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Results for “Reproducibility”

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PubMed2004

Validation of commercial dry-form broth microdilution panels and test reproducibility for susceptibility testing of dalbavancin, a new very long-acting glycopeptide.

Results from dalbavancin dry-form commercial broth microdilution MIC panels (Sensititre, TREK Diagnostics) were compared with reference frozen-form MIC values to assure the validity and reproducibility of the extended shelf-life product. A collection of 402 organisms from four major organism groups were used in the validation trial and 10 strains for reproducibility replicate tests. A total of 98.6% commercial dalbavancin MIC results were within +/-1 log(2) dilution of reference values (76.2% were identical) and reproducibility trials produced identical MIC results in 88.9-92.2% of dalbavancin MIC comparisons. These dalbavancin MIC results demonstrated the acceptable accuracy of commercially-prepared broth microdilution products for use in subsequent clinical trials.

Bacterial Infections↗

PubMed2004

Low variation and high reproducibility in plaque volume with intravascular ultrasound.

BACKGROUND: Intravascular ultrasound (IVUS) has several advantages compared to angiography when evaluating coronary atherosclerosis in the vessel wall. METHODS: The accuracy, reproducibility, and short-time spontaneous variation in volume of vessel, plaque and lumen were studied by electrocardiographic-gated three-dimensional (3D) IVUS in 20 male patients with ischaemic heart disease (IHD). RESULTS: The study lesions were angiographically insignificant, with a length of the analysed segment on 11.4+/-5.9 mm. At baseline the mean minimal lumen diameter was 2.41+/-0.59 mm, minimal lumen area 4.82+/-2.38 mm2, and maximal plaque burden 65.61+/-9.57%. Mean reference diameter was 3.1+/-0.6 mm. No significant changes were observed in volumes of total vessel, lumen or plaque. The coefficient of variation (CV) for two volume measurements at baseline was: vessel 0.8%, plaque 1.3%, and lumen 1.4%. For measurements recorded at baseline and after 12.6+/-1.5 weeks, CV was respectively 3.5%, 3.3% and 6.6%. Reproducibility and interobserver and intraobserver variation showed very high correlations. A linear correlation was present in percent changes over 12.6+/-1.5 weeks between vessel volume and lumen volume (r=0.804; p<0.001) and between percent changes in plaque volume and vessel volume (r=0.581; p=0.007). No correlation was found between changes in plaque volume and lumen volume (r=0.015; p=0.950). CONCLUSION: ECG-gated 3D IVUS is a highly reproducible method when applied on coronary artery atherosclerosis. CV for lumen volume over 12.6+/-1.5 weeks is twice that of plaque volume indicating the superiority of the 3D IVUS compared to coronary angiography (CAG).

Aged↗

PubMed2006

Reproducibility of sonotubometry as Eustachian tube ventilatory function test in healthy children.

OBJECTIVES: To devise a simple and reliable diagnostic procedure to test Eustachian tube function routinely in an ENT outpatient setting. One method to measure ET ventilatory function is sonotubometry. The reproducibility of a recently updated sonotubometry set-up was tested in healthy children. METHODS: The test population comprised 61 school children aged from 6 to 8 years. Only otologically healthy children were included. Health state was established by means of a 12-item questionnaire. To test reproducibility, sonotubometric testing took place in two sessions of 10 acts of swallowing each. Spearman's coefficient was used to test the correlation between the two sets of measurements. All testing took place at a primary school in a nearby village. RESULTS: Opening of the ET was recorded in at least one of the two measurement sessions in 82% of the children. The first and second sessions were highly correlated, with a Spearman's coefficient of 0.89. CONCLUSIONS: In otologically healthy children, opening of the ET was recorded frequently using the updated sonotubometry set-up. Measurement results had high reproducibility. Therefore, the test forms a useful method to assess ET ventilatory function in otologically healthy children. The performance of this updated version needs to be established in children with otological diseases.

Acoustic Impedance Tests↗

PubMed2005

A phase I/II trial to evaluate three-dimensional conformal radiation therapy confined to the region of the lumpectomy cavity for Stage I/II breast carcinoma: initial report of feasibility and reproducibility of Radiation Therapy Oncology Group (RTOG) Study 0319.

