High Test-retest Repeatability Research Articles

Torque-Cadence Profile and Maximal Dynamic Force in Cyclists: A Novel Approach.

We aimed to determine the feasibility, test-retest reliability and long-term stability of a novel method for assessing the force (torque)-velocity (cadence) profile and maximal dynamic force (MDF) during leg-pedaling using a friction-loaded isoinertial cycle ergometer and a high-precision power-meter device. Fifty-two trained male cyclists completed a progressive loading test up to the one-repetition maximum (1RM) on a cycle ergometer. The MDF was defined as the force attained at the cycle performed with the 1RM-load. To examine the test-retest reliability and long-term stability of torque-cadence values, the progressive test was repeated after 72 h and also after 10 weeks of aerobic and strength training. The participants' MDF averaged 13.4 ± 1.3 N·kg-1, which was attained with an average pedal cadence of 21 ± 3 rpm. Participants' highest power output value was attained with a cadence of 110 ± 16 rpm (52 ± 5% MDF). The relationship between the MDF and cadence proved to be very strong (R2 = 0.978) and independent of the cyclists' MDF (p = 0.66). Cadence values derived from this relationship revealed a very high test-retest repeatability (mean SEM = 4 rpm, 3.3%) and long-term stability (SEM = 3 rpm, 2.3%); despite increases in the MDF following the 10-week period. Our findings support the validity, reliability and long-term stability of this method for the assessment of the torque-cadence profile and MDF in cyclists.

Repeatability of quantitative T1rho magnetic resonance imaging in normal brain tissues at 3.0T

PurposeT1rho imaging is a promising MRI technique for imaging of brain disease. This study aimed to assess the repeatability of quantitative T1rho imaging in the normal brain grey and white matter. MethodsThe study prospectively recruited 30 healthy volunteers without a history of neurological diseases or brain injury, and T1rho was performed and quantified from three imaging sessions. Repeat measures analysis of variance (ANOVA) and within-subject coefficients of variation (wCoV) was used to detect differences in T1rho values between the three scans. ResultsThe results showed low wCoVs of less than 4.3% (range 0.92–4.27%) across all the brain structures. No significant differences were observed in T1rho measurement between the three scans (p > 0.05). The amygdala and hippocampus showed the highest T1rho values of 91.79 ± 2.55 msec and 91.07 ± 2.11 msec respectively, and the palladium and putamen had the lowest values of 67.60 ± 1.84 msec and 71.83 ± 1.85 msec respectively. ConclusionT1rho shows high test–retest repeatability for whole brain imaging in serial imaging sessions, indicating it to be a reliable sequence for quantitative brain imaging.

A fast algorithm for the measurement of stimulus-frequency otoacoustic emission suppression tuning curves based on multi-level swept suppressor tones

Algorithms for measuring stimulus-frequency otoacoustic emission (SFOAE) suppression tuning curves (STCs) typically use pure tones as suppressors, leading to procedures which are time-consuming and difficult to apply in clinical settings. A fast algorithm based on multi-level swept suppressor tones (MLSST) is proposed in this study. Taking advantage of the time-varying frequencies of swept tones, the suppression effects on SFOAE produced by swept suppressor tones are obtained within a single test. Further, a SFOAE STC may be extracted by interpolation from a set of suppression-effect functions at multiple suppressor levels. In the present study, SFOAE STCs were obtained in twenty-six normal-hearing subjects using the fast MLSST and the traditional pure-tone algorithms. SFOAE STCs were measured with high test–retest repeatability using the MLSST algorithm (average mean absolute errors of 2.12 dB) and were nearly consistent with the SFOAE STCs obtained by the pure-tone algorithm (average mean absolute errors of 3.13 dB). In addition, with>1.8 times frequency solution of the acquired curves, the measurement speed of our MLSST algorithm was approximately 2.14 times faster than the traditional one.

Cerebellar noninvasive neuromodulation influences the reactivity of the contralateral primary motor cortex and surrounding areas: a TMS-EMG-EEG study.

