Differences In Test-retest Reliability Research Articles

Sex Differences in Test-Retest Reliability of Near-Infrared Spectroscopy During Postocclusive Reactive Hyperemia of the Vastus Lateralis.

Shoemaker, ME, Smith, CM, Gillen, ZM, and Cramer, JT. Sex differences in test-retest reliability of near-infrared spectroscopy during postocclusive reactive hyperemia of the vastus lateralis. J Strength Cond Res 38(2): e40-e48, 2024-The purpose of this study was to determine test-retest reliability for vascular reactivity measures and ranges for normalization of near-infrared spectroscopy (NIRS) variables from the vastus lateralis using postocclusive reactive hyperemia (PORH) procedure in male subjects, female subjects, and combined. Concentrations of oxygenated hemoglobin (Hb) + myoglobin (Mb) (O 2 Hb) and deoxygenated Hb + Mb (HHb) to derive total Hb + Mb (THb), difference in Hb + Mb signal (Hbdiff), and muscle tissue oxygen saturation (StO 2 ) from the vastus lateralis were measured during the PORH in 12 male subjects (age: 23.17 ± 1.77 years; stature: 180.88 ± 4.59 cm; and mass: 81.47 ± 9.68 kg) and 10 female subjects (age: 23.80 ± 2.07 years; stature: 165.95 ± 4.92 cm; and mass: 70.93 ± 10.55 kg) on 2 separate days. Adipose tissue thickness at the NIRS site was measured with ultrasonography. There were no significant differences between the mean values from visit 1 to visit 2 ( p > 0.076-0.985). In the composite sample, intraclass correlation coefficient (ICC) and coefficient of variation (CV) ranged from 0.35 to 0.91 and 4.74 to 39.18%, respectively. In male subjects, ICC and CV values ranged from 0.57 to 0.89 and 2.44 to 28.55%, respectively. In female subjects, ICC and CV values ranged from -0.05 to 0.75 and 7.83 to 61.19%, respectively. Although NIRS variables were overall reliable during PORH, when separated by sex, reliability in male subjects generally increased, whereas female subjects were not reliable, suggesting adipose tissue thickness may be a contributing factor. Understanding sex differences in reliability is important when using this technique for normalization or examining vascular reactivity during athletic performance. With greater utilization of NIRS monitoring in athletes to examine training adaptations, it is important for practitioners to understand the capabilities and potential limitations of the tool.

Fractal-Based Analysis of fMRI BOLD Signal During Naturalistic Viewing Conditions

Background: Temporal fractals are characterized by prominent scale-invariance and self-similarity across time scales. Monofractal analysis quantifies this scaling behavior in a single parameter, the Hurst exponent (H). Higher H reflects greater correlation in the signal structure, which is taken as being more fractal. Previous fMRI studies have observed lower H during conventional tasks relative to resting state conditions, and shown that H is negatively correlated with task difficulty and novelty. To date, no study has investigated the fractal dynamics of BOLD signal during naturalistic conditions.Methods: We performed fractal analysis on Human Connectome Project 7T fMRI data (n = 72, 41 females, mean age 29.46 ± 3.76 years) to compare H across movie-watching and rest.Results: In contrast to previous work using conventional tasks, we found higher H values for movie relative to rest (mean difference = 0.014; p = 5.279 × 10−7; 95% CI [0.009, 0.019]). H was significantly higher in movie than rest in the visual, somatomotor and dorsal attention networks, but was significantly lower during movie in the frontoparietal and default networks. We found no cross-condition differences in test-retest reliability of H. Finally, we found that H of movie-derived stimulus properties (e.g., luminance changes) were fractal whereas H of head motion estimates were non-fractal.Conclusions: Overall, our findings suggest that movie-watching induces fractal signal dynamics. In line with recent work characterizing connectivity-based brain state dynamics during movie-watching, we speculate that these fractal dynamics reflect the configuring and reconfiguring of brain states that occurs during naturalistic processing, and are markedly different than dynamics observed during conventional tasks.

