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P.j. Dyck - One of the best experts on this subject based on the ideXlab platform.
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patterns of quantitative sensation testing of hypoesthesia and hyperalgesia are predictive of diabetic polyneuropathy a study of three cohorts
Journal of The Peripheral Nervous System, 2000Co-Authors: P.j. Dyck, J.a. Velosa, T.s. Larson, P C ObrienAbstract:OBJECTIVE—To test quantitative sensation testing (QST) patterns of hypoesthesia and hyperalgesia as indicators of diabetic polyneuropathy (DPN) and its severity. RESEARCH DESIGN AND METHODS—We used Computer-Assisted Sensory Examination IV characterized the QST results of the foot of each patient in three diabetic cohorts (similar to 1,500 patients) as hyperesthetic (less than or equal to 2.5th Percentile), low-normal (2.5th–50th Percentiles), high-normal (50th–97.5th Percentiles), or hypoesthetic (greater than or equal to 97.5th Percentile), and tested associations with symptoms, impairments, and test abnormalities. RESULTS—Overall neuropathic impairment was most severe in the pancreas-renal transplant and nerve growth factor cohorts, but it was much less severe in the population-based Rochester Diabetic Neuropathy Study (RDNS) cohort. The frequency distribution of sensory abnormalities mirrored this difference. When the QST spectra of diabetic cohorts were compared with those of the control subject cohort for vibration and cooling sensations, the only abnormality observed was hypoesthesia, which was expressed as an increased number of subjects with values at or above the 97.5th Percentile or by an increased percentage of cases with high-normal values. Symptoms and impairments of DPN were significantly more frequent in the subjects with Values at or above the 97.5th Percentile than in the subjects whose values were between the 50th and 97.5th Percentiles. For heat pain (HP) sensation thresholds (intermediate pain severity [HP:5], pain threshold [HP:0.5], and pain-stimulus response slope [HP:5-0.5]), an increased frequency of both hypoalgesia and hyperalgesia was observed (especially in the RDNS cohort). Steeper pain-stimulus response slopes were significantly associated with sensory symptoms, including severity of pain. CONCLUSIONS—1) Decreased vibratory sensation (hypoesthesia) appears to be characteristic of mild DPN, whereas pan-modality hypoesthesia is characteristic of severe DPN. 2) A shift of vibratory and cold detection thresholds and also of attributes of nerve conduction and a measure of autonomic dysfunction from low-normal (2.5th–50th Percentiles) to high-normal (50th–37.5th Percentiles) appears to precede overt expression of DPN and to thereby provide evidence of subclinical abnormality. 3) Heat stimulus-induced hyperesthesia (low thresholds) occurs especially in mild DPN, and, because it correlates with DPN symptoms and impairments, it must be attributed to hyperalgesia rather than to supersensitivity. Therefore, hypoalgesia or hyperalgesia may be an indicator of early DPN.
