Misspecified regression model for the subdistribution hazard of a competing risk.
Explore the source record for details and available documents.
Data Interpretation, Statistical↗
Biomedical subjects
Martin Schumacher
Publications and source records attributed to Martin Schumacher.
A test for publication bias in meta-analysis with sparse binary data.
A new test for the detection of publication bias in meta-analysis with sparse binary data is proposed. The test statistic is based on observed and expected cell frequencies, and the variance of the observed cell frequencies. These quantities are utilized in a rank correlation test. Type I error rate and power of the test are evaluated in simulations; results are compared to those of two other commonly used test procedures. Sample sizes were generated according to findings in a survey of eight German medical journals. Simulation results indicate that, in contrast to existing test procedures, the new test holds the prescribed significance level when data are sparse. However, the power of all tests is low in many situations of practical importance.
Anemia↗
C-reactive protein, carotid atherosclerosis, and cerebral small-vessel disease: results of the Austrian Stroke Prevention Study.
BACKGROUND AND PURPOSE: C-reactive protein (CRP) is an inflammatory marker known to be a risk factor for stroke. We examined the associations between CRP, carotid atherosclerosis, white matter lesions, and lacunes as manifestations of cerebral large- and small-vessel disease. METHODS: In the community-based Austrian Stroke Prevention Study, CRP concentrations were measured by a highly sensitive assay in 700 participants at baseline. All underwent carotid duplex scanning, and a subset of 505 subjects underwent brain magnetic resonance imaging. Imaging was repeated after 3 and 6 years. We graded carotid atherosclerosis in both common and internal carotid arteries on a 5-point scale and calculated the sum of scores as an index of the severity of carotid atherosclerosis. The volume of white matter lesions and the number of lacunes were considered small vessel disease-related brain abnormalities. RESULTS: After adjustment for vascular risk factors, the severity and progression of extracranial carotid atherosclerosis increased with increasing quintiles of CRP. Only study participants in the fourth and fifth quintile (>2.50 mg/L) had significantly more baseline atherosclerosis and greater progression when we used the first quintile (<0.80 mg/L) as a reference. No interactions were seen between CRP quintiles and vascular risk factors for carotid atherosclerosis. The associations between severity and progression of small vessel disease-related brain abnormalities and CRP were nonsignificant. CONCLUSIONS: We found evidence for differential effects of CRP in different beds of the arterial brain supply. CRP was a marker for active carotid atherosclerosis but not for small vessel disease-related brain lesions.
Aged↗
The relationship between quality of research and citation frequency.
BACKGROUND: Citation counts are often regarded as a measure of the utilization and contribution of published articles. The objective of this study is to assess whether statistical reporting and statistical errors in the analysis of the primary outcome are associated with the number of citations received. METHODS: We evaluated all original research articles published in 1996 in four psychiatric journals. The statistical and reporting quality of each paper was assessed and the number of citations received up to 2005 was obtained from the Web of Science database. We then examined whether the number of citations was associated with the quality of the statistical analysis and reporting. RESULTS: A total of 448 research papers were included in the citation analysis. Unclear or inadequate reporting of the research question and primary outcome were not statistically significantly associated with the citation counts. After adjusting for journal, extended description of statistical procedures had a positive effect on the number of citations received. Inappropriate statistical analysis did not affect the number of citations received. Adequate reporting of the primary research question, statistical methods and primary findings were all associated with the journal visibility and prestige. CONCLUSION: In this cohort of published research, measures of reporting quality and appropriate statistical analysis were not associated with the number of citations. The journal in which a study is published appears to be as important as the statistical reporting quality in ensuring dissemination of published medical science.
Bibliometrics↗
Case report: brain and liver abscesses caused by oral infection with Streptococcus intermedius.
Organ abscesses are a rare and life-threatening complication mostly of hematogenously disseminated infections. We report a case of brain and liver abscesses. Identification of the lesions was made by contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), respectively. An oral examination comprised an oral focus of infection. Streptococcus intermedius was isolated from oral smear, liver and ventricular drainage, and blood sample. After the commencement of antibiotic therapy, drainage of abscesses and oral rehabilitation, complete recovery was noted.