ADHEAR device in bone conduction audiometry.

ADHEAR is a bone conduction hearing aid that uses an adhesive skin adapter. In the current study, the use of ADHEAR as an audiometric bone stimulator was investigated in normal-hearing subjects by comparing it to the standard Radio-Ear B71. Bone conduction thresholds of 15 normal-hearing subjects (aged 21-36 years) were measured four times in a randomized order, twice with the B71 and twice with the ADHEAR. There were no significant differences in test-retest reliability between the two devices. Subjectively rated comfort was better for the ADHEAR. The development of a specific audiometric adhesive bone stimulator may be warranted.

Test-retest reliability of distortion-product thresholds compared to behavioral auditory thresholds

When referred to baseline measures, serial monitoring of pure-tone behavioral thresholds and distortion-product otoacoustic emissions (DPOAEs) can be used to detect the progression of cochlear damage. Semi-logarithmic DPOAE input-output (I/O) functions enable the computation of estimated distortion-product thresholds (EDPTs) by means of linear regression, a metric that provides a quantitative estimate of hearing loss due to cochlear-amplifier degradation. DPOAE wave interference and a suboptimal choice of stimulus levels limit the accuracy of EDPTs. This work identifies the test-retest reliability of EDPTs derived from short-pulse DPOAE level maps (EDPTLM), a method that circumvents limitations associated with both wave interference and suboptimal choice of stimulus levels. The test-retest reliability was compared to that of EDPTs derived from semi-logarithmic I/O functions (EDPTI/O) and that of behavioral thresholds acquired with pure-tone audiometry (PTA) and modified Békésy tracking audiometry (TA) to provide a foundation for identifying and interpreting significant threshold shifts.The DPOAE-based auditory thresholds (EDPTLM and EDPTI/O) and behavioral thresholds (PTA and TA) were recorded seven times within three months at 14 frequencies with f2 = 1–14 kHz in 20 ears from ten subjects with normal hearing (4PTA0.5–4kHz < 20 dB HL). To obtain EDPTLM, short-pulse DPOAEs were recorded using 21 L1,L2 pairs. Reconstruction of DPOAE growth behavior as a function of L1 and L2 using nonlinear curve fitting enabled the derivation of EDPTLM for each frequency.Test-retest reliability was determined using three different approaches: 1) centered thresholds, 2) average threshold differences, and 3) average absolute threshold differences, between each possible test session (N = 21). Test-retest reliability based on centered thresholds and average threshold differences showed no statistically significant difference between EDPTLM, EDPTI/O, PTA, and TA for the pooled analysis incorporating all stimulus frequencies. Average absolute threshold differences presented small but significant differences in test-retest reliability with median values of 3.00 dB for PTA, 3.20 dB for TA, 3.34 dB for EDPTLM, and 3.51 dB for EDPTI/O. A considerable frequency dependence of test-retest reliability was found; namely, the highest test-retest reliability was for EDPTLM at f2 = 11 – 14 kHz. Otherwise, at lower frequencies, the highest test-retest reliability was for TA at f2 =1 – 2 kHz.Overall, the test-retest reliability of EDPTLM was better than that of EDPTI/O and was similar to that for behavioral thresholds. Hence, deriving EDPTLM from individual level maps is a promising and sensitive method for objectively monitoring the state of the cochlea. Furthermore, the detection of an equidirectional threshold change at a single frequency in both EDPTLM and TA might allow reducing the threshold shift as indication of a follow-up examination from the clinical standard of 10 dB down to 5 dB. This stricter indicator might be beneficial when monitoring cochlear damage, for example ototoxicity, in the presence of (remnant) cochlear amplification at baseline.

