Regularisation in discrete survival models: A comparison of lasso and gradient boosting

2021 ◽  
Vol 55 (1) ◽  
pp. 29-44
Author(s):  
Alphonce Bere ◽  
Godfrey H. Sithuba ◽  
Coster Mabvuu ◽  
Retang Mashabela ◽  
Caston Sigauke ◽  
...  
Keyword(s):  
Hazard Function ◽  
False Positive Rate ◽  
Real Life ◽  
Survival Models ◽  
Gradient Boosting ◽  
Penalization Method ◽  
Baseline Hazard ◽  
Real Life Data ◽  
Positive Rate ◽  
The Mean

We present the results of a simulation study performed to compare the accuracy of a lasso-type penalization method and gradient boosting in estimating the baseline hazard function and covariate parameters in discrete survival models. The mean square error results reveal that the lasso-type algorithm performs better in recovering the baseline hazard and covariate parameters. In particular, gradient boosting underestimates the sizes of the parameters and also has a high false positive rate. Similar results are obtained in an application to real-life data.

Ultrasonographic Transabdominal Measurement of Uterine Cervical Length for the Prediction of a Midtrimester Short Cervix

2020 ◽  
Author(s):  
Paul Guerby ◽  
Annie Beaudoin ◽  
Geneviève Marcoux ◽  
Mario Girard ◽  
Jean-Charles Pasquier ◽  
...  
Keyword(s):  
Roc Curve ◽  
False Positive Rate ◽  
Cervical Length ◽  
Ultrasound Measurement ◽  
Singleton Pregnancy ◽  
Short Cervix ◽  
Nulliparous Women ◽  
Key Points ◽  
Positive Rate ◽  
The Mean

Objective This study was aimed to estimate the value of transabdominal (TA) ultrasound measurement of cervical length (CL), as an alternative of transvaginal (TV) ultrasound, for universal screening of short cervix in the midtrimester. Study Design We conducted a prospective cohort study of nulliparous women with singleton pregnancy at 20 to 24 weeks of gestation. All participants underwent TA ultrasound followed by TV ultrasound with acquisitions of images and videos of the uterine cervix. A second sonographer, blinded to the participants' data and pregnancy outcomes, measured the CL using TA and TV images and videos. Pearson's correlation test and receiver operating characteristic (ROC) curve analyses were performed. Results A total of 805 participants were recruited, including 780 (97%) where TA CL measurement was feasible. We observed a strong correlation of CL between TA and TV (correlation coefficient: 0.57; p < 0.0001) with a mean TA measurement being 4 mm (95% confidence interval [CI]: −6 to 14 mm) below the mean TV measurement (mean of differences: 5 ± 4 mm). We observed that a TA CL <30 mm was highly predictive of a short cervix defined as a TV CL ≤25 mm (area under the ROC curve: 0.97; 95% CI: 0.95–0.99; p < 0.0001) with a sensitivity of 100% and a false-positive rate of 22%. Conclusion Universal short cervix screening in nulliparous women could be performed using TA ultrasound, which could allow the avoidance of TV ultrasound in more than three quarter of women. In low-risk population, TV ultrasound could be reserved to women with TA CL <30 mm. Key Points

scholarly journals Vitamin D assessment in perioperative medicine and critical care

2019 ◽  
Author(s):  
Paul Zajic ◽  
Stefan Heschl ◽  
Michael Schörghuber ◽  
Petra Srekl-Filzmaier ◽  
Tatjana Stojakovic ◽  
...  
Keyword(s):  
Vitamin D ◽  
Vitamin D Deficiency ◽  
False Positive Rate ◽  
Fluid Loading ◽  
Vitamin D Levels ◽  
Positive Rate ◽  
25 Hydroxy Vitamin D ◽  
The Mean ◽  
Clinical Trials Registry ◽  
The Impact

