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Results for “Repeatability and Reproducibility”

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PubMed1992

[The permeability of the barrier of the gastrointestinal tract for the macromolecules of polyethylene glycol-4000: an assessment of the mechanism and its reproducibility].

Polyethylene glycol (PEG)-4000 is proposed as a tracer of intestinal macromolecular permeability. The reproducibility of permeability testing with PEG-4000 and the mechanism of its penetration through intestinal mucosa were studied in adult rats. Permeability measurement for PEG-4000 was reproducible when repeated twice for 2 days. This makes it possible to repeat PEG-4000 permeability testing before and after any experimental impact on the intestine. I.p. administration of colchicine to rats (125 micrograms/100 g b. w.) significantly inhibited intestinal absorption of PEG-4000 fed to the animals 3 hours later. Hence, PEG-4000 penetration through the intestinal mucosa is mediated by the system of enterocyte cytoplasmic microtubules. Mucosal permeability for PEG-4000 may be consequently considered as a valuable model of permeability for protein macromolecules.

Animals↗

PubMed2004

A high-performance liquid chromatographic method for determination of praziquantel in plasma.

A simple, sensitive, selective and reproducible method based on a reversed-phase chromatography was developed for the determination of praziquantel in human plasma. Praziquantel was separated from the internal standard (diazepam) on a Luna C18 column (250 mm x 4.6mm, 5 microm particle size), with retention times of 4.8 and 6.2 min, respectively. Ultraviolet detection was set at 21 7 nm. The mobile phase consisted of acetonitrile and distilled water (70:30, v/v), running through the column at a flow rate of 1.0 ml/min. The chromatographic analysis was operated at 25 degrees C. Sample preparation (1 ml plasma) was done by a single step liquid-liquid extraction with the mixture of methyl-tert-butylether and dichloromethane at the ratio of 2:1 (v/v). Calibration curves in plasma at the concentrations 0, 50, 100, 200, 400, 800 and 1600 ng/ml were all linear with correlation coefficients better than 0.999. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) was below 15% (relative standard deviation: R.S.D.). Good accuracy was observed for both the intra-day or inter-day assays, as indicated by the minimal deviation of mean values found with measured samples from that of the theoretical values (below +/-15%). Limit of quantification (LOQ) was accepted as 5 ng using 1 ml samples. The mean recovery for praziquantel and the internal standard were greater than 90% for both praziquantel and internal standard. The method was free from interference from the commonly used antibiotic and antiparasitic drugs. The method appears to be robust and has been applied to a pharmacokinetic study of praziquantel in three healthy Thai volunteers following a single oral dose of 40 mg/kg body weight praziquantel.

Adult↗

PubMed1999

Evaluation of a standardised procedure to assess the shape of pellets using image analysis.

The influence of threshold definition, number of pellets counted, image magnification and lightning technique on the assessment of pellet shape has been investigated using three batches of pellets and an image analysis system. The pellet parameters measured were 'aspect ratio', 'circularity', 'projection sphericity', 'e(R)' and 'Feret diameter.' The methodical error, reproducibility and repeatability of the results were chosen as statistical test parameters. The position of the light source is crucial in providing an accurate particle size value. Top light was identified as the illumination technique that gave a mean pellet size similar to the true pellet size. The use of a light table produced significantly larger pellet size values. A minimum pixel resolution appears necessary for an accurate shape parameter definition. One pixel should not cover more than 30 microm for pellets of an average particle size of 1.2 mm. Shape descriptors, which are based on a multiple combination of area and perimeter data such as the circularity, are greatly dependent on the number of pellets counted. Shape factors, which do not (aspect ratio) or only as a single value do involve an area or perimeter measurement (e(R), projection sphericity) are, however, nearly independent of the number of pellets counted, as long as the magnification is sufficiently large and the pellets are randomly drawn from the batch. For nearly spherical particles, the methodical error is below 1%, but for elongated particles this error can reach 5%. The repeatability is also very good for nearly spherical particles (<2%), but increases to very large values if the particles are clearly elongated. The limiting values for the various shape factors should be reconsidered. An upper value for the aspect ratio of 1.1 and a lower value of 0.6 for e(R) are recommended. The circularity should not be used as the shape factor to characterise spheres, because errors in image recognition can affect strongly the applicability of this shape factor. The projection sphericity has only a limited sensitivity to variations in particle shape.