Translation, cross-cultural adaptation and validation of the Pulmonary Rehabilitation Adapted Index of Self-efficacy (PRAISE) scale for Brazilian patients with chronic obstructive pulmonary disease

Background: Patients with Chronic Obstructive Pulmonary Disease (COPD) present a progressive chronic airflow obstruction. Pulmonary Rehabilitation (PR) promotes the reversal of the extrapulmonary effects of the disease and improves the quality of life. Despite the physiological benefits, the major challenge of PR is to promote change in lifestyle. In this sense, it has been emphasized the study of psychological variables such as self-efficacy. Aim: To translate, cross-culturally adapt and validate the PRAISE scale for Brazilian COPD patients. Methods: The PRAISE scale was applied on the first day by two raters and 15-20 days later by one rater. Patients were assessed for self-efficacy with the General Self-Efficacy Scale (GSS) and the COPD Self-Efficacy Scale (CSES); functional limitation for activities of daily living with the London Chest Activity of Daily Living (LCADL) scale; anxiety and depression symptoms with the Hospital Anxiety and Depression Scale (HADS); quality of life with Saint George’s Respiratory Questionnaire (SGRQ); resilience with the Resilience Scale; and basic psychological needs with the Basic Psychological Needs in Exercise Scale (BPNES). The tests used were: Student’s t-test or Wilcoxon’s test (PRAISE score comparison); intraclass correlation coefficient (ICC), interrater reliability and test-retest and Cronbach’s alpha; and Spearman’s or Pearson’s correlation coefficient to assess validity. Results: The scale was pre-tested in 10 patients to evaluate translation accuracy and cross-cultural adaptation. Thirty-four patients with COPD took part (22 men; FEV1=42.2±15.7%pred). The interrater and test-retest ICCs were excellent (0.82 and 0.86, respectively), with no significant differences in test-retest reliability (p>0.05). Cronbach’s alpha interrater and testretest were 0.90 and 0.92, respectively (p<0.001). There were no floor and ceiling effects. The scale showed weak to moderate correlations with GSS, CSES, LCADL, HADS, SGRQ, Resilience Scale, and BPNES. Conclusions: The PRAISE scale proved to be valid and reliable for Brazilian patients with COPD.

Test-retest reliability and predictive validity of the Implicit Association Test in children.

The Implicit Association Test (IAT) is increasingly used in developmental research despite minimal evidence of whether children's IAT scores are reliable across time or predictive of behavior. When test-retest reliability and predictive validity have been assessed, the results have been mixed, and because these studies have differed on many factors simultaneously (lag-time between testing administrations, domain, etc.), it is difficult to discern what factors may explain variability in existing test-retest reliability and predictive validity estimates. Across five studies (total N = 519; ages 6- to 11-years-old), we manipulated two factors that have varied in previous developmental research-lag-time and domain. An internal meta-analysis of these studies revealed that, across three different methods of analyzing the data, mean test-retest (rs of .48, .38, and .34) and predictive validity (rs of .46, .20, and .10) effect sizes were significantly greater than zero. While lag-time did not moderate the magnitude of test-retest coefficients, whether we observed domain differences in test-retest reliability and predictive validity estimates was contingent on other factors, such as how we scored the IAT or whether we included estimates from a unique sample (i.e., a sample containing gender typical and gender diverse children). Recommendations are made for developmental researchers that utilize the IAT in their research. (PsycINFO Database Record

Age-related differences in Fukuda stepping and Babinski-Weil tests, within-day variability and test-retest reliability.

