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PubMed1987

Interactive statistical analysis of survival data.

This paper describes a SAS macro which facilitates the interactive analysis of right-censored survival data. Such data commonly occur in medical studies. The program produces Kaplan-Meier survival curves on a wide variety of graphics devices. The program also performs log-rank and generalized Wilcoxon significance tests among all plotted curves and for each pairwise contrast if desired. Because the program is intelligent and does not prompt the user for information that it can independently obtain, it is quite easy to use.

Computer Graphics↗

PubMed1988

The size of infarction as judged enzymatically in 1974 patients with acute myocardial infarction. Relation with symptomatology, infarct localization and type of infarction.

A common data base of six coronary care units containing personal and clinical data of 17462 patients was used to investigate the relation between clinical symptoms of patients with acute myocardial infarction and size of infarction. In 1974 of the 5110 patients, in whom a final diagnosis of infarction was made, size of infarction was determined according to serially measured levels of serum alpha-hydroxybutyrate dehydrogenase. The episode of infarction was the first in 1396 patients, was recurrent in 497, and undetermined in 81 patients. We calculated the size factor (defined as the mean size of infarction of patients with a particular symptom divided by the mean size of infarction of patients without that symptom) to evaluate the role of the size of infarction to manifestation of certain clinical symptoms. Bradycardia, shock and right-sided failure when noted on admission to the coronary care unit, had factors for size of infarction significantly greater than 1.0 (1.15, 1.79 and 1.30, respectively) in patients suffering an initial infarction, but not significantly different from 1.0 in patients with recurrent infarction. The occurrence of primary and secondary ventricular tachycardia and/or fibrillation, left heart failure (Killip class II-IV), symptomatic supraventricular tachycardia, high-degree atrioventricular blocks, ruptures and death in the coronary care unit was associated with factors significantly greater than 1.0 in those patients having both initial and recurrent infarctions. The size of infarction as judged enzymatically was significantly larger in patients with anterior than inferior and lateral infarction. The size of infarctions without Q waves was judged to be generally 35% smaller than infarctions producing Q waves. It is concluded that the size of infarction determines the occurrence of several symptoms and complications diagnosed at admission or during stay in the coronary care unit.

Adult↗

PubMed1994

Petroleum hydrocarbons in the nearshore marine sediments of the United Arab Emirates.

The concentrations of total petroleum hydrocarbons (TPH) were determined in nearshore sediment samples collected from 28 sampling sites along the United Arab Emirates shorelines on the Arabian Gulf, the Gulf of Oman and seven major creeks (khors) extending from them. Concentrations were highly variable and ranged between <0.4 and 212 microg g(-1) dry weight, and the highest values obtained were in the top sediment (1 cm) layer near a fuel filling station and port areas. Locally high levels of TPH were found in Dubai, Sharjah and Ajman semi-enclosed creeks where boat activities and land-based wastewater discharges are most common. Data support the premise that port activities, fuel filling stations and land-based wastewater discharges are major sources of pollution in the study area. Correlations with sediment grain size, total organic carbon (TOC) and distance from pollution sources are discussed.

Journal Article↗

PubMed1992

Approaches to evaluating the toxicity and carcinogenicity of man-made fibers: summary of a workshop held November 11-13, 1991, Durham, North Carolina.

