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BMC Medical Research Methodology Mar 2016Although some nonparametric methods have been proposed in the literature to test for the equality of median survival times for censored data in medical research, in... (Comparative Study)
Comparative Study
BACKGROUND
Although some nonparametric methods have been proposed in the literature to test for the equality of median survival times for censored data in medical research, in general they have inflated type I error rates, which make their use limited in practice, especially when the sample sizes are small.
METHODS
In this paper, we propose a new nonparametric test with a simple test statistic to compare median survival times.
RESULTS
The results from our comprehensive simulation study show the new test controls type I error rate very well under all situations considered, even for small sample sizes. In addition, it has comparable detecting power compared to existing methods. Another advantage of the proposed test is its relatively simple formula that requires less computation.
CONCLUSIONS
We propose a new statistical method for comparing survival curves based on their medians. The new method can be easily implemented and applied to censored event time data.
Topics: Biometry; Computer Simulation; Female; Humans; Kaplan-Meier Estimate; Male; Models, Statistical; Sample Size; Sensitivity and Specificity; Survival Analysis; Time Factors
PubMed: 26983640
DOI: 10.1186/s12874-016-0133-3 -
IEEE Transactions on Image Processing :... 2002A class of robust weighted median (WM) sharpening algorithms is developed in this paper. Unlike traditional linear sharpening methods, weighted median sharpeners are...
A class of robust weighted median (WM) sharpening algorithms is developed in this paper. Unlike traditional linear sharpening methods, weighted median sharpeners are shown to be less sensitive to background random noise or to image artifacts introduced by JPEG and other compression algorithms. These concepts are extended to include data dependent weights under the framework of permutation weighted medians leading to tunable sharpeners that, in essence, are insensitive to noise and compression artifacts. Permutation WM sharpeners are subsequently generalized to smoother/sharpener structures that can sharpen edges and image details while simultaneously filter out background random noise. A statistical analysis of the various algorithms is presented, theoretically validating the characteristics of the proposed sharpening structures. A number of experiments are shown for the sharpening of JPEG compressed images and sharpening of images with background film-grain noise. These algorithms can prove useful in the enhancement of compressed or noisy images posted on the World Wide Web (WWW) as well as in other applications where the underlying images are unavoidably acquired with noise.
PubMed: 18244668
DOI: 10.1109/TIP.2002.800893 -
The Journals of Gerontology. Series A,... Oct 2021Deficit accumulation frailty indices (FIs) are widely used to characterize frailty. FIs vary in number and composition of items; the impact of this variation on...
BACKGROUND
Deficit accumulation frailty indices (FIs) are widely used to characterize frailty. FIs vary in number and composition of items; the impact of this variation on reliability and clinical applicability is unknown.
METHOD
We simulated 12 000 studies using a set of 70 candidate deficits in 12 080 community-dwelling participants 65 years and older. For each study, we varied the number (5, 10, 15, 25, 35, 45) and composition (random selection) of items defining the FI and calculated descriptive and predictive estimates: frailty score, prevalence, frailty cutoff, mortality odds ratio, predicted probability of mortality for FI = 0.28 (prevalence threshold), and FI cutoff predicting 10% mortality over the follow-up. We summarized the estimates' medians and spreads (0.025-0.975 quantiles) by number of items and calculated intraclass correlation coefficients (ICCs).
RESULTS
Medians of frailty scores were 0.11-0.12 with decreasing spreads from 0.04-0.24 to 0.10-0.14 for 5-item and 45-item FIs. The median cutoffs identifying 15% as frail was 0.19-0.20 and stable; the spreads decreased with more items. However, medians and spreads for the prevalence of frailty (median: 11%-3%), mortality odds ratio (median: 1.24-2.19), predicted probability of mortality (median: 8%-17%), and FI cutoff predicting 10% mortality (median: 0.38-0.20) varied markedly. ICC increased from 0.19 (5-item FIs) to 0.84 (45-item FIs).
CONCLUSIONS
Variability in the number and composition of items of individual FIs strongly influences their reliability. Estimates using FIs may not be sufficiently stable for generalizing results or direct application. We propose avenues to improve the development, reporting, and interpretation of FIs.