Chemistry, Pharmaceutical↗

PubMed2005

Diurnal variation of blood pressure; reproducibility and association with left ventricular hypertrophy in hemodialysis patients.

OBJECTIVE: The objective of this paper is to describe the pattern of diurnal blood pressure (BP) change in hemodialysis patients, determine the association of the non-dipping pattern of diurnal BP with left ventricular mass index (LVMI), and to determine if the nocturnal profile of BP is reproducible when repeated over time. METHODS: In a cross-sectional study, ambulatory blood pressure monitoring (ABPM) was performed over a midweek 44-h period and echocardiography was performed on the interdialytic day. Patients with a night/day systolic and diastolic BP ratio on both days >0.9 were defined as non-dippers. Ambulatory blood pressure monitoring was repeated at 6 and 12 months follow-up. RESULTS: Of the 59 patients, 88% were African-American, and 48% were non-dippers. Mean LVMI was significantly higher in the non-dipper (68.3+/-25 g/height) compared to the dipper patients (55.6+/-16, P<0.05). Mean nocturnal systolic BP (r=0.35) and the night/day systolic BP ratio (r=0.39) had a higher correlation with M-mode LVMI than pre-dialysis (r=0.32). After adjustment for 44-h mean SBP, night/day systolic BP ratio remained independently associated with LVMI (beta coefficient 147.62, P=0.004). Of 12 patients who had a non-dipper profile at baseline, 11 (92%) demonstrated the same profile after 6 months and 1 year of follow-up. CONCLUSION: Many hemodialysis patients demonstrate a non-dipper profile; the degree of decline in nocturnal BP is independently associated with LVMI even after adjustment for mean BP. Patients who are identified as non-dippers consistently reproduce the same profile over time.

Adult↗

PubMed1996

Sensitivity, reproducibility, and accuracy in short tandem repeat genotyping using capillary array electrophoresis.

The Human Genome Initiative has increased significantly the rate at which disease-causing genes are being mapped and sequenced. New cost-effective methods to locate the genes and to characterize disease-causing mutations require robust, reproducible, and accurate protocols for measuring DNA fragment lengths. Capillary array electrophoresis (CAE) offers rapid, high-resolution separations, high throughput, and sensitive detection. To assess the utility of CAE for the accumulation of genetic information, we tested both sizing accuracy and reproducibility using 48-capillary prototype systems. Two multiplex PCR allelic ladder standards and several CA-repeat markers were analyzed in > 100 runs. Reproducibility in typing > 8000 genotypes reveals a standard deviation of less than 0.2 bp on these systems under optimized conditions. However, sequence-dependent migration anomalies were observed at most simple sequence loci even when analyzed under denaturing conditions, resulting in a systematic bias in estimated fragment sizes. We show here that, by normalizing results to known typing controls, one can obtain locus-averaged accuracies of < 0.06 bp and normalized results within 1 bp of actual. We detect as little as a 1:30,000 dilution of a DNA quantitation standard stained with highly sensitive intercalating dyes, indicating an 80-zeptomole sensitivity limit. However, to obtain reproducible electrokinetic injection, approximately 200 attomoles of fluorescein-labeled DNA is required. These sensitivity limits, sizing precision, and accuracy, together with the 1-hr run times for 48-96 samples, indicate that CAE is a viable method for high-throughput genetic analysis of simple sequence repeat polymorphisms.

Capillary Action↗

PubMed1982

Relation between regional myocardial uptake of rubidium-82 and perfusion: absolute reduction of cation uptake in ischemia.

