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PubMed2002

A direct test for lateralization of language activation using fMRI: comparison with invasive assessments in children with epilepsy.

This study introduces a direct method of assessing cerebral lateralization for language based on fMRI activation. The method, derived from a voxel-based morphometry study by C. H. Salmond et al. (2000, Hum. Brain Mapping 11, 223-232), bases lateralization on the direct statistical comparison of the magnitude of task-induced activation in homotopic regions of the two hemispheres. Lateralization results obtained with this direct method were compared to those obtained with a widely used method which involves the calculation of a laterality index (LI) based on the number of significantly activated voxels in the inferior frontal gyrus of each hemisphere. In order to compare the validity of the two methods, a covert verb-generation task was performed by eight children with epilepsy whose language lateralization was examined using invasive techniques. Lateralization results derived from fMRI activation showed that the calculation of a LI presented some limitations. Importantly, the LI value was dependent on the activation threshold chosen to calculate that LI. As a consequence, the correlation between the LI and the invasive methods could vary with the chosen threshold. By contrast, the proposed direct method gave some indication of the reliability of the lateralization and provided results that, in all eight children, were consistent with those obtained using invasive techniques. It is suggested that the direct method could be used in future fMRI studies to establish hemispheric lateralization for cognitive functions.

Adolescent↗
PubMed2003

[Examination of preschool children for refractive errors. First experience using a handheld autorefractor].

BACKGROUND: Since ametropia is a leading cause of amblyopia refractive screening of preschool children is recommended. Measurement of refraction using tabletop autorefractors can be difficult or impossible due to lack of cooperation in this age group. The intention of the present study is to evaluate the use of a new handheld autorefractor for screening in kindergartens. METHODS: A total of 216 children aged 3.5-4.5 years were examined without cycloplegia using the handheld autorefractor (SureSight, Welch Allyn) in their kindergartens. RESULTS: Using the test device the majority of the examined eyes showed mild hyperopia (on average +1.18+/-0.87 dpt spherical equivalent) and mild astigmatism (on average 0.60+/-0.46 dpt cylinder power). The reproducibility of repeated autorefractor readings was higher for cylinder power and axis than for the spherical equivalent. Autorefractor readings of 55 eyes could be compared with the results of cycloplegic retinoscopy. The results were similar between the two measurements with differences of no more than 0.5 dpt in 18.2% for the spherical equivalent, in 82.1% for cylinder power, and in 66.6% for axis (weighted axis difference). There was adequate cooperation in 99.5% of the children. CONCLUSION: The handheld autorefractor proved an accuracy of measurement comparable to that of conventional tabletop autorefractors for cylinder power and axis with limitations in accuracy for the spherical equivalent. Validity and threshold values for relevant abnormalities are to be evaluated in further studies. By the high cooperation rate the instrument proved useful for screening examinations in preschool children.

Child, Preschool↗
PubMed2000

Can a battery of functional and sensory tests corrobrate the sensorineural complaints of subjects working with vibrating tools?

OBJECTIVES: The objective of the present paper is to study the relationship between the early sensorineural symptoms, classified according to the Stockholm scale, and the results of the main functional and sensory tests described in the literature, in subjects working with vibrating tools. METHODS: Three groups of male workers were selected from industry: one group (69 subjects) exposed to hand-arm vibration in several workplaces, one group (62) performing heavy and repetitive hand and arm work but without exposure to vibration, and one control group (46) performing light and non-repetitive tasks without vibration. All the workers were interviewed by questionnaire, about their personal characteristics, their health status, their actual and past working conditions and the episodes of tingling at the level of the fingers. From these reported symptoms, the sensorineural stage of the hand-arm vibration was determined using the Stockholm scale. Based on the review of the literature, we selected six functional and sensory tests: maximum voluntary grip force, maximum angles of the wrist, pressure perception threshold test, vibration perception threshold test, distal sensory latency and the Purdue Pegboard test. Each test was performed by the workers in the three groups. RESULTS: No main differences were observed between the personal characteristics of the three groups. According to the Stockholm scale, the sensorineural symptoms were mainly at stage SN1, with 9% at stage SN2 and none at stage SN3. These symptoms are associated with exposure to vibration, and had a prevalence of 40% in group 1, versus 20% in the two other groups. Furthermore, 25% of the workers exposed to vibration complained of symptoms at least once a week, compared with only 2% in the other groups. The multivariate logistic regression analysis showed an association between the existence of symptoms and a decrease in the maximum flexion angle of the wrist and an increase in the pressure perception threshold. This association, however, was too low to determine limit values with a sensitivity and specificity sufficiently high to make a reliable diagnosis. CONCLUSIONS: The sensorineural symptoms at stage N1 on the Stockholm scale, experienced occasionally by some 40% of the users of vibrating tools, could not be corroborated by the functional and sensory tests.

