Analysis of dose distribution changes in radiation processing using a continuous variable F-test and p-value

This article considers two related issues concerning the analysis of interactions in complex linear models. The first issue concerns the omnibus test for interaction. Apparently, it is not well known that the usual F test for interaction can be replaced, in many applications, by a test that is more powerful against a certain class of alternatives. The competing test is based on the maximal product interaction contrast F statistic and achieves its power advantage by focusing solely on product contrasts. The maximal product interaction F test is reviewed and three new results are reported: (a) An extended table of exact critical values is computed, (b) a table of moment functions useful for approximating the p-value corresponding to an observed maximal F statistic is computed, and (c) a simulation study concerning the null distribution of the maximal F statistic when data are unbalanced or covariates are present is reported. It is conjectured that lack of balance or presence of covariates has no effect on the null distribution. The simulation results support the conjecture. The second issue concerns follow-up tests when the omnibus test is significant. It appears that researchers, in general, do not perform coherent follow-up tests on interactions. To make it easier for researchers to do so, an exposition on the use of product interaction contrasts and partial interactions in complex fixed-effects models is provided. The recommended omnibus and follow-up tests are illustrated on an educational data set analyzed using SAS ( SAS Institute, 1988 ) and SPSS (1990) .

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The IC50 Assay Is Predictive of Molecular Response, and Indicative of Optimal Dose in De-Novo CML Patients.

Blood ◽

10.1182/blood.v112.11.1109.1109 ◽

2008 ◽

Vol 112 (11) ◽

pp. 1109-1109

Author(s):

Deborah L White ◽

Verity A Saunders ◽

Thea Kalebic ◽

Timothy P Hughes

Keyword(s):

De Novo ◽

Statistical Significance ◽

Continuous Variable ◽

Rank Test ◽

P Value ◽

Molecular Response ◽

Optimization Strategy ◽

Log Reduction ◽

Significant Difference ◽

The Impact

Abstract We have previously demonstrated significant interpatient variability in the IC50imatinib, a measure of the intrinsic sensitivity of a patient to imatinib induced kinase inhibition. Furthermore, this measure is predictive of the achievement of major molecular response (MMR > 3 log reduction in BCR-ABL) in de-novo CML patients treated with imatinib (n=60)1. In an expanded patient pool (n=116) we now perform an evaluation of the IC50 as a predictor of response, and address the IC50imatinib as a guide to dose selection. Samples were obtained with informed consent from de novo CML patients enrolled to either the TIDEL (600mg imatinib) or TOPS (randomised 400mg vs 800mg imatinib) trials. Blood was collected pre therapy, and the IC50 was performed as previously1. Outcome data was assessed using Kaplan Meier Analysis and the log rank test was used to assess statistical significance. In our previous analysis the IC50imatinib was divided about the median value for the cohort (0.6μM) into low and high IC50, with a significantly greater proportion of patients with low IC50imatinib achieving MMR by 12 months. In this expanded patient pool, we confirm this finding (<median of 0.7μM for this patient group) (low IC50 65% of patients achieve MMR by 12 mo vs high IC50 39% of patients p=0.014) Dividing the IC50’s into quartiles we now demonstrate that the IC50imatinib is a continuous variable with a greater proportion of patients in the lower quartile achieving MMR than those in the higher (Table 1 Total). Addressing the issue of dose we demonstrate that no patients with IC50>0.95uM achieve MMR on 400mg, and that this is statistically significantly when compared to all other groups. At 600mg while there is no overall significant difference there is a statistically relevant difference between groups 1, 2 and 4 as indicated. In contrast, at 800 mg the effect of IC50imatinib is overcome. MMR by 12 months Total 400mg 600mg 800mg p value Group1 <0.5μM 67% (27) 83% (12)* 50% (8)* 86% (7) 0.470 Group 2 >0.5<0.7μM 63% (30) 67% (6)* 53% (17)* 71% (7) 0.337 Group 3 >0.7<0.95μM 45% (31) 40%(5)* 30% (10) 56% (16) 0.139 Group 4>0.95μM 32% (28) 0% (7)* 22% (9)* 58% (12) 0.016 P value 0.042 0.018 0.108 0.778 Table 1: Dividing the patients into quartile based on the IC50 imatinib and assessing the Impact of dose on the achievement of MMR by 12 month. *p value <0.05 between groups (n). The failure to achieve a Complete Cytogenetic Response by 12 months is considered a suboptimal response. Assessing the molecular equivalent (≥2 log reduction in BCR-ABL) we demonstrate that a significantly greater proportion of patients with IC50imatinib>0.7μM fail to achieve a 2 log reduction when treated with 400mg (IC50 <0.7μM 11%: >0.7μM 33% p=0.034), and 600mg (IC50 <0.7μM 12%: >0.7μM 22% p=0.036). However, there is no significant difference in the 800mg patient cohort (IC50 <0.7μM 7%: >0.7μM 14% p=0.79). This analysis confirms that the IC50imatinib, is predictive of imatinib response. Patients with an IC50imatinib <0.7μM are likely to respond well to doses of 400mg imatinib, as suggested by evaluation of statistically relevant outcome benefit. In contrast patients with higher IC50imatinib (>0.7μM) may benefit from higher dosing regimens (p=0.012). Thus, the accurate assessment of IC50imatinib could support dose optimization strategy for patients with a suboptimal response.