Experiments were undertaken using rubidium-82 and position tomography to examine the relation between myocardial perfusion and cation uptake during acute ischemia. Rubidium-82 was repeatedly eluted from a strontium-82-rubidium-82 generator. In six dogs emission tomograms were used to measure the delivered arterial and myocardial concentrations at rest and after coronary stenosis, stress and ischemia. There was a poor overall relation between regional myocardial uptake and flow measured by microspheres and a large individual variability. Extraction of rubidium-82 was inversely related to flow. Significant regional reduction of cation uptake was detected in the tomograms when regional flow decreased by more than 35 percent. This reduction was significantly greater when ischemia was present. A small but significantly greater when ischemia was present. A small but significant decrease (33.0 +/- 9.1 percent, mean +/- standard deviation) in the myocardial uptake of rubidium-82 was detected only when flow was increased by more than 120 percent in relation to a control area after administration of dypiridamole. The technique using rubidum-82 and tomography was applied in five volunteers and five patients with angina pectoris and coronary artery disease. Myocardial tomograms recorded at rest and after exercise in the volunteers showed homogeneous uptake of cation in reproducible and repeatable scans. In contrast, the patients with coronary artery disease showed an absolute mean decrease of 36 +/- 14 percent in regional myocardial uptake of rubidium-82 after exercise. These abnormalities persisted in serial tomograms for more than 20 minutes after the symptoms and electrocardiographic signs of ischemia.

Adult↗

PubMed1992

Syntactic structure analysis in invasive breast cancer: analysis of reproducibility, biologic background, and prognostic value.

The reproducibility, biologic background, and prognostic value of syntactic structure analysis were studied in a group of 94 patients with invasive primary breast cancer. Using an interactive digitizing video overlay system, the centers of malignant breast cancer nuclei were marked in the five (subjectively) most cellular fields of vision for each case at a final magnification of X1,200, and the corresponding minimum spanning tree was composed for each field. From each minimum spanning tree, 10 syntactic structure features were derived; subsequently, the mean, standard deviation, minimum, and maximum values of the five fields analyzed were calculated for further statistical analysis. Forty statistics thus were available for each case. The reproducibility of repeatedly measuring the same field (independent of nuclearity) and the same patient twice by the same or different observers was good for most of the syntactic structure features. When comparing the statistics of the syntactic structure features with other established prognosticators, correlations were found with (in this order) standard deviation and mean nuclear area (expressing nuclear differentiation), volume percentage epithelium (expressing architectural differentiation), and mitotic activity index. In univariate survival analysis several syntactic structure statistics yielded prognostic significance, the best being the maximum of the number of nuclei with two neighbors (P = .002; Mantel-Cox test, 12.4). Multivariate analysis revealed that syntactic structure features did not provide additional prognostic values with regard to each other. However, they did show additional prognostic values with regard to the multivariate prognostic index (currently one of the best prognosticators in breast cancer), which combines the mitotic activity index, lymph node status, and tumor size. Measurement of syntactic structure features could therefore contribute to an improved prediction of prognosis of breast cancer patients. In conclusion, syntactic structure analysis is a simple, fast, and highly reproducible technique that shows prognostic value in invasive breast cancer and also has important prognostic value with regard to the well-established and prognostically strong morphometric features. It seems to be a promising new method of analyzing tissue architecture in breast cancer and perhaps in many other tumors.

Breast Neoplasms↗

PubMed1998

Reproducibility of volumetric measurements of normal maculae with the Heidelberg retina tomograph.

AIMS: The Heidelberg retina tomograph (HRT) is a scanning laser ophthalmoscope with confocal optics. The reproducibility of the optic nerve head topography is accurate and reliable. The authors describe a new technique for the assessment of macular thickening by volumetric quantification and present the results of its reproducibility in normal subjects. METHODS: Topographic images of the macula, centred on the fovea were obtained in one eye of 44 normal subjects. The volumes above the reference plane bound by a 1 mm, 2 mm, and 3 mm diameter circle were measured. The reference plane was adjusted to the lowest point of the height variation of the contour line at each examination. The reproducibility of repeated measurements within a 2 mm diameter circle was assessed in 20 eyes selected at random. Three HRT scans of each eye were obtained. The measurements of volume above reference plane of each scan were repeated three times on three separate days. RESULTS: The intrascan coefficients of variability measured 7.12-9.57%. The 95% confidence interval for the geometric mean ratio of single volume measurements was 0.92 to 1.24 for scans 1 and 2, 0.89 to 1.17 for scans 1 and 3, and 0.81 to 1.12 for scans 2 and 3. When the mean of three measurements of one scan were compared with the mean of three measurements of a second scan, the 95% confidence interval for their geometric mean ratio was 0.89 to 1.20 for scans 1 and 2, 0.89 to 1.16 for scans 1 and 3, and 0.84 to 1.13 for scans 2 and 3. The average standard deviation (SD) for one measurement per scan was 0.02 mm3, and 0.019 mm3 for two or three measurements per scan. Linear regression demonstrated a significant increase in SD as volumetric measurements increased (p = 0.003). Age did not significantly affect the SD of volumetric measurements (p = 0.797). The authors found no significant differences in volumetric measurements across all ages for all three circles (p = 0.314, p = 0.471, p = 0.267). CONCLUSION: Good reproducibility for volumetric measurements at the macula was found with the HRT using the above technique in normal subjects. This method may be extremely useful for the identification and quantification of diabetic macular oedema and for monitoring the effects of argon laser photocoagulation.