Summary Background There is controversy about the impact of acute illness on vitamin D levels. This study was carried out to assess the influence of perioperative fluid loading on 25-hydroxy-vitamin D [25(OH)D] levels. The study evaluated the clinical utility of a commonly available chemiluminescence assay (ECLIA, IDS-iSYS) and liquid chromatography/mass spectrometry (LC-MS/MS) in the diagnosis of vitamin D deficiency in this setting. Methods In this prospective observational pilot study in adult patients undergoing cardiovascular surgery on cardiopulmonary bypass (CPB), blood samples drawn at preoperative baseline (t1), after weaning from CPB (t2), on intensive care unit (ICU) admission (t3) and on the first (t4) and second (t5) postoperative days were analyzed. Results A total of 26 patients (130 samples) were included in this study. Fluid loading by CPB led to a median reduction of 25(OH)D by −22.6% (range −54.5% to −19.5%) between t1 and t2. Cohen’s kappa (κ) for method agreement for vitamin D deficiency (tested cut-off values 20 ng/ml and 12 ng/ml), was κ = 0.291 (p < 0.001) and κ = 0.469 (p < 0.001), respectively. The mean difference between measurements by ECLIA and LC-MS/MS was 4.8 ng/ml (±5.7), Pearson’s r for correlation was 0.73 (p < 0.001). The biologically inactive C3-epimer did not contribute to 25(OH)D levels assessed by LC-MS/MS. Conclusion The 25(OH)D measurements by chemiluminescence assays can noticeably deviate from those measured by LC-MS/MS, which can be considered the unequivocal gold standard. These assays may still be acceptably reliable in the screening for vitamin D deficiency, especially in the setting of low vitamin D levels. Stricter definitions, e.g. serum 25(OH)D levels lower than 12 ng/ml, may be used to diagnose deficiency with low false positive rate. Trial Registration DRKS00009216, German Clinical Trials Registry (www.drks.de)

scholarly journals Pregnancy data enable identification of relevant biomarkers and a partial prognosis of autism at birth

2020 ◽  
Author(s):  
Hugues Caly ◽  
Hamed Rabiei ◽  
Perrine Coste-Mazeau ◽  
Sebastien Hantz ◽  
Sophie Alain ◽  
...  
Keyword(s):  
Behavioral Interventions ◽  
Statistical Tests ◽  
False Positive Rate ◽  
Familial Risk ◽  
Autism Spectrum ◽  
Gradient Boosting ◽  
Decision Tree Classification ◽  
Positive Rate ◽  
History Of

AbstractAttempts to extract early biomarkers and expedite detection of Autism Spectrum Disorder (ASD) have been centered on postnatal measures of babies at familial risk. Here, we suggest that it might be possible to do these tasks already at birth relying on ultrasound and biological measurements routinely collected from pregnant mothers and fetuses during gestation and birth. We performed a gradient boosting decision tree classification analysis in parallel with statistical tests on a population of babies with typical development or later diagnosed with ASD. By focusing on minimization of the false positive rate, the cross-validated specificity of the classifier reached to 96% with a sensitivity of 41% and a positive predictive value of 77%. Extracted biomarkers included sex, maternal familial history of auto-immune diseases, maternal immunization to CMV, IgG CMV level, timing of fetal rotation on head, femoral length in the 3rd trimester, white cells in the 3rd trimester, fetal heart rate during labour, newborn feeding and newborn’s temperature difference between birth and one day after. Statistical models revealed that 38% of babies later diagnosed with ASD had significantly larger fetal cephalic perimeter than age matched neurotypical babies, suggesting an in-utero origin of the bigger brains of toddlers with ASD. Results pave the way to use pregnancy follow-up measurements to provide an early prognosis of ASD and implement pre-symptomatic behavioral interventions to attenuate efficiently ASD developmental sequels.

An evaluation of tail paint as an aid or alternative to oestrus detection

1983 ◽  
Vol 37 (2) ◽  
pp. 221-227 ◽  
Author(s):  
M. J. Ducker ◽  
Rosemary A. Haggett ◽  
W. J. Fisher ◽  
Glenys A. Bloomfield ◽  
S. V. Morant
Keyword(s):  
False Positive ◽  
Detection Rate ◽  
False Positive Rate ◽  
Critical Time ◽  
Successful Pregnancy ◽  
Service Period ◽  
Significant Difference ◽  
Positive Rate ◽  
The Mean ◽  
Paint Removal