Adult↗
Analbuminemic Nagase rats: blood pressure response to dietary salt challenge.
BACKGROUND: The role of albumin on blood pressure response to different salt challenges is not known. Therefore, we studied the blood pressure response of analbuminemic Nagase rats (NAR) to different salt challenges. 11beta-Hydroxysteroid dehydrogenase type 2 (11beta-HSD2), the enzyme regulating the glucocorticoid access to the mineralocorticoid receptor, an enzyme that is decreased in humans with salt sensitive hypertension and other diseases with abnormal renal salt retention, was assessed during salt challenges. METHODS: Blood pressure was measured continuously by an intra-arterial catheter and a telemetry system in NAR (n = 8). NAR were set successively for 7 days on a normal (0.45% NaCl), high (8% NaCl), low (0.1% NaCl) and normal salt diet again, to assess salt related response in mean systolic (SBP) and diastolic blood pressure (DBP). 11beta-HSD2activity was assessed by measuring the urinary (THB + 5alpha-THB)/THA ratio with gas chromatography - mass spectrometry. RESULTS: Mean SBP and DBP increased with high salt intake (normal salt vs. high salt: SBP: 114 +/- 1 vs.119 +/- 3 mm Hg, p < 0.01; DBP: 84 +/- 1 vs. 88 +/- 3 mm Hg; n = 8; p < 0.01). Urinary (THB +5alpha-THB)/THA ratio increased during the high-salt period when compared to the normal-salt period (high salt vs. normal salt: 0.52 +/- 0.10 vs. 0.37 +/- 0.07; p = 0.05) indicating decreased 11beta-HSD2activity. CONCLUSION: Analbuminemic Nagase rats express increased blood pressure and reduced 11beta-HSD2 activity in response to a high-salt diet.
Adaptation, Physiological↗
Prognostic and predictive effects of immunohistochemical factors in high-risk primary breast cancer patients.
PURPOSE: To analyze prognostic and predictive effects of immunohistochemical factors within a randomized study of high-dose versus standard-dose chemotherapy in high-risk breast cancer with >10 involved lymph nodes. EXPERIMENTAL DESIGN: Histopathologic specimens in 188 of 302 patients were analyzed for Ki-67, p16, maspin, Bcl-2, Her2/neu, and p53. RESULTS: In a univariate analysis after adjustment for therapy, tumor size, and estrogen receptor, Her2/neu positivity (P = 0.001) was a negative and Bcl2 positivity (P = 0.003) was a positive prognostic factor for event-free survival. In a multivariate analysis, Her2/neu positivity (hazard ratio, 3.68; 95% confidence interval, 2.01-6.73; P = 0.0001) had a negative influence on event-free survival, whereas p53 positivity (hazard ratio, 0.57; 95% confidence interval, 0.34-0.95; P = 0.03) and Bcl2 positivity (hazard ratio, 0.35; 95% confidence interval, 0.19-0.64; P = 0.0006) were associated with a better event-free survival. Analyzing the predictive effect of the immunohistochemical factors, an interaction between p53 and treatment could be shown (P = 0.005). The hazard ratio for high-dose chemotherapy versus standard chemotherapy is estimated as 2.3 (95% confidence interval, 0.67-7.92) in p53-negative patients and as 0.46 (95% confidence interval, 0.2-1.07) in p53-positive patients, which indicates a superiority of high-dose chemotherapy in p53-positive patients and an inferiority in p53-negative patients. No interactive effect could be shown for the other factors. CONCLUSIONS: Her2/neu and Bcl-2 are prognostic but not predictive factors in patients with high-risk primary breast cancer; p53-positive patients might benefit more from high-dose chemotherapy than from standard chemotherapy, and p53-negative patients might benefit more from standard chemotherapy than from high-dose therapy.
