Catalan’s SPPN, a measure of solvent polarity/polarizability has been analysed in terms of molecular properties derived from computational chemistry. The results show that SPPN correlates positively ...with the molecular dipole moment and quadrupolar amplitude and negatively with the molecular polarizability. These correlations are shared with Kamet and Taft’s π* and Reichardt and Dimroth’s ET(30). Thus, one can associate the solvent polarity with non-specific interactions involving the permanent charges on solvent molecules. It is also noted that the opposite correlations, all three parameters increasing with increasing solvent polarity but decreasing with increasing solvent polarizability, creates an ambiguity in their use, for example, in linear free energy relationships.
The use of experimental parameters to quantify solvent properties, for example in linear free energy relationships, is well established and several scales of solvent acidity, basicity and ...polarity/polarizability have been developed. The success of this approach raises questions of which molecular properties contribute to particular solvent parameters and whether these contributions are found in all parameters representing a particular solvent property. In the present study, Catalan’s hydrogen bond basicity and acidity parameters,
SB
and
SA
, and Gutmann’s acceptor number,
AN
, a measure of a solvent’s Lewis acidity, are correlated with molecular properties derived from computational chemistry. The results are compared with the results of similar correlations with Kamlet and Taft’s
β
and
α
Solvent Scales, Gutmann’s donor number
DN
) and Abraham’s
B
and
A
solute scales. The results show that measures of solvent basicity,
SB
,
β
and
DN
all correlate strongly with the partial charge on the most negative atom in the solvent molecule and the energy of the donor orbital and, in all cases, the parameter values for hydrogen-bonded solvents are anomalous. Abraham’s
B
, a measure of solute hydrogen basicity, depends only on the partial charge on the most negative atom and there is no anomaly in the values for solutes that, in the pure state, form hydrogen-bonded liquids. Similarly, all measures of solvent acidity,
SA
,
α
and
AN
, and Abraham’s
A
, a measure of solute hydrogen bond acidity, depend on the partial charge on the most positive hydrogen on the molecule.
To the Editor.-An increase in the use of biotin supplements by the general public is producing an increase in the number of reports of analytic interference in biotin-based immunoassays (BBAs) used ...to evaluate endocrine function.1,2 The fact that BBAs of similar design are currently used to diagnose and manage a wide range of other medical conditions, including anemias, malignancies, autoimmune and infectious diseases, and cardiac damage, raises the concern that the accuracy of results for other routine tests are compromised as well.3 Methods that use immunometric ("sandwich") or competitive formats are at the greatest risk for producing falsely decreased or falsely increased results, respectively, when biotin is present in the sample. Eighty-two of these were immunometric or competitive methods that had manufacturer-reported interference thresholds (IFTs) (ie, the concentrations above which exogenous biotin in the sample caused a difference of greater than ±10% in the test result) of less than 51 ng/mL. In this case, the risk of an erroneous test result could persist for up to 8 elimination half-lives (>6 days) for a method with an IFT of 2.4 ng/mL. ...it might be necessary to avoid the use of some BBAs altogether when testing subjects who are using the 100-mg biotin supplements that are now available overthe-counter.2,5 The confluence of increased biotin supplement use by patients and the design limitations of many of the BBAs have already led to the misdiagnosis and mismanagement of patients.1-3 We are convinced that the risk of analytic interference by biotin supplements is a serious problem that needs to be more widely recognized and promptly addressed by health care providers, directors of clinical laboratories, and decision makers in the clinical diagnostics industry.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
A theorem presented by Professor Ben-Naim (J Phys Chem 82:874–885,
1978
) states that the standard state enthalpy and entropy changes arising from changes in the solvent structure that are induced by ...solvation of a solute cancel exactly in the standard state Gibbs energy. In this paper this is explored by consideration of the thermodynamics of transfer of electrolytes in mixed solvents, using previously developed models of the solvation process. Two cases are considered. One is random solvation, where curvatures in plots of the transfer enthalpies and entropies, which arise from changes in solvent–solvent interactions, exactly compensate in the transfer Gibbs (free) energies, which are sensibly linear with solvent composition. The second type of system are those with strong preferential solvation where it is found that the transfer Gibbs energies can be accounted for quantitatively in terms of changes in the solute–solvent interactions, with no contribution from changes in solvent–solvent interactions. The results are entirely consistent with the Ben-Naim theorem.
Abraham’s measure of the solute hydrogen bond basicity,
β
2
H
, is analyzed in terms of molecular properties derived from computational chemistry. It is found that the solute basicity is largely ...determined by the partial charges on negative centers on the solute molecule. For
β
2
H
< 0.5 the basicity is determined by the partial charge on the most negative atom of the solute molecule but for multifunctional solutes with higher
β
2
H
values there are contributions from the basicity of other basic centers. The
β
2
H
values of amines are not reproduced by the equation defined by correlation of the other solutes considered.