Understanding cerebellar-cortical physiological interactions is of fundamental importance to advance the efficacy of neurorehabilitation strategies for patients with cerebellar damage. Previous works have aimed to modulate this pathway by applying transcranial electrical or magnetic stimulation (TMS) over the cerebellum and probing the resulting changes in the primary motor cortex (M1) excitability with motor-evoked potentials (MEPs). While these protocols produce changes in cerebellar excitability, their ability to modulate MEPs has produced inconsistent results, mainly due to the MEP being a highly variable outcome measure that is susceptible to fluctuations in the excitability of M1 neurons and spinal interneurons. To overcome this limitation, we combined TMS with electroencephalography (EEG) to directly record TMS-evoked potentials (TEPs) and oscillations from the scalp. In three sessions, we applied intermittent theta-burst stimulation (iTBS), cathodal direct current stimulation (c-DC) or sham stimulation to modulate cerebellar activity. To assess the effects on M1 and nearby cortex, we recorded TMS-EEG and MEPs before, immediately after (T1) and 15min (T2) following cerebellar neuromodulation. We found that cerebellar iTBS immediately increased TMS-induced alpha oscillations and produced lasting facilitatory effects on TEPs, whereas c-DC immediately decreased TMS-induced alpha oscillations and reduced TEPs. We also found increased MEP following iTBS but not after c-DC. All of the TMS-EEG measures showed high test-retest repeatability. Overall, this work importantly shows that cerebellar neuromodulation influences both cortical and corticospinal physiological measures; however, they are more pronounced and detailed when utilizing TMS-EEG outcome measures. These findings highlight the advantage of using TMS-EEG over MEPs when assessing the effects of neuromodulation.

The Cambridge Colour Test: Reliability of discrimination trivectors in colour space

Background: The reliable assessment of colour discrimination has become increasingly important as some ophthalmic diseases and systemic conditions manifest themselves via acquired impairments of colour vision. The Cambridge Colour Test (CCT) is a computerised procedure, developed using the basic principles of traditional pseudoisochromatic plates to evaluate colour function or discrimination. Aim: The study investigated reliability of the CCT, with emphasis on the Trivector subtest, which measures thresholds along the three protan, deutan and tritan confusion lines to probe the sensitivity of the long, medium and short wavelength cones. Setting: The study used a prospective observational and quantitative design and took place in a research and clinical environment within the Department of Optometry at the University of Johannesburg, South Africa. Participants were 20 young adults of both genders aged 19–24 years with normal colour vision. Methods: Two measurements (test and retest) of the Trivector test were measured monocularly (right eye) for all participants to assess the reliability of repeated measurements. Reliability was assessed using coefficients of repeatability, coefficients of variation and Bland–Altman plots with limits of agreement (LoA). Results: Outcomes for the Bland–Altman LoA showed good intra-individual agreement and coefficients of repeatability and reliability revealed generally high test–retest repeatability. Multivariate stereo-pair scatter plot comparisons of means and differences of test and retest measurements show that points cluster tightly within the same region in the three-dimensional colour space, and the centroids of the ellipsoids representing the mean differences are close to the origin at zero. Conclusion: Although departure from normality and outlying values can have important influences, essentially the CCT provides very similar test and retest results for the Trivector test.

Sensor-to-body calibration procedure for clinical motion analysis of lower limb using magnetic and inertial measurement units

Magnetic and Inertial measurement units (MIMUs) have become exceedingly popular for ambulatory human motion analysis during the past two decades. However, measuring anatomically meaningful segment and joint kinematics requires virtual alignment of the MIMU frame with the anatomical frame of its corresponding segment. Therefore, this paper presents a simple calibration procedure, based on MIMU readouts, to align the inertial frame of the MIMU with the anatomical frames, as recommended by ISB. The proposed calibration includes five seconds of quiet standing in a neutral posture followed by ten consecutive hip flexions/extensions. This procedure will independently calibrate MIMUs attached to the pelvis, thigh, shank, and foot. The accuracy and repeatability of the calibration procedure and the 3D joint angle estimation were validated against the gold standard motion capture system by an experimental study with ten able-bodied participants. The procedure showed high test-retest repeatability in aligning the MIMU frame with its corresponding anatomical frame, i.e., the helical angle between the MIMU and anatomical frames did not significantly differ between the test and retest sessions (except for thigh MIMU). Compared to previously introduced procedures, this procedure attained the highest inter-participant repeatability (inter-participant coefficient of variations of the helical angle: 20.5–42.2%). Further, the proposed calibration would reduce the offset errors of the 3D joint angle estimation (up to 12.8 degrees on average) compared to joint angle estimation without calibration (up to 26.3 degrees on average). The proposed calibration enables MIMU to measure clinically meaningful gait kinematics.

