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PubMed2005

Intravital leukocyte detection using the gradient inverse coefficient of variation.

The problem of identifying and counting rolling leukocytes within intravital microscopy is of both theoretical and practical interest. Currently, methods exist for tracking rolling leukocytes in vivo, but these methods rely on manual detection of the cells. In this paper we propose a technique for accurately detecting rolling leukocytes based on Bayesian classification. The classification depends on a feature score, the gradient inverse coefficient of variation (GICOV), which serves to discriminate rolling leukocytes from a cluttered environment. The leukocyte detection process consists of three sequential steps: the first step utilizes an ellipse matching algorithm to coarsely identify the leukocytes by finding the ellipses with a locally maximal GICOV. In the second step, starting from each of the ellipses found in the first step, a B-spline snake is evolved to refine the leukocytes boundaries by maximizing the associated GICOV score. The third and final step retains only the extracted contours that have a GICOV score above the analytically determined threshold. Experimental results using 327 rolling leukocytes were compared to those of human experts and currently used methods. The proposed GICOV method achieves 78.6% leukocyte detection accuracy with 13.1% false alarm rate.

Algorithms↗

PubMed1994

Outlier reduction by an option-3 measurement scheme.

Detecting changes in longitudinal data is important in medical research. However, the existence of measurement outliers can cause an unexpected increase in the false alarm rate in claiming changes. To reduce the outliers, a new method has been developed. In this scheme, two measures are initially taken and, if they are closer than a specified threshold, the average of the two is considered to be the estimate of the true mean; otherwise a third measurement is taken, and the mean of the closest pair is considered to be the estimate. It is shown that this method has considerable sample size advantage over naive repeated measurements. Moreover, this scheme is robust for outlier error distribution. Evidence on outlier removal in dental attachment probing is used as an example.

Analysis of Variance↗

PubMed2006

The emerging pandemic of obesity and diabetes: are we doing enough to prevent a disaster?

Obesity is growing into a global epidemic and alarming trends are seen in Asian countries. Although obesity is defined by body mass index (BMI), waist circumference has emerged as a more specific marker of metabolic risk. BMI and waist circumference thresholds vary between ethnicities and values are lower for Asian populations. Asians are at an increased risk of developing diabetes and early death from cardiovascular complications at lower levels of BMI and waist circumference. Obesity, especially central obesity is strongly associated with development and worsening of type 2 diabetes. The developing countries may find it difficult to face a surge in diabetes with early death and loss of productivity. Therefore, early action to contain an epidemic of obesity should be considered an urgent global priority.

Adolescent↗

PubMed1993

Laboratory test of an automated cell analysis system for cervical screening.

An automated cell analysis system (Autoplan-MIAC) for the early detection of precancerous lesions of the cervix was tested under semi-routine conditions in a clinical cytology laboratory. A set of 1500 specimens, highly enriched with abnormal cases, was analysed. Cervical scrapings were collected in suspension and processed by cytocentrifugation for microscopy. Two slides were prepared from each sample: one for staining according to Papanicolaou for the visual reference diagnosis and one for Feulgen staining for automated analysis. The specimens were evaluated in two ways: the first one, which is referred to as the automated machine classification system (AMC), classifies the specimens according to the number and ratio of selected objects (alarms) and is a fully automated system. The second system classifies the specimens after visual evaluation of the stored alarms as they are displayed on a TV monitor, and is designated the interactive machine classification system (IMC). The AMC results showed a false positive rate of 16.5% when the cut-off threshold was selected so that all 117 positively diagnosed specimens were classified 'positive' by the system. In that case 87.4% of the CIN I and 96.9% of the CIN II cases were AMC-positive. The IMC results showed a false positive rate of 2.5%, when 86.3% of the CIN I cases, 96.9% of the CIN II cases and all CIN III and invasive carcinoma cases were positively classified.

Cervix Uteri↗

PubMedDate not supplied

Construction noise: exposure, effects, and the potential for remediation; a review and analysis.