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Patterns Of Quantitative Sensation Testing Of Hypoesthesia And Hyperalgesia Are Predictive Of Diabetic Polyneuropathy—a Study Of Three Cohorts
Journal of the Peripheral Nervous System, 2000Co-Authors: P.j. Dyck, J.a. Velosa, T.s. Larson, P.c. O'brienAbstract:OBJECTIVE—To test quantitative sensation testing (QST) patterns of hypoesthesia and hyperalgesia as indicators of diabetic polyneuropathy (DPN) and its severity. RESEARCH DESIGN AND METHODS—We used Computer-Assisted Sensory Examination IV characterized the QST results of the foot of each patient in three diabetic cohorts (similar to 1,500 patients) as hyperesthetic (less than or equal to 2.5th Percentile), low-normal (2.5th–50th Percentiles), high-normal (50th–97.5th Percentiles), or hypoesthetic (greater than or equal to 97.5th Percentile), and tested associations with symptoms, impairments, and test abnormalities. RESULTS—Overall neuropathic impairment was most severe in the pancreas-renal transplant and nerve growth factor cohorts, but it was much less severe in the population-based Rochester Diabetic Neuropathy Study (RDNS) cohort. The frequency distribution of sensory abnormalities mirrored this difference. When the QST spectra of diabetic cohorts were compared with those of the control subject cohort for vibration and cooling sensations, the only abnormality observed was hypoesthesia, which was expressed as an increased number of subjects with values at or above the 97.5th Percentile or by an increased percentage of cases with high-normal values. Symptoms and impairments of DPN were significantly more frequent in the subjects with Values at or above the 97.5th Percentile than in the subjects whose values were between the 50th and 97.5th Percentiles. For heat pain (HP) sensation thresholds (intermediate pain severity [HP:5], pain threshold [HP:0.5], and pain-stimulus response slope [HP:5-0.5]), an increased frequency of both hypoalgesia and hyperalgesia was observed (especially in the RDNS cohort). Steeper pain-stimulus response slopes were significantly associated with sensory symptoms, including severity of pain. CONCLUSIONS—1) Decreased vibratory sensation (hypoesthesia) appears to be characteristic of mild DPN, whereas pan-modality hypoesthesia is characteristic of severe DPN. 2) A shift of vibratory and cold detection thresholds and also of attributes of nerve conduction and a measure of autonomic dysfunction from low-normal (2.5th–50th Percentiles) to high-normal (50th–37.5th Percentiles) appears to precede overt expression of DPN and to thereby provide evidence of subclinical abnormality. 3) Heat stimulus-induced hyperesthesia (low thresholds) occurs especially in mild DPN, and, because it correlates with DPN symptoms and impairments, it must be attributed to hyperalgesia rather than to supersensitivity. Therefore, hypoalgesia or hyperalgesia may be an indicator of early DPN.
Gordon C. S. Smith - One of the best experts on this subject based on the ideXlab platform.
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Comparison of estimated fetal weight Percentiles near term for predicting extremes of birthweight Percentile.
American journal of obstetrics and gynecology, 2020Co-Authors: Ulla Sovio, Gordon C. S. SmithAbstract:Background The INTERGROWTH-21st estimated fetal weight Percentiles are recommended for predicting extremes of birthweight Percentile, although evidence for their superiority over the widely employed Hadlock method is lacking. Objective This study aimed to compare the ability of estimated fetal weight Percentiles calculated using the Hadlock method and the INTERGROWTH-21st method to predict extremes of birthweight Percentile. Study Design A prospective cohort study of blinded serial ultrasonography in nulliparous women with a singleton pregnancy, The Pregnancy Outcome Prediction study was conducted in Cambridge, United Kingdom. The study participants who had a research estimated fetal weight performed at 36 weeks’ gestation were eligible for the analysis. Estimated fetal weight Percentiles for gestational age calculated using (1) the Hadlock method or (2) the INTERGROWTH-21st method were used as exposures. Birthweight Percentiles of 90th (large for gestational age) for gestational age and fetal sex using the United Kingdom 1990 reference or the INTERGROWTH-21st birthweight reference were analyzed as outcomes using receiver operating characteristic curve analysis. Screening statistics from 2×2 tables were calculated for dichotomized exposures and each outcome. Results The Hadlock estimated fetal weight Percentile performed better than the INTERGROWTH-21st estimated fetal weight Percentile at discriminating both small for gestational age birthweight (areas under the receiver operating characteristic curves, 0.87 vs 0.85; 95% confidence intervals, 0.85–0.89 vs 0.83–0.87, respectively; P Conclusion Replacing the Hadlock method by the INTERGROWTH-21st method may lead to less effective screening for extremes of birthweight Percentile.