BACKGROUND: This prospective study (Radiation Therapy Oncology Group Study 0319) examines the use of three-dimensional conformal external beam radiation therapy to deliver accelerated partial breast irradiation. Reproducibility, as measured by technical feasibility, was the primary end point with the goal of demonstrating whether the technique is widely applicable in a multicenter setting before a Phase III trial is undertaken. METHODS AND MATERIALS: This study was designed such that if fewer than 5 cases out of the first 42 patients evaluable were scored as unacceptable, the treatment would be considered reproducible. Patients received 38.5 Gy in 3.85 Gy/fraction delivered twice daily. The clinical target volume included the lumpectomy cavity plus a 10-15-mm margin bounded by 5 mm within the skin surface and the lung-chest wall interface. The planning target volume (PTV) included the clinical target volume plus a 10-mm margin. Treatment plans were judged as follows: (1) No variations (total coverage), 95% isodose surface covers 100% of the PTV and all specified critical normal tissue dose-volume histogram (DVH) limits met. (2) Minor variation (marginal coverage), 95% isodose surface covers between > or = 95% and <100% of the PTV. No portion of PTV receives <93% of prescription (isocenter) dose. All specified critical normal tissue DVH limits fall within 5% of the guidelines. (3) Major variation (miss), 95% isodose surface covers <95% of the PTV. Portion of PTV receives <93% of prescription isocenter dose. Any critical normal tissue DVH limit exceeds 5% of the specified value. RESULTS: A total of 58 patients were enrolled on this study between 8/15/03 and 4/30/04, 5 of whom were ineligible or did not receive protocol treatment. Two additional patients were excluded, one because the on-study form was not submitted, and the other because no treatment planning material was submitted. This primary end point analysis is based on the first 42 (out of 51) evaluable patients, which were accrued from 17 different institutions (31 centers were credentialed for case enrollment, but because of rapid accrual, not all centers were able to submit cases before trial closure). These 42 patients had the following characteristics: median age was 61 years; 48% had a maximum tumor dimension of <1 cm; 86% had invasive ductal carcinoma; 64% were postmenopausal; the location of tumor was upper outer for 40% and upper central for 21%; 79% had no chemotherapy, and 64% had no hormonal therapy. There were 4 cases with major variations (all 4 related to normal tissue DVHs exceeding 5% of the specified limit). A total of 32 cases with minor variations in treatment plans were detected (16 related to normal tissue DVHs exceeding the specified limits [by < or = 5%], 6 related to suboptimal coverage of the PTV, and 10 related to both). There were 6 cases with no variations. Of the 51 total evaluable patients, 1 additional major variation was noted (PTV receiving <93% of the prescription dose). An additional 5 cases with minor variations in treatment plans were detected (3 related to normal tissue DVHs exceeding the specified limits [by < or = 5%], 1 related to suboptimal coverage of the PTV, and 1 related to both). There were 3 more cases with no variations. CONCLUSION: Accelerated partial breast irradiation using three-dimensional conformal external beam radiation therapy was shown in this preliminary analysis of the first 42 evaluable patients to be technically feasible and reproducible in a multi-institutional trial using exceptionally strict dosimetric criteria.

Adult↗

PubMed2006

Reproducibility of chronic and acute infarct size measurement by delayed enhancement-magnetic resonance imaging.

OBJECTIVES: The aim of this study was to evaluate the reproducibility of acute and chronic infarct size (IS) by delayed enhancement (DE) magnetic resonance imaging (MRI). BACKGROUND: Infarct size measurements can be used as surrogate end point to reduce the sample size in studies comparing different reperfusion strategies in myocardial infarction (MI). Delayed enhancement MRI is a rather new technique, and so far infarct IS reproducibility has not been established appropriately. METHODS: In 21 patients (10 acute MI and 11 chronic MI), IS was assessed repeatedly on consecutive days by DE-MRI. Reproducibility, interobserver, and intraobserver variabilities were assessed and compared by the Bland-Altman method. RESULTS: Acute and chronic IS were 17.1 +/- 19.6% (range 5.1% to 69.8%) of LV mass (%LV) and 16.9 +/- 9.9 %LV (range 2.0% to 36.0%), respectively. Infarct size difference (bias) between scan I and scan II was -0.5 %LV, and limits of agreement were +/-2.4 %LV. Mean bias (-0.7 %LV) and limits of agreement (+/-3.2%) were slightly higher for acute in comparison with chronic MI with -0.4 +/- 1.3 %LV. Intraobserver and interobserver variability was low with a mean bias of 0.3 %LV (limits of agreement +/- 1.7 %LV) and -0.7 %LV (limits of agreement +/- 2.2 %LV), respectively. CONCLUSIONS: Infarct size measurement by DE-MRI is an excellent tool for IS assessment, owing to its excellent repeatability in chronic and acute MI. It has therefore the potential to serve as a surrogate end point to uncover advantages of new reperfusion strategies.