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A retrospective analysis of patients with poor-risk germ cell tumor (PRGCT) treated at Indiana University from 2000 to 2010.

Journal of Clinical Oncology ◽

10.1200/jco.2013.31.15_suppl.4557 ◽

2013 ◽

Vol 31 (15_suppl) ◽

pp. 4557-4557

Author(s):

Nabil Adra ◽

Costantine Albany ◽

Daniel Sonnenburg ◽

Yan Tong ◽

Nasser H. Hanna ◽

...

Keyword(s):

Germ Cell ◽

Retrospective Analysis ◽

Tumor Markers ◽

Germ Cell Tumor ◽

Germ Cell Tumors ◽

Continuous Variable ◽

Cell Tumor ◽

P Value ◽

Indiana University ◽

Poor Risk

4557 Background: PRGCT represents 14% of germ cell tumors, with 2-year PFS of 50%. PRGCT is defined by primary mediastinal non-seminomatous germ cell tumor (PMNSGCT), non-pulmonary visceral metastasis (NPVM), AFP > 10,000 or hCG > 50,000. This analysis attempts to identify subsets of patients with more or less favorable outcomes among the poor risk groups. Methods: Retrospective analysis of all patients with testicular cancer seen at Indiana University (IU) from 2000-2010. 291 patients with PRGCT identified of whom 79 received initial therapy at IU. We analyzed the following variables: primary site testis/retroperitoneal (T/RP) vs. PMNSGCT, pulmonary vs. NPVM, and the amplitude of serum tumor markers. We identified groups of patients according to the level of tumor marker elevation with cutoff points of AFP 20,000 and hCG 200,000. Results: Mean age 29, mean AFP 8,283, mean hCG 185,667. 24% had PMNSGCT, 48% NPVM, 11% AFP>20,000, and 25% hCG>200,000. When hCG was analyzed as a continuous variable, every 10,000 unit increase in hCG caused the hazard of progression to increase by 1% (p value 0.01). Patients with NPVM had significantly worse PFS. NPVM with elevated hCG had worse outcome than NPVM with normal hCG. This did not correlate as well with AFP. PFS was worse with NPVM than elevated pre-chemotherapy tumor markers. Multiple different criteria for poor risk disease carried significantly worse impact on PFS and OS when compared to having a single criterion for poor risk disease. Conclusions: Our data indicate that patients with NPVM or more than one criteria for PRGCT have a worse outcome compared to other PRGCT subgroups. [Table: see text]

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Plasma glucose levels in the association between serum trans-β-carotene and obesity among children and adolescents

10.21203/rs.3.rs-17018/v1 ◽

2020 ◽

Author(s):

xiaodong zang ◽

Hui Liu ◽

Junqiang Zheng ◽

Ming Fan ◽

Xian Shen ◽

...

Keyword(s):

