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PubMed1989

Plain film assessment of spinal stenosis: method comparison with lumbar CT.

Methods to determine the sagittal diameter of spinal canal on plain film radiographs have been previously proposed by Eisenstein in 1975 and Buehler in 1978. The purpose of this study was to determine the accuracy of these methods as compared to computed tomography (CT) and to compare the accuracy of each method. The AP diameter of the lumbar canal was evaluated at the L3 through L5 levels. Results indicate that the Buehler method was significantly (p less than or equal to 0.05) more accurate than Eisenstein method at the L3 level. At L4 and L5, there were no significant (p less than or equal to 0.01 p less than or equal to 0.20, respectively) differences between either of the plain film measurements and the mean value of the corresponding CT scans. The standard deviation (SD) showed less dispersity of the measurements with the Buehler method at all three levels examined.

Humans↗
PubMed1976

[Problems in the determination of color coordinates after the visual comparison method on the fundus of the eye (author's transl)].

A short description of color measurements on the fundus according to the method of visual comparison. The Zeiss Fundus camera equipped with an attachment served as the basic instrument. The method will not have clinical value until exact statistical values for the range of error of the different methods of measurement are available. A large number of color measurements in a short period of time on one patient's eye for gauging purposes is not possible. Therefore series of measurements are carried out on a phantom eye in order to determine the range of error in the color measurements under different conditions. Description of the results. The accuracy of the measurements which can be reached under ideal conditions with the phantom eye cannot always be reached with the patient's eye. Description of a model case for further series of measurements. The same errors of measurement appeared for reddish, yellow-orangeish, and almost white color areas. The fact that the adjustable lamp had to be replaced had practically no consequences. A series of measurements conducted according to the highest and lowest luminary densities allowed by the German Industrial Norms justifies the decision to limit the luminary density for the color measurements on the ocular fundus to 40 to 70 asb. Under the described conditions the error of measurement is smaller than is necessary clinically.

Colorimetry↗
PubMed1988

Method comparison of two test kits for the determination of elastase/alpha 1-proteinase-inhibitor complex.

A method comparison of the 4 h-elastase/alpha 1-proteinase-inhibitor test kit with a newly developed 2 h-version was performed. The within-run and between-days coefficients of variation as well as the recovery of the assigned values were satisfactory for both test kits. Good agreement was found between the 2 h- and 4 h-test kits using specimens from 160 patients. In conclusion, the 2 h-test kit can be used as an alternative for the determination of elastase/alpha 1-proteinase-inhibitor complex.

Adolescent↗
PubMed1975

Statistical evaluation of method-comparison data.

Comparison of two methods for determining a substance is a common procedure in clinical chemistry. Almost without exception, normal theory statistics are used with the tacit assumption that the data under test show gaussian distributions. Experience has led us to question this assumption for populations of differences between values obtained by two methods applied to common samples and for populations of paired values for each method as used in correlation analysis. Data are presented from our laboratory to illustrate these points, as well as an examination of data from relevant papers that appeared in this journal from 1968 through 1973. These examples indicate that incorrect interpretation of results because of insufficient attention to non-gaussian distribution is a real and present danger. We present a systematic approach to the statistical aspect of comparing methods that enables one to avoid this problem.

Blood Chemical Analysis↗
PubMed1990

[Detection of papilloma virus of the human uterine cervix by in situ hybridization method--comparison with immunohistochemistry].

The usual methods for pathological diagnosis of HPV infection of the uterine cervix include screening in cytodiagnosis and histodiagnosis and confirmation by immunohistochemistry (IHC) method. However, some institutes have recently begun to use in situ hybridization (ISH) method for definitive diagnosis using a DNA probe. We compared IHC with ISH with regards to the localization and rate of detection of HPV in lesions of the uterine cervix such as dysplasia and squamous cell carcinoma in the present study. The cases found positive by IHC showed brownish nuclei of the epithelium and those positive in ISH showed purple to purplish-black nuclei. The comparison of cases positive by both methods revealed that the number of cells positive by IHC was smaller than that by ISH, and the cells positive by IHC were localized in the superficial layer. HPV was detected by the IHC various lesions of the uterine cervix in 13 (12.3%) of 106 patients, while it was detected by the ISH in 39 (36.8%) of 106 patients. The results of both methods were in accordance in 66.0% (77 patients; positively in 8 and negatively in 62). The detection sensitivity of IHC is lower than that of ISH. IHC cannot be used to identify the type of HPV, and it is impossible to confirm the presence or absence of virus by this method in cases of malignant changes. ISH is therefore necessary for identification of HPV and investigation of a histopathological relationship between HPV type and malignant change.

Carcinoma, Squamous Cell↗
PubMed1992

Analytical method comparison based upon statistical power calculations.