Adult↗
Kidney transplantation procedures in rats: assessments, complications, and management.
Kidney transplantation in rats is an experimental model often used for the development of general microsurgical or transplantation techniques, for immunologic studies, and for analyzing transplant-associated long-term arterial blood-pressure changes. The aim of the present study was to analyze different surgical techniques of kidney transplantation in rats, with emphasis on minimizing surgical complications and establishing guidelines for their prevention and management. Complications were categorized into general (e.g., core body temperature drop, ischemic time) and surgically related vascular and urinary tract complications. In conclusion, a significant reduction of the complication rate in renal transplantation in rats can be achieved by placing the animal on a heating pad at an appropriate temperature. To reduce the risk of vascular thrombosis, ice-cold saline with heparin and careful flushing of the donor kidneys are recommended. Vascular complications can be avoided by performing "end-to-end" anastomosis techniques. The use of stents and cannulas in the urinary tract is associated with a high risk of urinary tract obstruction, and therefore is not recommended.
Anastomosis, Surgical↗
Twenty years experience with an ileal orthotopic low pressure bladder substitute--lessons to be learned.
PURPOSE: We present the long-term results of a large consecutive series of patients undergoing ileal orthotopic bladder substitution following radical cystectomy. MATERIALS AND METHODS: Between April 1985 and 2005 orthotopic bladder substitution with an ileal low pressure reservoir was performed in 482 patients (including 40 women) after radical and, if possible, nerve sparing cystectomy. In 447 cases the procedure was combined with an afferent ileal isoperistaltic tubular segment. The patients were followed prospectively. RESULTS: In the 482 patients 61 early (less than 30 days) diversion related complications requiring prolonged hospital stay or readmission were noted and 115 late complications required treatment. At 1 year continence was good in 92% of patients during the day and in 79% at night. At last followup 93% of patients could void spontaneously. Of 442 evaluable men 99 (22.4%) reported having erections without and 68 (15.4%) with medical assistance. Ureteroileal stenosis was observed in 12 of 447 (2.7%) patients. Urethral recurrence was detected in 25 of 482 (5%) patients. A total of 15 (5%) patients received vitamin B12 substitution. Renal parenchyma decreased only in patients with preoperative or postoperative ureteral obstruction. After 10 years patients with normal renal function had no long-term acidosis and in 20 patients the incidence of osteoporosis resembled that of the normal population. CONCLUSIONS: Ileal orthotopic bladder substitution combined with an afferent ileal tubular segment allows for good long-term functional results provided patients are restrictively selected, postoperative instructions are followed carefully, and typical complications such as outlet obstruction and hernias are treated early.
Adult↗
Nerve sparing open radical retropubic prostatectomy--does it have an impact on urinary continence?
PURPOSE: We prospectively assessed the role of nerve sparing surgery on urinary continence after open radical retropubic prostatectomy. MATERIALS AND METHODS: We evaluated a consecutive series of 536 patients who underwent open radical retropubic prostatectomy with attempted bilateral, unilateral or no nerve sparing, as defined by the surgeon, without prior radiotherapy at a minimum followup of 1 year with documented assessment of urinary continence status. Because outlet obstruction may influence continence rates, its incidence and management was also evaluated. RESULTS: One year after surgery 505 of 536 patients (94.2%) were continent, 27 (5%) had grade I stress incontinence and 4 (0.8%) had grade II stress incontinence. Incontinence was found in 1 of 75 (1.3%), 11 of 322 (3.4%) and 19 of 139 patients (13.7%) with attempted bilateral, attempted unilateral and without attempted nerve sparing, respectively. The proportional differences were highly significant, favoring a nerve sparing technique (p <0.0001). On multiple logistic regression analysis attempted nerve sparing was the only statistically significant factor influencing urinary continence after open radical retropubic prostatectomy (OR 4.77, 95% CI 2.18 to 10.44, p = 0.0001). Outlet obstruction at the anastomotic site in 33 of the 536 men (6.2%) developed at a median of 8 weeks (IQR 4 to 12) and was managed by dilation or an endoscopic procedure. CONCLUSIONS: The incidence of incontinence after open radical retropubic prostatectomy is low and continence is highly associated with a nerve sparing technique. Therefore, nerve sparing should be attempted in all patients if the principles of oncological surgery are not compromised.