Dance Functional Outcome Survey: Development and Preliminary Analyses.

The Dance Functional Outcome Survey (DFOS) was developed as a self-report questionnaire for healthy and injured ballet and modern dancers, focusing on the low back and lower extremities. Our aim was to determine factor analysis and internal consistency of the 16 items and to investigate test-retest and equivalence reliability and validity of the DFOS compared to three orthopedic outcomes instruments. Data were collected from 80 healthy and injured adult ballet and modern pre-professional and professional dancers. DFOS Likert-type and visual analog scales were completed twice within 4–9 days to study test-retest reliability. The Cincinnati Knee Rating System, Olerud and Molander Foot-Ankle Questionnaire, and Oswestry Disability Index were used to assess concurrent validity using intraclass correlation coefficients in SPSS, p<0.05. To determine instrument dimensions and internal consistency of the items, we conducted exploratory factor analysis and calculated Cronbach’s α in JASP. DFOS demonstrated single factor loading and high Cronbach’s α; high test-retest repeatability and equivalence reliability ( r =0.74–0.99) and acceptable criterion validity compared to the orthopedic outcomes instruments (r≥0.67). These results support further study of a revised 14 item Likert-version DFOS for repeatability, validity and responsiveness.

Cone photoreceptor macular function and recovery after photostress in early non-exudative age-related macular degeneration.

PurposeTo identify parameters from cone function and recovery after photostress that detect functional deficits in early non-exudative age-related macular degeneration (AMD) and to determine the repeatability of these parameters.MethodsCone-mediated visual function recovery after photostress was examined in three groups of subjects: young normal subjects (ages 20–29; N=8), older normal subjects (ages 50–90; N=9), and early non-exudative AMD subjects (ages 50–90; N=12). Eight AMD and four normal subjects were retested 1 year after the initial evaluation. Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity (VA) and parameters of cone function (baseline cone sensitivity and cone recovery half-life following photobleach) were measured and compared between AMD and normal subjects. Short-term repeatability was assessed for each subject’s initial evaluation. Long-term repeatability was assessed by comparing outcomes from the initial evaluation and 1-year follow-up.ResultsThe mean baseline cone threshold was significantly worse in subjects with early AMD compared to older normal subjects (−1.80±0.04 vs −1.57±0.06 log cd/m2 p=0.0027). Moreover, the baseline cone threshold parameter exhibited good short-term (intraclass correlation coefficient [ICC]=0.88) and long-term (ICC=0.85) repeatability in all subjects. The cone intercept parameter and ETDRS VA were not significantly different between AMD and older normal subject groups. Cone recovery half-life was significantly different between older normal and AMD subject groups (p=0.041). Neither ETDRS VA nor cone function parameters were significantly different for any group at the 1-year follow-up.ConclusionThe baseline cone threshold shows potential as a novel parameter to assess visual dysfunction in early AMD. This outcome consistently detected deficits in AMD subjects, and differentiated them from age-matched controls with high test–retest repeatability.

VISUAL FUNCTION MEASURES IN EARLY AND INTERMEDIATE AGE-RELATED MACULAR DEGENERATION.

