Low rank updated LS-SVM classifiers for fast variable selection

Least squares support vector machine (LS-SVM) classifiers are a class of kernel methods whose solution follows from a set of linear equations. In this work we present low rank modifications to the LS-SVM classifiers that are useful for fast and efficient variable selection. The inclusion or removal of a candidate variable can be represented as a low rank modification to the kernel matrix (linear kernel) of the LS-SVM classifier. In this way, the LS-SVM solution can be updated rather than being recomputed, which improves the efficiency of the overall variable selection process. Relevant variables are selected according to a closed form of the leave-one-out (LOO) error estimator, which is obtained as a by-product of the low rank modifications. The proposed approach is applied to several benchmark data sets as well as two microarray data sets. When compared to other related algorithms used for variable selection, simulations applying our approach clearly show a lower computational complexity together with good stability on the generalization error.     

Detection of Pi Z phenotype individuals by alpha-1-antitrypsin (AAT) immunohistochemistry in paraffin-embedded liver tissue specimens

Immunostaining for alpha-1-antitrypsin (AAT) was applied on paraffin-embedded liver specimens from 38 Pi Z phenotype (27 Pi MZ; 9 Pi ZZ; 2 Pi SZ) individuals (33 adults, 5 newborns). Histological diagnoses included normal liver, various forms of chronic hepatitis, cirrhosis. A positive hepatocytic staining for AAT was revealed in all cases, whereas on PAS-D staining 5 cases were negative. Immunostaining revealed different patterns: type I: fine solid granules or coarse laminated globules filling the whole liver cell cytoplasm; type II: positive granules marginated towards the cell's periphery; type III: positive granules restricted to focal areas in the cytoplasm. Type I and III patterns were observed in all specimens. Association of type I and III with type II was seen in all Pi MZ and Pi SZ cases, but only in 3 of the 9 Pi ZZ specimens. To check the specificity of these staining patterns for the Z allele of AAT in adults and newborns, 180 further cases were investigated blindly by immunohistochemistry. Recognition of hepatocytic staining patterns type I, II and III allowed to reliably diagnose the Pi Z phenotype in 6 cases, whose heterozygous state was confirmed by independent serum phenotyping (5 Pi MZ, 1 Pi SZ). These results allow to conclude that: (1) immunohistochemistry is a reliable technique (superior to PAS-D staining) to identify Pi Z individuals (homo- and heterozygotes) on paraffin-embedded liver sections; (2) heterozygotes Pi MZ and Pi SZ cannot be differentiated without serum phenotyping; (3) immunohistochemistry is helpful in distinguishing between Z homozygotes from heterozygotes, but determination of AAT serum concentration is required to allow confident distinction without phenotyping. AAT immunohistochemistry thus allows to diagnose the Z allele of AAT when phenotyping procedures are not available or in retrospective studies on biopsy and autopsy material.     

A review of the pathophysiology,causes and prognosis of acute renal failure in the elderly

This paper reviews some of the pathophysiological, causal and prognostic aspects of acute renal failure (ARF) in the elderly patient. In the discussion on the factors predisposing the aged kidney to acute insults, the hypothesis is advanced that impairment of the autoregulatory capacity of renal blood flow and glomerular filtration rate plays a major role in the pathophysiology of ARF in the elderly patient. Recent data suggest that the relative increase of elderly patients in the overall population of patients with ARF can only partly be explained by the absolute increase of aged people. The major causes of ARF in the elderly are discussed. They show the same spectrum of etiologies of ARF as younger patients but within that spectrum, a significantly higher incidence of acute prerenal failure, iatrogenic hemodynamically-mediated ARF, renal vascular syndromes, glomerulonephritis, and post-ischemic acute tubular necrosis is observed. As far as the severity of the prognosis of ARF in the elderly is concerned, the review of published data does not allow definite conclusions on this subject. The main reason is the lack of information in a form that allows an easy and meaningful comparison. The adoption of scoring systems like the APACHE II system should overcome these problems. At present, the supposition that old age by itself is a bad prognostic factor in the outcome of ARF is dubious and it is certainly not strong enough to deny individual elderly patients with ARF the opportunity of aggressive therapy.     

Prevalence of malocclusion and need for orthodontic treatment in Saudi Arabia

Abstract The prevalence of different malocclusion features was investigated in 500 14-yr-old male Saudi Arabian children, using a modification of the registration method described by Björk . et al. (3). Most of the children were in dental stage DS4 (all permanent teeth anterior to the first molars erupted). Totally 62.4% of the children had one or more malocclusion features related to dentition, occlusion, or space. The treatment need was evaluated according to the guidelines used in the Norwegian Health Service. About 40% were found to need treatment with fixed appliances, and for 33% extraction of permanent teeth would be part of the treatment. Only about 2.5% would benefit from treatment with simple removable appliances.     

Methods to monitor response to chemotherapy in non-small cell lung cancer with 18F-FDG PET.