Adult↗

PubMed2002

Calibrated real-time PCR assay for quantitation of human herpesvirus 8 DNA in biological fluids.

Accurate laboratory tests for the diagnosis of active human herpesvirus 8 (HHV-8) infection are becoming essential to study the pathogenesis of HHV-8-associated tumors and for the clinical management of HHV-8-infected individuals. We have developed a highly sensitive, calibrated quantitative real-time PCR assay for the measurement of cell-free HHV-8 DNA in body fluids, based on the addition of a synthetic DNA calibrator prior to DNA extraction. The calibrator controls each sample for the presence of PCR inhibitors, determines a cutoff value of sensitivity for negative samples, and normalizes positive samples for the efficiency of DNA recovery. The assay shows a wide dynamic range of detection (between 1 and 10(6) viral genome equivalents/reaction) and a high degree of accuracy even in the presence of high amounts (up to 1 micro g) of human genomic DNA. Moreover, the assay has a very high sensitivity (lower detection limit, 10 genome equivalents/ml) and a high degree of reproducibility and repeatability with a coefficient of variation (CV) of <15 and 23%, respectively. Furthermore, the use of the calibrator improves the accuracy of quantitation and decreases the intersample variability (CV, 9 and 6%, respectively). The sensitivity and specificity of the assay were tested with a series of clinical specimens obtained from patients affected by various HHV-8-related diseases, as well as from a wide number of controls. In conclusion, our calibrated real-time PCR assay provides a reliable high-throughput method for quantitation of HHV-8 DNA in clinical and laboratory specimens.

AIDS-Related Opportunistic Infections↗

PubMed1993

A novel computer-driven, servo-controlled fluid replacement technique and its application to renal function studies in conscious rats.

1. A new rat model has been developed allowing body fluid status to be accurately controlled and maintained throughout experimentation by computer-driven, servo-controlled replacement of spontaneous urinary fluid losses. 2. Experiments in vitro were performed to test the accuracy of the servo system, and experiments in vivo were carried out to re-assess basic renal function in servo-controlled vasopressin-replete Long Evans and vasopressin-deficient Brattleboro rats. The model was further evaluated in water-diuretic Wistar rats with or without administration of a vasopressin V2-receptor agonist, 1-desamino-8-D-arginine vasopressin. 3. The data gained from the present study indicate the suitability of the servo-controlled replacement system for conscious renal function studies in three different rat strains. Haemodynamic and renal function variables measured were demonstrated to be stable throughout a 5 h experimental procedure and reproducible between repeated experimental occasions over a 14 day post-operative period. 4. Using the servo-control technique, the expected action of 1-desamino-8-D-arginine vasopressin on renal water handling was demonstrated, but the natriuretic effect reported by some workers was not evident. 5. Since the servo-controlled fluid replacement technique maintains many of the inherent differences between vasopressin-replete Long Evans and vasopressin-deficient Brattleboro rats and eliminates the changes in body fluid volume during transition from a diuretic to an antidiuretic state, the model confers an advantage over previously employed constant infusion protocols.

Animals↗

PubMed2000

Capillary isotachophoretic analysis of serum lipoproteins using a carrier ampholyte as spacer ion.

