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PubMed1996

Reliability of transient-evoked otoacoustic emissions.

OBJECTIVE: This investigation addressed four factors affecting transient-evoked otoacoustic emission (TEOAE) reliability: 1) The effect of evoking-stimulus level, 2) the effect of analyzing bandwidth, 3) the effect of slight-mild hearing loss, and 4) the effect of variability in the stimulus spectrum. DESIGN: TEOAEs at 80, 74, 68, and 62 dB pSPL evoking-stimulus levels were measured in 25 ears spanning a range of hearing levels from normal to mild hearing loss for a minimum of 10 test sessions. Reliability was assessed for 1/6-, 1/3-, 1/2-, and 1-octave analyzing bandwidths. RESULTS: Evoking-stimulus level, hearing loss, and center frequency did not significantly affect reliability. With decreasing analyzing bandwidth, reliability decreased. Intrasubject test-retest standard deviations were 1.2 dB for a broadband analyzing bandwidth and 1.4, 1.5, 1.6, and 1.8 dB for 1-, 1/2-, 1/3-, and 1/6-octave analyzing bandwidths, respectively. Stimulus variability within narrower bandwidths was of sufficient magnitude to influence test-retest reliability, and attempts to correct for the variations in stimulus spectrum were unsuccessful. Slopes of the input-output functions differed across frequencies, with shallower slopes at higher frequencies. CONCLUSIONS: In general, TEOAE amplitude is highly reliable. For those individuals in this study who were more variable, the variability was at low frequencies or across the entire frequency spectrum. For clinical applications, the choice of analyzing bandwidth should be based on consideration of both frequency specificity (where narrow analyzing bandwidths are optimal) and reliability (where wide analyzing bandwidths are optimal).

Acoustic Impedance Tests↗
PubMed1998

Strategies to manipulate reliability: impact on statistical associations.

OBJECTIVE: To examine the effects of improving measurement reliability on associations between risk factors and childhood psychiatric disorder. METHOD: Data were from a general population sample of parents (N = 211) with children aged 6 to 16 years. Reliability of measurement was improved in three ways: by increasing the number of items in a scale (internal-consistency reliability), by averaging assessments of the same variables collected on two different occasions, and by constructing latent variable measures. To assess the effects of improving reliability, selected risk factors were regressed on parental assessments of childhood oppositional defiant disorder (ODD) and overanxious disorder (OAD). RESULTS: Improving reliability led to systematic increases in the magnitude of standardized regression coefficients between family dysfunction and ODD (beta = .30-.51) and between family dysfunction and OAD (beta = .24-.48). In multiple regression, improving reliability served to strengthen the specificity of associations between ODD, OAD, and family dysfunction and maternal depressed mood. Although latent variable methods produced the largest associations, the standard errors of these estimates were also larger, resulting in wider confidence intervals and slightly larger significance values. CONCLUSIONS: Improving reliability of measurement results in larger associations between risk factors and childhood disorder and may increase the opportunity of revealing differential associations between variables.

Adolescent↗
PubMedDate not supplied

Patient rating of wrist pain and disability: a reliable and valid measurement tool.

OBJECTIVE: The goal of this study was to develop a reliable and valid tool for quantifying patient-rated wrist pain and disability. DESIGN: Survey, tool development, reliability, and validity study. SETTING: Upper extremity unit. PARTICIPANTS: One hundred members of the International Wrist Investigators were surveyed by mail to assist in development of the scale. Patients with distal radius (n = 64) or scaphoid (n = 35) fractures were enrolled in a reliability study, and 101 patients with distal radius fractures were enrolled in a validity study. INTERVENTION: Information from the expert survey, biomechanical literature, and patient interviews was used as a basis for item generation and definition of structural limitations for a scale that would be practical in the clinic. Patients with distal radius or scaphoid fractures completed the Patient-Rated Wrist Evaluation (PRWE) on two occasions to determine test-retest reliability. Patients with distal radius fractures (n = 101) completed the PRWE and the SF-36 and were tested with traditional impairment measures at baseline and at two, three, and six months after fracture to determine construct and criterion validity. MAIN OUTCOME MEASURES: Reliability coefficients (ICCs) and validity correlations (Pearson product moment correlations). RESULTS: Patient opinions on pain and on ability to do activities of daily living and work were thought to be the most important dimensions to include in subjective outcome tools. Brevity and simplicity were seen as essential in the clinic environment. A fifteen-item questionnaire (the PRWE) was designed to measure wrist pain and disability. Test-retest reliability was excellent (ICCs > 0.90). Validity assessment demonstrated that the instrument detected significant differences over time (p < 0.01) and was appropriately correlated with alternate forms of assessing parameters of pain and disability. CONCLUSIONS: The PRWE provides a brief, reliable, and valid measure of patient-rated pain and disability.

