the hemolytic–uremic syndrome.
doi:10.1056/NEJM200006293422601
PMCID: PMC3659814  PMID: 10874060
2.  PATTERNS OF BRAIN ACTIVATION IN PEOPLE AT RISK FOR ALZHEIMER’S DISEASE 
The New England journal of medicine  2000;343(7):450-456.
Background
The ε4 allele of the apolipoprotein E gene (APOE) is the chief known genetic risk factor for Alzheimer’s disease, the most common cause of dementia late in life. To determine the relation between brain responses to tasks requiring memory and the genetic risk of Alzheimer’s disease, we performed APOE genotyping and functional magnetic resonance imaging (MRI) of the brain in older persons with intact cognition.
Methods
We studied 30 subjects (age, 47 to 82 years) who were neurologically normal, of whom 16 were carriers of the APOE ε4 allele and 14 were homozygous for the APOE ε3 allele. The mean age and level of education were similar in the two groups. Patterns of brain activation during functional MRI scanning were determined while subjects memorized and recalled unrelated pairs of words and while subjects rested between such periods. Memory was reassessed in 14 subjects two years later.
Results
Both the magnitude and the extent of brain activation during memory-activation tasks in regions affected by Alzheimer’s disease, including the left hippocampal, parietal, and prefrontal regions, were greater among the carriers of the APOE ε4 allele than among the carriers of the APOE ε3 allele. During periods of recall, the carriers of the APOE ε4 allele had a greater average increase in signal intensity in the hippocampal region (1.03 percent vs. 0.62 percent, P<0.001) and a greater mean (±SD) number of activated regions throughout the brain (15.9±6.2 vs. 9.4±5.5, P=0.005) than did carriers of the APOE ε3 allele. Longitudinal assessment after two years indicated that the degree of base-line brain activation correlated with degree of decline in memory.
Conclusions
Patterns of brain activation during tasks requiring memory differ depending on the genetic risk of Alzheimer’s disease and may predict a subsequent decline in memory.
doi:10.1056/NEJM200008173430701
PMCID: PMC2831477  PMID: 10944562
3.  RETINOPATHY AND NEPHROPATHY IN PATIENTS WITH TYPE 1 DIABETES FOUR YEARS AFTER A TRIAL OF INTENSIVE THERAPY 
The New England journal of medicine  2000;342(6):381-389.
Background
Among patients with type 1 diabetes mellitus, intensive therapy (with the aim of achieving near-normal blood glucose and glycosylated hemoglobin concentrations) markedly reduces the risk of microvascular complications as compared with conventional therapy. To assess whether these benefits persist, we compared the effects of former intensive and conventional therapy on the occurrence and severity of retinopathy and nephropathy for four years after the end of the Diabetes Control and Complications Trial (DCCT).
Methods
At the end of the DCCT, the patients in the conventional-therapy group were offered intensive therapy, and the care of all patients was transferred to their own physicians. Retinopathy was evaluated on the basis of centrally graded fundus photographs in 1208 patients during the fourth year after the DCCT ended, and nephropathy was evaluated on the basis of urine specimens obtained from 1302 patients during the third or fourth year, approximately half of whom were from each treatment group.
Results
The difference in the median glycosylated hemoglobin values between the conventional-therapy and intensive-therapy groups during the 6.5 years of the DCCT (average, 9.1 percent and 7.2 percent, respectively) narrowed during follow-up (median during 4 years, 8.2 percent and 7.9 percent, respectively; P<0.001). Nevertheless, the proportion of patients who had worsening retinopathy, including proliferative retinopathy, macular edema, and the need for laser therapy, was lower in the intensive-therapy group than in the conventional-therapy group (odds reduction, 72 percent to 87 percent; P<0.001). The proportion of patients with an increase in urinary albumin excretion was significantly lower in the intensive-therapy group.
Conclusions
The reduction in the risk of progressive retinopathy and nephropathy resulting from intensive therapy in patients with type 1 diabetes persists for at least four years, despite increasing hyperglycemia.
PMCID: PMC2630213  PMID: 10666428
4.  RANDOMIZED, CONTROLLED TRIALS, OBSERVATIONAL STUDIES, AND THE HIERARCHY OF RESEARCH DESIGNS 
The New England journal of medicine  2000;342(25):1887-1892.
Background
In the hierarchy of research designs, the results of randomized, controlled trials are considered to be evidence of the highest grade, whereas observational studies are viewed as having less validity because they reportedly overestimate treatment effects. We used published meta-analyses to identify randomized clinical trials and observational studies that examined the same clinical topics. We then compared the results of the original reports according to the type of research design.
Methods
A search of the Medline data base for articles published in five major medical journals from 1991 to 1995 identified meta-analyses of randomized, controlled trials and meta-analyses of either cohort or case–control studies that assessed the same intervention. For each of five topics, summary estimates and 95 percent confidence intervals were calculated on the basis of data from the individual randomized, controlled trials and the individual observational studies.
Results
For the five clinical topics and 99 reports evaluated, the average results of the observational studies were remarkably similar to those of the randomized, controlled trials. For example, analysis of 13 randomized, controlled trials of the effectiveness of bacille Calmette–Guérin vaccine in preventing active tuberculosis yielded a relative risk of 0.49 (95 percent confidence interval, 0.34 to 0.70) among vaccinated patients, as compared with an odds ratio of 0.50 (95 percent confidence interval, 0.39 to 0.65) from 10 case–control studies. In addition, the range of the point estimates for the effect of vaccination was wider for the randomized, controlled trials (0.20 to 1.56) than for the observational studies (0.17 to 0.84).
Conclusions
The results of well-designed observational studies (with either a cohort or a case–control design) do not systematically overestimate the magnitude of the effects of treatment as compared with those in randomized, controlled trials on the same topic. (N Engl J Med 2000;342:1887-92.)
PMCID: PMC1557642  PMID: 10861325

Results 1-4 (4)