Acute Disease↗

PubMed2005

Measurement and reproducibility of magnetocardiographic filtered atrial signal in patients with paroxysmal lone atrial fibrillation and in healthy subjects.

Magnetocardiography (MCG) is a method complementary to electrocardiography (ECG). We examined recording and reproducibility of atrial depolarization signal by MCG. Multichannel MCG over anterior chest and orthogonal 3-lead ECG were recorded in 9 patients who had paroxysmal lone atrial fibrillation and in 10 healthy subjects in duplicate at least 1 week apart. Data were averaged using atrial wave template and high-pass filtered at 25, 40, and 60 Hz. Atrial signal duration with automatic detection of onset and offset and root mean square amplitudes of the last portion of atrial signal were determined. Coefficient of variation of atrial signal duration by MCG at 40 Hz was 3.3% and difference between the measurements was 3.5 milliseconds on average. The corresponding figures obtained by signal-averaged ECG (SAECG) were 6.1% and 6.9 milliseconds. Coefficient of variation for root mean square of the last 40 milliseconds of atrial signal were 16% in MCG and 17% in SAECG. Reproducibility was best at 40-Hz filter and similar in patients and healthy subjects. In conclusion, the reproducibility of atrial signal variables in MCG is adequate and somewhat better than in SAECG and equal in patients with lone atrial fibrillation and healthy subjects. Magnetocardiography seems to be a potentially valuable method to evaluate features of atrial depolarization in patient studies.

Adult↗

PubMed2006

The effect of signal averaging on the reproducibility and reliability of measures of T-wave morphology.

Electrocardiographic repolarization abnormalities characterized by T-wave morphology parameters such as the principal component analysis ratio and the relative and the absolute T-wave residuum (TWR(rel) and TWR(abs)) are predictive of cardiovascular and/or all-cause mortality. However, when using a "10-second median beat" for analysis, the reported mean values for TWR(rel) vary widely and parameter reproducibility is somewhat suspect. In repeated electrocardiographic recordings conducted 1 month and 1 year apart on 15 and 27 healthy individuals, respectively, we studied the said T-wave morphology parameters in single complexes and in reduced noise signal averages containing 10 and 200 complexes. Considering all subjects, the mean (+/-SD) TWR(rel) was highest in a single complex (0.0345% +/- 0.0183%), intermediate in the 10-beat signal-averaged complexes (0.0125% +/- 0.0051%), and lowest in the 200-beat signal-averaged complexes (0.0078% +/- 0.0036%) (P < .0001), with the same trend also observed in the TWR(abs) but not in the principal component analysis ratio. Reproducibility as quantified by within-subject variance and reliability as quantified by the intraclass (intrasubject) correlation coefficient also improved as the number of T-wave complexes analyzed increased. We conclude that signal averages consisting of more than 10 complexes (or more than 10 seconds worth of complexes) are required to produce reproducible and reliable values for TWR(rel) and TWR(abs).

Action Potentials↗

PubMed2005

Reproducibility of surface EMG variables in isometric sub-maximal contractions of jaw elevator muscles.

The aims of this study were: (1) to develop and assess reproducibility of a new method for measuring masticatory force in the intercuspal position; (2) to test the reproducibility of surface EMG signal amplitude and spectral variables in constant force contractions of jaw elevator muscles and its dependency on inter-electrode distance. The study was performed on the masseter and temporalis anterior muscles of both sides of nine healthy volunteers. An intraoral compressive-force sensor was used to measure maximal voluntary contraction forces in the intercuspal position and to provide a visual feedback on sub-maximal forces to the subject. Three experimental sessions were performed in three days. In each session, three isometric contractions at 80% of the maximal force were sustained by the subjects for 30s. The intra-class correlation coefficient (ICC) of the maximal force measure was 71.9%. ICC of average rectified value and mean power spectral frequency of the EMG signal increased with inter-electrode distance, with values larger than 70% with 30 mm inter-electrode distance. It was concluded that surface EMG variables measured in isometric contractions of the jaw elevator muscles with the proposed force recording system show good reproducibility for clinical applications when a 30 mm inter-electrode distance is considered.

Adult↗

PubMed2006

Digital venous photoplethysmography in the seated position is a reproducible noninvasive measure of lower limb venous function in patients with isolated superficial venous reflux.