Plasma Glucose ◽

Inflection Point ◽

Continuous Variable ◽

P Value ◽

Inverse Association ◽

Linear Regression Models ◽

Lower Plasma ◽

Glucose Levels ◽

Lower Plasma Glucose ◽

Β Carotene

Abstract Background Results on the association between trans-β-carotene and obesity are less clear and little is known about how their relationship may be affected by plasma glucose levels.The present study aimed to evaluate the relationships between trans-β-carotene and obesity and to investigate whether plasma glucose levels had a modifying effect on these relationships. Methods Children aged 6-18 years were selected from the National Health and Nutrition Examination Survey(NHANES) (2001–2006) (n =8030). The serum trans-β-carotene levels were divided into tertiles, and their associations with obesity were evaluated using multivariable-adjusted linear regression models adjusted for potential confounding factors. The interaction effects between trans-β-carotene levels and plasma glucose levels on obesity were further evaluated. Results In the fully adjusted model, using serum trans-β-carotene as natural log-transformed continuous variable, the negative association between trans-β-carotene level and obesity were confirmed. In addition, plasma glucose levels significantly modified the inverse association between trans-β-carotene and obesity (p value for interaction: 0.09). A stronger association of trans-β-carotene levels with obesity was found in higher plasma glucose levels (more than100 mg/dl) than in lower plasma glucose levels. Further, a non-linear relationship was detected between trans-β-carotene and obesity in participants with higher plasma glucose levels, with an inflection point of 2.7 (trans-β-carotene =14.88 ug/dl). The effect sizes and confidence intervals for the left and right sides of the inflection point were 0.10 (0.00 to 0.2) and 6.7 (0.1 to 348.2), respectively. Conclusion Our findings indicate that the association between trans-β-carotene concentration and obesity is stronger in individuals with higher plasma glucose population than in those with lower plasma glucose levels.

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Analysis of outcome of diabetic foot ulcer following topical phenytoin and betadine use: a comparative study

International Surgery Journal ◽

10.18203/2349-2902.isj20171009 ◽

2017 ◽

Vol 4 (4) ◽

pp. 1263

Author(s):

Arshad Azeez ◽

N. S. Venkatesh ◽

T. Shivakumar

Keyword(s):

Hospital Stay ◽

Granulation Tissue ◽

Diabetic Foot ◽

Foot Ulcer ◽

Continuous Variable ◽

P Value ◽

Tissue Formation ◽

Diabetic Ulcer ◽

Granulation Tissue Formation ◽

Split Skin Grafting

Background: Diabetic ulcer is the major cause of morbidity and excess hospital care cost for the patients with diabetes and most frequent reason for hospitalization in patients. Diabetic foot ulcers precede almost 85% of amputations in India. Though there are many modes for care of the wound, treating diabetic wounds are still an enormous problem. Aim of the study was to analyse the outcome of topical phenytoin dressing as compared to conventional wound dressing in diabetic ulcers and thus to know if phenytoin is a better and cheaper alternative option in the management of diabetic ulcersMethods: A sample of 90 patients were selected using purposive sampling technique. Of which 45 underwent topical phenytoin dressings, remaining 45 underwent conventional wound care. Daily dressing was done for 14 days and then was subjected to split skin grafting. The variables were compared based on rate of granulation tissue formation, graft uptake & duration of hospital stay. The categorical variable was compared by chi square test and continuous variable by student t-test. A p value <0.05 was considered significant.Results: In Phenytoin group, mean rate of granulation tissue formation was 92.51%. Mean graft up-take was 92.98% and mean hospital stay was 35.68 days. In Conventional group, mean rate of granulation formation was 83.31%. The Mean graft up-take was only 78.09%, mean hospital stay was 47.31 days.Conclusions: Topical phenytoin helps in faster healing of the diabetic ulcer and better graft up-take and reduces hospital stay.

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KOMBINASI ANALISIS TEKNIS DAN ALGORITMA GRADIENT BOOSTING UNTUK MEMPREDIKSI INDEKS HARGA SAHAM GABUNGAN

10.31219/osf.io/2wxyv ◽

2020 ◽

Author(s):

danu salam ◽

Mustarum Musaruddin ◽

Hasmina Tari Mokui

Keyword(s):

Gradient Boosting ◽

P Value ◽

F Test

Saham merupakan surat berharga yang dapat diperdagangkan. Fluktuasi harga saham dapat dimanfaatkan oleh trader untuk mendapatkan keuntungan. Untuk melihat pergerakan harga saham dapat dilihat dari Indeks Harga Saham Gabungan (IHSG). Pada penelitian ini bertujuan untuk memprediksi indeks harga saham gabungan dengan mengkombinasikan antara analisis teknis dan menggunakan algoritma gradient boosting. Hasil eksperimen didapatkan perbedaan akurasi antara model dengan kombinasi dan tanpa kombinasi. Akurasi model kombinasi sebesar 86,79% dan RMSE sebesar 0,00786, dibandingkan dengan model tanpa kombinasi akurasinya 74.60% dan RMSE 0,01048. Sedangkan dari F-test didapatkan, P-value sebesar 1,457x10-147. Nilai P<0,05 memiliki nilai signifikansi penerimaan sehingga model yang diusulkan dapat diterima.