The Fukuda stepping and Babinski-Weil tests are associated with unperceived body rotation and linear displacements in young adults, but performance in older adults on these two tests has yet to be determined. The main purpose was to compare the performance and reliability of the Fukuda stepping and Babinski-Weil tests in young and older adults. Fifty older and 50 young adults executed three trials of each test on day 1 (test) and day 2 (retest). Lateral and longitudinal displacements and body rotation relative to the starting position were measured. Means and standard deviations (SD) were compared between the two groups with Mann-Whitney tests. Test-retest reliability was assessed with intra-class correlation coefficients (ICC). Foot preference was determined from the score on the Waterloo Footedness Questionnaire and correlated with test scores. Lateral and longitudinal displacements were significantly larger in older than young participants on the Fukuda stepping test (p<.01) and significantly smaller on the Babinski-Weil test (p<.001). Older participants displayed a significantly smaller SD on the three Babinski-Weil test trials (p<.001). Displacement and rotation measures ICC ranged between 0.25 and 0.77 in older and between 0.58 and 0.80 in young participants. Foot preference correlated with rotation on the Fukuda stepping test in young (p<.05), but not in older participants (p>.05). Linear displacements, but not body rotation, were different between older and young adults. There was no clear age-related differences in test-retest reliability, but the moderate reliability indicates that performance can vary from day to day in both age groups.

Gap detection measured with electrically evoked auditory event-related potentials and speech-perception abilities in children with auditory neuropathy spectrum disorder.

This study aimed (1) to investigate the feasibility of recording the electrically evoked auditory event-related potential (eERP), including the onset P1-N1-P2 complex and the electrically evoked auditory change complex (EACC) in response to temporal gaps, in children with auditory neuropathy spectrum disorder (ANSD); and (2) to evaluate the relationship between these measures and speech-perception abilities in these subjects. Fifteen ANSD children who are Cochlear Nucleus device users participated in this study. For each subject, the speech-processor microphone was bypassed and the eERPs were elicited by direct stimulation of one mid-array electrode (electrode 12). The stimulus was a train of biphasic current pulses 800 msec in duration. Two basic stimulation conditions were used to elicit the eERP. In the no-gap condition, the entire pulse train was delivered uninterrupted to electrode 12, and the onset P1-N1-P2 complex was measured relative to the stimulus onset. In the gapped condition, the stimulus consisted of two pulse train bursts, each being 400 msec in duration, presented sequentially on the same electrode and separated by one of five gaps (i.e., 5, 10, 20, 50, and 100 msec). Open-set speech-perception ability of these subjects with ANSD was assessed using the phonetically balanced kindergarten (PBK) word lists presented at 60 dB SPL, using monitored live voice in a sound booth. The eERPs were recorded from all subjects with ANSD who participated in this study. There were no significant differences in test-retest reliability, root mean square amplitude or P1 latency for the onset P1-N1-P2 complex between subjects with good (>70% correct on PBK words) and poorer speech-perception performance. In general, the EACC showed less mature morphological characteristics than the onset P1-N1-P2 response recorded from the same subject. There was a robust correlation between the PBK word scores and the EACC thresholds for gap detection. Subjects with poorer speech-perception performance showed larger EACC thresholds in this study. These results demonstrate the feasibility of recording eERPs from implanted children with ANSD, using direct electrical stimulation. Temporal-processing deficits, as demonstrated by large EACC thresholds for gap detection, might account in part for the poor speech-perception performances observed in a subgroup of implanted subjects with ANSD. This finding suggests that the EACC elicited by changes in temporal continuity (i.e., gap) holds promise as a predictor of speech-perception ability among implanted children with ANSD.

Age-related differences in test-retest reliability in resting-state brain functional connectivity.

