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PubMed2004

Age-related changes in radiation-induced micronuclei among healthy adults.

The aim of the present study was to establish the extent of in vitro radioresponse of lymphocytes among 62 healthy adults of both genders and to estimate the distribution of baseline micronuclei and radiosensitivity among individuals of the study population using the cytochalasin block micronucleus test. A younger study group consisted of 10 males (mean age, 22.4 years; range, 21-27) and 12 females (mean age, 24.8 years; range, 20-29), whereas an older study group consisted of 18 males (mean age, 35.1 years; range, 30-44) and 22 females (mean age, 38.5 years; range, 30-48). For evaluation of radiosensitivity blood samples were irradiated in vitro using 60Co gamma-ray source. The radiation dose employed was 2 Gy, the dose rate 0.45 Gy/min. The study revealed a significant gender effect on baseline micronuclei favoring females (Z = 3.25, P < 0.001), while yields of radiation-induced micronuclei did not differ significantly (Z = 0.56, P < 0.56) between genders. The distribution of baseline micronuclei among the individuals tested followed Poisson distribution in both study groups and in both genders, whereas the distribution of radiosensitivity among individuals of the older study group did not fulfill Poisson expectations (Kolmogorov-Smirnof test, P < 0.01). In contrast to a nonsignificant difference in radiosensitivity between males and females of the same age group (Z = 1.97, P < 0.56), a statistically significant difference in radiosensitivity between younger and older group for both genders was found (Z = 3.03, P < 0.03). Since the individuals tested were healthy, the observed variability in radiation response is considered to be an early effect of ageing.

Adult↗
PubMed2005

Direct determination of band broadening in size exclusion chromatography.

A simple method to correct the measured extent of band broadening in size exclusion chromatography for the contribution of narrow (polydisperse) standards is presented. It is based on the assumptions that commercial polymer standards can be described by a Poisson distribution and the additivity of peak variances. Two sets of standards (polystyrene from two suppliers) were investigated under normal working conditions, i.e. a combination of four columns with different porosities and a flow rate of 1 ml/min. Furthermore, the polystyrene standards were used to determine the extent of band broadening for four additional combinations of columns (varying in their separation range and porosities) as a function of the elution volume. The assumption of a constant peak variance for band broadening turned out to be a (very) rough approximation for some combinations of columns, but all results taken together demonstrate that this assumption is not generally applicable. Qualitative agreement between theory and experiment was found with a rearranged van Deemter equation.

Chromatography, Gel↗
PubMed2001

A statistical approach to an outbreak of endophthalmitis following cataract surgery at a hospital in the West of Scotland.

The number of cases of endophthalmitis following cataract surgery caused considerable concern in a West of Scotland hospital throughout 1998 and early 1999. A multi-disciplinary team including infection control nurses, doctors, public health officials,epidemiologists and statisticians was set up to investigate the situation. This paper examines the statistical issues surrounding the investigation. A method based on the Poisson distribution showed that the number of cases was significantly higher than expected. Fisher's Exact Test and Logistic Regression were then applied to the data from two related case control studies. These analyses showed that a higher risk of endophthalmitis was associated with being female, having a vitrectomy or having a previous history of respiratory disease. Finally, a method was devised to enable staff to recognize more quickly when the number of cases of endophthalmitis was becoming higher than expected. The method should find application in other clinical situations where the probability of rare events is known.

Case-Control Studies↗
PubMed2003

Kawasaki disease in parents and children.

AIM: To estimate the probability that the parents of patients with Kawasaki disease also had a history of the same disease. METHODS: Self-reported parents' histories of Kawasaki disease were collected from data of the 16th nationwide survey of the disease conducted in Japan from January 1999 to December 2000. The incidence of Kawasaki disease was calculated by using data reported in all 16 nationwide surveys and live births in the Japanese vital statistics. The expected number of parents with a history of Kawasaki disease in the general population, which was calculated by using the assumed number of parents in the vital statistics and the incidence of this disease, was compared with the observed number. RESULTS: Among 14,163 parent pairs of patients with Kawasaki disease, 33 parents (25 mothers and 8 fathers) had a history of the disease. The number of parents expected to have a history of Kawasaki disease was 16.1 (8.4 mothers and 7.7 fathers). From a Poisson distribution, the probability of the observed number was less than 0.001 among parents or mothers. The prevalence of a recurrence of Kawasaki disease and incidences involving siblings of patients whose parents had a history of the disease were five or six times higher than those of all patients who were reported in the 16th survey. CONCLUSION: When compared with parents in the general population, the probability of a history of Kawasaki disease was significantly higher in those parents whose children suffered from the same disease. This suggests that, epidemiologically, a genetic predisposition to Kawasaki disease may be implicated in its occurrence.