Topics: Aged; Aging; Canada; Frail Elderly; Frailty; Humans; Longitudinal Studies; Reproducibility of Results
PubMed: 34097017
DOI: 10.1093/gerona/glab161 -
Archives of Pathology & Laboratory... Apr 2004Several studies report the role of dimeric inhibin-A in assessing risk for fetal Down syndrome. The majority, however, use the Serotec inhibin-A assay and not the newer... (Comparative Study)
Comparative Study
CONTEXT
Several studies report the role of dimeric inhibin-A in assessing risk for fetal Down syndrome. The majority, however, use the Serotec inhibin-A assay and not the newer Diagnostic Systems Laboratories inhibin-A enzyme-linked immunosorbent assay (ELISA).
OBJECTIVES
To establish normal gestational age day-specific medians, to compare our results against previous studies pertaining to the inhibin-A ELISA, and to evaluate long-term assay performance.
DESIGN
Using the inhibin-A ELISA, 100 specimens were assayed for each completed week of gestation for weeks 15 to 20, 50 specimens for 14 weeks, and 54 specimens for 21 weeks or older. Regressed inhibin-A medians were calculated employing a second-degree polynomial fit of the arithmetic medians. Thereafter, inhibin-A ELISA lot comparisons were performed to evaluate consistency.
RESULTS
Regressed values of 182, 174, 175, 184, 201, and 226 pg/mL resulted for weeks 15 to 20, respectively [pg/mL inhibin-A = 4.1528(gestational age)2 - 136.49(gestational age) + 1294.9]. A comparison with 2 other studies shows our values to be lower overall by 15 +/- 11.4% and 16 +/- 2.6%. However, variability between kit lots was as high as 30%.
CONCLUSIONS
The equation derived provides for the calculation of gestational age day-specific inhibin-A medians for integration into maternal serum screening programs with a subsequent decrease in false-positives expected and observed. Our medians differ considerably from those of other studies, with limited data, using the Diagnostic Systems assay. However, lot changes since the initial analysis have exhibited similar inconsistencies. Therefore, we recommend that others incorporating the assay into their screening programs carefully establish, monitor, and adjust their medians accordingly as a result of potential variations.
Topics: Biomarkers; Chorionic Gonadotropin; Dimerization; Down Syndrome; Enzyme-Linked Immunosorbent Assay; Estriol; Female; Fetal Diseases; Gestational Age; Humans; Inhibins; Predictive Value of Tests; Pregnancy; Pregnancy Trimester, Second; Prenatal Diagnosis; Reagent Kits, Diagnostic; Reference Values; Reproducibility of Results; alpha-Fetoproteins
PubMed: 15043467
DOI: 10.5858/2004-128-415-EOADIA -
Biological Trace Element Research Oct 2021Selenium (Se) is an essential nutrient element for human health, and middle-aged and elderly people (age ≥ 45 years old) are at higher risk of nutrient deficiency...
Selenium (Se) is an essential nutrient element for human health, and middle-aged and elderly people (age ≥ 45 years old) are at higher risk of nutrient deficiency including Se due to their physiological characteristics. This study investigated the hair Se content of middle-aged and elderly people in China with the purpose of providing a reference for prescription of hair Se normal range in this population. In this study, the hair Se content of 2155 middle-aged and elderly people was detected with atomic fluorescence photometry. The participants were recruited from 15 provinces or municipalities spreading from south to north of China with a diverse Se content in soil. Additionally, the relationships between hair Se content with sex, age, and BMI were analyzed. The results found that the median and 95% quantile of hair Se content were 0.36 μg/g and 0.60 μg/g respectively, with a range of 0.08 to 20.04 μg/g in middle-aged and elderly Chinese. The hair Se content mostly concentrated at 0.23~0.48 μg/g in 81.11% of participants. The participants in Guangdong and Hunan provinces had the highest hair Se levels (medians were 0.51 and 0.50 μg/g, respectively), while Henan and Shaanxi provinces had the lowest levels (medians were 0.30 and 0.29 μg/g, respectively). In addition, the Se content of males was higher than that of females (p < 0.05), whereas there was no significant difference between different ages and BMI (p > 0.05). In conclusion, this study found that the hair Se content of middle-aged and elderly Chinese ranges from 0.08 to 20.04 μg/g, with median and 95% quantile of 0.36 μg/g and 0.60 μg/g, respectively. Our results provide a reference for the establishment of hair Se content in this population and suggest that the differences of region and sex should be considered when setting up the range.
