Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Error Sources”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed1989

Arterial-venous concentration gradient as a potential source of error in pharmacokinetic studies. Plasma concentration differences of 6-chloro-2-pyridylmethyl nitrate on constant infusion to rats.

1. Plasma concentrations of 6-chloro-2-pyridylmethyl nitrate (CPMN) at different sampling sites in the circulation were determined during and after constant infusion in the rat. 2. An arterial-venous CPMN concentration gradient was found and characterized by the following trends. During CPMN infusion into the right atrium, plasma concentrations were higher in arterial (aortic arch) than venous (inferior vena cava) plasma. After cessation of infusion the venous plasma concentrations were significantly higher (P less than 0.05) than those in arterial samples. There was a low concentration gradient between the right atrium and the peripheral artery, but substantial difference between the peripheral artery and the vein. There was a 1.8-2.4 extraction ratio of CPMN across the arterial-venous bed.

Animals↗
PubMedDate not supplied

Polyvinylpyrrolidone storage disease: a source of error in the diagnosis of signet ring cell gastric adenocarcinoma.

False-positive and false-negative diagnoses of cancer seldom occur during evaluation of gastric mucosal biopsy specimens obtained during flexible fiberoptic endoscopy of the stomach. When they do occur, false-negative diagnoses are usually the result of undersampling of the lesion, whereas false-positive diagnoses are the result of overinterpretation of benign histologic lesions. The diagnosis of diffuse signet ring cell adenocarcinoma is associated with both false-positive and false-negative diagnoses of cancer. The signet ring cell can be easily overlooked. Mucicarminophilic cells can be overinterpreted as diffuse signet ring cell adenocarcinoma. Polyvinylpyrrolidone is an unusual cause of this type of false-positive diagnosis of gastric adenocarcinoma. Judicious use of histochemical stains, immunohistochemistry, and electron microscopy plays a significant role in avoiding the false-positive diagnosis of diffuse signet ring cell adenocarcinoma.

Biopsy↗
PubMedDate not supplied

Cardiac cycle phase uncertainty: another source of error in indirect blood pressure measurement.

Cardiac cycle phase uncertainty causes a small error in indirect estimation of arterial blood pressure by sphygmomanometry. A simple analysis yields a statistical description of the error and a rule for its reduction: correct bias by adding to the systolic estimate and subtracting from the diastolic estimate one-half of the per-cardiac-cycle cuff deflation decrement. If several measurements are taken, the least-square estimate is approximately the arithmetic mean of the greatest and least of the bias corrected estimates.

Blood Pressure Determination↗
PubMed2000

Sources of error in comparing functional magnetic resonance imaging and invasive electrophysiological recordings.

OBJECT: Several authors have recently reported studies in which they aim to validate functional magnetic resonance (fMR) imaging against the accepted gold standard of invasive electrophysiological monitoring. The authors have conducted a similar study, and in this paper they identify and quantify two characteristics of these data that can make such a comparison problematic. METHODS: Eight patients in whom surgery for epilepsy was performed and five healthy volunteers underwent fMR imaging to localize the part of the sensorimotor cortex responsible for hand movement. In the patient group subdural electrode mats were subsequently implanted to identify eloquent regions of the brain and the epileptogenic zone. The fMR imaging data were processed to correct for motion during the study and then registered with a postimplantation computerized tomography (CT) scan on which the electrodes were visible. The motion during imaging in the two groups studied, and the deformation of the brain between the preoperative images and postoperative scans were measured. The patients who underwent epilepsy surgery moved significantly more during fMR imaging experiments than healthy volunteers performing the same motor task. This motion had a particularly increased out-of-plane component and was significantly more correlated with the stimulus than in the volunteers. This motion was especially increased when the patients were performing a task on the side affected by the lesion. The additional motion is hard to correct and substantially degrades the quality of the resulting fMR images, making it a much less reliable technique for use in these patients than in others. Also, the authors found that after electrode implantation, the brain surface can shift more than 10 mm relative to the skull compared with its preoperative location, substantially degrading the accuracy of the comparison of electrophysiological measurements made in the deformed brain and fMR studies obtained preoperatively. CONCLUSIONS: These two findings indicate that studies of this sort are currently of limited use for validating fMR imaging and should be interpreted with care. Additional image analysis research is necessary to solve the problems caused by patients' motion and brain deformation.

Cerebral Cortex↗
PubMed1984

Skin absorption as a source of error in biological monitoring.

Concentrations of toluene, tetrachloroethylene, and 1,1,1-trichloroethane were determined in blood collected from both forearms of subjects after one of their hands was soaked for 5 min in the corresponding solvent or in a thinner containing toluene, as a simulation of the washing of hands with solvent after work. The concentrations of toluene, tetrachloroethylene, and 1,1,1-trichloroethane on the soaked side were high, maximally 5.4, 9.0, and 4.0 mumol/l, respectively, and 20-, 130-, and 35-fold, respectively, compared to the contralateral side. Intraindividual differences were very marked, and dramatic changes were detected within a short period of time. It was not until after 3 h with toluene and 5 h with the chlorinated solvents that the difference between the two arms vanished. It is concluded that analyses of solvents in blood specimens drawn during or immediately after the workday may lead to markedly erroneous estimations of exposure.

Environmental Exposure↗