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Results for “Normal Distribution”

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At least 217 records · Page 12Linked to original sources
PubMed2004

Preoperative sensitivity and specificity for early-stage ovarian cancer when combining cancer antigen CA-125II, CA 15-3, CA 72-4, and macrophage colony-stimulating factor using mixtures of multivariate normal distributions.

PURPOSE: In CA-125-based ovarian cancer screening trials, overall specificity and screening sensitivity of ultrasound after an elevated CA-125 exceeded 99.6% and 70%, respectively, thereby yielding a positive predictive value (PPV) exceeding 10%. However, sensitivity for early-stage disease was only 40%. This study aims to increase preoperative sensitivity for early-stage ovarian cancer while maintaining the annual referral rate to ultrasound at 2% by combining information across CA-125II, CA 15-3, CA 72-4, and macrophage colony-stimulating factor (M-CSF). For direct comparisons between marker panels, all sensitivity results correspond to a 98% fixed first-line specificity (referral rate 2%). PATIENTS AND METHODS: Logistic regression, classification tree, and mixture discriminant analysis (MDA) models were fit to a training data set of preoperative serum measurements (63 patients, 126 healthy controls) from one center. Estimates from the training set applied to an independent validation set (60 stage I to II patients, 98 healthy controls) from two other centers provided unbiased estimates of sensitivity. RESULTS: Preoperative sensitivities for early-stage disease of the optimal panels were 45% for CA-125II; 67% for CA-125II and CA 72-4; 70% for CA-125II, CA 72-4, and M-CSF; and 68% for all four markers (latter two results using MDA). CONCLUSION: Efficiently combining information on CA-125II, CA 72-4, and M-CSF significantly increased preoperative early-stage sensitivity from 45% with CA-125II alone to 70%, while maintaining 98% first-line specificity. Screening trials with these markers using MDA followed by referral to ultrasound may maintain previously high levels of specificity and PPV, while significantly increasing early-stage screening sensitivity. MDA is a useful, biologically justified method for combining biomarkers.

Biomarkers, Tumor↗
PubMed1996

Normal distribution of apolipoprotein E alleles in progressive supranuclear palsy.

Apolipoprotein E (Apo E) genotype is a genetic risk factor influencing the development of Alzheimer's disease (AD). Progressive supranuclear palsy (PSP), like AD, is a dementing illness with neurofibrillary tangles. We determined the frequencies of Apo E alleles in 52 PSP patients and 52 age- and gender-matched controls. The distribution of Apo E allele frequencies and genotypes showed no difference between PSP and controls. Apo E allele status does not influence the development of PSP.

Aged↗
PubMed1992

Knee effusion: normal distribution of fluid.

Although visualization of articular fluid on MR images of the knee is common, no specific MR criteria that enable assessment of the quantity of the effusion have been established. We performed MR of three cadaveric knee specimens after the instillation of increasingly large volumes of fluid and studied the distribution of the fluid. When 4 ml of fluid was injected, the anteroposterior diameter of the suprapatellar recess was 4 mm on midline sagittal MR images and 10.0-12.5 mm on lateral sagittal MR images, corresponding to the usual routine radiographic criteria for a knee effusion.

Humans↗
PubMed2000

"Prefrontal deficits" discriminate young offenders from age-matched cohorts: juvenile delinquency as an expected feature of the normal distribution of prefrontal cerebral development.

A total of 36 male adolescent delinquents and 19 age-matched students from a male secondary school were administered several different performance-based tests. Although estimates of intelligence did not differ significantly between the groups, the incarcerated delinquents displayed more impulsivity, lower conceptual level, less conceptual flexibility, and poorer critical thinking than the reference group. The linear combination of only three variables, critical thinking, conceptual level, and numbers of errors during a conditioned spatial association task, correctly classified 89% of the 55 subjects. The results were considered consistent with the hypothesis that delayed or different development of complex functions associated with the left and (particularly) the right prefrontal cortices and their limbic inputs may be responsible for antisocial behavior. This variation will always be present due to the statistical variations in ontogeny and less than optimal parental structure within a consistent but small proportion of any generational cohort.

Adolescent↗
PubMed1987

Hyaluronan in the middle ear of the rat. The normal distribution of hyaluronan and the clearance of exogenously administered hyaluronan from the middle ear.

The content of hyaluronan (HA), a common connective tissue component, was determined in well defined areas of the rat middle ear. The HA concentration in the pars flaccida of the tympanic membrane was considerably greater than in the pars tensa and areas on the medial wall of the middle ear cavity. The fate of exogenous HA introduced into the middle ear was also studied in rats. Tritium-labelled HA disappeared through the Eustachian tube (ET) and was followed by analysis of the nasopharyngeal secretion. The radioactivity in the secretion reached a peak at 3 h and decreased to almost zero within 12 h, indicating that most of the HA was removed. By autoradiography and direct analysis of the HA concentration and molecular weight distribution the fate of HA after obstruction of the ET was followed. Radioactive HA was confined to the middle ear and no uptake into surrounding tissues could be traced by autoradiography 4 days after application. The amount of HA that could be recovered from the middle ear was constant for up to 6 days. Analysis of the molecular weight distribution of the deposited HA indicated only slow degradation during these 6 days.

Animals↗
PubMed1975

[The normal distribution of human parotid salivary proteins according to disc electrophoresis in alkaline and acidic gel systems].

Discelectrophoresis from 67 stimulated human parotid saliva samples was carried out in acidic and alkaline polyacrylamide gel-systems. Characteristical standard disc-electropherograms were obtained by means of quantitative densitometry and following statistical analysis. Application of standardized parotid discelectropherograms for diagnostics was discussed.

Acids↗
PubMed1992

[The normal distribution of oxygen tension on the surface of the brain radial arterioles and in their surrounding tissues and under normobaric hyperoxia].

The pO2 on the arterioles' wall was shown to depend on the diameter of the vessels under study in rats. In normoxia, the pO2 tissue gradients are small and do not depend on the vessel diameter, whereas in hyperoxia a sharp drop of the tissue pO2 occurs at some distance from the vessel and the dependence of the pO2 on the arteriole diameter can be registered practically in all the sites of measuring. Radical arterioles and adjacent tissues of the brain cortex were shown to be most affected by a high arterial pO2 in hyperoxemia.

Animals↗
PubMed2003

Which kind of data (normally distributed, standardized, transformed) for a realistic factor analysis?

Taking into account that the problem of the best pretreatment of data for factor analysis has not yet arrived at generally accepted solutions, it has been tried to estimate, by an empiric procedure, the goodness of the results of repeated factor analyses with different pretreatments, conditions and statistical distribution of variables. Sets of multivariate data for river waters have been constructed firstly, after fixing the number and nature of the latent factors corresponding to the sources of pollution. A series of R-mode factor analyses has then been performed on these data, using various pretreatments (autoscaling, logarithmic transformation and their combinations), various factor rotations (rigid and oblique) and methods of computation of significant factors (40 data processing on the whole). Factor analyses have also been performed on real data of the Po river in the Piedmont region. Comparisons between the results obtained by factor analysis and the actual situation of the systems investigated have made it possible to draw some conclusions on how to proceed in order to obtain realistic results with this chemometric technique.

Factor Analysis, Statistical↗