We have developed a novel analytical method for serum lipoproteins using a commercially available capillary electrophoresis apparatus, BioFocus 3000 (Bio-Rad Laboratories Co Ltd, USA). The analytical principle is isotachophoresis (ITP), using a carrier ampholyte, BioLyte 7/9, as a spacer ion. The method allows a much higher resolution of lipoproteins than of amino acid mixtures. Serum lipoproteins are normally separated into 13-15 peaks, including some shoulder peaks. The reproducibility of repeated analysis within a day was relatively good with the coefficient of variation within the range 0.9-1.1%. VLDL, LDL and HDL prepared by discontinuous density ultracentrifugation could be further separated by capillary ITP. This high-resolving ability of our method enabled detection of small amounts of abnormal lipoprotein species. For example, small dense LDL, which is thought to be an atherogenic lipoprotein, could be detected within the LDL group peak. Moreover, an abnormal HDL, apolipoprotein E-rich HDL, was also detected by a single analysis. These findings suggest that our capillary ITP method is a useful means for detailed analysis of lipoproteins and thus for clinical diagnosis of hyperlipoproteinaemic subjects.

Ampholyte Mixtures↗

PubMed2003

High-performance liquid chromatographic method for determination of 2-difluoromethyl-DL-ornithine in plasma and cerebrospinal fluid.

A simple, sensitive, selective and reproducible method based on anion-exchange liquid chromatography with post-column derivatisation was developed for the determination of eflornithine (2-difluoromethyl-DL-ornithine; DFMO) in human plasma and cerebrospinal fluid. The 1-alkylthio-2-alkyl-isoindoles fluorescent derivative of the drug was separated from the internal standard (MDL 77246A) on an anion-exchange column (PRP-X300, 250x2.1 mm, 7-microm particle size: Hamilton, USA), with retention times of 6.9 and 10.7 min, respectively. Fluorescence detection was set at 430/340 nm (emission/excitation wavelength). The elution solvent consisted of a solution of 30 mM potassium dihydrogen phosphate buffer (pH 2.2) and acetonitrile (50:50, v/v), running through the column at a flow-rate of 0.3 ml/min. The chromatographic analysis was operated at 37 degrees C. Sample preparation for either plasma or CSF (100 microl) was done by single-step protein precipitation with 20% trichloroacetic acid after incubation at 4 degrees C for 1 h. Calibration curves for plasma (100, 200, 400, 600, 800 and 1200 nmol/100 microl, and 10, 20, 40, 80, 120 and 160 nmol/100 microl for the high and low concentration range curves, respectively) and CSF (1, 2, 4, 8, 16, 32 nmol/100 microl) were all linear with correlation coefficients better than 0.999. The precision of the method based on within-day repeatability and reproducibility (day-to-day variation) at high concentration range was below 15%, whereas at low concentration range was below 20% (% coefficient of variations: %C.V.) Good accuracy was observed for both the intra-day or inter-day assays, as indicated by the minimal deviation of mean values found with measured samples from that of the theoretical values (below +/-15 and +/-20% at high and low concentration range, respectively. The limit of quantification was accepted as 0.1 nmol using 100-microl samples. The mean recovery for DFMO and the internal standard were greater than 95%. The method was free from interference from commonly used drugs including antimalarials and antihelminthics. The method appears to be robust and has been applied to a pharmacokinetic study of DFMO in patients with African trypanosomiasis following oral doses of Ornidyl (Aventis Pharma, Frankfurt, Germany) at 500 mg/kg body weight (125 mg q.i.d.) for 14 days.

Calibration↗

PubMed1996

Determination of natural killer cell function by flow cytometry.

Natural killer cells (NK cells) are a subset of peripheral blood lymphocytes that mediate non-major histocompatibility complex-restricted cytotoxicity of foreign target cells. The "gold standard" assay for NK cell activity has been the chromium release assay. This method is not easily performed in the clinical laboratory because of difficulties with disposal of radioactive and hazardous materials, short reagent half-lives, expense, and difficulties with assay standardization. We describe a flow cytometric assay for the clinical measurement of NK cell activity. This study compared the chromium release assay and the flow cytometric assay by using clinically relevant specimens. There were no significant differences between the two assays in the measurement of lytic activity for 17 peripheral blood specimens or in reproducibility in repeated samplings of healthy individuals. We also established a normal range of values for NK activity in healthy adults and identified a small cluster of individuals who have exceptionally high or low levels of NK activity. The flow cytometric assay was validated by testing specimens from subjects expected to have abnormally low levels of NK activity (pregnant women) and specimens from healthy individuals in whom the activity of NK cells was enhanced by exposure to interleukin-2 or alpha interferon. Treatment with these agents was associated with a significant increase in NK activity. These results confirm and extend those of others, showing that the flow cytometric assay is a viable alternative to the chromium release assay for measuring NK cell activity.