Activities of Daily Living↗
PubMed2000

Radiographic fracture assessments: which ones can we reliably make?

OBJECTIVE: To identify the fracture characteristics that can be reliably assessed by analysis of plain radiographs of tibial plateau fractures. DESIGN: Radiographic review study. PARTICIPANTS: Five orthopaedic traumatologists served as observers. INTERVENTION: Observers made assessments based on the radiographs of fifty-six tibial plateau fractures. Precise definitions of the assessments to be made were agreed on by all observers. The tested assessments included raters' abilities to identify and locate fracture lines, identify the presence of fracture displacement and comminution, make quantitative measurements of displacement, and characterize qualitative features of fractures. For thirty-eight of the fractures that had a computed tomography (CT) scan available, assessments were repeated using both radiographs and CT scans. MAIN OUTCOME MEASURES: To characterize interobserver reliability, percentage agreement and kappa statistics were calculated for categorical variables, and intraclass correlation coefficients (ICC) were calculated for noncategorical variables. RESULTS: Reliability of the assessments varied widely. Determining the location of fracture lines had the greatest reliability, whereas the subjective assessments of fracture stability and energy showed the poorest reliability. Although the ICCs for quantitative measurements approached acceptable levels, the tolerance limits were extremely wide. The addition of a CT scan improved the reliability of most assessments, but not to a statistically significant degree. CONCLUSIONS: Many basic radiographic interpretations relied on in making treatment decisions are made variably by observers. Using experienced raters and precise definitions of fracture assessments does not guarantee a high level of agreement. Discrete assessments have higher interrater agreements than do more qualitative assessments. Quantitative measures have wide tolerance limits and, therefore, probably cannot be used reproducibly to classify fractures or make treatment decisions. We conclude the reliability of fracture classification is limited by raters' abilities to agree on basic radiographic assessments.

Humans↗
PubMed1997

Reliability of variables in the kinematic analysis of spring hurdles.

The purpose of this study was to investigate the reliability of kinematic variables in spring hurdles and to find out how many trials are needed to achieve reliable data. Seven British National level athletes in sprint hurdles were videotaped and all eight trials of each athlete were digitized from two camera views to produce three dimensional coordinates. The reliability of 28 kinematic variables across eight trials ranged from 0.54 to 1.00 for females and from 0.00 to 0.99 for males. The number of trials needed to reach a certain reliability level was evaluated using Spearman-Brown prophecy formula, and in the worst case (horizontal velocity lost for males) 78 trials would be needed to reach 0.90 reliability. The results showed reasonably high reliability, and the values for the female trials were generally higher than the male trials. The relative height of the hurdles enforces a more demanding clearance for males that can lead to increased variation within the subjects and thus lowered reliability. Subsequently, the results indicate that often more than one trial is needed to provide accurate quantitative results of the technique.

Adult↗
PubMed1998

A study of the reliability of the Canada Fitness Survey questionnaire.

PURPOSE: The purposes of this study are to assess the reliability of the physical activity components of the Canada Fitness Survey (CFS) questionnaire (N = 64 males, N = 63 females) and the Canadian Aerobic Fitness Test (N = 44 males, N = 52 females) in a sample of subjects between 15 and 80 yr. RESULTS: The intraclass correlation (rI) for the fitness scores was 0.98. The activity variables showed low to moderate correlations (rI = 0.48-0.53). Correlations were higher for males (rI = 0.38-0.65) than females (rI = 0.28-0.60) for most of the activity variables reported. Males generally report leisure activity more reliably than nonleisure activity, whereas the opposite was true for females. Males reported strenuous activity with higher reliability (rI = 0.86) than females (rI = 0.31). There was considerable variation in the reliability of specific activities. Of the components of physical activity (time, intensity, duration) that comprise the energy expenditure (EE) variable, the least reliably reported is intensity for both males (rI = 0.43) and females (rI = 0.55). CONCLUSIONS: The CFS questionnaire is moderately reliable for most measures of physical activity. Estimates of reliability vary considerably among the various activities and components of these activities and between males and females.