More than one-half million construction workers are exposed to potentially hazardous levels of noise, yet federal and state Occupational Safety and Health Administration (OSHA) programs provide little incentive to protect them against noise-induced hearing loss. Construction noise regulations lack the specificity of general industry noise regulations. In addition, problems that characterize the construction industry, such as worker mobility and the large proportion of small businesses, make implementing hearing conservation measures more difficult. The apparent severity of exposure depends greatly on the measurement method, with the 3-dB exchange rate almost always showing higher average exposure levels than the 5-dB (OSHA) rule. Construction workers demonstrate hearing threshold levels that generally conform to those expected in manufacturing. The prevalence of hearing protection device (HPD) use among U.S. construction workers is very poor, partly because of perceived difficulties in hearing and understanding speech communication and warning signals. In addition, masking by noise of necessary communication and warning signals is of particular concern in construction, where recent research demonstrated the association between fatalities and the failure to hear reverse alarms. Judicial use of HPDs is of the utmost importance, along with avoiding overattenuation, selecting HPDs with uniform attenuation, and using noise-attenuating communication systems when possible. A successful hearing conservation program in British Columbia can serve as a model for the United States, with a long-standing positive safety culture, a high percentage of HPD use, improvement in average hearing threshold levels over the last decade, and a centralized record-keeping procedure, which helps solve the problem of worker mobility. However, controlling construction noise at the source is the most reliable way to protect worker hearing. U.S. manufacturers and contractors should benefit from the activities of the European Community, where noise control and product labeling in construction has been carried out for more than 20 years.

Ear Protective Devices↗

PubMed2006

Coherence detection: effects of frequency, frequency uncertainty, and onset/offset delays.

The detectability of a sequence of equal-frequency (coherent) tonal components embedded in random, multiburst maskers was evaluated. The masker was comprised of tonal components located in a time-by-frequency spectrogram with eight 30 ms time columns and 29 frequency rows ranging logarithmically from 200 to 5000 Hz. The probability that a tone occurred in any one cell of the spectrogram, p, was the independent variable. The signal and masker components were of equal duration and equal level. Using a yes/no procedure, threshold values of p were estimated for five signal frequencies (220, 445, 1000, 2245, 4490 Hz) and when the signal frequency was random. Thresholds were worst for the random-frequency signal and best for the fixed 1000 Hz signal. In additional conditions, the value of p was fixed and the signal components were delayed relative to the masker components. A 1 ms delay provided better sensitivity (d' grew from 0.5 to 1) for all but the lowest signal frequency tested. An analysis of no-signal trials revealed that false alarm rates were higher when components falling at the signal frequency were consecutive than when they were distributed across bursts. Thus, coherence rather than total energy at the signal frequency is important for signal detection.

Acoustic Stimulation↗

PubMed2000

Neuroethology of the katydid T-cell. I. Tuning and responses to pure tones.

The tuning and pure-tone physiology of the T-cell prothoracic auditory interneuron were investigated in the nocturnal katydid Neoconocephalus ensiger. The T-cell is extremely sensitive and broadly tuned, particularly to high-frequency ultrasound (>20 kHz). Adult thresholds were lowest and showed their least variability for frequencies ranging from 25 to 80 kHz. The average best threshold of the T-cell in N. ensiger ranged from 28 to 38 dB SPL and the best frequency from 20 to 27 kHz. In females, the T-cell is slightly more sensitive to the range of frequencies encompassing the spectrum of male song. Tuning of the T-cell in non-volant nymphs was comparable with that of adults, and this precocious ultrasound sensitivity supports the view that it has a role in the detection of terrestrial sources of predaceous ultrasound. In adults, T-cell tuning is narrower than that of the whole auditory (tympanic) organ, but only at audio frequencies. Superthreshold physiological experiments revealed that T-cell responses were ultrasound-biased, with intensity/response functions steeper and spike latencies shorter at 20, 30 and 40 kHz than at 5, 10 and 15 kHz. The same was also true for T-cell stimulation at 90 degrees compared with stimulation at 0 degrees within a frequency, which supports early T-cell research showing that excitation of the contralateral ear inhibits ipsilateral T-cell responses. In a temporal summation experiment, the integration time of the T-cell at 40 kHz (integration time constant tau =6.1 ms) was less than half that measured at 15 kHz ( tau =15.0 ms). Moreover, T-cell spiking in response to short-duration pure-tone trains mimicking calling conspecifics (15 kHz) and bat echolocation hunting sequences (40 kHz) revealed that temporal pattern-copying was superior for ultrasonic stimulation. Apparently, T-cell responses are reduced or inhibited by stimulation with audio frequencies, which leads to the prediction that the T-cell will encode conspecific song less well than bat-like frequency-modulated sweeps during acoustic playback. The fact that the T-cell is one of the most sensitive ultrasound neurons in tympanate insects is most consistent with it serving an alarm, warning or escape function in both volant and non-volant katydids (nymphs and adults).

