Precision and Agreement of Individual and Simultaneous Macular and Optic Disc Volumetric Measurements With Spectral Domain Optical Coherence Tomography

Purpose: To evaluate the precision of individual and combined macula and optic disc volumetric analysis, and the agreement between these two scan modes with spectral domain optical coherence tomography (OCT).Methods: Macular and optic disc volumetric measurements were performed with individual and combined scan protocols in one eye of 75 healthy subjects. Three repeated measurements were performed with each protocol. From the macular area, retinal thickness in nine different sectors and ganglion cell complex thickness in eight different sectors were analyzed from both scan modes. From the optic disc area, the peripapillary retinal nerve fiber layer (pRNFL) thickness in 12 clock sectors and the optic disc parameters were evaluated. For all the parameters, repeatability limit and agreement analysis were performed.Results: For the retinal thickness measurements in macula, the combined scan had two to three times larger repeatability limit than the individual scan for all the sectors except the central sector, where the repeatability limit was five times larger. The limits of agreement intervals were lower than 20 μm for all sectors, except the central. The ganglion cell complex measurements also had larger repeatability limits for the combined scans, and the limits of agreement intervals were <10 μm for all sectors. For the pRNFL thickness, the repeatability values were distributed like a vertically elongated ellipse for both scans, but still the repeatability was better for individual scan compared to the combined scan. The shortest and widest interval are obtained for sectors 9 (9 μm) and 12 (40 μm), respectively. The repeatability limit was <0.15 units for all disc parameters with both scan modes.Conclusion: The individual macula and optic disc scans had better repeatability than the combined scan mode, and the two scan modes cannot be used interchangeability due to the wide limits of agreement.

Validation of quantitative determination of original substance of dipeptide threonylthreonine

Validation of the quantitative determination of the threonylthreonine substance was carried out in terms of specificity, linearity, correctness, precision, including repeatability and reproducibility. The linearity correlation coefficient of the method was 0.99998 in the range of 80–120 % of the standardized value. The calculated Student’s coefficients for the range 80, 100, 120 % are respectively equal to 1.32; 0.31; 0.55 and do not exceed the permissible limit values. The open rate was 100.07 %. The repeatability limit for one measurement group was – 0.20; for two – 0.366 in accordance with the eligibility criteria. The calculated Student’s (t = 1.34) and Fisher’s (F = 2.00) criteria for two groups of measurements did not exceed the permissible values. The developed technique for potentiometric titration of the threonylthreonine substance in a non-aqueous medium is valid.

Use of Resampling Method to Construct Variance Index and Repeatability Limit of Damage Characteristic Curve

The simplified viscoelastic continuum damage model has been widely accepted as a tool to predict fatigue performance of asphalt concrete. One key component in the model is the damage characteristic curve that results from a cyclic fatigue test. This curve characterizes the relationship between material integrity (stiffness) and the level of damage in the material. As with any experimental measurement, it is important to know and quantify the variability of the damage curve, but traditional statistical methods are ill-suited for experiments that yield functional data as opposed to univariate data. In this study, a variance index of the damage characteristic curve is first proposed and compared with the expert judgment of the variance of a set of nine different asphalt mixtures. Then, an example analysis for establishing the repeatability limit of a specific mixture as the application of the variance index is presented using the resampling method and hypothesis test. The major findings are as follows: 1) the proposed variance index can match the expert judgment of variability; 2) the shape of the damage characteristic curve can affect the performance of the variance index; 3) the resampling method and hypothesis test can be applied to flag inconsistent data in multi-user or multi-laboratory results; and 4) the resampling method can also be used to construct the repeatability limit of the variance index.