Adolescent↗
PubMed2000

Inter-rater and intra-rater reliability in the interpretation of MTI Photoscreener photographs of Native American preschool children.

PURPOSE: To evaluate inter- and intra-rater reliability for the interpretation of MTI Photoscreener photographs taken in a population of Native American preschool children with a high prevalence of astigmatism. METHODS: Photographs of 369 children were rated by 11 nonexpert and 3 expert raters. Photographs for each child were scored as pass, refer, or retake. Nonexpert raters scored photos on two separate occasions, permitting analysis of intra-rater reliability. RESULTS: Analyses of pass/refer responses only: inter-rater reliability was moderate to substantial among nonexpert raters and substantial among expert raters. Intra-rater reliability among nonexperts was substantial. Analyses of all responses (pass, refer, and retake): inter-rater reliability for pass and refer scores was moderate among nonexperts and substantial among experts; for retake scores inter-rater reliability was slight for nonexperts and moderate for experts. Intra-rater reliability among nonexperts was substantial for pass and refer scores and moderate for retake scores. CONCLUSIONS: In this population with a high prevalence of astigmatism, whether MTI photoscreening results are interpretable is much more variable among and within raters than whether an interpretable photograph should be scored as pass or refer. The level of agreement among raters in the current study was influenced by the experience of the raters. In addition, nonexpert raters were more likely to deem a photograph uninterpretable than expert raters.

Arizona↗
PubMed1997

Interexaminer reliability in physical examination of patients with low back pain.

STUDY DESIGN: Seventy-one patients with low back pain were examined by two physiotherapists (50 patients) and two physicians (21 patients). The two physiotherapists had worked together for many years, but the two physicians had not. The interexaminer reliability of the clinical tests included in the physical examination was evaluated. OBJECTIVES: To evaluate the interexaminer reliability of clinical tests used in the physical examination of patients with low back pain under ideal circumstances, which was the case for the physiotherapists. SUMMARY OF BACKGROUND DATA: Numerous clinical tests are used in the evaluation of patients with low back pain. To reach the correct diagnosis, only tests with an acceptable validity and reliability should be used. Previous studies have mainly shown low reliability. It is important that clinical tests not be rejected because of low reliability caused by differences between examiners in performance of the examination and in their definition of normal results. METHODS: Two examiners, either two physiotherapists or two physicians, independently examined patients with low back pain. RESULTS: In approximately half of the clinical tests studied, an acceptable reliability was demonstrated. CONCLUSION: On the basis of the physiotherapists series, the reliability was acceptable for a number of clinical tests that are used in the evaluation of patients with low back pain. The results suggest that clinical tests should be standardized to a much higher degree than they are today.

Adolescent↗
PubMed1997

Apophysial joint degeneration, disc degeneration, and sagittal curve of the cervical spine. Can they be measured reliably on radiographs?

STUDY DESIGN: Interexaminer reliability study. OBJECTIVES: To determine the reliability of grading apophysial joint and disc degenerative changes and the reliability of measuring sagittal curves on lateral cervical spine radiographs. SUMMARY OF BACKGROUND DATA: Several authors have proposed that the presented of degenerative changes and the absence of lordosis in the cervical spine are indicators of poor recovery from neck injuries caused by motor vehicle collisions. The validity of those conclusions is questionable because the reliability of the methods used in their studies to measure the presence of degenerative changes and the absence of lordosis has not been determined. METHODS: Kellgren's classification system for apophysial joint and disc degeneration, as well as the pattern and magnitude of the sagittal curve on 30 lateral cervical spine radiographs were assessed independently by three examiners. RESULTS: Moderate reliability was demonstrated for classifying apophysial joint degeneration with an intraclass correlation coefficient of 0.45 (95% confidence interval, 0.09-0.71). Classifying degenerative disc disease had substantial reliability, with an intraclass correlation coefficient of 0.71 (95% confidence interval, 0.23-0.88). Measuring the magnitude of the sagittal curve from C2 to C7 had excellent interexaminer agreement, with an intraclass correlation coefficient of 0.96 (95% confidence interval, 0.88-0.98) and an interexaminer error of 8.3 degrees. CONCLUSIONS: The classification system for degenerative disc disease proposed by Kellgren et al and the method of measurement of sagittal curves from C2 to C7 demonstrated an acceptable level of reliability and can be used in outcomes research.

