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 433 records · Page 24Linked to original sources
PubMed1980

Image alterations in the teaching microscope. A source of error in synovial fluid crystal identification.

An erroneous identification of sodium urate and calcium pyrophosphate crystals in synovial fluid may occur when utilizing compensated polarized microscopy with a dual-viewing-head teaching microscope. This is due to alteration of the observed image orientation with respect to the actual orientation of the crystal in space. By viewing a simple geometric figure through each microscope head, two basic types of image alterations are identified: a 180-degree rotation and a mirror-image transformation. Combinations of these two may also occur. This problem is clarified and illustrated and suggestions are offered to avoid erroneous crystal identification.

Calcium Pyrophosphate↗
PubMed1988

A source of error in phenylketonuria screening.

The escalating number of blood specimens from late-fed premature or very sick newborns greatly increases the risk of missing the diagnosis of phenylketonuria (PKU). Babies receiving antibiotics have uninterpretable "clear-zone" results with the traditional Guthrie bacteriologic inhibition assay (BIA). For the past year the authors have reexamined the blood phenylalanine level on specimens giving the "clear-zone" effect by BIA by use of the McCaman-Robins chemical-fluorescent assay (CFA). Spuriously high blood phenylalanine levels occurred in four babies who were receiving ampicillin and whose specimens were collected on filter paper and autoclaved in preparation for the BIA. None of the babies proved to have PKU. The fluorescent interference caused by ampicillin resulted from the heat of autoclaving the specimen. The authors recommend that the blood specimen should not be autoclaved before analysis by either BIA or CFA.

Agar↗
PubMed1987

Overcoming retention time shifts as a source of error in HPLC analysis.

When used for physiologic fluid analysis, shifts in retention times, even at constant flow rates, can cause integrators to function inadequately as tools for peak identification and thus result in concentration errors. A system capable of data collection, identification, quantification, and long-term storage that primarily uses retention times only for identification of elution sequence is described. Operator identification, aided by manipulation of x and y coordinates of the chromatograph, enhances positive identification of compounds for the experienced chromatographer.

Amino Acids↗
PubMed1985

Liver damage as a potential source of error in the estimation of myocardial infarct size from plasma creatine kinase activity.

The occurrence of liver damage was investigated in patients with uncomplicated acute myocardial infarction (AMI). Cumulative plasma release of creatine kinase (CK) and alpha-hydroxybutyrate dehydrogenase (HBD) was compared with release of alanine aminotransferase (ALT). Up to 48 h after AMI, the appearance of ALT could be fully explained by myocardial ALT release. Thereafter additional release of ALT occurred, indicating liver damage. A possible effect of liver function on the rate of elimination of CK from plasma was studied in the dog. Complete temporary arrest of hepatic blood supply was obtained after previous implantation of a portacaval shunt, ligation of secondary inflows and blockade of retrograde perfusion. Neither these preliminary haemodynamic interventions nor the acute arrest of hepatic blood flow had any effect on the disappearance rate of CK from plasma. It is concluded that some liver damage commonly occurs in patients after AMI. However, this phenomenon does not interfere with the estimation of infarct size because the elimination of CK from plasma is unaltered during total hepatic ischaemia.

Alanine Transaminase↗
PubMedDate not supplied

Determination of carboxyhemoglobin in heated blood--sources of error and utility of derivative spectrophotometry.

The cause for discrepancies in results from different methods of the carboxyhemoglobin (HbCO) analysis on the blood from bodies of burn victims was investigated. Blood samples with 0, 50, and 100% carbon monoxide (CO) saturation were heated at various temperatures for some time and then analyzed. Carboxyhemoglobin content was determined by the fourth-derivative spectrophotometric method and compared with results from the usual two-wavelength method. For total hemoglobin measurement, the fourth-derivative technique and cyanmethemoglobin method were used. Turbidity in blood samples, which occurred when samples were heated above 50 degrees C, affected the analysis. At about 70 degrees C, coagulation and hemoglobin degeneration occurred accelerating the errors of determined values. The fourth-derivative technique, however, proved to be independent of the turbidity and would be useful for the analysis on the blood without hemoglobin degeneration.

Carboxyhemoglobin↗
PubMed2003

Gas exchange measurements, what can they tell us about the underlying limitations to photosynthesis? Procedures and sources of error.

The principles, equipment and procedures for measuring leaf and canopy gas exchange have been described previously as has chlorophyll fluorescence. Simultaneous measurement of the responses of leaf gas exchange and modulated chlorophyll fluorescence to light and CO2 concentration now provide a means to determine a wide range of key biochemical and biophysical limitations on photo synthesis in vivo. Here the mathematical frameworks and practical procedures for determining these parameters in vivo are consolidated. Leaf CO2 uptake (A) versus intercellular CO2 concentration (Ci) curves may now be routinely obtained from commercial gas exchange systems. The potential pitfalls, and means to avoid these, are examined. Calculation of in vivo maximum rates of ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) carboxylation (Vc,max), electron transport driving regeneration of RuBP (Jmax), and triose-phosphate utilization (VTPU) are explained; these three parameters are now widely assumed to represent the major limitations to light-saturated photosynthesis. Precision in determining these in intact leaves is improved by the simultaneous measurement of electron transport via modulated chlorophyll fluorescence. The A/Ci response also provides a simple practical method for quantifying the limitation that stomata impose on CO2 assimilation. Determining the rate of photorespiratory release of oxygen (Rl) has previously only been possible by isotopic methods, now, by combining gas exchange and fluorescence measurements, Rl may be determined simply and routinely in the field. The physical diffusion of CO2 from the intercellular air space to the site of Rubisco in C3 leaves has long been suspected of being a limitation on photosynthesis, but it has commonly been ignored because of the lack of a practical method for its determination. Again combining gas exchange and fluorescence provides a means to determine mesophyll conductance. This method is described and provides insights into the magnitude and basis of this limitation.

Botany↗
PubMed1987

Inappropriate left ventricular hypertrophy in minor aortic valve disease: a source of error in clinical assessment.

A group of patients with minor aortic valve disease and inappropriately severe left ventricular hypertrophy is described. Clinical, electrocardiographic and echocardiographic assessment of the degree of left ventricular hypertrophy suggested that they had haemodynamically severe aortic stenosis but this was not borne out at cardiac catheterisation. Although a chance association between non-obstructive hypertrophic cardiomyopathy and mild aortic stenosis may have been responsible, an abnormally severe hypertrophic response to minor aortic outflow obstruction is proposed as another possible explanation. The association between minor aortic valve disease and severe left ventricular hypertrophy should be considered when assessing aortic stenosis since the prognosis with medical management seems good and valve replacement is likely to be of no benefit in such cases.

Aged↗