Aged↗
Antegrade endopyelotomy for treatment of ureteropelvic junction obstruction in transplanted kidneys.
BACKGROUND AND PURPOSE: Little is known about the incidence and treatment of ureteropelvic junction (UPJ) obstruction of renal grafts. We report on three cases treated by endopyelotomy. PATIENTS AND METHODS: Graft function declined in three patients 98, 135, and 144 days after kidney transplantation. Acute rejection was excluded by renal biopsy. Ultrasonography revealed a dilated collecting system, and a percutaneous nephrostomy tube was placed. An antegrade nephrostogram showed UPJ obstruction. Percutaneous antegrade endopyelotomy was performed with the cold-knife technique, and the area was stented for 6 weeks using a 14F/8.2F Smith endopyelotomy stent. RESULTS: No intraoperative or postoperative complications occurred. The endopyelotomies were successful, and the creatinine clearances returned to normal. CONCLUSION: Antegrade endopyelotomy in patients with UPJ obstruction of a renal graft is feasible and effective. Normal kidney function was restored after correction of the obstruction.
Endoscopy↗
Coating the wall of an injured intracranial carotid artery during tumor removal with n-butyl-2-cyanoacrylate: technical case report.
OBJECTIVE: Carotid artery injury close to the clinoid process is difficult to repair, and is even more so when the vessel is firmly attached to a calcified tumor. We treated a patient with an intraoperative carotid lesion by coating the vessel wall with n-butyl-2-cyanoacrylate (NBCA). CLINICAL PRESENTATION: A 7-year-old boy was referred to our clinic with a 3-month history of somnolence, apathy, and headache. Neurological examination revealed bitemporal hemianopsia. The cranial magnetic resonance imaging and computed tomographic scans showed a sellar and suprasellar calcified mass with heterogeneous contrast enhancement, a cyst component in the upper part of the tumor displaced upward and back from the mesencephalic and diencephalic structures. INTERVENTION: The patient underwent a pterional craniotomy. Using a microsurgical technique, the suprasellar part of the craniopharyngioma was removed. In an attempt to dissect the calcified mass from the carotid artery on the right side, the vessel was unintentionally injured, followed by severe bleeding. Temporary occlusion and suturing of the vessel was impossible because of the overlying hard mass. To avoid a permanent occlusion, we decided to coat the injured artery wall with 100% NBCA. For this, 0.5 ml of NBCA was distributed on the surface of the injured segment and surrounding subarachnoid space by injection through a needle. An excellent hemostasis could be obtained immediately after coating. The patient woke up with no new neurological deficits. A digital cerebral angiogram obtained a few days after the procedure did not show vasospasm, stenosis, or pseudoaneurysm in the supraclinoidal segment of the carotid artery. A magnetic resonance angiogram obtained 3 years later showed a normal shape of the internal carotid artery and a stable residual tumor without inflammatory signs. The child is now attending school and is under hormonal therapy. CONCLUSION: For hemostatic purposes, the technique of coating an injured arterial wall with NBCA may be useful in cases in which a microsuture is impossible and a permanent artery occlusion is unwanted because of a risk of an ischemic stroke. It could serve as a transitory measure until a microsurgical bypass or the balloon test occlusion tolerance allow the trapping of the affected artery.
Brain Neoplasms↗
Subarachnoid hemorrhage due to isolated spinal arteries: Rare cases with controversy about the treatment strategy.
Explore the source record for details and available documents.
Aneurysm↗
Tamoxifen versus control after adjuvant, risk-adapted chemotherapy in postmenopausal, receptor-negative patients with breast cancer: a randomized trial (GABG-IV D-93)--the German Adjuvant Breast Cancer Group.