Analysis of Variance↗
PubMed2002

Multisurgeon assessment of coronal pattern classification systems for adolescent idiopathic scoliosis: reliability and error analysis.

STUDY DESIGN: Three scoliosis surgeons and one orthopedic fellow were presented the anteroposterior radiographs of 70 patients with adolescent idiopathic scoliosis. All the reviewers assigned a type to each curve according to the classification systems of H. A. King and R. W. Coonrad. OBJECTIVES: To compare multisurgeon reliability in applying the classification systems of H. A. King and R. W. Coonrad, and to analyze controversially classified curve patterns. SUMMARY OF BACKGROUND DATA: The system most commonly used to classify adolescent idiopathic scoliosis is King's classification. However, because of poor interobserver reliability, the validity of this system is questioned. In contrast, high interobserver reliability is reported for Coonrad's classification system, which is used less frequently in clinical practice. METHODS: Interobserver agreement and intraobserver reproducibility were tested. Kappa coefficients were used to test reliability. Between the observers, the divergent assignments to curve patterns were analyzed in both quantitative and qualitative terms. An error analysis was performed. RESULTS: Paired comparisons showed a mean interobserver kappa coefficient of 0.45 for King's and 0.38 for Coonrad's classification systems. According to Svanholm et al, these values indicate poor reliability in terms of interobserver agreement. Error analyses for both classification systems showed that the reason for poor reproducibility is disagreement among the observers about structural upper thoracic and structural lumbar curves. CONCLUSIONS: Neither the King nor the Coonrad method appears to have sufficient interobserver reliability. To improve reliability, the authors recommend that the structural stigmas of the upper thoracic and lumbar curves be unequivocally described.

Adolescent↗
PubMed2003

Reliability of the visual assessment of cervical and lumbar lordosis: how good are we?

STUDY DESIGN: Blinded test-retest design. OBJECTIVE: To measure the intrarater and interrater reliability of the visual assessment of cervical and lumbar lordosis. SUMMARY OF BACKGROUND DATA: Cervical and lumbar lordoses are frequently evaluated using visual assessment, but little attempt has previously been made to measure the reliability of visual assessment. METHODS: Twenty-eight chiropractors, physical therapists, physiatrists, rheumatologists, and orthopedic surgeons were recruited to evaluate the posture of photographed subjects (with and without back pain). Each clinician rated the lordosis of the cervical and lumbar spines as normal, increased, or decreased. Kappa coefficients (kappa) were calculated to determine intrarater and interrater reliability. RESULTS: Twenty-eight clinicians evaluated photographs of 36 individuals (17 with back pain, 19 without). Mean intrarater reliability was kappa = 0.50 (95% confidence interval 0.02-0.98) and mean interrater reliability was kappa = 0.16 (95% confidence interval 0.00-0.48). No statistically significant difference existed among the five groups of clinicians or between the evaluation of the subjects with and without back pain. CONCLUSION: Intrarater reliability of the visual assessment of cervical and lumbar lordosis was statistically fair, whereas interrater reliability was poor.

Adolescent↗
PubMed2003

Reliability of the ICD-10 classification of adverse familial and environmental factors.