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MO517EFFECT MODIFIERS OF SERUM POTASSIUM AND MORTALITY IN THE IRISH HEALTH SYSTEM: THE NATIONAL KIDNEY DISEASE SURVEILLANCE SYSTEM (NKDSS)

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfab087.0037 ◽

2021 ◽

Vol 36 (Supplement_1) ◽

Author(s):

Leonard Browne ◽

Austin Stack

Keyword(s):

Kidney Disease ◽

Health System ◽

Surveillance System ◽

Disease Surveillance ◽

Index Date ◽

Continuous Variable ◽

P Value ◽

Medical Supervision ◽

Disease Surveillance System ◽

Baseline Health

Abstract Background and Aims Serum potassium (K+) exhibits a u-shaped association with mortality but uncertainty exists regarding optimal thresholds for survival and influencing factors. We examined the impact of serum K* on mortality in the Irish Health System with particular focus on kidney function and location of medical supervision. Method We utilised data from the Irish Kidney Disease Surveillance System (NKSS) to explore the association of serum K+ and mortality in a longitudinal cohort study. We identified all adult individuals (age > 18 years) who accessed health care from 2007 and 2012 in a regional health system with complete data on serum K+, associated laboratory indicators and vital status up to 31st December 2013 (n = 32,643). We randomly selected a single K+ measurement per patient with date of measurement as index date. Chronic kidney disease was defined as eGFR <60ml/min/1.73m² vs greater recorded at index date. Location of medical supervision was recorded as emergency room, inpatient location; outpatient clinic, and general practice location. The association of serum K+ was explored in categories and as a continuous variable in restricted cubic splines with mortality. Multivariable Cox regression determined hazard ratios and 95% confidence intervals with adjustment for baseline health indicators. Results Mean age was 57.1 years, 5,056 died (15.4%) with a median follow-up of 5.1 years. With adjustment, for age, sex, baseline health status, and location of medical supervision, the pattern of mortality was non-linear and u-shaped with greatest risks for patients with extreme values. Modelled as a continuous variable, the serum K +thresholds for optimal survival were from 4.1 to 5.2 mmol/L. Compared to patients without baseline CKD, the risks were attenuated for patients with CKD (p-value interaction 0.012). The associated risk thresholds were wider for CKD patients with significant increased risk above 5.8 mmol/L whereas, for those without CKD, serum K +thresholds for optimal survival were between 4.2-5.4 mmol/L. Similarly, mortality patterns were greatly attenuated for patients who were managed in the outpatient and general practice locations (p-value interaction <0.001) than the emergency room or inpatient settings (Figure 1). Conclusion Risk thresholds for optimal survival for serum K+ vary according to CKD and location of medical supervision in real-world clinical cohorts. Better understanding of these thresholds and effect modifiers are essential for inform decision making and therapeutic interventions. Funding Source Health Research Board (HRB-SDAP-2019-036), Midwest Research and Education Foundation (MKid), Vifor Pharma.

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The F test for Comparing Two Normal Variances: Correct and Incorrect Calculation of the Two-Sided p-value?

Teaching Statistics ◽

10.1111/j.1467-9639.2006.00244.x ◽

2006 ◽

Vol 28 (2) ◽

pp. 58-60 ◽

Cited By ~ 4

Author(s):

James Gallagher

Keyword(s):

P Value ◽

F Test

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Study on the ability of the three-dose-volume-histogram-gamma (3DVH-γ) analysis and bio-mathematical model in detecting dose changes caused by dose-calculation-grid-size (DCGS)

10.21203/rs.3.rs-17543/v2 ◽

2020 ◽

Author(s):

Han Bai ◽

Sijin Zhu ◽

Xingrao Wu ◽

Xuhong Liu ◽

Feihu Chen ◽

...