Resting-state functional MRI (rs-fMRI) has emerged as a powerful tool for investigating brain functional connectivity (FC). Research in recent years has focused on assessing the reliability of FC across younger subjects within and between scan-sessions. Test-retest reliability in resting-state functional connectivity (RSFC) has not yet been examined in older adults. In this study, we investigated age-related differences in reliability and stability of RSFC across scans. In addition, we examined how global signal regression (GSR) affects RSFC reliability and stability. Three separate resting-state scans from 29 younger adults (18–35 yrs) and 26 older adults (55–85 yrs) were obtained from the International Consortium for Brain Mapping (ICBM) dataset made publically available as part of the 1000 Functional Connectomes project www.nitrc.org/projects/fcon_1000. 92 regions of interest (ROIs) with 5 cubic mm radius, derived from the default, cingulo-opercular, fronto-parietal and sensorimotor networks, were previously defined based on a recent study. Mean time series were extracted from each of the 92 ROIs from each scan and three matrices of z-transformed correlation coefficients were created for each subject, which were then used for evaluation of multi-scan reliability and stability. The young group showed higher reliability of RSFC than the old group with GSR (p-value = 0.028) and without GSR (p-value <0.001). Both groups showed a high degree of multi-scan stability of RSFC and no significant differences were found between groups. By comparing the test-retest reliability of RSFC with and without GSR across scans, we found significantly higher proportion of reliable connections in both groups without GSR, but decreased stability. Our results suggest that aging is associated with reduced reliability of RSFC which itself is highly stable within-subject across scans for both groups, and that GSR reduces the overall reliability but increases the stability in both age groups and could potentially alter group differences of RSFC.

Hand-held dynamometry: tester strength is paramount, even in frail populations

To determine test-retest and inter-rater reliability of hand-held dynamometry when used to measure knee--extensor strength in patients with advanced cancer. Adults with metastatic or locally advanced cancer recruited from palliative care services to a study of the risk factors for falls. Consecutive recruits (n = 30) underwent repeat testing after an interval of 1 h, by the same researcher, to assess test-retest reliability. The subsequent 15 patients underwent retesting by a second researcher. The intra-class correlation coefficient and limits of agreement were calculated. The test-retest reliability difference between measurements increased with the magnitude of measurement, mean leg strength = 113 N (standard deviation 43.1), 95% ratio limits of agreement 0.81-1.5, intra-class correlation coefficient = 0.9. The inter-rater testing mean leg strength = 128.5 N (standard deviation 35.1), 95% limits of agreement = -57.24 to 36.06 N. Intra-class correlation coefficient = 0.83. Test-retesting and inter-rater testing yielded high intra-class correlation coefficients, but the limits of agreement were wide. In test-retesting, the difference between tests increased as the magnitude of measurement increased. It has been widely reported that hand-held dynamometry is reliable when used to measure knee-extensor strength in frail or elderly persons. However, our results show that, even in these populations, reliability may be compromised by inadequate tester strength.

Nuisance Signal in Resting-State fMRI Study

AbstractWe systematically presented various nuisance signals in resting-state fMRI (R-fMRI) dataset. First, we examined the impact of different extraction methods on the default-mode pattern seeded by posterior cingulate cortex (PCC). Second, we compared their differences in test-retest reliability. Finally, we speculated the equivalence of removing global mean signal to removing gray matter mean signal.

Nuisance Signal in Resting-State fMRI Study

We systematically presented various nuisance signals in resting-state fMRI (R-fMRI) dataset. First, we examined the impact of different extraction methods on the default-mode pattern seeded by posterior cingulate cortex (PCC). Second, we compared their differences in test-retest reliability. Finally, we speculated the equivalence of removing global mean signal to removing gray matter mean signal.

Reliability of health-related quality-of-life indicators in cancer survivors from a population-based sample, 2005, BRFSS

The current emphasis in cancer survivorship research, which includes health-related quality of life (HRQoL), drives the need to monitor the nation's cancer burden. Routine, ongoing public health surveillance tools, such as the Behavioral Risk Factor Surveillance System (BRFSS), may be relevant for this purpose. A subsample of the 2005 Missouri BRFSS was used to estimate test-retest reliability of HRQoL questions among persons who did and did not report a personal cancer history. Retest interviews were conducted by telephone 14-21 days after the initial data collection (n=540, 67% response rate). Reliability was estimated overall and by cancer history using intraclass correlation coefficients (ICCs) and kappa statistics. The majority of retest respondents were White, female and married, with 13% reporting a history of cancer. Overall, point estimates of the reliability coefficients ranged from moderate to excellent (kappa=0.57-0.75). There were no statistically significant differences in test-retest reliability between persons with and without a history of cancer, except for self-reported pain (ICC=0.59 and ICC=0.78, respectively). In general, BRFSS questions appear to have adequate reliability for monitoring HRQoL in this community-dwelling population, regardless of cancer history.