Adult↗
PubMed2006

Instrumental assessment of atopic eczema: validation of transepidermal water loss, stratum corneum hydration, erythema, scaling, and edema.

BACKGROUND: Quantification of skin diseases can be carried out in many ways. Clinical scores are widely used in atopic eczema (AE), and noninvasive instruments are a relevant supplement. OBJECTIVE: Our purpose was to validate 5 noninvasive instruments in quantification of AE severity. METHODS: In all, 101 patients with AE and 30 control subjects were assessed twice in a clinical cross-sectional examination. Assessment of transepidermal water loss, stratum corneum hydration, erythema, scaling, and subepidermal edema was assessed on 3 predetermined skin sites. RESULTS: The methods discriminated among various severity degrees and correlated significantly with objective assessment of disease severity. High correlations were found among instruments assessing acute symptoms of AE. Threshold values for transepidermal water loss and capacitance were found. LIMITATIONS: No gold standard exists for severity assessment of atopic eczema. Therefore, the methods used cannot be validated in relation to such a standard. Furthermore, atopic eczema is a generalized disease and the methods used assess target lesions. By assessing target lesions, information about the disease is reduced. CONCLUSION: Noninvasive instruments are valuable in quantification of disease severity in a mixed group of patients with active AE. Assessment with ultrasound has contributed new information about the pathophysiology in AE.

Adolescent↗
PubMed1977

Inhibition of the human eyeblink reflex: an evaluation of the sensitivity of the Wendt-Yerkes method for threshold detection.

In two experiments, human subjects showed a reduced eyewink reflex to an airpuff (S2) if it was preceded by a light flash or a noise burst (S1). The first (N=6) showed that a light inhibited the blink maximally at a 100-msec lag. In the second (N=8), thresholds for noise pips were established with the method of limits. Then the pips were presented in multiples of threshold values as S1 100 msec before S2. Sujbects pressed a button whenever they heard the sound, on S1-S2 pairs, on S1 alone, or on S2 alone trials. Eyeblinks to S2 declined in amplitude and increased in latency as S1 intensity increased. The threshold S1 (approximately 2 dB over a 50-dB background) produced reliable inhibition in 7 of 8 subjects, and a weaker S1 which never evoked a button press was sufficient to produce reliable inhibition for the group as a whole. Inhibition in any particular trial was unrelated to button pressing. The sensitivity of the reflex technique and its relative invariance to task demands suggest its usefulness as a behavioral psychophysical procedure.

Acoustic Stimulation↗
PubMed2003

Homocysteine plasma concentration levels for the prediction of preeclampsia in women with chronic hypertension.

OBJECTIVE: The purpose of this study was to evaluate prospectively midtrimester homocysteine concentration levels for the prediction of superimposed preeclampsia in women with chronic hypertension. STUDY DESIGN: Between March 1, 2000, and February 1, 2002, pregnancies that were complicated by chronic hypertension that required medication had homocysteine, vitamin B(12), and folate concentrations measured between 16 and 20 weeks of gestation. All women received folate supplementation. An upper limit threshold for increased homocysteine was defined as the mean value plus 2 SDs. RESULTS: Fifty-seven women were enrolled. Mean homocysteine concentration levels were 5.1+/-1.7 micromo/L for the 16 women who had preeclampsia compared with 4.7+/-1.3 micromo/L for the 41 women without preeclampsia (P=.56). Two of 16 women with preeclampsia (13%) had concentration levels that exceeded the 95th percentile (6.9 micromo/L) compared with 2 of 41 women (5%) without preeclampsia (P=.31). The sensitivity and specificity were 13% (95% CI, 1.6-38.3) and 95.1% (95% CI, 83.5-99.4), respectively. CONCLUSION: Second-trimester homocysteine concentration levels were not helpful in the prediction of preeclampsia in chronically hypertensive women.