PET using 18F-FDG is a promising technique to monitor response in oncology. Unfortunately, a multitude of analytic methods is in use. To date, it is not clear whether simplified methods could replace complex quantitative methods in routine clinical practice. The aim of this study was to select those methods that would qualify for further assessment in a future prospective response-monitoring study by comparing results with patient outcome. METHODS: Dynamic 18F-FDG PET scans were obtained on 2 groups of patients. First, 10 patients with advanced non-small cell lung cancer (NSCLC) were scanned on consecutive days before treatment to assess test-retest variability. Second, 30 scans were obtained on 19 patients with locally advanced NSCLC as part of an ongoing response-monitoring study. These scans were analyzed by 2 observers to assess observer variability. In addition, these studies were used to compare various methods with the gold standard, full kinetic analysis (nonlinear regression [NLR]). RESULTS: Using an image-derived input function, NLR showed excellent test-retest and observer agreement confirming that it could be used as a gold standard method. From a total of 34 analytic methods, 10 showed good correlation with NLR. Taking into account the degree of complexity of the methods, 4 remain for further evaluation. CONCLUSION: The optimal method for analysis of 18F-FDG PET data was determined for several levels of complexity. Four methods need to be evaluated further to determine the optimal trade-off between simplicity and accuracy for routine clinical practice.     

Access to kidney transplantation in European adults aged 75–84 years and related outcomes: an analysis of the European Renal Association–European Dialysis and Transplant Association Registry

To what extent access to, and allocation of kidney transplants and survival outcomes in patients aged ≥75 years have changed over time in Europe is unclear. We included patients aged ≥75–84 years (termed older adults) receiving renal replacement therapy in thirteen European countries between 2005 and 2014. Country differences and time trends in access to, and allocation of kidney transplants were examined. Survival outcomes were determined by Cox regression analyses. Between 2005 and 2014, 1392 older adult patients received 1406 transplants. Access to kidney transplantation varied from ~0% (Slovenia, Greece and Denmark) to ~4% (Norway and various Spanish regions) of all older adult dialysis patients, and overall increased from 0.3% (2005) to 0.9% (2014). Allocation of kidney transplants to older adults overall increased from 0.8% (2005) to 3.2% (2014). Seven‐year unadjusted patient and graft survival probabilities were 49.1% (95% confidence interval, 95% CI: 43.6; 54.4) and 41.7% (95% CI: 36.5; 46.8), respectively, with a temporal trend towards improved survival outcomes. In conclusion, in the European dialysis population aged ≥75–84 years access to kidney transplantation is low, and allocation of kidney transplants remains a rare event. Though both are increasing with time and vary considerably between countries. The trend towards improved survival outcomes is encouraging. This information can aid informed decision‐making regarding treatment options.     

Brainstem hemorrhage in descending transtentorial herniation (Duret hemorrhage)

OBJECTIVES: To review clinical and radiological findings in patients with Duret hemorrhages and to discuss the pathophysiology and differential diagnosis of these lesions. PATIENTS AND METHODS: We reviewed the case records of four patients with Duret hemorrhages who had been admitted to the neurological intensive care unit with supratentorial mass lesions. RESULTS: Descending transtentorial and subfalcine herniations were present in all cases. Three patients were admitted with acute subdural hematoma and one with intraparenchymal hemorrhage. Computed tomography revealed the presence of blood in the mesencephalon and upper pons. Three patients died; one survived with severe disabilities. DISCUSSION: Duret hemorrhages are typically located in the ventral and paramedian aspects of the upper brainstem (mesencephalon and pons). The pathophysiology of Duret hemorrhage remains under debate: arterial origin (stretching and laceration of pontine perforating branches of the basilar artery), versus venous origin (thrombosis and venous infarction). Multifactorial causation seems likely. CONCLUSION: Duret hemorrhages are delayed, secondary brainstem hemorrhages. They occur in craniocerebral trauma victims with rapidly evolving descending transtentorial herniation. Diagnosis is made on computed tomography of the brain. In most cases the outcome is fatal. On the basis of our observations we believe that arterial hypertension and advanced age are risk factors for the development of Duret hemorrhage.     

Clinical diagnosis of diabetic polyneuropathy with the diabetic neuropathy symptom and diabetic neuropathy examination scores

OBJECTIVE: To evaluate the discriminative power of the Diabetic Neuropathy Symptom (DNS) and Diabetic Neuropathy Examination (DNE) scores for diagnosing diabetic polyneuropathy (PNP), as well as their relation with cardiovascular autonomic function testing (cAFT) and electro-diagnostic studies (EDS). RESEARCH DESIGN AND METHODS: Three groups (matched for age and sex) were selected: 24 diabetic patients with neuropathic foot ulcers (DU), 24 diabetic patients without clinical neuropathy or ulcers (DC), and 21 control subjects without diabetes (C). In all participants, the DNS and DNE scores were assessed and cAFT (heart rate variability [HRV], baroreflex sensitivity [BRS]), and EDS were performed (Nerve Conduction Sum [NCS] score; muscle fiber conduction velocity: fastest/slowest ratio [F/S ratio]). RESULTS: Both the DNS and the DNE scores discriminated between the DU and DC groups significantly (P < 0.001). The DNE score even discriminated between DC and C (P < 0.05). Spearman's correlation coefficients between both DNS and DNE scores and cAFT (HRV -0.42 and -0.44; BRS -0.30 and -0.29, respectively) and EDS (NCS 0.51 and 0.62; F/S ratio 0.44 and 0.62, respectively) were high. Odds ratios were calculated for both DNS and DNE scores with cAFT (HRV 4.4 and 5.7; BRS 20.7 and 14.2, respectively) and EDS (NCS 5.6 and 16.8; F/S ratio 7.2 and 18.8, respectively). CONCLUSIONS: The DNS and DNE scores are able to discriminate between patients with and without PNP and are strongly related to cAFT and EDS. This further confirms the strength of the DNS and DNE scores in diagnosing diabetic PNP in daily clinical practice.