ABSTRACTOne hundred Friesian heifers were tail-painted between 14 and 21 days after calving. Once a week the paint strip was renewed if any paint had been removed. Over the whole period of observation the ovulation detection rate by definite signs of oestrus was high (0·79), whilst the proportion of silent ovulations detected by tail paint removal was low (0·10). In addition, tail paint was not removed on 0·28 of the occasions when definite oestrus with ovulation occurred and on 0·26 of the occasions when all the paint was removed it was not associated with any reproductive event. In practice, the critical time for tail paint to be effective is during the service period. Again, tail paint identified fewer (P < 0·001) ovulations than definite signs of oestrus (0·66) and had a significantly higher false positive rate (P < 0·001). Month of calving did not affect these results but the accuracy of tail paint declined as the season progressed (P < 0·001). False positive indications were not associated with individual animal characteristics. In a second trial 43 cows were tail-painted and 43 were not. There was no significant difference in the mean number of days from calving to first insemination or successful pregnancy between the two groups. It is concluded that in these trials tail paint was not an effective or reliable aid or alternative to oestrus detection.

Diagnostic utility of fluorodeoxyglucose positron emission tomography in prosthetic joint infection based on MSIS criteria

2019 ◽  
Vol 101-B (8) ◽  
pp. 910-914 ◽  
Author(s):  
M. Kiran ◽  
T D. Donnelly ◽  
C. Armstrong ◽  
B. Kapoor ◽  
G. Kumar ◽  
...  
Keyword(s):  
Prosthetic Joint Infection ◽  
False Positive ◽  
Fdg Pet ◽  
Preoperative Evaluation ◽  
Joint Infection ◽  
False Positive Rate ◽  
Prosthetic Joint ◽  
Positron Emission ◽  
Positive Rate ◽  
The Mean

Aims Prosthetic joint infection (PJI) and aseptic loosening in total hip arthroplasty (THA) can present with pain and osteolysis. The Musculoskeletal Infection Society (MSIS) has provided criteria for the diagnosis of PJI. The aim of our study was to analyze the utility of F18-fluorodeoxyglucose (FDG) positron emission tomography (PET) CT scan in the preoperative diagnosis of septic loosening in THA, based on the current MSIS definition of prosthetic joint infection. Patients and Methods A total of 130 painful unilateral cemented THAs with a mean follow-up of 5.17 years (sd 1.12) were included in this prospective study. The mean patient age was 67.5 years (sd 4.85). Preoperative evaluation with inflammatory markers, aspiration, and an F18 FDG PET scan were performed. Diagnostic utility tests were also performed, based on the MSIS criteria for PJI and three samples positive on culture alone. Results The mean erythrocyte sedimentation rate, C-reactive protein, and white cell count were 47.83 mm/hr, 25.21 mg/l, and 11.05 × 109/l, respectively. The sensitivity, specificity, accuracy, negative predictive value, and false-positive rate of FDG PET compared with MSIS criteria were 94.87%, 38.46 %, 56.38%, 94.59 %, and 60.21%, respectively. The false-positive rate of FDG PET compared with culture alone was 77.4%. Conclusion FDG PET has a definitive role in the preoperative evaluation of suspected PJI. This the first study to evaluate its utility based on MSIS criteria and compare it with microbiology results alone. However, FDG PET has a high false-positive rate. Therefore, we suggest that F18 FDG PET is useful in confirming the absence of infection, but if positive, may not be confirmatory of PJI. Cite this article: Bone Joint J 2019;101-B:910–914.

scholarly journals Routine follow-up of native valve disease: real life data from a physiologist-led valve clinic

2021 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
K Hyams ◽  
K Balkhausen ◽  
C Townsend
Keyword(s):  
Real Life ◽  
Heart Association ◽  
Native Valve ◽  
Conservative Strategy ◽  
Funding Sources ◽  
Real Life Data ◽  
Number Of Patients ◽  
The Mean ◽  
Funding Acknowledgements