BACKGROUND: The tenth revision of the International Classification of Diseases (ICD-10) contains a number of categories and guidelines for coding different types of adverse familial and environmental situations. These categories have been selected on the basis of empirical evidence that the adverse situations might represent important psychiatric risk factors. Prior studies, using written case vignettes or video- or audiotaped semi-structured interviews, showed that the interrater reliability of these classifications is satisfactory. METHOD: We have tested the interrater reliability of the categories in a multicentre study by using an 'in vivo' design. Classifications were performed in day-to-day practice, using information that is normally available. Three hundred children from 0 to 13 years were involved in the study. These cases had been admitted to various institutes for children with psychiatric disorders, developmental delays and/or adverse psychosocial circumstances. Two clinicians and a student classified the psychosocial situation of each child. In total, 51 clinicians and 6 undergraduate students were involved in the study. RESULTS: It was found that, with the exception of more or less objective categories, the reliability is not satisfactory. Post hoc analyses showed that the insufficient reliability is only partly due to confounding factors: no clear indications were found for information variance, but observation variance may have played a part. Having additional information from two family questionnaires hardly contributes to a better reliability. CONCLUSIONS: The reliability of the psychosocial axis of the ICD-10 is not satisfactory if tested in day-to-day practice. In comparing this result with other reliability studies, it seems that the absence of adequate information to code the psychosocial axis may be a fundamental problem in obtaining sufficient interrater agreement. Apparently, the classification of this axis requires information that is often not available in common practice.

Adolescent↗
PubMed2001

The reliability and validity of three dimensional ultrasound volumetric measurements using an in vitro balloon and in vivo uterine model.

OBJECTIVE: To evaluate the reliability and validity of two and three dimensional ultrasound volumetric measurements using balloon and uterine models. DESIGN: Prospetive observational study. SETTING: Obstetric ultrasound department at a university teaching hospital. METHOD: Two and three dimensional ultrasound volumetric measurements (with 5, 10 and 15 ultrasonic slices) were performed on 30 different sets of ultrasound images obtained from 15 water filled balloons with volumes ranging from 19 to 697mL. The measurements were performed independently by two observers who were blinded to the true volumes of the balloons. For the uterine model, only three dimensional ultrasonic volume measurements were performed independently on 16 uteri by two observers who were again unaware of the definitive uterine volumes. OUTCOME MEASURE: For the assessment of intra-and inter-rater reliability, the intraclass correlation coefficient was used. The index of concordance between the ultrasonic volumes and those obtained by the reference standard (validity) was assessed with the conventional Pearson's correlation coefficient, limits of agreement method and the intra-class correlation coefficient. RESULTS: High levels of reliability and validity were obtained for both two and three dimensional ultrasound balloon volume measurements. For two dimensional ultrasonic volume measurements, the intra-class correlation coefficient ranged from 0.992 to 0.998 for reliability and validity whereas the Pearson's correlation coefficient for validity was 0.996. With three dimensional ultrasonic volume measurements, the intra-class correlation coefficient ranged from 0.991 to 0.999 for reliability and validity whereas the Pearson's correlation coefficient for validity was 0.999. Both two and three dimensional ultrasonic measurements tended to underestimate the true balloon volume with the largest observed mean difference obtained with three dimensional ultrasound measurements using five ultrasonic slices and the smallest value obtained with three dimensional ultrasound measurements employing 15 ultrasonic slices. The mean difference in volume measurement for two dimensional ultrasound was intermediate between these two values. However, two dimensional ultrasound volume measurement generated the largest range between the limits of agreement whereas the smallest range was obtained with three dimensional ultrasound using 10 ultrasonic slices. The intra-class correlation coefficient for reliability and validity with three dimensional ultrasonic uterine volume estimation ranged from 0.956 to 0.996 whereas the Pearson's correlation coefficient for validity ranged from 0.993 to 0.999). The use of three dimensional ultrasound also consistently under-estimated the actual uterine volumes. The larger the number of ultrasonic slices employed for three dimensional ultrasound, the smaller was the mean difference between the ultrasonic and true uterine volume measurements and the smaller the limits of agreement. CONCLUSIONS: The reliability and validity of balloon and uterine volume measurement by three dimensional ultrasound is high. This allows further research on three dimensional ultrasound for measuring pelvic organ volumes in the prediction of pelvic pathology.

Female↗
PubMed1986

Teaching DSM-III to clinicians. Some problems of the DSM-III system reducing reliability, using the diagnosis and classification of depressive disorders as an example.