The objectives of this study were to evaluate 1) the feasibility of performing computerized tests of low luminance visual acuity (LLVA), cone-specific contrast (Cone Contrast Test [CCT]), contrast sensitivity, and microperimetry and 2) the test-retest repeatability of these outcomes in dry age-related macular degeneration (AMD). This prospective study enrolled 30 subjects at a single site (8 controls, 8 early AMD, and 12 intermediate AMD). Subjects underwent LLVA, contrast sensitivity, CCT, and microperimetry with eye tracking. Low luminance deficit was defined as best-corrected visual acuity minus LLVA in EDTRS letters. Follow-up testing was administered at approximately 1 month. There was high test-retest repeatability at one month for all visual function metrics (intraclass correlations >0.7) except log contrast sensitivity (intraclass correlations 0.6). Compared with controls, patients with intermediate AMD showed significant deficits on best-corrected visual acuity, LLVA, low luminance deficit, percent-reduced threshold on microperimetry, and red CCT (P < 0.05), but not on contrast sensitivity, green and blue CCT. This pilot study supports the feasibility and reliability of using LLVA, microperimetry, and CCT in early dry AMD. Our data suggest these measures can be used as alternative future clinical trial endpoints. A larger, prospective natural history study of alternative visual function measures in dry AMD is warranted.

Validation of modified open field behaviour as a measure of trait anxiety in the dog

Trait anxiety may be a predisposing factor for anxiety-related behavioural problems in dogs. This study aimed to measure and quantify trait anxiety using novel behavioural paradigms. Diazepam is an anxiolytic drug which can be used to validate behavioural paradigms that are designed to measure anxiety. Greyhound dogs from a Canine Blood Bank were recruited. Dogs were individually tested in two behavioural paradigms, named the modified open field and the unconditioned substrate preference. The modified open field test consisted of a standard open field test of 10min duration, followed by six individual 10kHz 110dB 1-second tones played every 30s, interspersed with continuous white noise played at increasing intensity from 10dB up to 90dB. For one group of dogs, the test was repeated three times, with two weeks between each test. The greyhounds were pre-treated orally with either an empty gel capsule (sham) or 1mg/kg diazepam 90min before the third trial (n=39). A second group was treated 90min before a single naïve exposure to the test (n=24). Video recordings of the trials were analysed using software which tracked the position of the dog over time. Total distance travelled demonstrated a high test-retest repeatability within subjects (Spearman’s r=0.813, 95% CI: 0.67–0.90, P<0.001) and was increased on average in both test-naïve (167.6m, 95% CI: 54.8–280.4, P=0.005) and test-experienced (139.0m, 95% CI: 89.1–189.0, P<0.001) dogs that had been pre-treated with diazepam when compared with sham. A noise tone as a distance-increasing signal over time had a reduced effect on mean midline distance following diazepam pre-treatment when compared with sham in the test-naïve (−0.79, 95% CI: −1.6 to 0.0, P=0.047), but not to the same extent in the test-experienced (−0.47, 95% CI: −1.5 to 0.6, P=0.370) dogs. The unconditioned substrate preference test consisted of a room that had a concrete floor with half the flooring covered with plastic (a floor substrate unfamiliar to the greyhounds). There was little effect of diazepam pre-treatment on preference for the novel plastic floor substrate. This study suggests that the anxiolytic effect of diazepam on dog behaviour may be measured through an increase in exploratory behaviour and a reduction in noise aversion. Furthermore, exploratory behaviour and noise aversion may represent aspects of underlying trait anxiety as these behaviours have reliable test-retest repeatability.

Repeatability, agreement, and feasibility of using the threshold equalizing noise test and fast psychophysical tuning curves in a clinical setting

Objective: To investigate repeatability, agreement, and clinical feasibility of the threshold equalizing noise (TEN) test and fast psychophysical tuning curve (PTC) measurements to detect off-frequency listening, an indicator of cochlear dead regions (DRs). Design: The TEN-test was carried out from 0.5 to 4 kHz and fast PTCs were carried out at ≥ 2 frequencies. Study sample: The TEN-test was completed on 70 ears; fast PTCs were measured on 20 ears. Results: TEN-test findings were repeatable in terms of meeting the criteria for a DR (97%) and identifying the same edge frequency (fe) (87%). In all cases, fast PTCs were repeatable in terms of meeting the criteria for DRs. There was 87% agreement between the two procedures in terms of the presence of off-frequency listening, and there was 73% agreement in terms of fe. Fast PTCs had a 10% lower ‘conclusive finding’ rate than the TEN-test and the test duration was typically 40 minutes longer. Conclusions: Both the TEN-test and fast PTCs have high test-retest repeatability. The TEN-test is more clinically feasible due to its shorter test duration and higher interpretation rate, but it may underestimate the extent of a DR because of its inability to precisely identify fe.