PURPOSE: To investigate the effect of adjuvant sequential tamoxifen after chemotherapy in postmenopausal patients with hormone receptor-negative breast cancer. METHODS: Patients were randomly assigned to oral tamoxifen (30 mg daily for 5 years; n = 421) or no additional treatment (n = 408) after risk-adapted polychemotherapy consisting of three 28-day cycles of CMF (cyclophosphamide, 500 mg/m(2), methotrexate, 40 mg/m(2), and fluorouracil, 600 mg/m(2)) in patients with negative or one to three positive lymph nodes and four 21-day cycles of epirubicin 90 mg/m(2), cyclophosphamide 600 mg/m(2) followed by three cycles of CMF in patients with four to nine positive lymph nodes. RESULTS: Thirty-six percent of the patients included were older than 60 years, 63% were node negative, 13% had four to nine positive nodes, 55% had tumor grade 3, and 41% received breast-preserving surgery. At 5.3 years' median follow-up, the first event of failure (recurrence, secondary tumor, or death) had occurred in 123 patients in the tamoxifen group and 107 patients of the control group. Event-free survival rates after 5 years were 70.3% (95% CI, 65.5% to 75.0%) and 72.8% (95% CI, 68.2% to 77.5%) for the tamoxifen and control groups, respectively. The estimated hazard ratio of tamoxifen versus control was 1.13 (95% CI, 0.87 to 1.48; P = .34), which gives no indication of an additional benefit of tamoxifen in these patients. CONCLUSION: This study contributes substantially to finalization of the presently emerging evidence that tamoxifen does not benefit women with receptor-negative breast cancer after chemotherapy.
Aged↗
Regulation of epithelial sodium channel in puromycin aminonucleoside-induced unilateral experimental nephrotic syndrome in normal and analbuminemic Nagase rats.
BACKGROUND: Nephrotic syndrome (NS) is characterized by renal sodium retention and edema formation. In nephrotic rats the site of enhanced sodium retention has been localized in the cortical collecting duct (CCD). The epithelial sodium channel (ENaC) is the rate-limiting constituent of sodium transport in CCD. Amiloride, an ENaC-blocking drug, corrects the abnormal rate of sodium transport in isolated perfused CCD from puromycin aminonucleoside (PAN)-treated rats. Therefore, we hypothesized that ENaC functional expression is increased in NS. METHODS: Unilateral NS was induced by PAN in Wistar rats and analbuminemic Nagase rats (NAR). Urinary protein excretion, renal abundance of mRNA and protein of ENaC subunits, as well as the ENaC regulatory serum glucocorticoid-inducible kinase (Sgk1) and Nedd4-2, were assessed. RESULTS: Proteinuria appeared at day 2 in the Wistar rats and NAR. Surprisingly a downregulation rather than the expected upregulation of alpha-, beta- and gamma-ENaC mRNA abundance was observed in both Wistar rats and NAR, when the treated kidney was compared with the untreated kidney. The amount of protein of alpha-, beta- and gamma-ENaC was not affected by the NS. Sgk1 mRNA expression did not change and Nedd4-2 protein expression was only decreased at days 1 and 2 in Wistar rats. CONCLUSION: ENaC mRNA and protein expression are not increased in the early phase of unilateral PAN-induced NS. Sgk1, Nedd4-2 and analbuminemia are not important regulatory factors of ENaC protein expression in experimental NS.
Acetylglucosaminidase↗
Economic impact of community-acquired and nosocomial lower respiratory tract infections in young children in Germany.