Abstract Funding Acknowledgements Type of funding sources: None. Purpose The 2014 American Heart Association (AHA) guidelines for the management of Valvular Heart Disease (VHD) suggest that patients with mild and moderate native VHD should be followed up with echocardiography at regular intervals. Following audits at our hospital in 2016, dedicated Physiologist Led Valve Clinics (PLVC) were initiated to improve guideline adherence. A conservative strategy for follow-up frequency based on AHA guidelines was chosen (3 years for mild VHD, and 1 year for moderate VHD). This audit aimed to ascertain adherence to this conservative follow-up strategy, and to assess the progression of VHD between echocardiographic assessments to inform a strategy for safe follow-up in our PLVC. Methods Our echocardiography database Cognos was searched for patients with isolated mild and moderate native VHD, seen in our PLVC between 2016-2018 and followed up between 2017-2019. Patients with severe, prosthetic, combined or significant mixed VHD were excluded. Echocardiography reports on McKesson were reviewed and the follow-up interval recorded for each patient. The severity of VHD at the index visit, and then at follow-up, was recorded to determine whether there had been a progression in VHD severity. For patients with progression, it was recorded whether they were symptomatic at follow-up or subsequently underwent valvular intervention. Results 466 index echocardiograms were reviewed; 134 patients were included (mean age 73.4) after removing those with exclusion criteria. The mean follow-up interval in mild VHD ranged between 587.6 ± 188.3 days, and 667.3 ± 174.6 days, well above the recommended 3 years (or 1095 days). The majority of patients with moderate VHD received follow-up well before the upper limit of AHA guidance (2 years, or 730 days). Mean follow-up ranged between 408.3 ± 80.8 days (in moderate aortic stenosis (AS)) and 504.0 ± 29.0 days (in moderate mitral stenosis (MS)). The number of patients followed up with mild VHD was very low. 1 patient in each group progressed to moderate VHD (out of 2, 3 and 5 respectively); none became symptomatic, and none progressed from mild to severe VHD. In moderate VHD, progression rates were highest in AS (34.8%). Patients with progressive disease were more frequently symptomatic (43%) or underwent valve intervention (25%). Fewer with mitral regurgitation (MR) (22%) progressed, 44.5% of whom were symptomatic, 11% undergoing intervention. Patients with moderate aortic regurgitation (AR) saw the lowest progression rates (11.4%), 50% of whom were symptomatic. There was no progression in moderate MS. Conclusions Patients with mild VHD can safely be followed up less conservatively in the PLVC setting, adhering to AHA guidance (3-5 years). Patients with moderate AS should be considered to remain under conservative follow-up (12-18 months). Follow-up for moderate AR, MR and MS can safely be adjusted towards the less conservative end of the AHA guidance (2 years). Abstract Figure.

scholarly journals A Hybrid Brain–Computer Interface for Real-Life Meal-Assist Robot Control

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4578
Author(s):  
Jihyeon Ha ◽  
Sangin Park ◽  
Chang-Hwan Im ◽  
Laehyun Kim
Keyword(s):  
User Interfaces ◽  
Information Transfer ◽  
Brain Computer Interface ◽  
False Positive Rate ◽  
Real Life ◽  
The Elderly ◽  
Computer Interface ◽  
Additional Time ◽  
Information Transfer Rate ◽  
Positive Rate

Assistant devices such as meal-assist robots aid individuals with disabilities and support the elderly in performing daily activities. However, existing meal-assist robots are inconvenient to operate due to non-intuitive user interfaces, requiring additional time and effort. Thus, we developed a hybrid brain–computer interface-based meal-assist robot system following three features that can be measured using scalp electrodes for electroencephalography. The following three procedures comprise a single meal cycle. (1) Triple eye-blinks (EBs) from the prefrontal channel were treated as activation for initiating the cycle. (2) Steady-state visual evoked potentials (SSVEPs) from occipital channels were used to select the food per the user’s intention. (3) Electromyograms (EMGs) were recorded from temporal channels as the users chewed the food to mark the end of a cycle and indicate readiness for starting the following meal. The accuracy, information transfer rate, and false positive rate during experiments on five subjects were as follows: accuracy (EBs/SSVEPs/EMGs) (%): (94.67/83.33/97.33); FPR (EBs/EMGs) (times/min): (0.11/0.08); ITR (SSVEPs) (bit/min): 20.41. These results revealed the feasibility of this assistive system. The proposed system allows users to eat on their own more naturally. Furthermore, it can increase the self-esteem of disabled and elderly peeople and enhance their quality of life.