BACKGROUND: The value of photoplethysmography (PPG) has been questioned because of a lack of reproducibility. We performed this study to determine whether new digital technology has improved the reproducibility of PPG in the noninvasive assessment of lower limb venous function in patients with isolated superficial venous reflux. METHODS: This was a prospective study of 140 legs in 110 patients (65% female; median age [interquartile range], 45 years [36-59.25 years]; CEAP clinical grade C2/3, n = 114; C4-6, n = 26) who underwent repeated digital PPG measurements of refilling time (RT) in both the sitting and standing position after standard exercise regimens by a single observer. RT was measured in all patients 2 to 5 minutes apart and in a randomly selected subgroup of 30 patients (38 limbs) 1 to 2 weeks apart. RT variability was assessed by using Bland and Altman's coefficient of repeatability (CR-RT), where the CR-RT was 1.96 times the standard deviation of the mean difference in RT between two tests. Venous duplex scanning of both the deep and superficial veins was also performed, and a reverse flow of greater than 0.5 seconds was considered abnormal. Only patients with isolated superficial venous reflux were included in the study. RESULTS: The CR-RT of the tests on 140 limbs performed 2 to 5 minutes apart was 10 seconds overall, 3 seconds for RT up to 10 seconds, and 16 seconds for RT between 20 and 40 seconds. The CR-RT of the 38 tests performed 1 to 2 weeks apart was also 10 seconds. No systematic variation due to a nonrandom error was found between the measurements performed either 2 to 5 minutes or 1 to 2 weeks apart. CONCLUSIONS: Digital PPG performed in the seated position in patients with isolated superficial venous reflux provides a reproducible method for the noninvasive assessment of lower limb venous function for both clinical and research purposes. However, the variation in precision of RT with the magnitude of the measurement must be taken into account when results are interpreted in individual patients.

Adult↗

PubMed2004

Brain metabolite concentration ratios in vivo: multisite reproducibility by single-voxel 1H MR spectroscopy.

Ten normal subjects were scanned identically at three separate sites (Little Rock, Houston, and New Orleans) to evaluate the reproducibility of brain metabolite ratios in single-voxel (1)H point-resolved spectroscopy sequence (PRESS) magnetic resonance (MR) spectroscopy in vivo. All scans were processed by a single individual at a single site. Coefficients of variation of the measured metabolite ratios generally were in the range found for previous single-voxel, single-site reproducibility studies. No differences were found among the sites for ratios of N-acetylaspartate to creatine (NAA/Cr) or choline to Cr (Cho/Cr) in left thalamus by multivariate ANOVA. Metabolite ratios of Cr or Cho relative to local brain H(2)O did not vary among the sites. However, by multivariate ANOVA, NAA/H(2)O differed between Little Rock and New Orleans, but not between those sites and Houston. Intraclass correlation coefficients suggested reasonable reproducibility between Little Rock and New Orleans, but not between those sites and Houston.

Adult↗

PubMed2004

Functional MRI of auditory verbal working memory: long-term reproducibility analysis.

Although functional MRI (fMRI) has shown to be a tool with great potential to study the normal and diseased human brain, the large variability in the detected hemodynamic responses across sessions and across subjects hinders a wider application. To investigate the long-term reproducibility of fMRI activation of verbal working memory (WM), eight normal subjects performed an auditory version of the 2-back verbal WM task while fMRI images were acquired. The experiment was repeated nine times with the same settings for image acquisition and fMRI task. Data were analyzed using SPM99 program. Single-session activation maps and multi-subject session-specific activation maps were generated. Regions of interest (ROIs) associated to specific components of verbal WM were defined based on the voxels' coordinates in Talairach space. Visual observation of the multi-subject activation maps showed similar activation patterns, and quantitative analysis showed small coefficients of variance of activation within ROIs over time, suggesting small longitudinal variability of activation. Visual observation of the activation maps of individual sessions demonstrated striking variation of activation across sessions and across subjects, and quantitative analysis demonstrated larger contribution from between-subject variation to overall variation than that from within-subject variation. We concluded that by multi-subject analysis of data from a relatively small number of subjects, reasonably reproducible activation for the 2-back verbal WM paradigm can be achieved. The level of reproducibility encourages the application of this fMRI paradigm to the evaluation of cognitive changes in future investigations. The quantitative estimation of the proportions of within-subject and between-subject variabilities in the overall variability may be helpful for the design of future studies.

