Biomedical subjects

A Wilcox

Publications and source records attributed to A Wilcox.

At least 19 recordsLinked to original sources

PubMed2001

Spiral computed tomography for the diagnosis of pulmonary embolism in critically ill surgical patients: a comparison with pulmonary angiography.

HYPOTHESIS: Spiral computed tomographic pulmonary angiography (CTPA) is sensitive and specific in diagnosing pulmonary embolism (PE) in critically ill surgical patients. DESIGN: Prospective study comparing CTPA with the criterion standard, pulmonary angiography (PA). SETTING: Surgical intensive care unit of an academic hospital. PATIENTS: Twenty-two critically ill surgical patients with clinical suspicion of PE. The CTPAs and PAs were independently read by 4 radiologists (2 for each test) blinded to each other's interpretation. Clinical suspicion was classified as high, intermediate, or low according to predetermined criteria. All but 2 patients had marked pulmonary parenchymal disease at the time of the event that triggered evaluation for PE. INTERVENTIONS: Computed tomographic pulmonary angiography and PA in 22 patients, venous duplex scan in 19. RESULTS: Eleven patients (50%) had evidence of PE on PA, 5 in central and 6 in peripheral pulmonary arteries. The sensitivity and specificity of CTPA was, respectively, 45% and 82% for all PEs, 60% and 100% for central PEs, and 33% and 82% for peripheral PEs. Duplex scanning was 40% sensitive and 100% specific in diagnosing PE. The independent reviewers disagreed only in 14% of CTPA and 14% of PA interpretations. There were no differences in risk factors or clinical characteristics between patients with and without PE. The level of clinical suspicion was identical in the 2 groups. CONCLUSIONS: Pulmonary angiography remains the gold standard for the diagnosis of PE in critically ill surgical patients. Computed tomographic pulmonary angiography needs further evaluation in this population.

Adult↗

PubMed2000

Why do Mexican Americans give birth to few low-birth-weight infants?

There are relatively few low-weight births among Mexican Americans, despite their socioeconomic disadvantages. Fewer low-birth-weight (LBW) births result when babies are heavier at term or when there are fewer preterm deliveries. The authors used 1994 US singleton livebirth birth certificates to compare Mexican Americans with non-Hispanic Whites. They found that the lower LBW rate among Mexican Americans (5.8%) compared with non-Hispanic Whites (6.1%) occurred because fewer small, preterm babies were born to Mexican Americans (3.4% vs. 3.9%). This result was obscured by two findings. First, the mean birth weight of Mexican American babies (3,343 g) was lower than that of non-Hispanic White babies (3,393 g). This finding again showed the independence of mean birth weight and LBW. Second, the overall preterm birth rate was higher among Mexican Americans (10.6%) than non-Hispanic Whites (9.3%). Our hypothesis is that this finding reflects errors in recorded gestational age, as illustrated by a strongly bimodal birth-weight distribution at young gestational ages for Mexican Americans. Further studies on the LBW paradox among Mexican Americans should thus focus on gestational age more than on birth weight.

Adolescent↗

PubMed2000

A European pest to control a new zealand weed: investigating the safety of heather beetle, Lochmaea suturalis (Coleoptera: Chrysomelidae) for biological control of heather, Calluna vulgaris.

Heather, Calluna vulgaris (L.) Hull, is a serious invasive weed in the central North Island of New Zealand, especially in Tongariro National Park, a World Heritage Area. Heather beetle, Lochmaea suturalis (Thomson), is a foliage-feeding pest of Calluna in Europe, that was selected as the most promising biological control agent for introduction into New Zealand, because it causes high levels of damage to Calluna in Europe. Host-range tests indicated that L. suturalis poses a negligible threat to native New Zealand plants. Cultivars of Calluna grown as ornamentals are suitable food plants, but are unlikely to be severely affected because L. suturalis requires a damp understorey of moss or litter for successful oviposition and pupation, which is rarely present in gardens. However, mosses and litter occurring under Calluna stands in Tongariro National Park are suitable substrates for eggs and pupae. Lochmaea suturalis released in New Zealand has been freed of parasitoids and a microsporidian disease that attack the beetles in Europe.