The objectives of this report are to review the mechanisms of biotin interference with streptavidin/biotin-based immunoassays, identify automated immunoassay systems vulnerable to biotin ...interference, describe how to estimate and minimize the risk of biotin interference in vulnerable assays, and review the literature pertaining to biotin interference in endocrine function tests.
The data in the manufacturer's "Instructions for Use" for each of the methods utilized by seven immunoassay system were evaluated. We also conducted a systematic search of PubMed/MEDLINE for articles containing terms associated with biotin interference. Available original reports and case series were reviewed. Abstracts from recent scientific meetings were also identified and reviewed.
The recent, marked, increase in the use of over-the-counter, high-dose biotin supplements has been accompanied by a steady increase in the number of reports of analytical interference by exogenous biotin in the immunoassays used to evaluate endocrine function. Since immunoassay methods of similar design are also used for the diagnosis and management of anemia, malignancies, autoimmune and infectious diseases, cardiac damage, etc., biotin-related analytical interference is a problem that touches every area of internal medicine.
It is important for healthcare personnel to become more aware of immunoassay methods that are vulnerable to biotin interference and to consider biotin supplements as potential sources of falsely increased or decreased test results, especially in cases where a lab result does not correlate with the clinical scenario.
FDA = U.S. Food & Drug Administration FT3 = free tri-iodothyronine FT4 = free thyroxine IFUs = instructions for use LH = luteinizing hormone PTH = parathyroid hormone SA/B = streptavidin/biotin TFT = thyroid function test TSH = thyroid-stimulating hormone.
The Kamlet and Taft solvent basicity parameter,
β
, and solvent polarity/polarizability parameter,
π
*, were analyzed in terms of properties of the solvent molecules derived from computational ...chemistry. The analysis of
β
, using a larger data set, confirms earlier conclusions that, for aprotic solvents, the basicity is determined by the partial charge on the most negative atom of the solvent molecule and by the energy of the highest energy molecular orbital associated with the donor site. For alcohols and nitrogen bases containing N–H moieties, the
β
values deviate systematically from those for the non-hydrogen bonding solvents. Analysis of the polarity/polarizability parameter,
π
*, shows that it depends directly on the dipole moment, and quadrupolar amplitude of the solvent and on the energy of the highest occupied molecular orbital, but decreases linearly with increasing solvent polarizability.
Regulatory standards mandate laboratories to perform studies to ensure accuracy and reliability of their test results. Method comparison and bias estimation are important components of these studies.
...We developed an interactive website for evaluating the relative performance of two analytical methods using R programming language tools. The website can be accessed at https://bahar.shinyapps.io/method_compare/.
The site has an easy-to-use interface that allows both copy-pasting and manual entry of data. It also allows selection of a regression model and creation of regression and difference plots. Available regression models include Ordinary Least Squares, Weighted-Ordinary Least Squares, Deming, Weighted-Deming, Passing-Bablok and Passing-Bablok for large datasets. The server processes the data and generates downloadable reports in PDF or HTML format.
Our website provides clinical laboratories a practical way to assess the relative performance of two analytical methods.
•We built a website (https://bahar.shinyapps.io/method_compare/) by R language for method comparison and bias estimation.•Available regression models: Ordinary Least Squares, Deming and Passing-Bablok•Available plots: scatter plot, coefficient plot and Bland-Altman plot•Generated reports can be download in PDF or HTML format.
To compare total 25-hydroxyvitamin D 25(OH) D results measured by 3 direct immunoassays, including the previous version of the DiaSorin Liaison2 assay and the current versions of the Siemens Centaur2 ...and the Abbott Architect assays, with results measured in serum extracts by liquid chromatography/tandem mass spectrometry (LC/MS) and radioimmunoassay (RIA).
Our study sample consisted of 163 consecutive clinical specimens submitted to our laboratory for 25(OH)D testing.
Regression and bias analyses of the data revealed that results measured by the 3 direct immunoassay methods had high degrees of random variability and bias relative to the results determined by LC/MS and RIA. The relative biases between results measured by the direct assays and the comparison methods exceeded a recommended criterion for the total allowable error of a 25(OH)D test in as many as 48% of our clinical specimens. Of the subjects in our study sample, 33, 37, 30, 45, and 71 were classified as vitamin D deficient based on results determined by LC/MS, RIA, Liaison2, Architect, and Centaur2, respectively.
Intermethod variability in 25(OH)D assays continues to limit our progress toward the establishment of reference values for 25(OH)D in health and our efforts to gain a better understanding of the role of vitamin D insufficiency as a risk factor for disease.
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