Acoustic Stimulation↗

PubMed2004

Optimizing the fMRI data-processing pipeline using prediction and reproducibility performance metrics: I. A preliminary group analysis.

We argue that published results demonstrate that new insights into human brain function may be obscured by poor and/or limited choices in the data-processing pipeline, and review the work on performance metrics for optimizing pipelines: prediction, reproducibility, and related empirical Receiver Operating Characteristic (ROC) curve metrics. Using the NPAIRS split-half resampling framework for estimating prediction/reproducibility metrics (Strother et al., 2002), we illustrate its use by testing the relative importance of selected pipeline components (interpolation, in-plane spatial smoothing, temporal detrending, and between-subject alignment) in a group analysis of BOLD-fMRI scans from 16 subjects performing a block-design, parametric-static-force task. Large-scale brain networks were detected using a multivariate linear discriminant analysis (canonical variates analysis, CVA) that was tuned to fit the data. We found that tuning the CVA model and spatial smoothing were the most important processing parameters. Temporal detrending was essential to remove low-frequency, reproducing time trends; the number of cosine basis functions for detrending was optimized by assuming that separate epochs of baseline scans have constant, equal means, and this assumption was assessed with prediction metrics. Higher-order polynomial warps compared to affine alignment had only a minor impact on the performance metrics. We found that both prediction and reproducibility metrics were required for optimizing the pipeline and give somewhat different results. Moreover, the parameter settings of components in the pipeline interact so that the current practice of reporting the optimization of components tested in relative isolation is unlikely to lead to fully optimized processing pipelines.

Adult↗

PubMed2005

Reproducibility of cortex-muscle coherence.

Cortex-muscle coherence is a frequency-analysis technique that has been increasingly applied in the investigation of movement disorders. To study the intra- and inter-session stability of the cortex-muscle coherence, we recorded from 12 healthy subjects magnetoencephalographic (MEG) and surface electromyographic (EMG) signals during unilateral isometric contractions of the left- and right-hand muscles. Two identical measurements were performed during one session, and the session was repeated once after about 1 year. In one experienced subject, the recordings were repeated seven times within 20 months. The MEG-EMG coherence exceeded the noise level in 10 out of 12 subjects. Both the frequency (correlation coefficient r = 0.77-0.93, P < 0.01) and strength (r = 0.78-0.91, P < 0.01) of coherence were well reproducible within each session for both left- and right-sided contractions. The inter-session reproducibility was high for the mean of cumulative coherence frequency (r = 0.90-0.95, P < 0.01), but relatively low for coherence strength (r = 0.43-0.59, P > 0.05). The results for one subject participating in 8 repeated sessions strongly supported the results of the whole group. Thus, intra-session reproducibility of both strength and frequency of the cortex-muscle coherence is good and studies comparing different conditions at the group level within one session are feasible. However, caution is needed when interpreting absolute levels or changes in the strength of coherence in single subjects between the sessions.

Adult↗

PubMed2006

Diffusion tensor imaging in primary brain tumors: reproducible quantitative analysis of corpus callosum infiltration and contralateral involvement using a probabilistic mixture model.

Diffusion tensor imaging (DTI) has been advocated as a promising tool for delineation of the extent of tumor infiltration by primary brain tumors. First reports show conflicting results mainly due to difficulties in reproducible determination of DTI-derived parameters. A novel method based on probabilistic voxel classification for a user-independent analysis of DTI-derived parameters is presented and tested in healthy controls and patients with primary brain tumors. The proposed quantification method proved to be highly reproducible both in healthy controls and patients. Fiber integrity in the corpus callosum (CC) was measured using this quantification method, and the profiles of fractional anisotropy (FA) provided additional information of the possible extent of infiltration of primary brain tumors when compared to conventional imaging. This yielded additional information on the nature of ambiguous contralateral lesions in patients with primary brain tumors. The results show that DTI-derived parameters can be determined reproducibly and may have a strong impact on evaluation of contralateral extent of primary brain tumors.

Adult↗

PubMed2006

Reproducibility of activation in Broca's area during covert generation of single words at high field: a single trial FMRI study at 4 T.

