Recognition of medication information from discharge summaries using ensembles of classifiers

ABSTRACT: BACKGROUND: Extraction of clinical information such as medications or problems from clinical text is an important task of clinical natural language processing (NLP). Rule-based methods are often used in clinical NLP systems because they are easy to adapt and customize. Recently, supervised machine learning methods have proven to be effective in clinical NLP as well. However, combining different classifiers to further improve the performance of clinical entity recognition systems has not been investigated extensively. Combining classifiers into an ensemble classifier presents both challenges and opportunities to improve performance in such NLP tasks. METHODS: We investigated ensemble classifiers that used different voting strategies to combine outputs from three individual classifiers: a rule-based system, a support vector machine (SVM) based system, and a conditional random field (CRF) based system. Three voting methods were proposed and evaluated using the annotated data sets from the 2009 i2b2 NLP challenge: simple majority, local SVM-based voting, and local CRF-based voting. RESULTS: Evaluation on 268 manually annotated discharge summaries from the i2b2 challenge showed that the local CRF-based voting method achieved the best F-score of 90.84% (94.11% Precision, 87.81% Recall) for 10-fold cross-validation. We then compared our systems with the first-ranked system in the challenge by using the same training and test sets. Our system based on majority voting achieved a better F-score of 89.65% (93.91% Precision, 85.76% Recall) than the previously reported F-score of 89.19% (93.78% Precision, 85.03% Recall) by the first-ranked system in the challenge. CONCLUSIONS: Our experimental results using the 2009 i2b2 challenge datasets showed that ensemble classifiers that combine individual classifiers into a voting system could achieve better performance than a single classifier in recognizing medication information from clinical text. It suggests that simple strategies that can be easily implemented such as majority voting could have the potential to significantly improve clinical entity recognition.     

Effects of non‐thermal atmospheric pressure pulsed plasma on the adhesion and durability of resin composite to dentin

This study investigated the effect of low‐power, non‐thermal atmospheric pressure plasma (NT‐APP) treatments, in pulsed and conventional modes, on the adhesion of resin composite to dentin and on the durability of the bond between resin composite and dentin. A pencil‐type NT‐APP jet was applied in pulsed and conventional modes to acid‐etched dentin. The microtensile bond strength (MTBS) of resin composite to dentin was evaluated at 24 h and after thermocycling in one control group (no plasma) and in two experimental groups (pulsed plasma and conventional plasma groups) using the Scotchbond Multi‐Purpose Plus Adhesive System. Data were analyzed using two‐factor repeated‐measures anova and Weibull statistics. Fractured surfaces and the bonded interfaces were evaluated using a field‐emission scanning electron microscope. Although there were no significant differences between the plasma treatment groups, the plasma treatment improved the MTBS compared with the control group. After thermocycling, the MTBS did not decrease in the control or conventional plasma group but increased in the pulsed plasma group. Thermocycling increased the Weibull moduli of plasma‐treated groups. In conclusion, plasma treatment using NT‐APP improved the adhesion of resin composite to dentin. Using a pulsed energy source, the energy delivered to the dentin was effectively reduced without any reduction in bond strength or durability.     

Injuries in Tae Kwon Do

In brief: Tae Kwon Do, the martial art of Korea, is a highly disciplined sport teaching well-coordinated, rapid, forceful techniques. It is typically associated with minor injuries, particularly contusions, sprains, and strains of the lower and upper extremities. More serious injuries rarely occur, although they have been recorded. A knowledge of injuries in other sports is useful in managing those in Tae Kwon Do. More thorough education of students and instructors will reduce morbidity and rehabilitation time.     

Effects of changing immunosuppressive regimen on the incidence, duration, and viral load of cytomegalovirus infection in renal transplantation: a single center report

Abstract: Background. In this retrospective single center study we have evaluated the relation between the immunosuppressive regimen and the incidence and characteristics of cytomegalovirus (CMV) infection in the setting without CMV prophylaxis from 1989 through 1998. Methods. All (470) first cadaveric renal transplantations in nonsensitized (PRA < 60%) patients were analyzed. Immunosuppression consisted of cyclosporine A (Sandimmune) and prednisolone from 1989 through 2-1993 (S; 189 patients), of cyclosporine microemulsion (Neoral) and prednisolone from 3-1993 through 5-1997 (N; 200 patients) and of mycophenolate mofetil, Neoral and prednisolone from 5-1997 until 1998 (M; 81 patients). The CMV pp65-antigenemia was measured routinely at least once weekly from day 10 till 12 weeks after transplantation or until pp65-antigenemia became negative. No CMV-prophylaxis was given. Results. By changing from Sandimmune to Neoral and by adding mycophenolate mofetil, respectively, we observed a higher frequency of especially secondary CMV infections (S vs. N vs. M, respectively, 28 vs. 50 vs. 63%, P  = 0.026; S vs. N, P  = 0.027; S vs. M, P  = 0.015; and N vs. M, n.s). The CMV infections lasted longer (median duration antigenemia S vs. N vs. M, respectively, 3 vs. 5 vs. 7 weeks, P  = 0.0003; S vs. N, P  < 0.002; S vs. M, P  < 0.001; and N vs. M, P  < 0.05). Viral load was higher in M (median maximal pp65-antigenemia S vs. N vs. M, respectively, 19 vs. 14.5 vs. 73, P  < 0.01; S vs. N, n.s.; S vs. M, P  < 0.001 and N vs. M, P  < 0.01). Conclusions. The use of Neoral and the addition of mycophenolate mofetil caused significant changes in the incidence, duration and viral load of CMV infections.     

A case of tuberculous pericarditis developing constrictive pericarditis

A case of constrictive pericarditis which developed after the onset of clinical manifestation of tuberculous pericarditis was reported. A 75-year-old male, complaining of anorexia, was admitted to our hospital. Adenosinedeaminase (ADA) level in pericardial effusion was found to be increased, and the culture of pericardial effusion was positive for tubercle bacilli. Diagnosed as having tuberculous pleuritis and pericarditis, he underwent chemotherapy for tuberculosis. However, massive pleural effusion developed later and pleural effusion drainage was carried out. Despite repeated drainage, pleural effusion continued to recur. Chest CT revealed apparent pericardial thickening, in addition, cardiac catheterization revealed elevation of mean right atrial pressure and marked deterioration of cardiac functions including decrease of cardiac output. These findings were compatible with constrictive pericarditis. After these investigations a diagnosis of constrictive pericarditis was established, and the patient underwent a pericardiectomy. Pathological examination of resected specimens revealed tuberculous inflammation.