Adult↗
PubMed2001

How to assess the relative range of two consecutive laboratory measurements to monitor patients.

An integral part of routine health checkups involves laboratory measurements on various analytes in the blood. It is then common to compare the value of two consecutive measurements sampled at different times from the same patient. A "significant" change requires an action (additional sample and/or clinical action). The current rule is to check whether the relative range of measurement is larger than a certain critical threshold. This rule should guarantee a specified confidence level (e.g., 95%), but its derivation was based on an approximation. We derive the exact distribution and show that it is related to the doubly noncentral F distribution. The currently used threshold values are compared with the exact ones, and some limited power calculations are presented to detect changes in the patient condition.

Algorithms↗
PubMed2005

Nonlinear dynamics of short traveling capillary-gravity waves.

We establish a Green-Nagdhi model equation for capillary-gravity waves in (2+1) dimensions. Through the derivation of an asymptotic equation governing short-wave dynamics, we show that this system possesses (1+1) traveling-wave solutions for almost all the values of the Bond number theta (the special case theta=1/3 is not studied). These waves become singular when their amplitude is larger than a threshold value, related to the velocity of the wave. The limit angle at the crest is then calculated. The stability of a wave train is also studied via a Benjamin-Feir modulational analysis.

Journal Article↗
PubMed1995

Detection of Chlamydia trachomatis antigen by enzyme immunoassay: importance of confirmatory testing.

AIM--To determine when a fluorescence assay for Chlamydia trachomatis elementary bodies in the specimen buffer is of most value as a verification test for genital specimens reactive on screening enzyme immunoassay (EIA). METHOD--Genital swabs from high and medium prevalence populations were tested using EIA. Samples with absorbance values greater than the positive threshold and those within the range of 30% below this value were verified by the MicroTrak direct fluorescence assay (DFA) test. Quotients derived from the threshold value and specimen absorbances were used to establish confidence limits for the EIA. RESULTS--Of 13,283 swabs tested, 474 from the high risk group and 236 from the medium risk group were reactive on EIA and confirmed by DFA. Thirty six (5.9%) patients with confirmed reactive samples would have been missed if the kit criteria alone were followed. When confidence limits were applied to the calculated quotients, only those samples with an EIA quotient of > or = 4.0 were universally confirmed by the DFA. CONCLUSION--A scheme of testing which uses the DFA to verify EIA reactive specimens over a specified range was found to improve the sensitivity and specificity of the EIA screening test.

Antigens, Bacterial↗
PubMed2003

[Compatibility of active implants in the professional environment].

The recommended limiting values of human exposure are much higher than the thresholds of immunity required by the standards of electromagnetic compatibility. It is thus impossible to guarantee the total absence of interference risk. So initially, the medico-legal responsibility suggested proscribing the aptitude for a potential exposure, the importance of psychosocial problems raised by such a step forces to better quantify this risk which appears altogether weak with the collective experiment. The principal sources of professional exposure and the levels of corresponding fields are presented, as well as current knowledge on the sensitivity of pacemakers and defibrillators with respect to these fields. Finally, information to be supplemented and the means of mitigating it are suggested.

Electromagnetic Fields↗
PubMedDate not supplied

[Multiple occupational exposure to solvents].

This article review papers published over the last 20 years on multiple occupational exposure to solvents. At low-levels of exposure the toxicokinetic interferences between solvents have generally not been observed in man and presumably a threshold limit exists. Conversely, at exposure levels close to the "limit values" metabolic interference has sometimes been observed and the behaviour of the biological indicators differs from what would be expected. Toxicodynamic interference between solvents can give rise to additive, potentiation, synergistic, antagonistic effects. For the identification of "limit values", it has generally been suggested in the literature that the possible effects deriving from multiple exposure be considered as additive. However, numerous potentiation effects have frequently been reported for combined exposure to substances of widespread use. In this paper lists of multiple exposure in which the doses of the substances, the types of interferences and the behaviour of the biological levels have been drawn up and proposed as a tool for easy consultation.

Alcohol Drinking↗
PubMed1982

A calibration procedure for the assessment of thresholds above 8000 Hz.

