Range Of Clinical Interest Research Articles

Microchip electrophoretic immunoassay for serum cortisol.

An immunoassay performed using a microchip electrophoretic system is described. Separation and quantitation of free and bound labeled antigen in a competitive assay are carried out in channels micromachined into fused silica substrates. Such microchips are attractive because of their small size, ruggedness, and amenability to automated handling. The assay achieves the determination of cortisol in blood serum over the range of clinical interest (1-60 micrograms/dL) without the need for extraction or other sample preparation steps. The separation is performed in less than 30 s. Very high throughput is possible by operating the assay in multiple channels in parallel. These characteristics make microchip electrophoretic systems a promising technology for the rapid analysis of clinical samples.

Using Linearity Assessment in the Laboratory

Assessment of linearity is an important part of the verification that an instrument or test method is in working order. Analyte levels should he chosen throughout the range of clinical interest, and the material should he as close as possible to that used clinically. After data are plotted, visual inspection often is all that is needed. Should mathematical analysis be required, the laboratorian will check the data for outliers and equality of variance before assessing how well data fit, that is, how closely the data points approximate a straight line (also known as goodness of fit,). Several means of assessing goodness of fit are described. This is the third article in a four-part continuing education update series on statistics. Other articles discuss the use of control charts, the use of linear regression to compare methods, and the creation and verification of reference intervals.

Screening of matrices and fibers for reinforced thermoplastics intended for dental applications

Plastics reinforced with continuous fibers (FRC) are being developed for dental applications, such as prosthodontic frameworks and orthodontic retainers. Flexure properties, stress relaxation and hydrolytic stability of FRC based on six thermoplastic matrices, three types of fibers, and three fiber volume fractions were evaluated. Samples with clinically relevant dimensions were tested. Polycarbonate was the preferred matrix material. Polycarbonate reinforced with 42 volume percent glass fibers exhibited the highest combination of flexure modulus (17.9 +/- 2.6 GPa), flexure strength (426 +/- 40 MPa), reinforcing efficiency (0.79), and resistance to stress relaxation. No statistically significant difference was observed between E and S2 glass reinforced composites under the experimental conditions used. Kevlar reinforced materials exhibited a low flexure modulus and strength. The apparent flexure moduli of all composites decreased with span length in the range of clinical interest. Generally, the prevalent mode of failure for all FRC investigated was brittle failure under flexure loading. Relatively large sample-to-sample variation in both composition and properties indicated that improved fabrication methods will be needed in future studies. The combination of good flexure properties, formability, and translucency suggests that novel appliance designs for dentistry are feasible with FRC, but further studies of its properties and particularly the effects of fiber/matrix interfacial quality are needed.

Study on analytical Magnetic Separation system of Bacterial Species

Ferrography, a magnetic separation method first developed for industrial sample analyses, has been modefied for application to biological analyses. Separation and quantitation of bacteria in the presence of paramagnetic trivalent metalion, erbium, using modified Ferrography, termed‘ Bactography’, was evaluated to quantitate bacterial concentrations in solutions in the clinical range of interest. Escherichia coli(E.coli)was used as a model bacterial system to optimize the separation protocol. Separation results were evaluated quantitatively by both light scattering and direct cell counting. The modified separation protocol with a newly designed sample processor and magnetic assembly provided higher cell deposition than the previous protocol. The modified protocol and direct cell counting allowed reliable detection and enumeration of concentrations of bacterial suspension of E.coli at105CFU/ml which is of significance in clinical diagnostic applications. Bactography offers promise as a method for quantitation of bacterial solutions.

Vitamin B 12 (cobalamin) and folate blood levels in geriatric reference group as measured by two kits

For serum vitamin B12 levels there was little apparent difference between a geriatric healthy reference group and a hospitalized group for the total population studied; however, the hospitalized males did have an increased prevalence of values less than normal range. The frequency distribution for both sexes of the geriatric reference group gave lower range limits than manufacturer's normal range. (68-632 vs 133-708 pmol/L for Becton Dickinson, and 125-609 vs 179-930 pmol/L for Bio-Rad, using 95% non-parametric limits). For folate there was an increased incidence in values of less than normal in the hospitalized group versus the geriatric reference group, but there was no difference in the ranges calculated for the latter compared to either manufacturer's normal range derived from a younger population. Comparison of results by two manufacturers' kit methods confirmed Bio-Rad's claim to increased low-end sensitivity of standard curve in range of clinical interest.

Cholesterol in high-density lipoprotein: use of Mg2+/dextran sulfate in its enzymic measurement.

We describe a method for measuring high-density lipoprotein cholesterol. MgCl2 and dextran sulfate are used to precipitate all low-density and very-low-density lipoproteins. The supernate contains only high-density lipoproteins, the cholesterol concentration of which is estimated by an enzymic method, with a discrete analyzer (Abbott Bichromatic Analyzer). Concentration and instrument response are linearly related to 50 mg/liter. The precision of the method is excellent in the range of clinical interest (100 to 1000 mg of cholesterol per liter). The precision and efficiency of the precipitation are shown at various concentrations of high-density lipoprotein cholesterol. The method was compared to that of two laboratories in the Cooperative Lipoprotein Phenotyping Study group by testing a number of split samples, and agreement was good.

Response optimization of drug dosage: Antiarrhythmie studies with tocainide

The benefits of using antiarrhythmic response to optimize dosage regimens of antiarrhythmic drugs in individual patients have been examined. Graded antiarrhythmic response and simultaneously measured plasma drug concentrations have been obtained in 15 patients receiving multiple oral doses of a new antiarrhythmic, tocainide. Plasma drug concentration-antiarrhythmic response data from each of 11 subjects responding to the drug have been fitted by a generalized concentration effect function which is valid over the entire range of response. With the use of experimentally determined pharmacokinetic parameters to define the dose-plasma concentration relationship and plasma drug concentration-response parameters estimated for individual patients, simulations were carried out to show the effect of various dosage regimens on antiarrhythmic response in individual patients. Such simulations provide a means of assessing antiarrhythmic effect in the range of clinical interest (80% to 100% of maximum effect), where the antiarrhythmic effect is a nonlinear function of dose, plasma drug concentration, or their logarithms. The simulations also demonstrate that for identical daily doses and dosing intervals patients show marked variability in antiarrhythmic response.

Expression of random analytical error as a precentage of the range of clinical interest.

I propose that random method error be expressed as a percentage of the range(s) of clinical interest (upper range limit minus lower range limit), in addition to its usual forms of presentation. The interpretation of this percent random error is simple because a given percentage error implies the same reliability, regardless of test or range of clinical interest. Two different upper limits for percent random analytical error are suggested, based on the medical application of the test and the statistical properties of various amounts of error. When the purpose of the test is to distinguish an upper medically defined limit from a lower medically defined limit, a maximum random error equivalent to 60% of the difference between the limits is proposed. If the purpose of the test is to monitor values in the neighborhood of a normal range or therapeutic range, an upper limit for random error equal to 20% of the difference between the limits of the range is suggested.