Animals↗

PubMed2000

Bone sarcoidosis.

Sarcoidosis is a disease that exhibits extremely heterogeneous clinical manifestations. Although the lungs are the most commonly involved organs, the extension of the granulomatous process may also affect the bones. Almost any bone can be involved; curiously, the small bones of the hands and feet are most frequently affected. Diagnosis and recognition of osseous sarcoidosis is easy, but the therapy is disappointing. Corticosteroids and antimalarials may control pain and swelling, but usually do not influence the course of osseous sarcoidosis.

Antimalarials↗

PubMed2000

Medical text representations for inductive learning.

Inductive learning algorithms have been proposed as methods for classifying medical text reports. Many of these proposed techniques differ in the way the text is represented for use by the learning algorithms. Slight differences can occur between representations that may be chosen arbitrarily, but such differences can significantly affect classification algorithm performance. We examined 8 different data representation techniques used for medical text, and evaluated their use with standard machine learning algorithms. We measured the loss of classification-relevant information due to each representation. Representations that captured status information explicitly resulted in significantly better performance. Algorithm performance was dependent on subtle differences in data representation.

Algorithms↗

PubMed1999

Classification algorithms applied to narrative reports.

Narrative text reports represent a significant source of clinical data. However, the information stored in these reports is inaccessible to many automated decision support systems. Data mining techniques can assist in extracting information from narrative data. Multiple classification methods, such as rule generation, decision trees, Bayesian classifiers, and information retrieval were used to classify a set of 200 chest X-ray reports according to 6 clinical conditions indicated. A general-purpose natural language processor was used to convert the narrative text into a coded form that could be used by the classification algorithms. Significant differences in performance were found between algorithms. The best performing algorithm applied to the processor output was significantly better than information retrieval applied to raw text. Predictor variables from the coded processor output were limited to avoid overfitting. Methods that limited by domain knowledge performed significantly better than those that limited by conditional probabilities of the variables in the training set. Algorithms were also shown to be dependent on training set size.

Algorithms↗

PubMed1998

Developing online support for clinical information system developers: the FAQ approach.

OBJECTIVE: We investigate a knowledge-based help system for developers of an integrated clinical information system (CIS). The first objective in the study was to determine the system's ability to answer users' questions effectively. User performance and behavior were studied. The second objective was to evaluate the effect of using questions and answers to augment or replace traditional program documentation. DESIGN: A comparative study of user and system effectiveness using a collection of 47 veritable questions regarding the CIS, solicited from various CIS developers, is conducted. Most questions were concerning the clinical data model and acquiring the data. MEASUREMENTS: Answers using current documentation known by users were compared to answers found using the help system. Answers existing within traditional documentation were compared to answers existing within question-answer exchanges (Q-A's). RESULTS: The support system augmented 39% of users' answers to test questions. Though the Q-A's were less than 5% of the total documentation collected, these files contained answers to nearly 50% of the questions in the test group. The rest of the documentation contained about 75% of the answers. CONCLUSIONS: A knowledge-based help system built by collecting questions and answers can be a viable alternative to large documentation files, providing the questions and answers can be collected effectively.

Artificial Intelligence↗

PubMed1998

Knowledge discovery and data mining to assist natural language understanding.

As natural language processing systems become more frequent in clinical use, methods for interpreting the output of these programs become increasingly important. These methods require the effort of a domain expert, who must build specific queries and rules for interpreting the processor output. Knowledge discovery and data mining tools can be used instead of a domain expert to automatically generate these queries and rules. C5.0, a decision tree generator, was used to create a rule base for a natural language understanding system. A general-purpose natural language processor using this rule base was tested on a set of 200 chest radiograph reports. When a small set of reports, classified by physicians, was used as the training set, the generated rule base performed as well as lay persons, but worse than physicians. When a larger set of reports, using ICD9 coding to classify the set, was used for training the system, the rule base performed worse than the physicians and lay persons. It appears that a larger, more accurate training set is needed to increase performance of the method.

Artificial Intelligence↗

PubMed1997

Genomic structure and chromosomal localization of a human myo-inositol monophosphatase gene (IMPA).