Adolescent↗
PubMed2004

Microdosimetry of astatine-211 single-cell irradiation: role of daughter polonium-211 diffusion.

A microdosimetric analysis of previously published data on 211At-albumin, free 211At, and 211At-C215 irradiation of Colo-205 cells in a slowly rotating single-cell suspension is presented. A custom-built computer program based on the Monte Carlo method was used to simulate the irradiation and the energy deposition in individual cell nuclei. Separate simulations were made for the assumption that the 211Po atom stays in the position where it is created, and that it diffuses away. The mean event number at which 37% of all cells survived, n37, and the frequency mean specific energy per event, zF, were estimated. The Poisson distribution of events and simulated single and multievent distributions of specific energy were used to find the single-cell specific energy at which the probability of survival is reduced to 37%, z37. The calculated single-cell radiosensitivity values show that 211Po atoms, created on a cell surface by the decay of 211At atoms, will diffuse from the cell during its life-span. The increasing distance to the cell nucleus will drastically decrease the probability of the emitted alpha particle to hit the nucleus. This will result in fewer alpha-particle events in the cell nucleus. For dispersed cells, the diffusion of 211Po atoms will reduce the total dose from cell-bound 211At by a factor of 2.

Alpha Particles↗
PubMed2006

Confidence intervals for an exposure adjusted incidence rate difference with applications to clinical trials.

To summarize safety data such as clinical adverse experiences in clinical trials with a moderate to long-term follow-up, we may use a measurement which accounts for the potential differences in the follow-up duration between treatment groups. The incidence rate, which uses the total person-time follow-up in a treatment group as the denominator, is one of these measures. When treatment comparisons are based on the difference of the incidence rates, it is of interest to construct confidence intervals for the rate differences. In this paper, we first discuss the assumptions and scenarios in which the exposure adjusted incidence rate may be appropriate. Then we review several methods of calculating confidence intervals for the difference of two incidence rates assuming that the number of events come from a Poisson distribution. The methods considered include Wald's method, the two-by-two table method, the Miettinen and Nurminen (MN) method, and the conditional MN method. For all but the MN method, explicit confidence intervals can be obtained. For the MN method, some numerical iterations are required. The properties of these methods are evaluated by simulations. The results show that the MN method outperforms the other three in terms of the coverage of the confidence interval, especially when the rates and therefore the number of events are small. Lastly, data from a clinical study are used to demonstrate the application of the methods.

Aged↗
PubMed2005

Cancer of the gastrointestinal tract and exposure to asbestos in drinking water among lighthouse keepers (Norway).

OBJECTIVE: Previous studies of predominantly ecological design have indicated a possible elevation of gastrointestinal cancer risk in population groups exposed to drinking water contaminated with asbestos from natural sources or asbestos-cement containing water pipes. In the present study the possible effect of ingested asbestos fibers on gastrointestinal cancer risk was investigated in an occupational group where a proportion of the employees was exposed to asbestos in their drinking water. METHOD: A cohort of 726 lighthouse keepers first employed between 1917 and 1967 were followed up for cancer incidence from 1960 to 2002. The standardized incidence ratio (SIR) was calculated as the number of new cancer cases divided by the expected number based on five-year age and sex specific incidence rates in the general rural population of Norway. A 95% confidence interval (CI) was calculated for all SIR values assuming a Poisson distribution of the cancer cases. RESULTS: Risk of stomach cancer was elevated in the whole cohort (SIR: 1.6, CI: 1.0-2.3), in the subgroup with definite asbestos exposure (SIR: 2.5, CI: 0.9-5.5), and when the group was followed for 20 years and more after first possible exposure (SIR: 1.7, CI: 1.1-2.7). Less consistent results were found for colon cancer; SIR was 1.5 (CI: 0.9-2.2) overall, 0.8 (CI: 0.1-2.9) among the exposed, and 1.6 (CI: 1.0-2.5) twenty years and more after first possible exposure. CONCLUSION: The results support the hypothesis of an association between ingested asbestos and gastrointestinal cancer risk in general and stomach cancer risk specifically.

Asbestos↗
PubMedDate not supplied

Testing deviation for a set of serial dilution most probable numbers from a Poisson-binomial model.