Assessment of corneal biomechanics, tonometry and pachymetry with the Corvis ST in myopia

To evaluate the repeatability of Corvis ST corneal biomechanical, tonometry and pachymetry measurements, and agreement of pachymetry measures with the Pentacam HR and RTVue OCT. Three consecutive measurements of the right eye of 238 myopic subjects were acquired with the Corvis ST, Pentacam HR, and RTVue OCT. Repeatability of Corvis ST was evaluated by within-subject standard deviation [Sw] and repeatability limit [r]. The agreement of central corneal thickness (CCT) measurements were compared among the three instruments using the Bland–Altman limits of agreement. Comparisons were further stratified by CCT (Corneathin ≤ 500 µm; Corneanormal = 500–550 µm; Corneathick > 550 µm). Sw was below 1 mmHg in Corneathin, Corneanormal, and Corneathick groups for IOP and bIOP. Sw for SP-A1 were 4.880, 6.128, 7.719 mmHg/mm respectively. Sw for CBI were 0.228, 0.157, 0.076, and correspondingly Sw for TBI and SSI were 0.094 and 0.056, 0.079 and 0.053, 0.070 and 0.053. The Bland–Altman plots for CCT implied poor agreement with mean differences of 29.49 µm between Corvis and OCT, 9.33 µm between Pentacam and OCT, and 20.16 µm between Corvis and Pentacam. The Corvis ST showed good repeatability with the exception of CBI in the various CCT groups. The CCT measured by Corvis ST was not interchangeable with Pentacam HR and RTVue OCT.

Evaluation of Automated Segmentation Algorithm for Macular Volumetric Measurements of Eight Individual Retinal Layer Thickness

Background: We evaluated the performance of an automated algorithm available on a clinical OCT (Canon-HS100) for macular volumetric measurements of eight individual retinal layers. Methods and Analysis: Two consecutive three-dimensional scans were acquired on 29 subjects with healthy retinas. Thickness measurements were obtained from eight individual retinal layers in nine macular sectors based on Early Treatment Diabetic Retinopathy Study (ETDRS) protocol. The repeatability was evaluated using the within-subject standard deviation from which the repeatability limits (Rlimit) and coefficient of variation (CoV) were calculated. Results: The repeatability metrics varied among different layers and sectors. The variation among the sectors was larger in two of the outer layers (plexiform and nuclear layer) and the retinal nerve fiber layer. For the other five layers, the repeatability limit was less than 5µm and CoV was less than 7.5% in all nine ETDRS sectors. Conclusions: The repeatability of the OCT-HS100 to measure eight individual retinal layers is good in general. Nevertheless, the repeatability is not homogeneous among different layers and sectors. This needs to be taken into account while designing clinical measurement protocols.

Akdeniz Bölgesinde Yetiştirilen Sebzelerin Nitrat Düzeylerinin Tespiti ve Validasyonu

In our study, validation was carried out at 24 and 200 mg/kg enrichment for residue analysis of nitrate active substance only in lettuce samples. Analyses were performed by using high performance liquid chromatography (HPLC) in lettuce, spinach, salad and arugula samples. In order to eliminate the matrix effect, matrix calibration was used, ie calibration of lettuce samples. Validation of the method was performed with criteria such as precision, repeatability, repeatability limit, reproducibility, repeatability limit, accuracy, linearity of calibration and recovery. The calibration curve was found as linear in the range of 0.2-40 mg/kg. The recovery from the samples is between 97.3-100.2 %. The repeatability and reproducibility values for the two concentrations were 1.89 (matrix+24 ppm) and 3.65 (matrix+200 ppm), 3.951 (matrix+24 ppm) and 3.456 (matrix+200 ppm), respectively. The repeatability and reproducibility limit values are within acceptable limits. Accuracy, precision, combined uncertainty and extended uncertainty (95% confidence: k=2) were found as 0.015 (matrix+24 ppm) and 0.004 (matrix+200 ppm), 0.039 (matrix+24 ppm) and 0.006 (matrix+200 ppm), 0.041 (matrix+24 ppm) and 0.007 (matrix+200 ppm), 0.082 (matrix+24 ppm) and 0.014 (matrix+200 ppm). In our study, the highest nitrate ratio was determined in spinach with 3486 mg/kg in total 102 samples. Lettuce following spinach (2825 mg/kg) showed lower nitrate content, while lower concentrations of nitrate were detected in iceberg (1985 mg/kg) and arugula (1870 mg/kg), respectively. The results may be useful in estimating body intake levels for research on the effects of nitrite and nitrate on human health in vegetable producers and in our daily diet. In addition, the nitrate content of the vegetables analysed in the study is an indicator of the use of nitrogenous fertilizers in the Mediterranean region, but showed no problem for human and animal health.

