Computational methods for single-point and multipoint analysis of genetic variants associated with a simulated complex disorder in a general population.

Several techniques for association analysis have been applied to simulated genetic data for a general population. We describe and compare the performance of three single-point methods and two multipoint approaches rooted in machine learning and data mining.

Clostridium difficile infection: risk factors, medical and surgical management.

BACKGROUND: Clostridium difficile has become recognized as a cause of nosocomial infection which may progress to a fulminant disease. METHODS: Literature review using electronic literature research back to 1966 utilizing Medline and Current Contents. All publications on antibiotic-associated diarrhea, antibiotic-associated colitis, and pseudomembranous colitis as well as C. difficile infection were included. We addressed established and potential risk factors for C. difficile disease such as an impaired immune system and cost benefits of different diagnostic tests. An algorithm is outlined for diagnosis and both medical and surgical management of mild, moderate and severe C. difficile disease. RESULTS: Diagnosis of C. difficile infection should be suspected in patients with diarrhea, who have received antibiotics within 2 months or whose symptoms started after hospitalization. A stool specimen should be tested for the presence of leukocytes and C. difficile toxins. If this is negative and symptoms persist, stool should be tested with 'rapid' enzyme immunoabsorbent and stool cytotoxin assays, which are the most cost-effective tests. Endoscopy and other imaging studies are reserved for severe and rapidly progressive courses. Oral metronidazole or vancomycin are the antibiotics of choice. Surgery is rarely required for selected patients refractory to medical treatment. The threshold for surgery in severe cases with risk factors including an impaired immune system should be low. CONCLUSION: C. difficile infection has been recognized with increased frequency as a nosocomial infection. Early diagnosis with immunoassays of the stool and prompt medical therapy have a high cure rate. Metronidazole has supplanted oral vancomycin as the drug of first choice for treating C. difficile infections.

Comparing peritonitis in continuous ambulatory peritoneal dialysis patients versus automated peritoneal dialysis patients.

The purpose of our study was to compare the incidence of peritonitis between continuous ambulatory peritoneal dialysis (CAPD) treatment (Group I) and automated peritoneal dialysis (APD) treatment (Group II) taking into account the same population. We compared 20 patients with a follow-up of 215 patient-months on CAPD and 252 patient-months on APD. Demographic data, diagnosis, peritoneal equilibration test (PET) results, adequacy, and peritonitis rate were analyzed. Diagnoses included glomerulopathy 35%, autosomal dominant polycystic kidney disease (ADPKD) 20%, Type II diabetes 10%, systemic lupus erythematosus 5%, interstitial nephritis 5%, nephrolitiasis 5%, and unknown 20%. PET results showed that the group consisted of 30% high transporters, 45% high-average transporters, and 25% low-average transporters. Kt/V for Group I was 1.3 +/- 0.3, and for Group II, 1.83 +/- 0.48. Creatinine clearance for Group I was 43.64 +/- 7.31 L/week/1.73 m2, and for Group II, 52.42 +/- 13.47 L/week/1.73 m2. Group I presented a peritonitis rate of 8.3 episodes/patient-month, and Group II presented a rate of 18.9 episodes/patient-month. Gram-positive organisms were responsible for 49.8% of episodes of peritonitis in Group I (S. aureus 26.6%, S. epidermidis 16.6%, others 10%) and 83% of peritonitis episodes in Group II (S. epidermidis 46.6%, S. aureus 20%). Gram-negative organisms were responsible for 16.5% of episodes of peritonitis in Group I. No gram-negative peritonitis was seen in Group II. APD patients developed two cases of candida peritonitis. Our preliminary results show that Group II exhibited a decrease in peritonitis rate while achieving better adequacy. In CAPD and APD peritonitis, gram-positive organisms predominated. In APD, we observed an increase in S. epidermidis incidence. No gram-negative organisms were observed in APD. It seems that APD is a safer treatment owing to the lower peritonitis incidence.

Metrics for cortical map organization and lateralization.

Cerebral lateralization refers to the poorly understood fact that some functions are better controlled by one side of the brain than the other (e.g. handedness, language). Of particular concern here are the asymmetries apparent in cortical topographic maps that can be demonstrated electrophysiologically in mirror-image locations of the cerebral cortex. In spite of great interest in issues surrounding cerebral lateralization, methods for measuring the degree of organization and asymmetry in cortical maps are currently quite limited. In this paper, several measures are developed and used to assess the degree of organization, lateralization, and mirror symmetry in topographic map formation. These measures correct for large constant displacements as well as curving of maps. The behavior of the measures is tested on several topographic maps obtained by self-organization of an initially random artificial neural network model of a bihemispheric brain, and the results are compared with subjective assessments made by humans.