Measuring the characteristic topography of brain stiffness with magnetic resonance elastography.

PurposeTo develop a reliable magnetic resonance elastography (MRE)-based method for measuring regional brain stiffness.MethodsFirst, simulation studies were used to demonstrate how stiffness measurements can be biased by changes in brain morphometry, such as those due to atrophy. Adaptive postprocessing methods were created that significantly reduce the spatial extent of edge artifacts and eliminate atrophy-related bias. Second, a pipeline for regional brain stiffness measurement was developed and evaluated for test-retest reliability in 10 healthy control subjects. ResultsThis technique indicates high test-retest repeatability with a typical coefficient of variation of less than 1% for global brain stiffness and less than 2% for the lobes of the brain and the cerebellum. Furthermore, this study reveals that the brain possesses a characteristic topography of mechanical properties, and also that lobar stiffness measurements tend to correlate with one another within an individual.ConclusionThe methods presented in this work are resistant to noise- and edge-related biases that are common in the field of brain MRE, demonstrate high test-retest reliability, and provide independent regional stiffness measurements. This pipeline will allow future investigations to measure changes to the brain’s mechanical properties and how they relate to the characteristic topographies that are typical of many neurologic diseases.

Postural Control Measured by Visual Feedback Posturography

The objective was to study the applicability and repeatability of visual feedback posturography (VFP) in assessing postural control of 23 healthy subjects. The subjects had to move their center of gravity (COG) marker on a computer screen to chosen targets by leaning their body on the platform, and the accuracy, velocity, and side difference of these movements were measured. The intraclass correlation coefficients for all parameters during repeated tests were significant (r = 0.93–0.96; p < 0.01). Hold percentage within the targets and COG marker velocity to the targets did not change significantly during repeated tests. Balance index and hit delay were significantly smaller during the 4th and 5th than during the 1st test session (p < 0.05), but they did not change significantly between the other test sessions. The normative limit for side difference in postural control was 22%. VFP can be used to follow active postural control due to its high test-retest repeatability. However, learning effects in some parameters must be taken into account when applying VFP repeatedly in different patient populations to assess the progress in postural control.

Lateral reach: a clinical measure of medio-lateral postural stability.

Medio-lateral postural instability has recently been identified as a risk factor for falls in the elderly community-dwelling population. However, few clinical tests involve challenges to stability limits in the medio-lateral direction. A lateral reach test was thus developed. Preliminary evaluation of the symmetry, accuracy, test-retest repeatability, and construct validity of the lateral reach test was undertaken to ensure its validity and repeatability prior to clinical application. Sixty healthy older female subjects (aged 72.5 +/- 5 years) participated in this study which involved two tasks. The first was the clinical test: a maximal lateral reach to the right and left, recorded by a clinical measure (observation of hand excursion) and a laboratory measure (3D analysis of hand marker excursion). The second was the recording of centre of pressure (COP) stability limits in the lateral direction by use of a dual force platform system. Eighteen subjects returned for repeatability testing. No significant differences in the measures were found between the sides. Lateral reach as measured by the clinical measure was significantly (p < 0.05) correlated with both the laboratory measure of reach (r = 0.650) and with COP stability limits (r = 0.331). The clinical measure of reach was not significantly different (p > 0.01) from the laboratory measure. High test-retest repeatability (r > 0.94) was found for all measures. The clinical lateral reach test was found to be an accurate measure of lateral reach ability. As it was significantly correlated with COP excursion it was deemed a valid indicator of lateral stability limits. In addition, the lateral reach test had high test-retest repeatability and was symmetrical between the sides. These promising results support both it's use where a clinical indicator of medio-lateral postural stability is desired and further investigation of the lateral reach test in clinical populations.