The Workshop on Approaches to Evaluating the Toxicity and Carcinogenicity of Man-Made Fibers (MMF) was held in Durham, North Carolina, on November 11-13, 1991. The goal of the workshop was to reach a consensus, or to determine the extent to which a consensus existed, in two areas. Participants were asked to identify scientifically sound approaches for evaluating the toxicity and carcinogenicity of man-made fibers based on today's science and to determine research appropriate for study during the next 5 years that can provide an improved scientific basis for future revisions of approaches used to evaluate man-made fiber toxicity and carcinogenicity. During the first day, a series of "state of knowledge" presentations were made to provide all participants with a common data base from which to interact and discuss scientific issues. The workshop participants were assigned to one of four discussion groups, which met separately in three half-day sessions following the first day of presentations. All groups discussed the same topics: exposure assessment, hazard identification, and dose-response information needed to integrate to characterize risk in the first session; approaches to obtaining the needed information in the second session; and recommended approaches and guidelines for evaluating the toxicity and carcinogenicity of MMF and research needs in the third session. The workshop participants reconvened as a whole after each discussion session, and one member from each group reported the group's conclusions. A closure period was also included at the end of the workshop for review and discussion of items that had been considered during the workshop. The primary conclusions reached were the following: -All fiber types capable of depositing in the thorax are not alike in their pathogenic potential. -Only fiber samples with dimensions similar to those to which humans can inhale should be tested. -A complete characterization (i.e., dimensions, fiber number, mass, and aerodynamic diameter) of the fiber aerosol and retained dose is essential. -Appropriate aerosol generation methods must be used for inhalation studies in order to preserve fiber lengths. -A tiered approach to toxicity evaluation is recommended that includes: 1. In vitro screening for durability, surface properties, cytotoxicity, and similar properties, etc; 2. Short-term inhalation or other in vivo studies; 3. That chronic inhalation studies are the "gold standard" (i.e., provide most appropriate data for risk characterization). -The rat is the most appropriate species for inhalation studies. -In chronic inhalation studies, animals should be retained to at least 20% survival after 2-year exposure. -Serial lung burden analyses are an essential component of inhalation studies and are essential for understanding exposure-dose-response relationships. -Studies oriented to understanding mechanisms of toxicity and carcinogenicity are important adjuncts to traditional toxicity studies. -Histopathological analyses of tissues of the respiratory tract represent primary endpoints for evaluating effects of inhaled fibers. Major effects include pulmonary fibrosis, lung tumors, and mesotheliomas. Experimental tissues should be archived for future studies; wherever possible, handling and preservation of tissues should be done in a way that maximizes their future use in mechanistic studies. -Potential human exposures throughout the entire life-cycle of the fiber must be considered and fibrous material for toxicologic studies prepared accordingly. -Intracavity studies are inappropriate for risk characterization but can play a useful screening role in assessing fiber toxicity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

In vitro wear performance of Proplast TMJ disc implants.

This study investigates the in vitro wear performance of Proplast-Teflon Interpositional Implants (PTIPI; Vitek, Inc, Houston, TX), employing a mechanical TMJ simulator. Predictions of in vivo service life of PTIPIs are presented based on the in vitro wear testing data. Commonly employed laboratory testing methodologies are discussed in the development of alloplastic TMJ devices. Penetrative wear rates of the PTIPI at a 20-lb (9.1 kg) load were calculated to be 2.29 mm/100,000 cycles, yielding a predicted in vivo service life of PTIPIs of approximately 3 years. These results combined with reported clinical fate of this implant indicate that the intermediate- and long-term survival of this implant are uncertain.

Cartilage, Articular↗

PubMed1985

Clinical experience with a computerized record and verify system.

To improve the quality of patient care by detecting and preventing many types of treatment mistakes, we have implemented a computerized system for recording and verifying external beam radiation treatments on our therapy machines. It inhibits the radiation beam if treatment machine settings do not agree with prescribed values to within maximum permissible deviations (tolerances). The tolerances are determined from experience and adjusted when necessary to make the system more effective and less susceptible to "false alarms." The system uses a common data base for all treatment machines. As a result, it permits statistical analysis and generation of reports based on data encompassing the entire patient population as well as verification of treatments of patients transferred from one machine to another. Reports of verification failures reveal patterns of mistakes. Knowing these, attempts can be made to reduce the frequency of verification failures. "Significant" mistakes that were prevented are extracted by treatment planning personnel from these reports. Analysis of data indicates a rate of approximately 150 "significant" mistakes detected and prevented per machine per year, representing 1.0% of all fields treated. We present and discuss our experiences with the system and with the frequency, patterns, and significance of verification failures. We selected a few of the patients for whose treatments significant set-up mistakes were made, and were detected and prevented by the Record and Verify System. We include discussions of the overall effect these mistakes would have had on dose distribution had they not been prevented.

Adult↗

PubMed2004

Issues and assumptions on the road from raw signals to metrics of frontal EEG asymmetry in emotion.