Experiences from teaching DSM-III to more than three hundred Norwegian psychiatrists and clinical psychologists suggest that reliable DSM-III diagnoses can be achieved within a few hours training with reference to the decision trees and the diagnostic criteria only. The diagnoses provided are more reliable than the corresponding ICD diagnoses which the participants were more familiar with. The three main sources of reduced reliability of the DSM-III diagnoses are related to: poor knowledge of the criteria which often is connected with failure of obtaining diagnostic key information during the clinical interview; unfamiliar concepts and vague or ambiguous criteria. The two first issues are related to the quality of the teaching of DSM-III. The third source of reduced reliability reflects unsolved validity issues. By using the classification of five affective case stories as examples, these sources of diagnostic pitfalls, reducing reliability and ways to overcome these problems when teaching the DSM-III system, are discussed. It is concluded that the DSM-III system of classification is easy to teach and that the system is superior to other classification systems available from a reliability point of view. The current version of the DSM-III system, however, partly owes a high degree of reliability to broad and heterogeneous diagnostic categories like the concept major depression, which may have questionable validity. Thus, the future revisions of the DSM-III system should, above all, address the issue of validity.

Depressive Disorder↗
PubMed1999

Measuring the effectiveness of cataract surgery: the reliability and validity of a visual function outcomes instrument.

AIMS: To assess test-retest reliability and validity of the "TyPE" patient self assessed visual function questionnaire, as part of a study in two hospitals measuring the effectiveness of cataract surgery. The American TyPE questionnaire had minor adaptations made for use in Britain. METHODS: Test-retest reliability was assessed on 63 out of 378 adult cataract surgery patients in the study, using Spearman correlation coefficients and kappa coefficients of agreement. "Construct" validity was evaluated by comparing the association between changes in visual function questionnaire scores after surgery, with patients' perception of change in visual function obtained by independent interview of 24 patients. RESULTS: The TyPE questionnaire items showed very good test-retest reliability. Average Spearman and kappa coefficients for 39 patients from hospital 1 were 0.93 and 0.84 respectively. Spearman and kappa coefficients of 0.9 and 0.81 were obtained for those nine patients in hospital 2 where both the test and retest questionnaires were filled in by the same people. However, for the 15 patients from hospital 2, where the questionnaire was filled in by different people in the retest, reliability was less good: the Spearman coefficients were still high, average 0.72, but the kappa coefficients were poor, 0.27. Good construct validity was exhibited, with a correlation of 0.79 between change in distance vision score from the questionnaires and the independent interview. CONCLUSIONS: The adapted TyPE questionnaire is both very reliable and has good construct validity. The kappa coefficient should be used wherever possible to evaluate reliability. The test-retest reliability and validity and practicability of other visual function questionnaires have not been assessed adequately, and further development should be carried out of all such questionnaires, so that they may be introduced into routine clinical care.

Activities of Daily Living↗
PubMed2003

Retest reliability of surveillance questions on health related quality of life.

STUDY OBJECTIVES: Health related quality of life (HRQoL) is an important surveillance measure for monitoring the health of populations, as proposed in the American public health plan, Healthy People 2010. The authors investigated the retest reliability of four HRQoL questions from the US Behavioral Risk Factor Surveillance System (BRFSS). DESIGN: Randomly sampled BRFSS respondents from the state of Missouri were re-contacted for a retest of the HRQoL questions. Reliability was estimated by kappa statistics for categorical questions and intraclass correlation coefficients for continuous questions. SETTING: Missouri, United States. PARTICIPANTS: 868 respondents were re-interviewed by telephone about two weeks after the initial interview (mean 13.5 days). Participants represented the adult, non-institutionalised population of Missouri: 59.1% women; mean age 49.5 years; 93.2% white race. MAIN RESULTS: Retest reliability was excellent (0.75 or higher) for Self-Reported Health and Healthy Days measures, and moderate (0.58 to 0.71) for other measures. Reliability was lower for older adults. Other demographic subgroups (for example, gender) showed no regular pattern of differing reliability and there was very little change in reliability by the time interval between the first and second interview. CONCLUSIONS: Retest reliability of the HRQoL Core is moderate to excellent. Scaling options will require future attention, as will research into appropriate metrics for what constitutes important population group differences and change in HRQoL.