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the effect of customization and use of a fetal growth standard on the association between birthweight Percentile and adverse perinatal outcome
American Journal of Obstetrics and Gynecology, 2017Co-Authors: Ulla Sovio, Gordon C. S. SmithAbstract:Background It has been proposed that correction of offspring weight Percentiles (customization) might improve the prediction of adverse pregnancy outcome; however, the approach is not accepted universally. A complication in the interpretation of the data is that the main method for calculation of customized Percentiles uses a fetal growth standard, and multiple analyses have compared the results with birthweight-based standards. Objectives First, we aimed to determine whether women who deliver small-for-gestational-age infants using a customized standard differed from other women. Second, we aimed to compare the association between birthweight Percentile and adverse outcome using 3 different methods for Percentile calculation: (1) a noncustomized actual birthweight standard, (2) a noncustomized fetal growth standard, and (3) a fully customized fetal growth standard. Study Design We analyzed data from the Pregnancy Outcome Prediction study, a prospective cohort study of nulliparous women who delivered in Cambridge, UK, between 2008 and 2013. We used a composite adverse outcome, namely, perinatal morbidity or preeclampsia. Receiver operating characteristic curve analysis was used to compare the 3 methods of calculating birthweight Percentiles in relation to the composite adverse outcome. Results We confirmed previous observations that delivering an infant who was small for gestational age ( Conclusion The independent association between birthweight Percentile and adverse outcome was similar when we compared actual birthweight standards and fetal growth standards and compared customized and noncustomized standards. Use of fetal weight standards and customized Percentiles for maternal characteristics could lead to stronger associations with adverse outcome through confounding by preterm birth and maternal obesity.
Patrick A. Tibbits - One of the best experts on this subject based on the ideXlab platform.
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Percentiles of von Mises Stress from Combined Random Vibration and Static Loading by Approximate Noncentral Chi Square Distribution
Journal of Vibration and Acoustics, 2012Co-Authors: Patrick A. TibbitsAbstract:Firstly, a calculation for Percentiles of von Mises stress in linear structures subjected to Gaussian random loads is extended to the case of Gaussian random loads having nonzero mean values, i.e.,the inclusion of static loads. The development is restricted to the case of plane stress. The method includes calculation of a given Percentile of von Mises stress to any desired accuracy, a rapid estimate of the Percentile, and upper and lower bounds on the von Mises stress. The calculation expands the cumulative distribution function of the von Mises stress as a series of noncentral chi-square distributions. Summation of a sufficient number of terms of the series calculates the Percentile to the desired accuracy. The rapid estimate of the Percentile interpolates the distribution of the von Mises stress in a small number of inverse noncentral chi-square2 distribution functions. The upper and lower bounds on the Percentiles take advantage of the noncentral chi-square distribution of summations of normally distributed stress components. Second and third calculation methods arise from approximations of the distribution of quadratic forms of noncentral normal variables, or equivalently, linear combinations of noncentral chi-square variables. These methods provide rapid estimates of Percentiles of von Mises stress in linear structures under random loads having nonzero mean values. The accuracy and computational efficiency of the methods are reviewed and compared. The methods are expected to have wide application in design of and prognostics for components subjected to constant structural loads coupled with random loading arising from vibrations caused by wind, waves, seismic events, engines, turbulence, acoustic noise, etc.
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Percentiles of von Mises Stress From Combined Random Vibration and Static Loading by Approximate Noncentral Chi Square Distribution
Volume 8: Mechanics of Solids Structures and Fluids; Vibration Acoustics and Wave Propagation, 2011Co-Authors: Patrick A. TibbitsAbstract:Firstly, a calculation for Percentiles of von Mises stress in linear structures subjected to Gaussian random loads is extended to the case of Gaussian random loads having nonzero mean values, i.e., the inclusion of static loads. The development is restricted to the case of plane stress. The method includes calculation of a given Percentile of von Mises stress to any desired accuracy, a rapid estimate of the Percentile, and upper and lower bounds on the von Mises stress. The calculation expands the cumulative distribution function of the von Mises stress as a series of noncentral chi square distributions. Summation of a sufficient number of terms of the series calculates the Percentile to the desired accuracy. The rapid estimate of the Percentile interpolates the distribution of the von Mises stress in a small number of inverse noncentral chi-square distribution functions. The upper and lower bounds on the Percentiles take advantage of the noncentral chi-square distribution of summations of normally distributed stress components. Second and third calculation methods arise from approximations of the distribution of quadratic forms of noncentral normal variables, or equivalently, linear combinations of noncentral chi square variables. These methods provide rapid estimates of Percentiles of von Mises stress in linear structures under random loads having nonzero mean values. The accuracy and computational efficiency of the methods are reviewed and compared. The methods are expected to have wide application in design of and prognostics for components subjected to constant structural loads coupled with random loading arising from vibrations caused by wind, waves, seismic events, engines, turbulence, acoustic noise, etc.© 2011 ASME
Bertil Lindahl - One of the best experts on this subject based on the ideXlab platform.