Neuropsychological testing of high school athletes Preliminary norms and test-retest indices

This study provides preliminary norms and test-retest indices on a brief battery of neuropsychological tests administered to a sample of 60 male and 40 female high school athletes. Forty-eight subjects completed retesting 8 weeks later. Analyses of baseline scores indicate that girls outperform boys on selected measures of processing speed and executive functions [Wechsler Adult Intelligence Scale-III (WAIS-III) Digit Symbol, Trails B, and Controlled Oral Word Association Test (COWAT)]. Test-retest reliability was low and varied widely among the tests. There were no gender differences in test-retest reliability. Reliable Change Indices (RCIs) were computed on the test-retest data for use in clinical interpretation. These preliminary results indicate that caution should be used in interpreting neuropsychological test data from high school athletes. The current findings indicate that separate norms for boys and girls are warranted. Caution should be used in interpreting discrepancies from baseline scores as a result of what may turn out to be poor test-retest reliability in this population.

Factors Affecting Reliability of the Biodex Balance System: A Summary of Four Studies

Purpose:To describe differences in test-retest reliability of balance measures produced by the Biodex Balance System.Methods:Subjects performed balance tests in 4 studies, each involving two 30-second tests under varying conditions. Test-retest reliability coefficients were calculated for the overall stability index (SI) under each condition. Test-retest reliability was computed for subjects' limits of stability (LOS).Results:Intraclass correlation coefficients (ICC3,1) ranged from .44 to .89 for static balance tests; variability between the 2 tests ranged from 21% to 37%. Tests at lower stability levels or without visual input produced the highest ICCs. ICCs for the LOS tests ranged from .64 to .89. These measures were less variable (6% to 8%) than the static measures of balance.Conclusions:Test-retest reliability of the SI produced by the Biodex Balance System is acceptable for clinical testing and is comparable to other balance measures currently in use.

Design and reliability of pediatric HealthQuiz: preliminary report of a comprehensive, computerized, self-administered child health assessment.

The time available for pediatric ambulatory visits is rarely sufficient to permit a truly comprehensive health assessment. We hypothesized that a reliable, computerized, self-administered questionnaire could be designed to screen for a full range of pediatric health issues and provide a comprehensive health database for pediatric patients. An age- and gender-specific pediatric questionnaire of 478 questions was formatted to elicit only a "Yes," "No," or "Not Sure" response and structured in a branched, decision-tree format. The initial draft was reviewed for content by pediatric experts in Canada and the United States and revised in accordance with their suggestions. The questionnaire was divided into two modules, Medical Peds, covering biomedical issues and Prevent Peds, covering prevention, psychosocial, educational, and safety topics. Cognitive interviews were carried out with 132 parents in pediatric ambulatory care centers in Chicago and Halifax, with use of scripted and nonscripted probe questions, to ensure comprehensibility among patients with widely varying educational levels and health knowledge. Reliability was tested in 100 parents of children aged 1 month to 12 years, through use of five different test-retest sequences. Respondents' impressions were surveyed on completion of the procedure. Following content reviews, and cognitive and reliability testing, the total bank of questions was reduced to 375. As a result of the use of branching logic, individual parents answered an average of 111 Prevent Peds and 144 Medical Peds questions. Average time required to complete the entire questionnaire was 13 minutes for Prevent Peds and 19 minutes for Med Peds. Retesting within 36 hours showed an overall 97% concordance of response pairs in the Medical Peds and Prevent Peds questionnaires. There were no statistically significant differences in test-retest reliability between different sequence formats used, (e.g., HealthQuiz followed by personal interview, or HealthQuiz vs. HealthQuiz). A few questions that frequently elicited "Not Sure" responses were eliminated. As a result, the majority of questions elicited either a "Yes" or "No" response. Pediatric HealthQuiz identified a wide spectrum of child health problems that are often overlooked in routine health visits. Parents completing Pediatric HealthQuiz indicated a high degree of satisfaction with the procedure. Most reported that they believed the information would improve their child's health care.