There exists a substantial literature examining frontal electroencephalographic asymmetries in emotion, motivation, and psychopathology. Research in this area uses a specialized set of approaches for reducing raw EEG signals to metrics that provide the basis for making inferences about the role of frontal brain activity in emotion. The present review details some of the common data processing routines used in this field of research, with a focus on statistical and methodological issues that have captured, and should capture, the attention of researchers in this field.

Electroencephalography↗

PubMed2005

Generalized modeling approaches to risk adjustment of skewed outcomes data.

There are two broad classes of models used to address the econometric problems caused by skewness in data commonly encountered in health care applications: (1) transformation to deal with skewness (e.g., ordinary least square (OLS) on ln(y)); and (2) alternative weighting approaches based on exponential conditional models (ECM) and generalized linear model (GLM) approaches. In this paper, we encompass these two classes of models using the three parameter generalized Gamma (GGM) distribution, which includes several of the standard alternatives as special cases-OLS with a normal error, OLS for the log-normal, the standard Gamma and exponential with a log link, and the Weibull. Using simulation methods, we find the tests of identifying distributions to be robust. The GGM also provides a potentially more robust alternative estimator to the standard alternatives. An example using inpatient expenditures is also analyzed.

Models, Statistical↗

PubMed2000

Recurrent hepatitis B, hepatitis C, and combined hepatitis B and C in liver allografts: a comparative pathological study.

Although recurrence of viral hepatitis in liver transplants is common, data comparing recurrent hepatitis B (HB), hepatitis C (HC), and co-existing dual hepatitis B and C (HB&C) are sparse. Posttransplantation liver biopsies, along with molecular, serological, immunohistochemical, and clinical data from 27 patients with pretransplantation diagnosis of chronic viral hepatitis, were reviewed. The patients were placed into 4 groups: Group I, with pretransplantation HB (n = 8); group II, with pretransplantation HC (n = 10); group III with pretransplantation HC and anti-HB surface or core antibody (n = 4); and group IV, with pretransplantation HB&C (n = 5). The histopathologic findings and patient outcome were compared in the 4 groups. A high rate of recurrence of viral hepatitis was seen for all 4 groups: Group I = 100%, group II = 90%, Group III = 100%, and group IV = 80%, with the mean (median) recurrence time of 308 (224), 82 (52), 61 (64), and 125 (70) days, respectively. The number of deaths (their median survival times) were: group I = 4 (374 days), group II = 4 (794 days), group III = 1 (1,143 days), and group IV = 5 (448 days). The earliest histological findings of lobular injury was the presence of acidophil bodies and Kupffer cell hyperplasia, the latter being more prominent in recurrent HC cases. Recurrent HB presented in 2 forms: early (before 150 days) with poor survival and with either severe necroinflammatory histology or with features of fibrosing cholestatic hepatitis, and delayed (after 150 days), with mild necro-inflammatory activity and prolonged survival. HC with or without anti-HB antibodies had early recurrence, but the course was slowly progressive. Patients with HB&C had recurrence of both viruses; however, the course was dictated by HB virus.

Hepatitis B, Chronic↗

PubMed1997

[Yersinia bacteremia and iron overload].

A retrospective multicentric study was conducted to determine the real prevalence of underlying iron overloads during Yersinia bacteremias. Ninety-seven cases of bacteremias (84 Yersinia enterocolitica, 13 Yersinia pseudotuberculosis) were registered between 1990 and 1996 in eastern France. Available data were collected in 70 cases (72.2%). Laboratory investigations of iron status were done in 53% (37/70). Three patients had a past record of known hemochromatosis, meanwhile in nine other cases an iron overload was discovered during the Yersinia bacteremia. Two cases of hemochromatosis were confirmed by liver histology. In all of these 12 cases, Yersinia enterocolitica was the causal agent. The effective prevalence of underlying iron overload in Yersinia bacteremias is 40% when researched, greater than data commonly published (1.8-14%), showing both epidemiological and clinical under estimation of iron's importance in Yersinia infection pathogenesis. A Yersinia bacteremia must be considered as an indicator of possible iron overload. Yersinia infection must be suspected in febrile hemochromatosic patients. A multicentric study must be conducted to evaluate incidence and characteristics of bacteremias in hemochromatosic patients.

Aged↗

PubMed1987

The proton pump ATPase of lysosomes and related organelles of the vacuolar apparatus.