Although functional magnetic resonance imaging (FMRI) has arguably become the most ubiquitously used imaging modality, questions remain about the reproducibility of the observed patterns of activation and the acquisition time required to achieve statistically significant and reproducible maps. In the current study, we investigated the reliability of activation in Broca's area, on both a voxel-wise and region of interest level, in response to the covert generation of a single word at 4 T. We also assessed the effects of different parametric (P < 0.01; P < 0.005; P < 0.001) and spatial thresholds (25%, 50% and 75%) on the reproducibility of activation within our region of interest and other randomly selected areas of the brain. We report that the inter-trial consistency of activation within Broca's area for a single trial design using multi-echo EPI is roughly equivalent to previous studies that averaged across a much larger number of trials. However, reliability estimates varied dramatically (approximately 55%) depending on the different parametric and spatial criteria thresholds that were applied to the data. These results show that increased sensitivity at high field strength can be used to reduce the time needed to localize functional activation patterns, which is beneficial for clinical studies such as pre-surgical mapping. Additional benefits of single trial designs, such as the ability to immediately assess for extraneous cognitive processes, are also discussed.

Adult↗

PubMed2006

The assessment of hemispheric lateralization in functional MRI--robustness and reproducibility.

Various methods have been proposed to calculate a lateralization index (LI) on the basis of functional magnetic resonance imaging (fMRI) data. Most of them are either based on the extent of the activated brain region (i.e., the number of "active" voxels) or the magnitude of the fMRI signal change. The purpose of the present study was to investigate the characteristics of various variants of these approaches and to identify the one that yields the most robust and reproducible results. Robustness was assessed by evaluating the dependence on arbitrary external parameters, reproducibility was assessed by Pearson's correlation coefficient. LIs based on active voxels counts at one single fixed statistical threshold as well as LIs based on unthresholded signal intensity changes (i.e., based on all voxels in a region of interest) yielded neither robust nor reproducible laterality results. Instead, the lateralization of a cognitive function was best described by "thresholded" signal intensity changes where the activity measure was based on signal intensity changes in those voxels in a region of interest that exceeded a predefined activation level. However, not all other approaches should be discarded completely since they have their own specific application fields. First, LIs based on active voxel counts in the form of p-value-dependent lateralization plots (LI=LI(p)) can be used as a straightforward measure to describe hemispheric dominance. Second, LIs based on active voxel counts at variable thresholds (standardized by the total number of active voxels) are a good alternative for big regions of interest since LIs based on signal intensity changes are restricted to small ROIs.

Adult↗

PubMed2004

Long-term reproducibility of in vivo measures of specific binding of radioligands in rat brain.

The long-term reproducibility of measures of in vivo specific binding of radiolabeled forms of (+)-alpha-dihydrotetrabenazine (DTBZ) and d-threo-methylphenidate (MPH) in rat brain was examined. All studies were done using a consistent bolus plus infusion protocol and calculation of equilibrium distribution volume ratios (DVR). Over a period of eight years striatal DVR values for DTBZ binding to the vesicular monoamine transporter 2 (VMAT2) in young adult (8-10 wks old) rats showed very good reproducibility (3.62+/-0.33, N=35). Equivalent values were obtained using either tritiated or carbon-11 labeled DTBZ, and were irrespective of sex of animals. Older animals (78 wks old) showed losses (-45%) of specific binding. Striatal binding of MPH to the dopamine transporter (DAT) showed a similar reproducibility over a five year period (DVR=2.17+/-0.39, N=52), again irrespective of radionuclide or sex. These studies demonstrate that use of a consistent in vivo technique can provide reliable measures of specific binding of radioligands to high affinity sites in the rat brain.

Aging↗

PubMed2006

Reproducibility of ultrasound pachymetry using the Sonogage Corneo-Gage Plus 2.

PURPOSE: The aim of this study was to determine the reproducibility of measurements made using the Sonogage Corneo-Gage Plus 2 (Cleveland, Ohio) ultrasound pachymeter of total corneal and corneal epithelial thickness in 5 different regions of the cornea. METHODS: Twenty-seven subjects at the New England College of Optometry (NECO) and 20 subjects at the Southern College of Optometry (SCO) were enrolled in this study. Measurements were taken of the central cornea as well as the nasal and temporal regions of the midperipheral and peripheral regions of the right cornea of each subject. Identical measurements were again taken in these subjects 1 week later at approximately the same time of day. Within-subject variations were then assessed using paired t tests. RESULTS: The only significant measurement differences that were found between visits were for full corneal thickness at both the nasal and temporal midperipheral locations. The mean differences for these locations were 13.5 microm and 13.7 microm, respectively. CONCLUSIONS: Epithelial corneal thickness and central and peripheral total corneal thickness measurements using the Corneo-Gage Plus 2 pachymeter were reproducible; however, midperipheral total corneal thickness measurements showed poor reproducibility.

Cornea↗