Manic-depressive illness is a serious psychiatric disorder that in many, but far from all, patients can be treated with lithium. The main causes for discontinuation of lithium therapy are unpleasant or serious side effects and lack of response. The reason for the striking variation in clinical efficacy of lithium treatment among bipolar patients is not known. The enzyme myo-inositol monophosphatase (IMPase) has been postulated as a target for the mood-stabilizing effects of lithium, but variation in the coding region of the human IMPA gene encoding IMPase activity has not been observed in manic-depressive patients (Steen et al., Pharmacogenetics, 1996, 6, 113-116). It is nevertheless conceivable that polymorphisms or mutations in the noncoding regions of this gene could influence the lithium response in psychiatric patients. As a first step in investigating this possibility, we here report the genomic structure of the human IMPA gene. The gene is composed of at least nine exons and covers more than 20 kb of sequence on chromosome 8q21.13-q21.3. In the 3'-untranslated part of the gene, we observed a polymorphism (a G to A transition) and also two short sequences similar to the inositol/cholin-responsive element consensus. Finally, we postulate that two additional IMPA-like transcripts originate from the human genome, one from a position close to IMPA itself on chromosome 8 and the other from chromosome 18p. Our data may contribute to the identification of genetic factors involved in the pathogenesis and determination of treatment response in manic-depressive illness.

Amino Acid Sequence↗

PubMed1997

The effect of substrate utilization, manipulated by nicotinic acid, on excess postexercise oxygen consumption.

Increased fat oxidation during the recovery period from exercise is thought to be a contributing factor for excess postexercise oxygen consumption (EPOC). In an attempt to study the effect of serum free fatty acid (FFA) availability during exercise and recovery on the EPOC, nicotinic acid, a potent inhibitor of FFA mobilization from adipose tissue, was administered to five trained male cyclists prior to, during, and after a bout of cycling at 65% VO2max. In the nicotinic acid trial, a 500 mg dose of nicotinic acid was ingested prior to exercise, and 100 mg doses were ingested at 15, 30, and 45 min exercise, and 30 min recovery. The cyclists also completed a trial under control conditions. Serum FFA, serum glycerol, RER and VO2 were monitored during rest, exercise, and recovery, each of which was 1-h in duration. Nicotinic acid ingestion prevented the increase in serum FFA that occurred during exercise in the control trial. FFA levels during the nicotinic acid trial were significantly lower than control values during both exercise and recovery. Serum glycerol levels were also significantly lower during exercise in the nicotinic acid trial, indicative of a reduction in lipolysis. RER was not significantly different at rest or during exercise; however, RER values were significantly lower during recovery in the control trial, indicative of greater fat oxidation. For both treatments, postexercise VO2 remained elevated above resting levels at the completion of the 1-h recovery period. However, the magnitude of EPOC was significantly reduced after FFA blockade with nicotinic acid (3.4 +/- 0.61 vs 5.5 +/- 0.71). These results support the hypothesis that increased FFA metabolism during exercise and recovery is an important contributing factor to the magnitude of EPOC.

Adipose Tissue↗

PubMed1997

Creating an environment for linking knowledge-based systems to a clinical database: a suite of tools.

A difficulty in using knowledge-based systems has been linking them to clinical databases. The challenge is in making a correct mapping from the data in the knowledge base to the data in the database. At Columbia-Presbyterian Medical Center, we have built a suite of tools developed to create queries that address this challenge. The tools were designed to allow users to easily retrieve data from the database without requiring the users have extensive database and vocabulary knowledge. The tools help users write correct queries (Query Builder), find correct terms in the clinical database (MED Browser), aggregate the resulting data into a useful form (Clinical Database Browser), and allow the user to test the query within the environment of the knowledge-based system (Event Playback). The tools have been in use for one year.

Artificial Intelligence↗

PubMed1996

Comparison of methods of assessing vitamin A status in children.