scholarly journals On modified Kies distribution and its applications

2017 ◽  
Vol 51 (1) ◽  
pp. 41-60
Author(s):  
C. SATHEESH KUMAR ◽  
S. H. S. DHARMAJA
Keyword(s):  
Maximum Likelihood ◽  
Hazard Function ◽  
Real Life ◽  
Simulated Data ◽  
Maximum Likelihood Estimators ◽  
Data Sets ◽  
Life Data ◽  
Real Life Data ◽  
Method Of Maximum Likelihood ◽  
Simulated Data Sets

In this paper, we consider a class of bathtub-shaped hazard function distribution through modifying the Kies distribution and investigate some of its important properties by deriving expressions for its percentile function, raw moments, stress-strength reliability measure etc. The parameters of the distribution are estimated by the method of maximum likelihood and discussed some of its reliability applications with the help of certain real life data sets. In addition, the asymptotic behavior of the maximum likelihood estimators of the parameters of the distribution is examined by using simulated data sets.

On designing a robust double exponentially weighted moving average control chart for process monitoring

2018 ◽  
Vol 40 (15) ◽  
pp. 4253-4265 ◽  
Author(s):  
Ishaq Adeyanju Raji ◽  
Nasir Abbas ◽  
Muhammad Riaz
Keyword(s):  
Moving Average ◽  
Real Life ◽  
Exponentially Weighted Moving Average ◽  
Data Set ◽  
Parameter Estimations ◽  
Real Life Data ◽  
Monitoring Process ◽  
The Mean ◽  
Weighted Moving Average ◽  
Exponentially Weighted

A double exponentially weighted moving average chart has been proven more efficient for monitoring process mean in comparison to the classical exponentially weighted moving average chart. We, in this article, made a careful investigation on how well this scheme performs with the presence of disturbances in the process under consideration. This investigation was motivated in exploring the scheme with some robust statistic, as the mean estimator performs woefully. We also evaluated the effects of parameter estimation on the phase II assuming the parameters are unknown. Adopting a 20% trimmed mean of trimeans (robust) reveals the effect of parameter estimations. We substantiated these claims by applying the scheme on a real-life data set. The findings of the study pronounced the trimean estimator to be the best of all the five estimators used, including the mean.

Free thyroxin measured in dried blood spots: results for 10 000 euthyroid and 29 hypothyroid newborns.

1985 ◽  
Vol 31 (11) ◽  
pp. 1829-1832 ◽  
Author(s):  
G Travert ◽  
F Lemonnier ◽  
Y Fernandez
Keyword(s):  
Birth Weight ◽  
False Positive Rate ◽  
Dried Blood Spots ◽  
Confirmatory Test ◽  
Screening Programs ◽  
Transient Hypothyroidism ◽  
Low Concentrations ◽  
Positive Rate ◽  
Preterm Babies ◽  
The Mean

Abstract We measured free thyroxin (FT4) in dried blood samples from 10 000 euthyroid and 29 hypothyroid newborns (three with transient hypothyroidism and 26 permanent). In euthyroids, the mean FT4 concentration was 16.9 (SD 4.5) pmol/L. Preterm babies had low concentrations of FT4, and values were closely related to birth weight when less than 2500 g. Assay of blood-spot FT4 appears to be specific as a test for hypothyroidism screening, yielding 0.42% false positives when a mean minus 2 SD cutoff value (8 pmol/L) was used. Correcting FT4 for birth weight further decreased the false-positive rate, to 0.07%. In all three newborns with transient hypothyroidism, FT4 was less than 8 pmol/L. In 25 of 26 permanent hypothyroids, FT4 ranged from undetectable to 5 pmol/L; in the 26th infant, who had a large ectopic gland, it was 8.2 pmol/L. We believe that FT4 assay offers an attractive improvement over total T4, whether performed as the first screening test or as a confirmatory test in thyrotropin screening programs.

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