Keyword(s):

Mathematical Model ◽

Cervical Cancer ◽

Dose Distribution ◽

Measurement Data ◽

Dose Calculation ◽

Grid Size ◽

Dose Effect ◽

P Value ◽

Data Set ◽

Calculation Grid

Abstract Objective : To explore the efficacy and sensitivity of 3DVH-γanalysis and bio-mathematical model for cervical cancer in detecting dose changes caused by dose-calculation-grid-size(DCGS). Methods： 17 patients’ plans for cervical cancer were enrolled（Pinnacle TPS，VMAT）, and the DCGS was changed from 2.0mm to 5.0mm to calculate the planned dose respectively. The dose distribution calculated by DCGS = 2.0mm as the “ reference ” data set (RDS) , the dose distribution calculated by the rest DCGS as the“measurement”data set (MDS), the 3DVH-γ passing rates and the (N)TCPs of the all structures under different DCGS were obtained , and then analyze the ability of 3DVH-γ analysis and (N)TCP model in detecting dose changes and what factors affect this ability. Results: The effect of DCGS on planned dose was obvious. When the γ-standard was 1.0mm, 1.0% and 10.0%, the difference of the results of the DCGS on dose-effect could be detected by 3DVH-γ analysis ( p s<0.05). With the decline of the standard, 3DVH-γ analysis’ ability to detect this difference shows weaker. When the standard was 1.0mm, 3.0% and 10.0%, the p value of >0.05 accounted for the majority. With DCGS=2.0mm being RDS, ∆γ-passing-rate presented the same trend with ∆(N)TCPs of all structures except for the femurs only when the 1.0mm, 1.0% and 10.0% standards were adopted for the 3DVH-γ analysis. Conclusions: The 3DVH-γ analysis and bio-mathematical model can be used to analyze the effect of DCGS on the planned dose. For comparison, the former’s detection ability has a lot to do with the designed standard, and the latter’s capability is related to the parameters and calculated accuracy instrinsically.

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A Comprehensive Systemic Literature review of Pericardial Decompression Syndrome: Often Unrecognized and Potentially Fatal Syndrome

Current Cardiology Reviews ◽

10.2174/1573403x16666200607184501 ◽

2020 ◽

Vol 16 ◽

Author(s):

Ahmed Amro ◽

Kanaan Mansoor ◽

Mohammad Amro ◽

Amal Sobeih ◽

Mohamed Suliman ◽

...

Keyword(s):

Ejection Fraction ◽

Early Recognition ◽

Case Reports ◽

Case Series ◽

Rare Condition ◽

Continuous Variable ◽

P Value ◽

Chi Square ◽

Therapeutic Modalities ◽

Hemodynamic Deterioration

Background: Pericardial Decompression Syndrome (PDS) is defined as paradoxical hemodynamic deterioration and/or pulmonary edema, commonly associated with ventricular dysfunction. This phenomenon was first described by Vandyke in 1983. PDS is a rare but formidable complication of pericardiocentesis which if not managed appropriately is fatal. PDS as an entity has dispersed literature; this review is to understand its epidemiology, presentation, and management. Methodology: Medline: Science Direct and Google Scholar databases were utilized to do a systemic literature search. PRISMA protocol was employed. Abstracts, case reports, case series and clinical studies were identified since 1983 to 2019. A total of 6508 articles were reviewed out of which 210 were short listed, after removal of duplicates 49 manuscripts were included in this review. For Statistical analysis, patient data was tabulated in SPSS version 20. Cases were divided into two categories surgical and percutaneous groups. T test was done for continuous variable and chi square test was done for categorical data was used for analysis. Results: A total of 42 full length case reports, 2 poster abstracts, 3 case series of 2 patients , 1 case series of 4 patient s and 1 case series of 5 patients were included in the study. A total of 59 cases were included in this manuscript. Our data had 45.8% (n=27) males and 54.2% (n=32) females. The mean age of patients was 48.04 ± 17 years. Pericardiocentesis was performed in 52.5% (n=31) cases, Pericardiostomy was performed in 45.8% (n=27). The most common identifiable cause pericardial effusion was found to be malignancy in 35.6% (n=21). 23 cases reported pre-procedural ejection fraction which ranged from 20%-75% with a mean of 55.8 ± 14.6%, while 26 cases reported post procedural ejection fraction which ranged from 10%-65% with a mean of 30% ± 15.1%. Data was further divided into two categories namely, pericardiocentesis and pericardiostomy. The outcome as death was significant in the pericardiostomy arm with a p-value of < 0.00. Use of inotropic agents for the treatment of PDS was more common in needle pericardiocentesis with a p-value of 0.04. Lastly, the computed recovery time did not yield any significance with a p-value of 0.275. Conclusion: Pericardial decompression syndrome is a rare condition with high mortality. Operators performing pericardial drainage should be aware of this complication following drainage of cardiac tamponade, since early recognition and expeditious supportive care are the only therapeutic modalities available for adequate management of this complication.

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