OBJECTIVE: A study of children (2-8 years; n = 613) in Belize, Central America, was conducted to determine what proportion of the children might be at risk of vitamin A (vit A) deficiency. The data provide an opportunity to compare results of three methods of assessing vit A status in a population which was not severely malnourished. Serum retinyl ester concentrations were also determined; their relevance to one of the tests, the relative dose response (RDR) test, is discussed. METHODS: The three methods of assessing vit A status were: RDR test, fasting serum retinol concentration, and conjunctival impression cytology (CIC). Retinol-binding protein (RBP), serum retinyl esters and serum zinc concentrations were also determined. RESULTS: Inadequate vit A status was indicated for 17% of subjects by the RDR test (14% cutoff), for 24% by fasting serum retinol concentration (< 0.87 mumol/L), and for 49% by "abnormal" CIC score. Retinyl esters constituted 24% of serum retinoids at the time (5 hours after a retinyl palmitate dose) at which the second blood sample is taken for the RDR test. Regression tree analyses (CART) indicated ethnicity was a predictor of RDR score; ethnicity, stunting and age were predictors of fasting serum retinol concentration; ethnicity and stunting were predictors of 0-hour retinyl ester concentration. CONCLUSION: The three indices of vit A status did not identify the same individuals nor indicate the same percentage of the population to be at risk for vit A deficiency. Increased concentrations of retinyl esters at 5 hours compared to those at 0 hours suggest that insufficient retinol may have been taken up by the liver at 5 hours to release all accumulated retinol-binding protein (RBP) in deficient individuals; prevalence of vit A deficiency might therefore be underestimated by the RDR test. The selection of ethnicity as a predictor of RDR score and of 0-hour retinol and retinyl ester concentrations suggests that factors other than vit A status affect vit A metabolism and may affect the RDR test.

Belize↗

PubMed1996

Serum carotenoid concentrations and their reproducibility in children in Belize.

Suggestions that carotenoid-containing foods are beneficial in maintaining health have led to several studies of circulating carotenoid concentrations of adults. Because few data are available for children, we report serum carotenoid concentrations of 493 children in Belize. Carotenoid concentrations were determined as part of a survey of vitamin A status of children, most between 65 and 89 mo of age. Reproducibility was tested by collecting a second blood sample 2 wk after the first collection from a subset of children (n = 23) who consumed their habitual diet with no treatment during the interim. Predominant serum carotenoids were lutein/zeaxanthin and beta-carotene, which accounted for 26% and 24% of median total carotenoids, respectively. The three provitamin A carotenoids, alpha- and beta-carotene and beta-cryptoxanthin, constituted 51% of median total carotenoid concentrations. Partial correlations of each carotenoid with fasting retinol concentration indicated that beta-carotene had the highest correlation. Concordance correlation coefficients (rc) for fasting carotenoid concentrations determined 2 wk apart were > or = 0.89 for lycopene, beta-cryptoxanthin, and alpha- and beta-carotene. The rc for lutein/zeaxanthin and total carotenoids was lower, 0.59 and 0.68, respectively, because of higher lutein/zeaxanthin concentrations at the second sampling than at the first. The reproducibility of the concentrations suggests both that individuals have characteristic profiles and that serum carotenoid concentrations can be measured randomly over > or = 2 wk without significant bias.

Belize↗

PubMed1996

Xenobiotic metabolism genes and the risk of recurrent spontaneous abortion.

We examined the relation between spontaneous abortion and polymorphisms in two genes, glutathione S-transferase (GSTM1) and N-acetyltransferase (NAT2), which are involved in the metabolism of xenobiotics. In a case-control study of 29 women, we found that, among women with the GSTM1 null genotype, the odds ratio (OR) was 3.1 [95% confidence interval (CI) = 1.3-7.0]. There was less evidence of a relation with NAT2 [Mantel-Haenszel adjusted OR (ORMH) = 1.4; 95% CI = 0.45-4.3]. We sought to replicate the GSTM1 finding in an independent case-control study from New York involving 89 cases. We found an inverse association (OR = 0.8; 95% CI = 0.4-2.4). Taken together, these data provide little evidence of an association between GSTM1 or NAT2 genotype and risk of spontaneous abortion.

Abortion, Habitual↗

PubMed1995

Birth weight and perinatal mortality. A comparison of the United States and Norway.