Adolescent↗
PubMed1994

SF 36 health survey questionnaire: I. Reliability in two patient based studies.

OBJECTIVE: To assess the reliability of the SF 36 health survey questionnaire in two patient populations. DESIGN: Postal questionnaire followed up, if necessary, by two reminders at two week intervals. Retest questionnaires were administered postally at two weeks in the first study and at one week in the second study. SETTING: Outpatient clinics and four training general practices in Grampian region in the north east of Scotland (study 1); a gastroenterology outpatient clinic in Aberdeen Royal Hospitals Trust (study 2). PATIENTS: 1787 patients presenting with one of four conditions: low back pain, menorrhagia, suspected peptic ulcer, and varicose veins and identified between March and June 1991 (study 1) and 573 patients attending a gastroenterology clinic in April 1993. MAIN MEASURES: Assessment of internal consistency reliability with Cronbach's alpha coefficient and of test-retest reliability with the Pearson correlation coefficient and confidence interval analysis. RESULTS: In study 1, 1317 of 1746 (75.4%) correctly identified patients entered the study and in study 2, 549 of 573 (95.8%). Both methods of assessing reliability produced similar results for most of the SF 36 scales. The most conservative estimates of reliability gave 95% confidence intervals for an individual patient's score difference ranging from -19 to 19 for the scales measuring physical functioning and general health perceptions, to -65.7 to 65.7 for the scale measuring role limitations attributable to emotional problems. In a controlled clinical trial with sample sizes of 65 patients in each group, statistically significant differences of 20 points can be detected on all eight SF 36 scales. CONCLUSIONS: All eight scales of the SF 36 questionnaire show high reliability when used to monitor health in groups of patients, and at least four scales possess adequate reliability for use in managing individual patients. Further studies are required to test the feasibility of implementing the SF 36 and other outcome measures in routine clinical practice within the health service.

Adolescent↗
PubMed1994

Action potential propagation through embryonic dorsal root ganglion cells in culture. II. Decrease of conduction reliability during repetitive stimulation.

1. The reliability of the propagation of action potentials (AP) through dorsal root ganglion (DRG) cells in embryonic slice cultures was investigated during repetitive stimulation at 1-20 Hz. Membrane potentials of DRG cells were recorded intracellularly while the axons were stimulated by an extracellular electrode. 2. In analogy to the double-pulse experiments reported previously, either one or two types of propagation failures were recorded during repetitive stimulation, depending on the cell morphology. In contrast to the double-pulse experiments, the failures appeared at longer interpulse intervals and usually only after several tens of stimuli with reliable propagation. 3. In the period with reliable propagation before the failures, a decrease in the conduction velocity and in the amplitude of the afterhyperpolarization (AHP), an increase in the total membrane conductance, and the disappearance of the action potential "shoulder" were observed. 4. The reliability of conduction during repetitive stimulation was improved by lowering the extracellular calcium concentration or by replacing the extracellular calcium by strontium. The reliability of conduction decreased by the application of cadmium, a calcium channel blocker, 4-amino pyridine, a fast potassium channel blocker, or apamin or muscarine, the blockers of calcium-dependent potassium channels. The reliability of conduction was not effected by blocking the sodium potassium pump with ouabain or by replacing extracellular sodium with lithium. 5. In the period with reliable propagation cadmium, apamin, and muscarine reduced the amplitude of the AHP. The shoulder of the action potential was more pronounced and not sensitive to repetitive stimulation when extracellular calcium was replaced by strontium. It disappeared when cadmium was applied. 6. In DRG somata changes of the intracellular Ca2+ concentration were monitored by measuring the fluorescence of the Ca2+ indicator Fluo-3 with a laser-scanning confocal microscope. During repetitive stimulation, an accumulation of intracellular calcium occurred that recovered very slowly (tens of seconds) after the AP trains. 7. Computer model simulations performed in analogy to the experimental protocols produced conduction failures during repetitive stimulation only when the calcium currents during the APs were reduced. 8. From these findings it is concluded that conduction failures during repetitive stimulation are dependent on an accumulation of intracellular calcium leading to an inactivation of calcium currents, combined with small contributions of an accumulation of extracellular potassium and a summation of slow potassium conductances.

Acetylcholine↗