Effect of instructions to simulate a back injury on torque reproducibility in an isometric lumbar extension task

The purpose of this study was to investigate the differences in test-retest reliability between maximal and "simulated back injury" efforts in an isometric lumbar extension task and to test the hypothesis that voluntary attempts to "simulate" a back injury would yield less consistent torque production than maximal efforts. Twenty subjects were asked to undergo lumbar extensor testing at seven different positions in a lumbar extension machine. Each subject was tested twice in a maximal effort condition and twice with instructions to "simulate" a back injury. The order of the conditions was counterbalanced across subjects so that half of the subjects performed the maximal effort tests first and half performed the "simulated" effort first. Results indicated high test-retest correlations at all angles in both conditions. There were no differences in test-retest reliability between effort conditions. Therapist ratings of consistency did not differ between conditions and therapists could not discriminate between conditions on the basis of effort consistency. In the "simulated" condition subjects produced reliable, submaximal torque plots consistent with previous data indicating similar reliability at submaximal levels. It was concluded that use of test-retest torque consistency as a measure of sincerity of effort is premature and may be misleading.

Reproducibility of Maximal Versus Submaximal Efforts in an Isometric Lumbar Extension Task

The purpose of this study was to investigate the differences in test-retest reliability between maximal and submaximal efforts in an isometric lumbar extension task and to test the hypothesis that submaximal efforts would be less consistent than maximal efforts. Twenty subjects were asked to produce maximum voluntary contractions at seven different positions in a lumbar extension machine. Each subject was tested twice in a maximal-effort condition and twice in a 50% effort condition. The order of the effort conditions was counterbalanced across subjects so that half of the subjects performed the maximal-effort tests first and half performed the submaximal effort first. Results indicated high test-retest correlations at all angles in both conditions. There were no differences in test-retest reliability between effort conditions. Therapist ratings of consistency did not differ between conditions, and therapists could not discriminate between conditions on the basis of effort consistency. Because subjects could reliably reproduce a submaximal effort, it was concluded that consistency interpretations of isometric strength testing may be misleading.

Heart rate and heart rate variability recorded in vivo in agoraphobics and nonphobics

Recent advances in technology have made it possible to monitor changes in physiological responses of phobics and other clinical subjects as they encounter real-life, emotion-inducing, situations. In order to assess the characteristics of heart rate as a measure of anxiety in agoraphobia, 10 agoraphobics and 10 matched yoked controls were each given seven repeated in vivo behavioral assessments during which heart rate was monitored. The behavioral test consisted of walking a specified course away from the clinic toward a downtown area. Agoraphobic subjects were given three repeated assessments from 1 to 9 days apart both immediately before and after receiving 12 weeks of exposure-based behavioral treatment for a total of 6 assessments. An additional assessment was administered at the midpoint of therapy. Yoked controls were assessed at identical times but, of course, did not receive treatment. Resting and walking baselines were also administered both before and after the behavioral test. Agoraphobics as a group had significantly higher heart rates than nonphobics both during the test as well as during baselines. In addition, agoraphobics displayed greater lability in heart rate during the walk. However, heart rate in both the treated group and the control group decreased significantly over sessions and there was no significant Group × Session interaction. There were no differences in test-retest reliability in heart rate between groups. For both groups, reliability was quite low. These data illustrate basic differences in physiological responding between agoraphobics and nonphobics but raise questions about the usefulness of physiological assessment as a measure of clinical change in the anxiety disorders.