Acoustic Stimulation↗

PubMed2004

Analysis of IR thermal imager for mass blind fever screening.

BACKGROUND: Obtaining meaningful temperature for the human body requires identifying a body site that will provide reliable data across a large population. It is important to understand that skin temperature does not solely depend on body-core temperature and may be affected by other physiological and environmental factors. Currently, there is lack of empirical data in correlating facial surface temperature with body core temperature. Present IR systems in use at airports/immigration checkpoints have not been scientifically validated particularly in regards to the false-negative rate. As a result, they may create a false sense of security by underestimating the number of febrile (and possibly infected) individuals. This article evaluates the effectiveness of thermal scanner when it is being used for mass blind screening of potential fever subjects such as SARS or bird flu patients. METHODS: Bio-statistics with regression analysis and ROC is applied to analyse the data collected (502) from the SARS hospital in Singapore and conclusive results are drawn from them. The results are vital in determining two very important pieces of information: the best and yet practical region on the face to take readings and optimal pre-set threshold temperature for the thermal imager. RESULTS: (1) The thermal scanner can be used as a first line tool for the mass blind screening of hyperthermia, (2) the readings from the scanner suggest good correlation with the ear temperature readings, (3) an imager temperature threshold should be determined by the environmental factors, outdoor condition in particular, the physiological site offset and the performance characteristics of thermal imager to warrant the most accurate and reliable screening operation. CONCLUSIONS: The analysis suggested that the thermal imager used holds much promise for mass blind screening when the readings from a specific region have a good correlation with the ear temperature. From the regression analysis, the best reading is taken from the maximum temperature in the eye region, followed by the maximum temperature in the forehead region. With ROC analysis, a randomly selected individual from the fever group has a test value larger than that for a randomly selected individual from the normal group in 97.2% of the time. The test can distinguish between the normal and febrile groups and an optimum threshold temperature for the thermal imager can be found. The pre-set threshold cut-off temperature for the current thermal imager was found to be 36.3 degrees C with reference to the associated environmental condition. Any temperature readings that exceed this reading will trigger off the alarm and a thermometer will be used to verify the whether the person is having fever.

Adult↗

PubMed2006

Methods for monitoring influenza surveillance data.

BACKGROUND: A variety of Serfling-type statistical algorithms requiring long series of historical data, exclusively from temperate climate zones, have been proposed for automated monitoring of influenza sentinel surveillance data. We evaluated three alternative statistical approaches where alert thresholds are based on recent data in both temperate and subtropical regions. METHODS: We compared time series, regression, and cumulative sum (CUSUM) models on empirical data from Hong Kong and the US using a composite index (range = 0-1) consisting of the key outcomes of sensitivity, specificity, and time to detection (lag). The index was calculated based on alarms generated within the first 2 or 4 weeks of the peak season. RESULTS: We found that the time series model was optimal in the Hong Kong setting, while both the time series and CUSUM models worked equally well on US data. For alarms generated within the first 2 weeks (4 weeks) of the peak season in Hong Kong, the maximum values of the index were: time series 0.77 (0.86); regression 0.75 (0.82); CUSUM 0.56 (0.75). In the US data the maximum values of the index were: time series 0.81 (0.95); regression 0.81 (0.91); CUSUM 0.90 (0.94). CONCLUSIONS: Automated influenza surveillance methods based on short-term data, including time series and CUSUM models, can generate sensitive, specific, and timely alerts, and can offer a useful alternative to Serfling-like methods that rely on long-term, historically based thresholds.

Algorithms↗

PubMed2004

Event-related potential correlates of judgment categories and detection sensitivity in a visual detection task.