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the applied statistical approach highly influences the 99th Percentile of cardiac troponin i
Clinical Biochemistry, 2016Co-Authors: Kai M Eggers, Lars Lind, Fred S Apple, Bertil LindahlAbstract:Abstract Background Cardiac troponin (cTn) is the biomarker of choice for assessment of patients with acute coronary syndromes. Guidelines recommend the cTn 99th Percentile derived from a cardiovascular healthy reference population as decision threshold. The importance of standardized criteria for the composition of such a reference population is well acknowledged. In this analysis, we investigated to which extent different statistical methods might have bearing on the calculated cTnI 99th Percentile. Methods cTnI (Abbott) 99th Percentiles were determined in 521 cardiovascular healthy community-dwelling subjects using the nonparametric method, the Harrell-Davis bootstrap method and the robust method together with different tests to identify potential outliers (Dixon, Tukey, Reed) and different statistical softwares. Results The cTnI 99th Percentiles (nonparametric method) were 37 ng/L (total population), 42 ng/L (men) and 25 ng/L (women). These estimates differed by − 7.4% to + 5.7% using the Harrell-Davis bootstrap method and were up to 64.1% lower using the robust method. For the robust method, cTnI 99th Percentiles varied by 44.2% depending on the applied software. The method of Tukey classified nine subjects as outliers while no outlier was detected using the other methods. Excluding these nine subjects resulted in up to 60.2% lower cTnI 99th Percentiles. Conclusions Our results emphasize the need of a standardized statistical approach to calculate cTnI 99th Percentiles. Our findings support the use of the nonparametric method and a conservative approach to detect outliers. This requires that the assessed population is sufficiently large and well selected on the basis of stringently applied clinical criteria.
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factors influencing the 99th Percentile of cardiac troponin i evaluated in community dwelling individuals at 70 and 75 years of age
Clinical Chemistry, 2013Co-Authors: Kai M Eggers, Lars Lind, Per Venge, Bertil LindahlAbstract:BACKGROUND: We aimed to investigate the effects of sex, prevalent cardiovascular disease (CVD), and aging on the 99th Percentile of cardiac troponin I (cTnI). METHODS: cTnI was measured using a high-sensitivity assay (Abbott Diagnostics) in 814 community-dwelling individuals at both 70 and 75 years of age. We determined the cTnI 99th Percentiles separately using nonparametric methods in the total sample, in men and women, and in individuals with and without CVD. RESULTS: The cTnI 99th Percentile at baseline was 55.2 ng/L for the total cohort. Higher 99th Percentiles were noted in men (69.3 ng/L) and individuals with CVD (74.5 ng/L). The cTnI 99th Percentile in individuals free from CVD at baseline (n = 498) increased by 51% from 38.4 to 58.0 ng/L during the 5-year observation period. Relative increases ranging from 44% to 83% were noted across all subgroups. Male sex [odds ratio, 5.3 (95% CI, 1.5–18.3)], log-transformed N-terminal pro-B-type natriuretic peptide [odds ratio, 1.9 (95% CI, 1.2–3.0)], and left-ventricular mass index [odds ratio, 1.3 (95% CI, 1.1–1.5)] predicted increases in cTnI concentrations from below the 99th Percentile (i.e., 38.4 ng/L) at baseline to concentrations above the 99th Percentile at the age of 75 years. CONCLUSIONS: cTnI concentration and its 99th Percentile threshold depend strongly on the characteristics of the population being assessed. Among elderly community dwellers, higher concentrations were seen in men and individuals with prevalent CVD. Aging contributes to increasing concentrations, given the pronounced changes seen with increasing age across all subgroups. These findings should be taken into consideration when applying cTnI decision thresholds in clinical settings.