Topics: Aged; China; Female; Hair; Humans; Male; Middle Aged; Selenium; Soil
PubMed: 33188457
DOI: 10.1007/s12011-020-02482-4 -
British Journal of Rheumatology Jul 1996Ultrasonography was used to measure flexor tendon sheath thickness in 14 insulin-dependent (IDDM) diabetics with diabetic cheiroarthropathy (DCA) and compared to 17 IDDM...
Ultrasonography was used to measure flexor tendon sheath thickness in 14 insulin-dependent (IDDM) diabetics with diabetic cheiroarthropathy (DCA) and compared to 17 IDDM patients without DCA along with 10 healthy volunteers. Assessment was also made of the presence of systemic diabetic microvascular disease complications. A blinded visual 'eyeball' report on the ultrasound scans by a radiologist found hypoechoic thickening of the flexor tendon sheaths in 12 of the 14 patients with DCA, three of the 17 unaffected diabetics and two of the healthy volunteers (Fisher's exact, P < 0.001). However, further quantitation of tendon sheath thickness separated patients with DCA from others. In all patients with DCA, tendon sheath thickness was > or = 1 mm (median 1.8 mm, range 1.0-2.3 mm) and < or = 1 mm in the other two groups (medians 0.6 and 0.5 mm, range 0.3-1.0 mm) (Kruskal-Wallis, P < 0.001). All patients with DCA had evidence of systemic microvascular disease complications, particularly proliferative retinopathy (82%). It appears that flexor tendon sheath thickening in the hand is an integral part of the pathology in DCA and is easily demonstrated by ultrasound. It is closely associated with overt diabetic microvascular disease complications.
Topics: Adult; Diabetes Mellitus, Type 1; Diabetic Angiopathies; Female; Hand; Humans; Joint Diseases; Joints; Male; Middle Aged; Single-Blind Method; Ultrasonography
PubMed: 8670603
DOI: 10.1093/rheumatology/35.7.676 -
Biomedical Reports May 2018Dual detection of α-fetoprotein (AFP) and free β-human chorionic gonadotropin (β-HCG) is a common screening method for Down syndrome in the second trimester and its...
Dual detection of α-fetoprotein (AFP) and free β-human chorionic gonadotropin (β-HCG) is a common screening method for Down syndrome in the second trimester and its efficacy is assessed by false-positive rate (FPR). The present study aimed to investigate the effects of the bias in median multiple of the median (mMoM) values of AFP and free β-HCG on FPR. The bias in mMoM values of AFP and free β-HCG and the bias in mMoM values under different gestational ages and weight groups were analyzed. Median equations were adjusted, and medians in LifeCycle software were replaced by local medians. Following two adjustments of the median equations, all indices including FPR, mMoM values of markers and mMoM values under different gestational ages and weight groups generally reached an ideal state. In conclusion, abnormal bias in mMoM values may prompt aberrant application of median equations, and regular monitoring of these indicators may be important for quality control in prenatal screening.
PubMed: 29725524
DOI: 10.3892/br.2018.1078 -
Diving and Hyperbaric Medicine Mar 2018This study aimed to compare the results from three Australian scuba diver surveys. As the surveys differed in recruitment methods, the expectation was that respondents... (Comparative Study)
Comparative Study
INTRODUCTION
This study aimed to compare the results from three Australian scuba diver surveys. As the surveys differed in recruitment methods, the expectation was that respondents would differ in some important characteristics.
METHODOLOGY
Anonymous, online, cross-sectional surveys of the demographics, health, diving practices and outcomes were distributed to: (1) Divers Alert Network Asia-Pacific (DAN AP) members; (2) Professional Association of Diving Instructors (PADI) Asia-Pacific members; and (3) divers who had received any PADI non-leadership certification within the previous four years. Only data from divers resident in Australia were analysed.