A technique is described to estimate the sound pressure level developed by a broad frequency response transducer at the tympanic membrane. Real-ear probe tube measurements near the tympanic membranes of 10 subjects were used to obtain frequency-dependent correction values for a custom-designed flat-plate coupler. These latter measures can be used for routine calibration of the transducer. Audiometric thresholds from 250 to 16000 Hz were obtained on 14 children (5-18 years). Threshold estimates were found to be comparable to previously reported values. Potential application and limitations of this technique are discussed.

Acoustics↗
PubMed1997

[Comparison of film-screen combination in a contrast detail diagram and with interactive image analysis. 1: Contrast detail diagram].

The following three film-screen combinations were compared: a) a combination of anticrossover film and UV-light emitting screens, b) a combination of blue-light emitting screens and film, and c) a conventional green fluorescing screen film combination. Radiographs of a specially designed plexiglass phantom (0.2 x 0.2 x 0.12 m3) were obtained that contained bar patterns of lead and plaster (calcium sulfate) to test high and intermediate contrast resolution and bar patterns of air to test low contrast resolution, respectively. An aluminum step wedge was integrated to evaluate dose-density curves of the radiographs. The dose values for the various step thicknesses were measured as percentage of the dose value in air for 60, 81, and 117 kV. Exposure conditions were the following: 12 pulse generator, 0.6 mm focus size, 4.7 mm aluminum prefilter, a grid with 40 lines/cm (12:1), and a focus-detector distance of 1.15 m. The thresholds of visible bars of the various pattern materials were assessed by seven radiologists, one technician, and the authors. The resulting contrast detail diagram could not prove any significant differences between the three tested screen film combinations. The pairwise comparison, however, found 8 of the 18 paired differences to be statistically significant between the conventional and the two new screen-film combinations. The authors concluded that subjective visual assessment of the threshold in a contrast detail study alone is of only limited value to grade image quality if no well-defined criteria are used (BIR report 20 [1989] 137-139). The statistical approach of paired differences of the estimated means appeared to be more appropriate.

Humans↗
PubMed1994

Factors associated with response to methotrexate in systemic-onset juvenile chronic arthritis.

We retrospectively investigated, in 19 children with systemic-onset juvenile chronic arthritis (SoJCA), the possible influence on the outcome of methotrexate (MTX) therapy of several independent variables, including age at onset of juvenile chronic arthritis, disease duration and severity of the disease at baseline. The dosage of MTX ranged from 7.5 to 11.0 mg/m2/week (median 9.3 mg/m2/week) and was given as a single, oral weekly dose. After 6 months of treatment, 12 (63%) patients were judged as responders on grounds of a > or = 50% reduction in the number of joints with active arthritis and/or an articular severity score; 7 (37%) did not respond to therapy. When the baseline values of the selected variables were compared, we found that the responder group had, with respect to the non-responder group, a lower percentage of radiographic lesions (p < 0.005), a shorter duration of the disease (p < 0.05) and a lower number of joints with limitation of motion (p < 0.01), functional limitation score (p < 0.05) and articular severity score (p < 0.05). A threshold value of disease duration of two years and the presence/absence of radiographic lesions gave a correct classification with respect to the treatment outcome of 73.7% and 83.3%, respectively. The predictive value of these two variables was confirmed by a multivariate analysis. We conclude that earlier treatment with MTX, possibly before the appearance of radiographic changes, may favourably influence the outcome of MTX treatment in those patients with SoJCA who require a second-line drug.

Adolescent↗
PubMed1985

Acoustics of a standing wave tank for studying the hearing capacity of fish.

In a standing wave tank responses of fish to sound stimuli used to investigate the hearing capacity of fish may perhaps be affected by unintended stimulation of the lateral line. Uniform oscillatory water flow patterns do not stimulate the lateral line. Departures from uniformity were derived from measurements to acoustic pressure and particle velocity at 5-cm spacings around the center in our standing wave tank containing six transducers suspended along three axes that are perpendicular to one another. These measurements are compared with the results of a model in which negligible influence of the tank wall and an incompressible water column in the tank are assumed. Deviations of computed values from measured values of sound pressure and the principal velocity components are less than 5 dB. The model underestimates velocity components perpendicular to the principal component. However, the model does appear a reliable aid for estimating the spatial function of sound pressure and velocity from the values of p and v measured at the tank center. Upper limits for the relative velocities between the fish body and the water can only approach threshold values for the lateral line stimulation under worst conditions (i.e., a velocity node at the tank center) in this setup.