Ulla Sovio - One of the best experts on this subject based on the ideXlab platform.
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Comparison of estimated fetal weight Percentiles near term for predicting extremes of birthweight Percentile.
American journal of obstetrics and gynecology, 2020Co-Authors: Ulla Sovio, Gordon C. S. SmithAbstract:Background The INTERGROWTH-21st estimated fetal weight Percentiles are recommended for predicting extremes of birthweight Percentile, although evidence for their superiority over the widely employed Hadlock method is lacking. Objective This study aimed to compare the ability of estimated fetal weight Percentiles calculated using the Hadlock method and the INTERGROWTH-21st method to predict extremes of birthweight Percentile. Study Design A prospective cohort study of blinded serial ultrasonography in nulliparous women with a singleton pregnancy, The Pregnancy Outcome Prediction study was conducted in Cambridge, United Kingdom. The study participants who had a research estimated fetal weight performed at 36 weeks’ gestation were eligible for the analysis. Estimated fetal weight Percentiles for gestational age calculated using (1) the Hadlock method or (2) the INTERGROWTH-21st method were used as exposures. Birthweight Percentiles of 90th (large for gestational age) for gestational age and fetal sex using the United Kingdom 1990 reference or the INTERGROWTH-21st birthweight reference were analyzed as outcomes using receiver operating characteristic curve analysis. Screening statistics from 2×2 tables were calculated for dichotomized exposures and each outcome. Results The Hadlock estimated fetal weight Percentile performed better than the INTERGROWTH-21st estimated fetal weight Percentile at discriminating both small for gestational age birthweight (areas under the receiver operating characteristic curves, 0.87 vs 0.85; 95% confidence intervals, 0.85–0.89 vs 0.83–0.87, respectively; P Conclusion Replacing the Hadlock method by the INTERGROWTH-21st method may lead to less effective screening for extremes of birthweight Percentile.
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the effect of customization and use of a fetal growth standard on the association between birthweight Percentile and adverse perinatal outcome
American Journal of Obstetrics and Gynecology, 2017Co-Authors: Ulla Sovio, Gordon C. S. SmithAbstract:Background It has been proposed that correction of offspring weight Percentiles (customization) might improve the prediction of adverse pregnancy outcome; however, the approach is not accepted universally. A complication in the interpretation of the data is that the main method for calculation of customized Percentiles uses a fetal growth standard, and multiple analyses have compared the results with birthweight-based standards. Objectives First, we aimed to determine whether women who deliver small-for-gestational-age infants using a customized standard differed from other women. Second, we aimed to compare the association between birthweight Percentile and adverse outcome using 3 different methods for Percentile calculation: (1) a noncustomized actual birthweight standard, (2) a noncustomized fetal growth standard, and (3) a fully customized fetal growth standard. Study Design We analyzed data from the Pregnancy Outcome Prediction study, a prospective cohort study of nulliparous women who delivered in Cambridge, UK, between 2008 and 2013. We used a composite adverse outcome, namely, perinatal morbidity or preeclampsia. Receiver operating characteristic curve analysis was used to compare the 3 methods of calculating birthweight Percentiles in relation to the composite adverse outcome. Results We confirmed previous observations that delivering an infant who was small for gestational age ( Conclusion The independent association between birthweight Percentile and adverse outcome was similar when we compared actual birthweight standards and fetal growth standards and compared customized and noncustomized standards. Use of fetal weight standards and customized Percentiles for maternal characteristics could lead to stronger associations with adverse outcome through confounding by preterm birth and maternal obesity.