Radiostereometric analysis using clinical radiographic views: Validation with model-based radiostereometric analysis for the knee

Radiostereometric analysis is a sophisticated radiographic technique with high measurement accuracy. In order to improve the accessibility of radiostereometric analysis for clinical use, a modified radiostereometric analysis procedure has been previously proposed that enables clinical radiographic views to be used for radiostereometric analysis. It has been successfully validated for its application to the hip wear study with the conventional bead–based radiostereometric analysis environment using computed radiography. In this study, we describe the implementation and validation of this technique for the knee study with the model-based radiostereometric analysis environment using digital radiography. A knee-joint phantom with 6 degrees of freedom was examined, and the bias and repeatability/reproducibility of the modified radiostereometric analysis approach were investigated following the newly updated ASTM recommendations. The bias parameters (mean ± 95% confidence interval) ranged from 0.008 ± 0.003 mm to 0.027 ± 0.006 mm for translation and from 0.014° ± 0.007° to 0.040° ± 0.020° for rotation. The repeatability standard deviation ranged from 0.004 to 0.020 mm for translation and from 0.005° to 0.015° for rotation. The 95% repeatability limit ranged from 0.011 to 0.055 mm for translation and from 0.014° to 0.041° for rotation. The reproducibility standard deviation ranged from 0.004 to 0.023 mm for translation and from 0.006° to 0.040° for rotation. The 95% reproducibility limit ranged from 0.012 to 0.063 mm for translation and from 0.016° to 0.112° for rotation. The modified procedure allows routine clinical radiographs to be used for radiostereometric analysis, which provides the possibility of adding quantitative measurements to current patient registries.

INDICATOR OF ANTHROPOGENIC ACTIVITY IN WATERS OF PARAÍBA DO SUL RIVER. DEVELOPMENT AND VALIDATION OF ANALYTICAL METHODOLOGY

The fast increasing concern about the quality and composition of water has also led to an increasing number of studies on natural waters monitoring. Caffeine has been used as suitable chemical marker because its source is exclusively anthropogenic. It is present in drugs, foods and beverages all of them highly consumed by population. The area chosen for this study was the basin of the Paraíba do Sul River. This is a heavily urbanized and industrialized area. To guarantee reliable results, it is necessary that the analysis methods are validated for this purpose. In this paper, we present the method developed and validated for analysis of caffeine in surface waters of the Paraíba do Sul River, concerning the parameters suggested by INMETRO to validate chemical analysis. The method have shown satisfactory results for validation including: adequate linearity with r2 of 0.99, good selectivity and specificity, accuracy and precision with z (Score) 2 and repeatability limit indicating low data dispersion. The method was considered to be robust after small variations and was used to quantify caffeine. Concentrations in the range between 0.080 µg L-1 (LOQ) and 0.106 µg L-1 were found in Pindamonhangaba River.

Repeatability of cold pain and heat pain thresholds: The application of sensory testing in migraine research

Normal heat pain threshold (HPT) and cold pain threshold (CPT) repeatability should be estimated in order to identify thermal allodynia in longitudinal studies, but such data are scarce in the literature. The aim of our study was to estimate normal HPT and CPT repeatability in the face, forehead, neck and hand. In addition, we reviewed briefly normative studies of thermal pain thresholds relevant for headache research. Thermal pain thresholds were measured on three different days in 31 healthy headache-free subjects. Coefficients of repeatability and normal limits were calculated. HPT and CPT were lowest in the face. Pooled across regions, the lower repeatability limit for the test/retest ratio was 63% for HPT and 55% for CPT. The upper normal CPT limit varied between 24.5°C and 29.7°C. Lower HPT limits ranged between 35.5°C and 40.8°C. Quantitative sensory methods provide useful information about headache and pain pathophysiology, and it is important to estimate the normal test/retest repeatability range in follow-up studies.