Event-related potentials were recorded from human subjects performing a visual detection task to find correlates of detection performance (d' and beta) in accordance with the theory of signal detection. Two spatial frequencies of square waves shifted horizontally with three shifting-step varieties were presented to the subjects who reported whether or not the waves were perceived to shift. Although three components of N1, P2, and P3 were observed for all of four response categories of hit, miss, false alarm, and correct rejection, only the amplitudes of the P3 component at vertex and parietal sites highly correlated to the detection sensitivity of d'. It was also found that coefficients of correlation between the P3 amplitudes at these sites and observed hit and false alarm rates were highly significant and a d'-extrapolation value reproduced by the normalized P3 amplitudes and the usual d' indicated a highly linear trend. Results suggest that generation of the P3 component is associated with "threshold-modulating" mechanisms which determine detection sensitivity of a task for each perceptual event.

Adult↗

PubMed1997

Statistical evaluation of hearing screening by distortion product otoacoustic emissions.

The aim of this study was to provide a statistical evaluation of the screening properties of distortion product otoacoustic emissions (DPOEs) in individuals with clinically normal hearing and in patients with pure sensorineural deafness of various degrees. The main informational parameters used were sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and the analysis of receiver operating characteristic (ROC) curves. For each frequency tested, ears were classified as a function of their audiometric threshold. Two groups were defined relative to an arbitrary reference, the "audiometric criterion." The PPV decreased and NPV increased with increases in the audiometric criterion. Each point of the ROC curve represents the relationship between the false alarm rate and the hit rate for each audiometric criterion ranging between 10 and 75 dB hearing level: the lower the audiometric criterion, the lower the hit rate value, and the lower the false alarm value. The audiometric criterion giving the highest hit rate and the lowest false alarm rate was 55 to 60 dB hearing level for primaries at 60 and 70 dB sound pressure level, or 25 to 30 dB hearing level for primaries at 30, 40, and 50 dB sound pressure level. These two different behaviors of ROC curves are consistent with the hypothesis that DPOEs do not represent activity at a single location along the basilar membrane.

Adolescent↗

PubMed2001

Age and alarm symptoms do not predict endoscopic findings among patients with dyspepsia: a multicentre database study.

INTRODUCTION: Symptoms of dyspepsia are common but most patients do not have major upper gastrointestinal pathology. Endoscopy is recommended for dyspeptic patients over the age of 45, or those with certain "alarm" symptoms. We have evaluated the effectiveness of age and "alarm" symptoms for predicting major endoscopic findings in six practising endoscopy centres. METHODS: Clinical variables of consecutive patients with dyspepsia symptoms undergoing upper endoscopy examinations were recorded using a common endoscopy database. Patients who had no previous upper endoscopy or barium radiography were included. Stepwise multivariate logistic regression was used to identify predictors of endoscopic findings. The accuracy of these for predicting endoscopic findings was evaluated with receiver operating characteristic analysis. The sensitivity and specificity of age thresholds from 30 to 70 years were evaluated. RESULTS: Major pathology (tumour, ulcer, or stricture) was found at endoscopy in 787/3815 (21%) patients with dyspepsia. Age, male sex, bleeding, and anaemia were found to be significant but weak independent predictors of endoscopic findings. A multivariate prediction rule based on these factors had poor predictive accuracy (c statistic=0.62). Using a simplified prediction rule of age > or =45 years or the presence of any "alarm" symptom, sensitivity was 87% and specificity was 26%. Increasing or decreasing the age cut off did not significantly improve the predictive accuracy. CONCLUSIONS: Age and the presence of "alarm" symptoms are not effective predictors of endoscopic findings among patients with dyspepsia. Better clinical prediction strategies are needed to identify patients with significant upper gastrointestinal pathology.

Adult↗

PubMed1996

Home documented monitoring of cardiorespiratory pattern and oxygen saturation in healthy infants.