A serial dilution experiment estimates the microbial concentration in a broth by inoculating several sets of tubes with various amounts of the broth. The estimation uses the Poisson distribution and the number of tubes in each of these sets that show growth. Several factors, such as interfering microbes, toxins, or disaggregation of adhering microbes, may distort the results of a serial dilution experiment. A mild enough distortion may not raise suspicion with a single outcome. The test introduced here judges whether the entire set of serial dilution outcomes appears unusual. This test forms lists of the possible outcomes. The set of outcomes is declared unusual if any occurrence of an observed outcome is on the first list, or more than one is on the first or second list, etc. A similar test can apply when there are only a finite number of possible outcomes, and each outcome has a calculable probability, and few outcomes have tied probabilities.

Chemistry↗
PubMed2001

Kinetic measurements of cell surface E-selectin/carbohydrate ligand interactions.

Selectin/ligand interactions initiate the multistep adhesion and signaling cascades in the recruitment of leukocytes from circulation to inflamed tissues and may also play a role in tumor metastasis. Kinetic properties of these interactions are essential determinants governing blood-borne cells' tethering to and rolling on the vessel wall. Extending our recently developed micropipette method, we have measured the kinetic rates of E-selectin/ligand interactions. Red cells coated with an E-selectin construct were allowed to bind HL-60 or Colo-205 cells bearing carbohydrate ligands. Specific adhesions were observed to occur at isolated points, the frequency of which followed a Poisson distribution. These point attachments were formed at the same rate with both the HL-60 and Colo-205 cells (0.14 +/- 0.04 and 0.13 +/- 0.03 microm2 s(-2) per unit density of E-selectin, respectively) but dissociated from the former at a rate twice as fast as did from the latter (0.92 +/- 0.23 and 0.44 +/- 0.10 s(-1), respectively). The reverse rates agree well with those measured by the flow chamber. The forward rates are orders of magnitude higher than those of Fcgamma receptors interacting with IgG measured under similar conditions, consistent with the rapid kinetics requirement for the function of E-selectin/ligand binding, which is to capture leukocytes on endothelial surfaces from flow.

Animals↗
PubMed2002

An efficient method for studying short-term plasticity with random impulse train stimuli.

In this article, we introduce an efficient method that models quantitatively nonlinear dynamics associated with short-term plasticity (STP) in biological neural systems. It is based on the Voterra-Wiener modeling approach adapted for special stimulus/response datasets. The stimuli are random impulse trains (RITs) of fixed amplitude and Poisson distributed, variable interimpulse intervals. The class of stimuli, we use can be viewed as a hybrid between the paired impulse approach (variable interimpulse interval between two input impulses) and the fixed frequency approach (impulses repeated at fixed intervals, varying in frequency from one stimulus dataset to the next). The responses are sequences of population spike amplitudes of variable size and are assumed to be contemporaneous with the corresponding impulses in the RITs they are evoked by. The nonlinear dynamics of the mechanisms underlying STP are captured by kernels used to create compact STP models with predictive capabilities. Compared to similar methods in the literature, the method presented in this article provides a comprehensive model of STP with considerable improvement in prediction accuracy and requires shorter experimental data collection time.

Action Potentials↗
PubMed1998

Cancer cluster among young Indian adults living near power transmission lines in Bom Jesus do Tocantins, Pará, brazil.

A case study was carried out to explore the occurrence of a cancer cluster in 1992 among young indian adults adults living in an Amazonian village near two 500 kV power transmission lines that began operating a decade ago. Current blood levels of DDT and organophosphorus pesticides and metal levels in hair samples were measured. Extremely low magnetic field exposure was determined during current daily activities carried out by the Indian villagers. Taking into account the cancer incidence rates in different Brazilian cities, the probability of the occurrence of this cluster by chance was considered remote (p< 0.003, Poisson distribution). High blood levels of p,p'-DDT (median levels ranging from 26 to 58 ppb) were observed. As a whole, this community showed a pattern of low exposure to organophosphorus pesticides, and high recent exposure was only observed in a few blood samples. Continuous exposure to extremely low electromagnetic fields originated in the power transmission lines (which reached 95.0 mG under the lines) was observed on several opportunities during daily activities carried out by Indian villagers. Further observational studies should evaluate the interaction between exposure to extremely low electromagnetic fields and prior exposure to tumor initiators in cancer development.

Adolescent↗
PubMedDate not supplied

Long-term prediction of female breast cancer mortality in Korea.