Testing for the equivalence of results generated by different analytical methodology is a common practice in the pharmaceutical sciences. Methodology changes are implemented for both scientific and economic reasons during a scientific study. Thus, the need to demonstrate the appropriateness of considering data generated by distinct methods as part of a single information population arises. This paper describes a rapid and simple approach to the statistical design and interpretation of method comparison experiments. The approach presented is based upon a statistical power calculation technique, a knowledge of the variability associated with the methods to be compared and the criteria for equivalence (the limits within which differences become immeasurable or, for practical purposes, insignificant). Reference tables are included which show necessary sample sizes for comparison experiments for common combinations of these three variables.

Chemistry Techniques, Analytical↗
PubMed1988

A general regression procedure for method transformation. Application of linear regression procedures for method comparison studies in clinical chemistry, Part III.

The biometrical treatment of laboratory data may require the estimation of a regression line for the transformation of one set of measurements to another. The regression procedure introduced in part I (1) of our work does not always yield unbiased results in such situations, since its estimators are not scale invariant. In part III we present the parameter estimation of a general regression equation which is scale invariant and retains all properties of the method comparison procedure, in particular its robustness. Its application is demonstrated by several examples, and the results are compared with other robust biometrical procedures. The mathematical aspects are explained in the appendix.

Biometry↗
PubMed1979

Incorrect least-squares regression coefficients in method-comparison analysis.

The least-squares method is frequently used to calculate the slope and intercept of the best line through a set of data points. However, least-squares regression slopes and intercepts may be incorrect if the underlying assumptions of the least-squares model are not met. Two factors in particular that may result in incorrect least-squares regression coefficients are: (a) imprecision in the measurement of the independent (x-axis) variable and (b) inclusion of outliers in the data analysis. We compared the methods of Deming, Mandel, and Bartlett in estimating the known slope of a regression line when the independent variable is measured with imprecision, and found the method of Deming to be the most useful. Significant error in the least-squares slope estimation occurs when the ratio of the standard deviation of measurement of a single x value to the standard deviation of the x-data set exceeds 0.2. Errors in the least-squares coefficients attributable to outliers can be avoided by eliminating data points whose vertical distance from the regression line exceed four times the standard error the estimate.

Blood Chemical Analysis↗
PubMed1986

The unlabeled antibody method: comparison of peroxidase-antiperoxidase with avidin-biotin complex by a new method of quantification.

Upon plotting of areas against optical densities in immunocytochemically stained tissue sections, hyperbolic curves were obtained which could be reduced to two straight lines, one representing variations in stained structures, and the other variations in background. The slopes of the stained structure lines reflected staining intensity independently of total area of stained structure in a section. The ratio of slopes of the stained structure and background lines reflected immunocytochemical sensitivity. A comparison of the peroxidase-antiperoxidase (PAP) method with the avidin-biotin complex (ABC) method showed that at usual antibody dilutions the PAP method was much more sensitive than the ABC method, while at impractically high antibody dilutions it was moderately more sensitive. Once sufficient dilutions of antibodies were reached, staining intensities dropped sharply with the PAP method. On the other hand, the dilution curves were flat with the ABC method. The ABC method consequently appeared unsuitable for estimating variations in concentration of antigen or for distinguishing high or low concentrations of antigen. The ABC method provided a stain for myelin even in the absence of any antibodies.

Animals↗
PubMed1975

The evaluation of left ventricular function in man. A comparison of methods.

Comparisons of the sensitivities of parameters for assessing left ventricular performance in man were made in 38 patients. The parameters compared were the ejection fraction, ventriculographic contraction patterns, the left ventricular end-diastolic pressure, and the contractile indices including the contractile element velocity at 10 mm Hg (Vce 10) and maximal contractile element velocity (Vmax). The contractile indices were obtained by catheter tip manometry, utilizing developed pressure (DP) to calculate the velocity of contractile element shortening (Vce) from the formula: dp/dt divided by 32 DP. Vce 10 was measured directly and Vmax was derived by linear manual extrapolation of the pressure-velocity plot to 0 mm Hg. Vmax values derived from linear manual extrapolation were compared with values obtained by computer least squares fitting of the Vce and developed pressure data points to single and double exponential equations. The Vce and developed pressure data points fit the single exponential equation better than the double exponential equation but the use of either equation resulted in slightly higher values for Vmax than obtained with linear manual extrapolation. The effect of heart rate on myocardial contractility was eliminated by making comparisons at both a basal and atrial paced rate of 100. Utilizing all methods, 24 patients were identified to have ventricular dysfunction. The contractile indices were significantly less sensitive than any other parameter (P smaller than 0.05) and identified seven patients while the left ventricular end-diastolic pressure, ejection fraction, and presence of asynergy identified 15, 15, and 12 patients, respectively. The use of a common atrial paced rate of 100 did not increase the sensitivity of the contractile indices. Since there was only partial overlapping between parameters in the identification of left ventricular dysfunction, the combination of different parameters was more sensitive than any single parameter alone. It is concluded that several methods are required to identify all patients with left ventricular dysfunction and that the contractile indices are the least sensitive indicator of left ventricular dysfunction.