The objective of this study was to establish longitudinal normative limits for home memory monitors during early infancy. Eighty-eight healthy infants were monitored overnight at 0.25-19 wk of age using the Healthdyne Smart Monitor. Apnea settings were 14 s for recording and 40 s for alarm; the bradycardia setting was 50 beats/min (5-s delay) for both recording and alarm. Arterial oxygen saturation (SaO2) was documented whenever an event was recorded. The monitor was used 77% of all possible days; median daily use was 8.0 h. Eighty-three percent of all monitor alarms were caused by loose leads, the other 17% by false apnea or false bradycardia. Of all recorded events, 68.9% were caused by false apnea or false bradycardia; the other 31.1% were central apneas that reached the recording threshold of 14 s. The longest apnea was 36 s (wk 1); the 95th percentile for longest apnea was 19.9 s in wk 1 and 18.0 s in wk 17-19 (p < 0.001). Periodic low SaO2 values occurred with periodic breathing; the lowest value was 72%. The 5th percentiles for lowest SaO2 were 82 and 86% in wk 1 and 13-19, respectively (p < 0.001), but the minimum value observed in any week was never > 81%. The median duration of SaO2 < 90% was only 5 s but the range was wide (1-183 s), and 39/527 episodes (7.4%) were > 10 s. In summary, these longitudinal data provide the first available normal limits for cardiorespiratory pattern and SaO2 during documented home monitoring in early infancy. Utilization of these normative data will improve the diagnostic validity and clinical usefulness of event recordings.

Apnea↗

PubMedDate not supplied

[Airborne asbestos fibers: law references, TLV, considerations].

The ACGIH proposal of 0.1 fibers/liter as TLV for airborne asbestos fibers isn't a properly parameter, because it is applicable in work environments and the Italian legislation has forbidden every work which employs asbestos from 1993 [Law 257/92 and Min.Dec. 6/9/94]. Actually in Italy the application of a TLV is only referred to two analytical results: A) 20 ff/liter by CPOM analysis, B) 2 ff/liter by SEM analysis. We think that a CPOM 4-5 ff/liter is a no trespassing limit and over this concentration alarm may be notified. Waste disposal of asbestos materials must be properly disposed in a restricted area.

Air Pollutants, Occupational↗

PubMed2003

Egrets as monitors of trace-metal contamination in wetlands of Pakistan.

Environments in Pakistan are subject to increasing pollution, but previous studies were very scanty. During 1999 and 2000, we assessed trace element contamination at three wetlands, Karachi Harbour (with presumed industrial-urban pollution), Taunsa Barrage (agricultural pollution), and Haleji Lake (relatively unpolluted), using as indicators the eggs and the feathers of colonial waterbirds, particularly Little Egrets, their prey, and the sediments collected within their foraging areas. The concentrations of As, Cd, Cr, Pb, Hg, Mn, Se, and Zn were generally within the normal background level, and mostly below the threshold that may affect bird survival or reproduction. However, somewhat high concentrations were found in fish from Karachi, for Pb that was at levels that may harm fish reproduction, and for Hg that was at limit concentration for human consumption. Alarming concentrations were found for Cr and Se in sediments from Karachi, that were above the critical levels for contaminated soil, and Se in eggs, that may affect egret reproduction. The differences among the three wetlands were less marked than hypothesized. The egret species within the same area differed in the concentration of certain elements in their eggs, possibly because females may have foraged in different habitats before breeding, whereas no interspecies difference was found in chick feathers, presumably because their food had been collected in similar habitats around the colony. High bioaccumulation from sediments to organic samples occurred for Hg, while Cd, Se, and Zn exhibited low accumulation; for all these elements, feathers of predatory birds such as the egrets are the best indicators of environmental contamination. On the other hand, As and Cr did not bioaccumulate, and the sediments, or the organisms low in the food chain, like fish or crustaceans, are better indicators of their presence in the environment than predatory birds.

Animals↗

PubMed2001

The variance theory of the mirror effect in recognition memory.