In this review, I hope to achieve the following: (a) to document the presence of a lysosome-like proton pump ATPase in many different membrane systems of animal, plant and microbial origin; (b) to glean from the diverse data common characteristics of these ATPases, especially as regards their similarities and differences with mitochondrial-type F1F0 proton pump ATPases; and (c) to consider questions of synthesis and regulation of a cellular proton pump system with such a widespread distribution.

Adenosine Triphosphatases↗

PubMed1993

Measuring case mix and severity of illness in Canada: case mix groups versus refined diagnosis related groups.

This study compares the effectiveness of Case Mix Groups (CMG*) groups and Refined Diagnosis Related Groups (RDRG) in reducing Canadian length of stay (LOS) variability. The effectiveness of the two case mix grouping methodologies was assessed with a common data base, 282,459 abstracts with ICD-9 CM diagnosis codes reported to the Hospital Medical Records Institute (HMRI) from January to March 1989. Death, signouts, transfers to or from acute care institutions and cases with an outlier LOS ("atypical" cases) were excluded from the analysis. HMRI utilization management reports to acute care hospitals use a data base defined in this way. On the basis of the variance reduction statistic (R2) from ordinary least squares regression analysis, CMG groups were found to be slightly more effective than RDRGs in reducing LOS variability. R2 statistics were 45.7 and 43.8 for CMG groups and RDRGs, respectively. Within subgroups of cases, CMG groups were found to be markedly more effective with the newborn/neonate group and to a lesser extent with non-surgical cases. The severity of illness categories within RDRGs did not, over all "typical" cases in the data base, yield more homogeneous groups of cases than CMG groups, which have half the number of categories. The value of tailoring severity measurement to Canadian medical practice and Canadian diagnosis coding is highlighted.

Acute Disease↗

PubMed2002

A computer program for period analysis of cancer patient survival.

Monitoring of long-term survival rates, which is now routinely performed by many cancer registries throughout the world, should be as up-to-date as possible. A few years ago, a new method of survival analysis, denoted period analysis, has been proposed which provides more up-to-date estimates of long-term survival rates than traditional survival analysis by exclusively reflecting the survival experience of patients within a recent calendar period. However, application of this method has so far been hindered by the lack of pertinent computer programs. In this paper, we present a simple and easy-to-use computer program (SAS macro) that enables one to carry out period analysis (as well as conventional analysis) of both absolute and relative survival rates with the type of data commonly available in population-based cancer registries. We illustrate application of the program with examples from the nationwide Finnish Cancer Registry.

Female↗

PubMed2002

RNAML: a standard syntax for exchanging RNA information.

Analyzing a single data set using multiple RNA informatics programs often requires a file format conversion between each pair of programs, significantly hampering productivity. To facilitate the interoperation of these programs, we propose a syntax to exchange basic RNA molecular information. This RNAML syntax allows for the storage and the exchange of information about RNA sequence and secondary and tertiary structures. The syntax permits the description of higher level information about the data including, but not restricted to, base pairs, base triples, and pseudoknots. A class-oriented approach allows us to represent data common to a given set of RNA molecules, such as a sequence alignment and a consensus secondary structure. Documentation about experiments and computations, as well as references to journals and external databases, are included in the syntax. The chief challenge in creating such a syntax was to determine the appropriate scope of usage and to ensure extensibility as new needs will arise. The syntax complies with the eXtensible Markup Language (XML) recommendations, a widely accepted standard for syntax specifications. In addition to the various generic packages that exist to read and interpret XML formats, an XML processor was developed and put in the open-source MC-Core library for nucleic acid and protein structure computer manipulation.

Databases, Nucleic Acid↗

PubMed1989

Combination versus sequential single agent chemotherapy in advanced breast cancer: associations with metastatic sites and long-term survival. The Western Cancer Study Group and The Southeastern Cancer Study Group.