RESULTS
A total of 2,275 responses were received from current Australian residents, comprising 1,119 of 4,235 (26.4%) DAN members; 350 of 2,600 (13.5%) PADI members; and 806 of 37,000 (2.2%) PADI divers. DAN and PADI members had similar diving careers (medians 14 and 15 years, respectively). PADI members had undertaken more dives (median 800) than DAN members (330) and PADI divers (28). A total of 692 respondents reported suffering from diabetes or a cardiovascular, respiratory, neurological or psychological condition and included 34% of the DAN members and 28% of each of the PADI cohorts. Eighty-four divers had been treated for decompression illness (approximately 5% of DAN and PADI member groups and 1% of the PADI divers). Eighty-seven of 1,156 (7.5%) PADI respondents reported a perceived life-threatening incident while diving.
CONCLUSIONS
Despite low response rates, this study indicates clear differences in the characteristics of the divers in the three cohorts. Therefore, a survey of a single cohort may represent that diving population alone and the findings may be misleading. This bias needs to be clearly understood and any survey findings interpreted accordingly.
Topics: Adult; Cross-Sectional Studies; Decompression Sickness; Diving; Female; Health Status; Humans; Male; Middle Aged; Reproducibility of Results; Surveys and Questionnaires
PubMed: 29557098
DOI: 10.28920/dhm48.1.23-30 -
Dermatologica 1987This study reports the results of the Ingram dithranol regimen for the treatment of psoriasis in 275 inpatients. The median duration of hospitalization until clearance... (Review)
Review
This study reports the results of the Ingram dithranol regimen for the treatment of psoriasis in 275 inpatients. The median duration of hospitalization until clearance was 25 days and the medians of the interval until a next treatment or hospitalization was needed were 11 and 8.5 months, respectively.
Topics: Anthralin; Humans; Length of Stay; Psoriasis; Retrospective Studies
PubMed: 3308543
DOI: 10.1159/000248788 -
Disability and Rehabilitation Jun 2021To examine physiological responses and perceived exertion during robot-assisted treadmill walking in non-ambulatory stroke survivors; compare these outcomes with aerobic...
PURPOSE
To examine physiological responses and perceived exertion during robot-assisted treadmill walking in non-ambulatory stroke survivors; compare these outcomes with aerobic exercise recommendations; and investigate the effect of robotic assistance.
MATERIALS AND METHODS
Twelve non-ambulatory stroke survivors (67 ± 11 years-old, 84 ± 38 d post-stroke) participated. Subjects walked three times 20 min (1 session/day) in the Lokomat: once with conventional exercise parameters, once with 60% robotic assistance and once with 100% robotic assistance. Gas exchange and heart rate were monitored continuously. Perceived exertion was assessed every 3 min during walking.
RESULTS
During conventional robot-assisted treadmill walking, net perceived exertion (0-14 scale) significantly increased between minute 6 (median = 2, interquartile range = 4) and 18 (median = 5, interquartile range = 4). Net physiological responses did not significantly change over time. Throughout exercise, percentage of predicted heart rate reserve was significantly below the 40% threshold (medians: 11-14%) and percentage of predicted maximum heart rate reached the 55% threshold (medians: 59-60%). Perceived exertion reached the 11-point threshold halfway. Net physiological responses and perceived exertion did not significantly differ between 60% and 100% robotic assistance.
CONCLUSIONS
The assistance level that non-ambulatory stroke survivors require at their highest tolerable walking speed seems too high to sufficiently stress the cardiorespiratory system during robot-assisted treadmill walking.Implications for rehabilitationThe exercise intensity of 20-minute conventional robot-assisted treadmill walking can be low, and might be too low to challenge the cardiorespiratory system of non-ambulatory stroke survivors.Lowering the level of robotic assistance from 100% to 60% does not seem to increase the exercise intensity of 20-minute robot-assisted treadmill walking.
Topics: Aged; Exercise Test; Humans; Middle Aged; Physical Exertion; Robotics; Stroke; Stroke Rehabilitation; Survivors; Walking
PubMed: 31588811
DOI: 10.1080/09638288.2019.1671502