OBJECTIVE: To compare perinatal mortality in the United States and Norway, using a new analytic approach based on relative birth weight. DESIGN: Comparison of linked birth and perinatal death records for US and Norwegian births from 1986 through 1987, the most recently available 2-year period. SETTING: Norway and the United States. PARTICIPANTS: A total of 7,445,914 US births and 105,084 Norwegian births. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Perinatal weight-specific mortality after adjustment for each country's own mean birth weight. RESULTS: The higher rate of perinatal death in the United States compared with Norway is due to an excess of preterm deliveries in the United States. Low-weight, preterm births comprise 2.9% of US births compared with 2.1% of Norwegian births. If the United States could eliminate this slight excess of preterm delivery, perinatal mortality in the United States would decrease to the level in Norway. Unexpectedly, the survival of newborns at any given birth weight is virtually the same in the United States and Norway when newborns' birth weights are considered relative to their own nation's mean weight. CONCLUSIONS: Low rates of perinatal mortality in the Scandinavian countries have usually been attributed to the heavier weights of their newborns. Higher mortality among US infants is in fact due entirely to a small excess of preterm deliveries. The lighter weights of US newborns at term appear not to affect perinatal survival. Furthermore, the apparent survival advantage of low-weight US newborns (used by policymakers as evidence of superior US intensive neonatal care) may be at least partly an artifact. When weight-specific mortality rates are adjusted to relative birth weight, low-weight newborns have the same survival in Norway as in the United States. The prevention of excess mortality among US infants depends on the prevention of preterm births, not on changes in mean birth weight.

Birth Weight↗

PubMed1994

GORA: a scoring system for the quantification of risk of graft occlusion.

Auditing the outcome from vascular surgery with regard to graft occlusion is made difficult by variations in the type of surgery performed and the case mix. These difficulties are compounded when attempting to compare units. In the present study we have attempted to develop a scoring system to predict the risk of graft occlusion, and thus compensate for these variables. Prospectively collected data from 214 consecutive patients undergoing vascular reconstructive surgery (233 arterial grafts) were analysed. Graft occlusion occurred in 82 patients (35.2%). Using a multivariate linear regression analysis of these data a five-factor, five-grade scoring system has been devised (GORA: Graft Occlusive Risk Assessment). Logistic regression analysis of the observed risk of occlusion with this derived score produced the following relationship between the odds ratio of occlusive risk and GORA score: (logeR/1 - R = (0.229 x score) - 4.165). The score was then validated in a different group of 186 patients (196 arterial grafts). In both groups the score was found to predict accurately the risk of graft occlusion (P < 0.001). There was no significant difference in the receiver operating characteristic curves between the estimation and validation groups.

Ankle↗

PubMed1993

Why do small twins have a lower mortality rate than small singletons?

OBJECTIVE: We propose an interpretation of the paradoxically better survival rate among low-birth-weight twins compared with low-birth-weight singletons. STUDY DESIGN: We used data from Belgian birth and death certificates for 1983 and 1984. The data include 229,964 singletons, 2175 first twins, and 2153 second twins. Weight-specific perinatal mortality rates of twins and singletons were compared; the birth-weight distributions were adjusted to a single mean and SD. RESULTS: After adjustment, mortality rates at every weight were higher for twins than for singletons. CONCLUSIONS: The appearance of better survival among small twins compared with small singletons disappears after adjustment to relative birth-weight. There is a large risk resulting from twinning that falls on all twins, regardless of their weight.

Birth Weight↗

PubMed1993

Comparative vascular audit using the POSSUM scoring system.

Comparative audit using overall mortality and morbidity figures can be misleading as they do not take into account variations in surgical procedure and patient fitness. To examine these effects we have compared vascular surgery in two differing hospitals, during a similar 9-month period, using the POSSUM scoring system. In one unit, 255 patients underwent vascular surgery with an operative mortality of 9.4%, and morbidity of 37.3%. In the other unit, 89 patients underwent vascular procedures with an operative mortality of 20.2% and morbidity of 47.2%. At first sight there appear to be significant differences in operative outcome between the two units. However, analysis using the POSSUM system predicts a mortality rate of 10.2% for unit A and 20.2% for unit B (morbidity rates of 38.4% for unit A and 50.6% for unit B). Receiver operating curve (ROC) analysis demonstrated no significant difference between the two units (see Table III). POSSUM analysis may be of use in comparative audit.

England↗