Data on the economic burden of lower respiratory tract infections (LRTI) in young children are lacking in Germany. The objective of the cost-of-illness study was to estimate the economic impact of community-acquired LRTI and nosocomial LRTI as well as of infections due to respiratory syncytial virus (RSV), parainfluenza viruses (PIV) and influenza viruses (IV). The economic analysis is part of the PRIDE study, a prospective, multi-centre, population-based epidemiological study on the impact of LRTI in children aged 0 to 36 months in Germany. The analysis includes children with community-acquired infections (1329 cases treated as outpatients, 2039 cases treated as inpatients) and nosocomial infections (90 cases). Medical services consumed were generated by chart abstraction and parental expenses data by telephone interviews within four weeks after physician visit or hospitalisation. Costs were evaluated from following perspectives: third party payer, parent and society. Total costs for outpatient treatment are Euro 123 per LRTI case. Stratified by virus type, total costs per case are Euro 163 (RSV), Euro 100 (PIV) and Euro 223 (IV). Total costs per hospitalised LRTI case amount to Euro 2579. Stratified by virus type, total costs per case are Euro 2772 (RSV), Euro 2374 (PIV) and Euro 2597 (IV). Total costs per nosocomial case are Euro 2814. Economic burden due to LRTI is Euro 213 million annually. It is concluded that treatment of LRTI in children up to age three causes a considerable economic burden in Germany. Presented results are the first data describing the economic burden of LRTI in young children assessed by means of the incidence data for Germany. This cost-of-illness study provides basic data for further decision-making, focusing on the economic assessment of preventive strategies for RSV, PIV and IV infections.
Age Distribution↗
Sample sizes for clinical trials with time-to-event endpoints and competing risks.
We consider clinical trials where the time to occurrence of events in the presence of competing risks is the primary endpoint for treatment evaluation. The number of events with regard to the defined primary endpoint required to ensure the specified power can be calculated according to Schoenfeld's formula like in classical survival studies. However, determination of the number of patients that have to be recruited to observe the calculated number of events requires specification of the length of the accrual period, the trial duration and assumptions about the event-specific hazard functions. Information from previous studies about expected failure rates for the reference treatment is useful and can be translated into assumptions about the appropriate model parameters. A formula for sample size computation is presented for two competing outcome states. Nomograms help to communicate different alternatives of duration and size of the trial to interdisciplinary committees whose members plan and monitor the clinical trial. The 4D trial (Die Deutsche Diabetes Dialyse Studie) designed to compare lipid lowering treatment with HMG-CoA reductase inhibitor atorvastatin with placebo in type 2 diabetic patients on hemodialysis with respect to time to the composite event "cardiovascular death or non-fatal myocardial infarction" is used as an example to outline the statistical methods.
Clinical Trials Data Monitoring Committees↗
Plasma vascular endothelial growth factor and serum soluble angiopoietin receptor sTIE-2 in patients with dural arteriovenous fistulas: a pilot study.
Our aim was to correlate concentrations of circulating vascular endothelial growth factor (VEGF) and serum soluble angiopoietin receptor (sTIE-2) before and after endovascular treatment with the grading in human dural arteriovenous fistulas (DAVFs). In ten patients with DAVFs undergoing diagnostic cerebral angiography and endovascular intervention, pre-treatment and post-treatment levels of plasma VEGF and serum TIE-2 were examined in a prospective study design. A total of 32 plasma samples and 19 serum samples was collected from the cubital vein, the arterial sheath before and--if applicable--after intervention. Plasma VEGF and serum Tie-2 levels were measured by standardized ELISA protocols. In eight of ten patients with DAVF increased circulating VEGF levels (elevation of more than mean + 2 SD of published normal values) were found, whereas two patients showed increased sTIE-2 levels. Six of the seven patients treated by endovascular embolization displayed a post-interventional decrease of VEGF values. The serum TIE-2 levels decreased slightly after intervention. Pre-treatment vVEGF levels varied significantly between patients with grades I and II/III fistulas according to the Cognards classification system. Our pilot study suggests that assessment of angiogenesis parameters in patients with DAVFs might correlate with the DAVFs' grade. To support the hypothesis that a change in angiogenic indicators may serve as indicators for a response to therapy, a larger number of patients should be followed for a longer time period.
Aged↗