The mirror effect refers to a rather general empirical finding showing that, for two classes of stimuli, the class with the higher hit rates also has a lower false alarm rate. In this article, a parsimonious theory is proposed to account for the mirror effect regarding, specifically, high- and low-frequency items and the associated receiver-operating curves. The theory is implemented in a recurrent network in which one layer represents items and the other represents contexts. It is shown that the frequency mirror effect is found in this simple network if the decision is based on counting the number of active nodes in such a way that performance is optimal or near optimal. The optimal performance requires that the number of active nodes is low, only nodes active in the encoded representation are counted, the activation threshold is set between the old and the new distributions, and normalization is based on the variance of the input. Owing to the interference caused by encoding the to-be-recognized item in several preexperimental contexts, the variance of the input to the context layer is greater for high- than for low-frequency items, which yields lower hit rates and higher false alarm rates for high- than for low-frequency items. Although initially the theory was proposed to account for the mirror effect with respect to word frequency, subsequent simulations have shown that the theory also accounts for strength-based mirror effects within a list and between lists. In this case, consistent with experimental data, the variance theory suggests that focusing attention to the more difficult class within a list affects the hit rate, but not the false alarm rate and not the standard deviations of the underlying density, leading to no mirror effect.

Adult↗

PubMed2005

Comparison perception of singular transcranial magnetic stimuli by subjectively electrosensitive subjects and general population controls.

Transcranial magnetic stimulation of the dorsolateral prefrontal cortex by single pulses of varying field intensities was used to measure thresholds of individual perception and motor response in three groups of subjects: subjectively electrosensitive people, general population controls with a high burden of complaints related to electromagnetic field (EMF) exposure in the literature (highest decile in complaint burden), and general population controls with a low burden of complaints (lowest decile in complaint burden). The major study endpoint was the ability of the subjects to differentiate between real magnetic stimulation and a sham condition. There were no significant differences between groups in the thresholds, neither of detecting the real magnetic stimulus nor in motor response. But the three groups differed significantly in differentiating between stimulation and sham condition, with the subjectively electrosensitive people having the lowest ability to differentiate and the control group with high level of EMF-related complaints having the best ability to differentiate. Differences between groups were mostly due to false alarm reactions in the sham condition reported by subjectively electrosensitives (SES). We found no objective correlate of the self perception of being "electrosensitive." Overall, our experiment does not support the hypothesis that subjectively electrosensitive patients suffer from a physiological hypersensitivity to EMFs or stimuli. Further research should focus on disposing factors explaining the unspecific sensory hyperresponsiveness of subjectively electrosensitive subjects.

Adolescent↗

PubMed1999

Prediction of conductive hearing loss based on acoustic ear-canal response using a multivariate clinical decision theory.

This study evaluated the accuracy of acoustic response tests in predicting conductive hearing loss in 161 ears of subjects from the age of 2 to 10 yr, using as a "gold standard" the air-bone gap to classify ears as normal or impaired. The acoustic tests included tympanometric peak-compensated static admittance magnitude (SA) and tympanometric gradient at 226 Hz, and admittance-reflectance (YR) measurements from 0.5 to 8 kHz. The performance of individual, frequency-specific, YR test variables as predictors was assessed. By applying logistic regression (LR) and discriminant analysis (DA) techniques to the multivariate YR response, two univariate functions were calculated as the linear combinations of YR variables across frequency that best separated normal and impaired ears. The tympanometric and YR tests were also combined in a multivariate manner to test whether predictive efficacy improved when 226-Hz tympanometry was added to the predictor set. Conductive hearing loss was predicted based on air-bone gap thresholds at 0.5 and 2 kHz, and on a maximum air-bone gap at any octave frequency from 0.5 to 4 kHz. Each air-bone gap threshold ranged from 5 to 30 dB in 5-dB steps. Areas under the relative operating characteristic curve for DA and LR were larger than for reflectance at 2 kHz, SA and Gr. For constant hit rates of 80% and 90%, both DA and LR scores had lower false-alarm rates than tympanometric tests-LR achieved a false-alarm rate of 6% for a sensitivity of 90%. In general, LR outperformed DA as the multivariate technique of choice. In predicting an impairment at 0.5 kHz, the reflectance scores at 0.5 kHz were less accurate predictors than reflectance at 2 and 4 kHz. This supports the hypothesis that the 2-4-kHz range is a particularly sensitive indicator of middle-ear status, in agreement with the spectral composition of the output predictor from the multivariate analyses. When tympanometric and YR tests were combined, the resulting predictor performed slightly better or the same as the predictor calculated from the use of the YR test alone. The main conclusion is that these multivariate acoustic tests of the middle ear, which are analyzed using a clinical decision theory, are effective predictors of conductive hearing loss.

Acoustic Impedance Tests↗