Two hundred and twenty-two patients with advanced breast cancer were randomised in two separate trials of similar design to either concomitant combination treatment or sequential use of the same drugs given as single agents changed only at disease progression. Both trials used cyclophosphamide, methotrexate, 5-fluorouracil and prednisone; the WCSG using triiodothyronine and the SECSG using vincristine as the remaining agent. A common data base was generated for these trials and combined for analysis. Considering all patients, combination treatment was associated with a significantly increased response (46 versus 25%, P less than 0.05) but not survival improvement. For the 141 patients without liver involvement, survival was closely comparable in both treatment arms. Combination therapy did result in significant survival benefit for patients with liver involvement (P less than 0.05). These studies demonstrate: (1) in the majority of breast cancer patients, sequential single agent therapy can result in survival comparable to combination treatment; and (2) sole consideration of response frequency does not represent the optimal criterion to compare therapeutic approaches in advanced breast cancer.

Adenocarcinoma↗

PubMed2002

Residential radon exposure and lung cancer: variation in risk estimates using alternative exposure scenarios.

The most direct way to derive risk estimates for residential radon progeny exposure is through epidemiologic studies that examine the association between residential radon exposure and lung cancer. However, the National Research Council concluded that the inconsistency among prior residential radon case-control studies was largely a consequence of errors in radon dosimetry. This paper examines the impact of applying various epidemiologic dosimetry models for radon exposure assessment using a common data set from the Iowa Radon Lung Cancer Study (IRLCS). The IRLCS uniquely combined enhanced dosimetric techniques, individual mobility assessment, and expert histologic review to examine the relationship between cumulative radon exposure, smoking, and lung cancer. The a priori defined IRLCS radon-exposure model produced higher odds ratios than those methodologies that did not link the subject's retrospective mobility with multiple, spatially diverse radon concentrations. In addition, the smallest measurement errors were noted for the IRLCS exposure model. Risk estimates based solely on basement radon measurements generally exhibited the lowest risk estimates and the greatest measurement error. The findings indicate that the power of an epidemiologic study to detect an excess risk from residential radon exposure is enhanced by linking spatially disparate radon concentrations with the subject's retrospective mobility.

Air Pollutants, Radioactive↗

PubMed1997

Large paraesophageal varices on endosonography predict recurrence of esophageal varices and rebleeding.

BACKGROUND & AIMS: Recurrence of varices and rebleeding after endoscopic therapy is very common. Data on the prediction of recurrent varices after initial obliteration by endoscopic therapy are few. The aim of this study was to correlate the presence and the size of paraesophageal varices (PEVs) in patients after endoscopic variceal ligation with recurrent varices and rebleeding. METHODS: Forty patients who underwent endoscopic banding ligation for esophageal variceal bleeding were studied by endosonography within 4 weeks after obliteration of varices. PEVs were classified as none, small, or large (maximum diameter, > or =0.5 cm). Esophagoscopy and endosonography were then repeated every 6 months for up to 1 year. RESULTS: Two patients (5%) were not detected to have PEVs. Small and large PEVs were identified in 24 (60%) and 14 (35%) patients, respectively. During the follow-up period of 1-year, recurrent submucosal esophageal varices were detected in 24 patients, including 13 patients (93%) with large PEVs and 11 patients (46%) with no or small PEVs (P = 0.0019). Recurrent bleeding occurred in 6 patients (43%) with large PEVs and in 3 patients (12%) with small PEVs (P = 0.044). CONCLUSIONS: Patients with large PEVs have a higher risk of developing recurrent varices and rebleeding.

Adult↗

PubMed2001

Radiographic assessment of uncemented humeral components in total shoulder arthroplasty.

Seventy-two total shoulder arthroplasties performed using Neer II press-fit humeral components and followed for an average of 4.1 years (range, 2-7.8 years) were analyzed radiographically. A humeral component was considered radiographically at risk for clinical loosening when a radiolucent line > or =2 mm in width was present in > or =3 zones or tilt or subsidence was identified on sequential radiographs by 2 of 3 or 3 of 3 independent observers. Forty components (55.6%) were judged to be at risk. There were no identifiable characteristics associated with the development of an at-risk humeral component except longer average follow-up of the at-risk group (4.7 years vs 3.3 years, P =.001). Humeral components at risk had a higher rate of endosteal erosion (P =.04) and greater number of zones with sclerosis. Radiographic changes around Neer II uncemented humeral components are common. Data from this study can be used as 1 benchmark to compare with alternate methods of humeral component fixation.

Adult↗