Blood Pressure Determination↗
PubMed1992

Lactate measured in diluted and undiluted whole blood and plasma: comparison of methods and effect of hematocrit.

We evaluated a new analyzer that measures lactate in undiluted whole blood by direct (or undiluted) amperometry [Nova Stat Profile 7 Analyzer (SP7); Nova Biomedical, Waltham, MA] by comparing it with two other analyzers, one for measuring lactate in whole blood by indirect (or diluted) amperometry [Model 2300; Yellow Springs Instrument Co. (YSI), Yellow Springs, OH] and another for measuring lactate in plasma by enzymatic colorimetry (aca; Du Pont Co., Wilmington, DE). All between-method comparisons of the three methods showed that the results for plasma were comparable (Sy/x = 0.24-0.33 mmol/L). Within-method comparisons by the YSI differed substantially between plasma and whole blood (Sy/x = 0.48 mmol/L), but within-method comparisons by the SP7 produced better agreement between plasma and whole blood (Sy/x = 0.18 mmol/L). The difference between whole blood and plasma by YSI is related to hematocrit, with the greatest differences noted for samples with the highest hematocrit. Serum lactate measured by SP7 had between-day imprecision (CV) ranging from 12% at 0.5 mmol/L to 4.2% at 3.7 mmol/L, showed a linear standard curve to at least 11.5 mmol/L, and was independent of hematocrit. There was a mean bias of approximately 0.4 mmol/L for results in the reference range for both plasma and whole blood by SP7 compared with plasma results by either aca or YSI.

Autoanalysis↗
PubMed1988

Antibiotic susceptibility testing of anaerobic organisms using the agar dilution method: comparison of three techniques.

Three currently used anaerobic susceptibility testing methods were compared: (1) the technique used at the Wadsworth Microbial Diseases Research Laboratory, (2) the technique listed as the reference standard by the National Committee on Clinical Laboratory Standards, and (3) the technique used at the Tufts New England Medical Center. Four-hundred-seventy anaerobic microorganisms, isolated from clinical specimens, were tested against cefoxitin, cefotetan, ceftizoxime, cefotaxime, ceftazidime, imipenem, and clindamycin. Significant differences were noted in mean inhibitory concentrations and percent susceptible at breakpoint among the three techniques used and varied with the antimicrobial agent and species tested.

Bacteria, Anaerobic↗
PubMed1979

A methods comparison: clonazepam by gas chromatography-electron capture and gas chromatography-mass spectroscopy.

Clonazepam is an antiepileptic drug for which a number of analytical procedures have been presented, none of which have been subjected to comparison studies. We present two gas chromatographic (GC) methods involving distinct forms of detection for determining plasma or serum drug levels. Both methods involve simple extractions, common GC conditions, and routine data reduction. Both employ nitrazepam as an internal standard, require 1 ml of sample, and have a detection limit of 1 ng/ml. The two methods, GC-electron capture and GC-mass spectroscopy, are precise and accurate. Correlation of the two methods paired sample analysis gave a regression equation of y = 0.988x - 0.14 (n = 30, r = 0.971, p less than 0.001). We suggest that either method is a reasonable alternative for the clinical laboratory with the proper instrumentation.

Benzodiazepinones↗
PubMed1988

Finite element method comparison of murine mandibular form differences.

The differences of adult female murine mandibular form between two inbred strains of mice (BALB/cBy and C57BL/6By) were analyzed by use of the finite element method (FEM). In the present instance, this method overcomes the conceptual and methodologic constraints of both craniometry and roentgenographic cephalometry by providing two-dimensional, reference-frame-invariant, independent comparisons of the size, shape, and location of the point continua enclosed within the boundaries for each local, finite element into which the mandible was discretized. At the present scale of observation, it is suggested that the FEM kinematic descriptions of form comparisons can be correlated with dynamic interpretations offered by the functional matrix hypothesis, i.e., that certain discrete, causal relationships exist between the continuum form of single elements and the form, or function, of anatomic structures associated with these elements. It is concluded that, in addition to its previously demonstrated use in the analysis of growth, the finite element method seems well suited for comparisons of form.

Animals↗
PubMed1990

Prognostic value of ovarian carcinoma grading methods--a method comparison study.

The prognostic value of subjective histological and morphometric grading was studied in 75 primary ovarian carcinomas. Histological grading methods recommended by Czernobilsky and by Russell and the morphometric method of Baak and co-workers were compared in a two-observer system. The 5-year survival could be correctly predicted in about two-thirds of the patients with all three methods. When mitotic counting (volume corrected mitotic index, M/V-index) was compared with the above grading methods by using a receiver operating characteristic curve) the M/V-index was generally superior in its prognostic power regardless of the sensitivity/specificity level chosen. The morphometric grading method and the grading method based on the M/V index were also shown to be readily reproducible.

Carcinoma↗