Adult↗

PubMed2006

Measurement of serotonin 5-HT1A receptor binding using positron emission tomography and [carbonyl-(11)C]WAY-100635-considerations on the validity of cerebellum as a reference region.

[Carbonyl-(11)C]WAY-100635 has been used extensively in positron emission tomography (PET) imaging of serotonin 1A receptors (5-HT1A) in vivo in the human brain. Specific binding to receptors is usually estimated using compartmental modeling with arterial plasma input function. The use of reference tissue input (cerebellum) enables quantification without the need of arterial blood sampling, but the accuracy of this method is highly dependent on the validity of the reference region in terms of both specific and nonspecific binding. In this paper, we report exceptionally high uptake of [carbonyl-(11)C]WAY-100635 in the gray matter of cerebellum in one healthy male subject, which was reproducible in repeated PET scanning and most likely represents specific binding to 5-HT1A receptors in cerebellar gray matter. Serotonin 1A receptors are transiently expressed in the human cerebellum during early childhood and usually level off until adolescence but may persist in some individuals. As a methodological implication, the results of this study with regard to test-retest characteristics of [carbonyl-(11)C]WAY-100635 measurements in healthy volunteers using both arterial plasma and reference tissue input functions support the use of cerebellar white matter as reference region, to avoid the potential bias originating from binding of [carbonyl-(11)C]WAY-100635 to 5-HT1A receptors in cerebellar gray matter.

Adult↗

PubMed2006

Evaluation of a commercial in-house test kit for the semi-quantitative assessment of microalbuminuria in cats.

Proteinuria was assessed in 100 randomly selected sick cats and 22 healthy cats by means of the urine protein:creatinine ratio, a traditional urine "dipstick" and a commercial ELISA-based dipstick designed to detect microalbuminuria (MA) semi-quantitatively. In addition the repeatability and reproducibility of the MA test was assessed by comparing results of five replicate tests of 26 urine samples, interpreted by two different readers. Discrepancies existed in the replicate test result in 23 and 27% of the samples examined by reader 1 and 2, respectively, and on several occasions this discrepancy was between whether the sample was "positive" or "negative" for MA. The inter-reader agreement was good (kappa=0.75), but again discrepancies were noted and part of the reason for these problems appeared to be the necessary subjectivity in the interpretation of colour changes when reading test results. Proteinuria was significantly (P< or =0.014) more prevalent in the sick than the healthy cats with 36 and 9%, respectively, having detectable MA, 34 and 5%, respectively, having a urine protein to creatinine (UPC) ratio >0.5, and 84 and 9%, respectively, having positive urine protein dipstick analysis. There was a moderate significant correlation between UPC ratio and MA concentrations (r(s)=0.68, P<0.0001). While 13/87 cats with a UPC ratio < or =0.5 had positive MA results, 10/84 cats with negative MA results had a UPC ratio >0.5, and none of these had evidence of lower urinary tract disease. This study confirmed that MA and proteinuria are commonly seen in cats with a variety of diseases, but they are not necessarily both elevated, and the UPC ratio can be elevated without an increase in MA results. Furthermore, some repeatability problems were demonstrated with the semi-quantitative MA test. These findings demonstrate that the semi-quantitative MA test should not be relied on as the sole determinant of proteinuria.

Animals↗

PubMed2003

[Examination of preschool children for refractive errors. First experience using a handheld autorefractor].