Acoustics↗
PubMed2005

Relationship between visual field loss and contrast threshold elevation in glaucoma.

BACKGROUND: There is a considerable body of literature which indicates that contrast thresholds for the detection of sinusoidal grating patterns are abnormally high in glaucoma, though just how these elevations are related to the location of visual field loss remains unknown. Our aim, therefore, has been to determine the relationship between contrast threshold elevation and visual field loss in corresponding regions of the peripheral visual field in glaucoma patients. METHODS: Contrast thresholds were measured in arcuate regions of the superior, inferior, nasal and temporal visual field in response to laser interference fringes presented in the Maxwellian view. The display consisted of vertical green stationary laser interference fringes of spatial frequency 1.0 c deg(-1) which appeared in a rotatable viewing area in the form of a truncated quadrant extending from 10 to 20 degrees from fixation which was marked with a central fixation light. Results were obtained from 36 normal control subjects in order to provide a normal reference for 21 glaucoma patients and 5 OHT (ocular hypertensive) patients for whom full clinical data, including Friedmann visual fields, had been obtained. RESULTS: Abnormally high contrast thresholds were identified in 20 out of 21 glaucoma patients and in 2 out of 5 OHT patients when compared with the 95% upper prediction limit for normal values from one eye of the 36 normal age-matched control subjects. Additionally, inter-ocular differences in contrast threshold were also abnormally high in 18 out of 20 glaucoma patients who had vision in both eyes compared with the 95% upper prediction limit. Correspondence between abnormally high contrast thresholds and visual field loss in the truncated quadrants was significant in 5 patients, borderline in 4 patients and absent in 9 patients. CONCLUSION: While the glaucoma patients tested in our study invariably had abnormally high contrast thresholds in one or more of the truncated quadrants in at least one eye, reasonable correspondence with the location of the visual field loss only occurred in half the patients studied. Hence, while contrast threshold elevations are indicative of glaucomatous damage to vision, they are providing a different assessment of visual function from conventional visual field tests.

Adult↗
PubMed1992

Evaluation of methods for automated Hemifield analysis in perimetry.

A new aid to perimetric analysis, the Glaucoma Hemifield Test, primarily evaluates up-down differences in automated static visual field tests. We analyzed the visual fields of 163 eyes of 163 normal subjects and 77 eyes of 77 patients with glaucoma diagnosed on bases other than perimetry using the Glaucoma Hemifield Test and a similar, previously developed, hemifield analysis method. The performance of the Glaucoma Hemifield Test was compared with that of the earlier method and the differences in test design were evaluated individually. The Glaucoma Hemifield Test allowed significantly improved separation between the normal group and the group with glaucoma than did the earlier method. This improvement was due to an increase in sensitivity, and was associated with the use of test point significances instead of threshold values, and a large normal database alone in the determination of normal limits.

Adult↗
PubMed1994

In vitro radiation sensitivity of the LNCaP prostatic tumor cell line.

Because there is extremely limited information on the intrinsic radiosensitivity of human prostatic cancer cells, we have investigated the in vitro radiation response of exponentially growing LNCaP cells. Due to the very poor colony-forming potential of the LNCaP cells, radiation survival was investigated using the dose-dependent (0-6 Gy) changes seen after X-irradiation in the shapes of regrowth curves. Survival was described using both the single-hit, multitarget (SHMT) equation and the linear-quadratic (LQ) equation. The values and 95% confidence limits of the extrapolation number (n), quasi-threshold dose (Dq), and mean lethal dose (D(o)) in SHMT terminology were respectively: 0.9 (0.7-1.0), 0.0 Gy, and 1.39 (0.11) Gy. The LQ alpha and beta parameters were respectively 6.80 (1.13) and -0.53 (2.89). The X-ray dose response of the LNCaP line is, therefore, purely exponential. The mean survival at the clinically relevant dose of 2 Gy (S2) was 51.2% for the LNCaP line. Comparison of the S2 value for the LNCaP line with previous investigations with other human prostatic cancer cell lines (DU145 and PC-3) indicates a mean S2 value of 47.6%, which suggests that human prostate cancer cells might lie toward the resistant side of the spectrum for various classes of human neoplasms.

Cell Survival↗