BACKGROUND: Since ametropia is a leading cause of amblyopia refractive screening of preschool children is recommended. Measurement of refraction using tabletop autorefractors can be difficult or impossible due to lack of cooperation in this age group. The intention of the present study is to evaluate the use of a new handheld autorefractor for screening in kindergartens. METHODS: A total of 216 children aged 3.5-4.5 years were examined without cycloplegia using the handheld autorefractor (SureSight, Welch Allyn) in their kindergartens. RESULTS: Using the test device the majority of the examined eyes showed mild hyperopia (on average +1.18+/-0.87 dpt spherical equivalent) and mild astigmatism (on average 0.60+/-0.46 dpt cylinder power). The reproducibility of repeated autorefractor readings was higher for cylinder power and axis than for the spherical equivalent. Autorefractor readings of 55 eyes could be compared with the results of cycloplegic retinoscopy. The results were similar between the two measurements with differences of no more than 0.5 dpt in 18.2% for the spherical equivalent, in 82.1% for cylinder power, and in 66.6% for axis (weighted axis difference). There was adequate cooperation in 99.5% of the children. CONCLUSION: The handheld autorefractor proved an accuracy of measurement comparable to that of conventional tabletop autorefractors for cylinder power and axis with limitations in accuracy for the spherical equivalent. Validity and threshold values for relevant abnormalities are to be evaluated in further studies. By the high cooperation rate the instrument proved useful for screening examinations in preschool children.

Child, Preschool↗

PubMed1998

The sodium hydroxide erosion assay: a revision of the alkali resistance test.

Burckhardt proposed the alkali resistance method as a means of assessing the integrity of the stratum corneum barrier in 1947. Researchers after Burckhardt largely found the test unreliable and nonreproducible; it therefore fell into disuse worldwide. We have upgraded the procedure by exposing the skin to 1.0 M sodium hydroxide under strictly specified conditions for successive 1-min periods until the emergence of the first erosions, revealed by staining with nitrazine yellow. Histology showed that the erosions were follicular and limited to the epidermis. The test was highly reproducible and repeatable. We demonstrated the usefulness of the test in the following ways: (1) the erosion time increased with aging, correlating with a thickened horny layer; (2) as few as five Scotch tape strippings greatly decreased the erosion time, although transepidermal water loss was only slightly increased; (3) slight damage to the horny layer by a 24-h exposure to 0.01% sodium lauryl sulfate sharply reduced the erosion time; (4) the erosion time decreased after daily open applications for 3 weeks of clobetasol propionate, corresponding to the thinned horny layer; (5) daily applications of petrolatum increased the erosion time. This new version of the alkali resistance test, renamed the sodium hydroxide erosion assay, promises to be a useful tool for studying the horny layer barrier in healthy and diseased skin.

Administration, Topical↗

PubMed2004

Interobserver variability of carotid Doppler peak velocity measurements among technologists in an ICAVL-accredited vascular laboratory.

OBJECTIVE: This study was designed to investigate interobserver variability in the measurement of internal carotid artery (ICA) peak systolic velocity (PSV). We hypothesize that the reproducibility of repeated duplex scanning parameters, in the hands of very experienced vascular technologists in a laboratory accredited by the Intersocietal Commission for Accreditation of Vascular Laboratories, would be excellent. METHODS: Thirty-one patients underwent carotid duplex scanning by three vascular technologists using the same duplex scanning system. They examined patients with the laboratory's standard protocol. Statistical analysis of the sources of variation was carried out with two-way analysis of variance. The Altman-Bland method was used to detect bias and evaluate the interval of agreement between technologists for the ICA PSV on a continuous scale. The kappa statistic enabled measurement of agreement for ICA PSV on a categorical scale of stenosis (<50%, 50%-70%, >70%). RESULTS: Patient variability was responsible for 97.2% of the total variance, with only 0.58% (P<.005) attributed to the technologists. The level of agreement on a continuous scale between the measurements of ICA PSV by our technologists is wide. For individual patients it ranged from -25% to 43% between technologists A and B, -27% to 43% between technologists A and C, and -27% to 31% between technologists B and C. When we compared the three technologists, no systematic overestimation or underestimation of the ICA PSV was found (ie, no fixed bias). The level of agreement between the technologists did not depend on the value of the PSV (ie, no proportional bias). However, analysis of ICA PSV agreement on a categorical scale revealed almost perfect agreement (kappa>0.8). CONCLUSION: From measurements of PSV, the severity of carotid stenosis can be reproducibly categorized into ranges (<50%, 50%-70%, >70). However, the unacceptably wide interobserver variation of ICA PSV on a continuous scale makes the interchangeability of our technologists' measurements problematic for clinical use, as in determination of progression of severity of stenosis. When an ICA PSV measurement is in the vicinity of a cutoff value, the diagnostic accuracy may be improved with the use of additional diagnostic testing.

Blood Flow Velocity↗