Not only the incidence but also the mortality of female breast cancer has been steadily increasing in Korea since the 1980s. Epidemiologic evidence on changes in lifestyle and risk factors related with breast cancer, and data from migrant studies strongly suggest that breast cancer might further increase. In order to estimate the long-term trend in mortality of breast cancer in Korean women, we analyzed age-specific mortality rates for breast cancer over the past 20 years, and made a projection up to 2020 using a linear regression model with the Poisson distribution. The age-adjusted mortality rates for breast cancer per 100,000 persons were 2.84 in 1983, 4.91 in 1993, and 6.26 in 2003. The predicted expected age-adjusted mortality rates for breast cancer are 6.51 for 2005, 7.37 for 2010, 8.22 for 2015, and 9.07 for 2020, with an estimated annual increment of breast cancer mortality of 0.1704. Accordingly, 1,564 women in 2005 and 3,087 in 2020 will be expected to die of breast cancer in Korea. Compared with the rate in 1983, this indicates a more than 3-fold increase by 2020. On the basis of our results, female breast cancer in Korea will linearly increase for the forseeable future if the trend over the past 20 years continues.

Adolescent↗
PubMed2006

[Prevalence of tuberculosis infection and its association with social class in children in the Autonomous Community of Madrid].

INTRODUCTION: The frequency of tuberculosis infection, particularly among children, indicates the magnitude of the disease reservoir. The aim of this study was to ascertain the prevalence of tuberculosis infection in children in the Autonomous Community of Madrid and its association with social class. MATERIAL AND METHODS: We performed a cross sectional study of 6-year-old schoolchildren living in the Autonomous Community of Madrid, selected through probabilistic sampling. From September 1999 through June 2000, information was collected on residence stratum, tuberculin test (positivity threshold 5 mm), social class (five categories), based on the occupation of the main earner in the family, and the formal education attained by the parents. We calculated 95% confidence intervals for the prevalence estimates according to a Poisson distribution. RESULTS: A total of 2,721 children were studied. The prevalence of tuberculosis infection for the total study population was 0.62% (95% CI: 0.29-0.95). The prevalence of tuberculosis infection was 0.42% (95% CI: 0.00-0.85) in social class I (the highest), 0.00% (95% CI: 0.00-1.17) in class II, 0.77% (95% CI: 0.00-1.86) in class III, 0.62% (95% CI: 0.00-1.32) in class IV, and 1.57% (95% CI: 0.00-3.40) in class V (the lowest). In both fathers and mothers, the highest prevalence of tuberculosis infection was found in the group that had only completed elementary school or basic general education (up to the age of 14). CONCLUSIONS: The prevalence of tuberculosis infection in the Autonomous Community of Madrid is similar to that in others areas of Spain. The results of our study are consistent with a lower prevalence in the higher socioeconomic groups.

Child↗
PubMed2003

Traffic related air pollution and acute hospital admission for respiratory diseases in Drammen, Norway 1995-2000.

The aim of this study was to estimate the associations between seven ambient air pollutants [particulate matter (PM10), nitrous dioxide (NO2), sulfur dioxide (SO2), ozone (O3), benzene, formaldehyde and toluene] and acute hospital admissions for respiratory diseases in Drammen, Norway 1995-2000. Time-series analysis of counts was performed by means of generalized additive models with log link and Poisson distribution. The results showed that benzene was the pollutant having the strongest association with respiratory diseases for the total study period, the relative risk of an interquartile increase of benzene was 1.095 with 95% confidence interval: 1.031-1.163. The corresponding results were 1.049 (0.990-1.112) for formaldehyde, 1.044 (1.000-1.090) for toluene, 1.064 (1.019-1.111) for NO2, 1.043 (1.011-1.075) for SO2, 0.990 (0.936-1.049) for O3 and 1.022 (0.990-1.055) for PM10. Dividing the total study period into two 3-year periods, there was a substantial reduction in the exposure levels of the volatile organic compounds (benzene, formaldehyde and toluene) from the first to the second period. Separate analyses for the second time period showed weaker association between these pollutants and the health outcome. This study provides further evidence for short-term respiratory health effects of traffic related air pollution.

Acute Disease↗
PubMed2007

Computerized indicators of potential drug-related emergency department and hospital admissions.

OBJECTIVES: To computerize indicators of potential drug-related emergency department and hospital admissions and to report the incidence of these potential drug-related morbidities for a managed care organization. STUDY DESIGN: Retrospective review of healthcare organizations' pharmacy and administrative claims databases. METHODS: Thirty-nine indicators were coded and were used in an automated search of claims data. The indicators of potential drug-related morbidities comprised a pattern of care and an associated adverse outcome. Poisson distribution regression analysis was performed to assess the association of patient factors with indicator positives. RESULTS: The incidence densities for indicator positives were 1.96 (95% confidence interval, 1.60-2.40) per 1000 patient-years in the general population and 13.6 (95% confidence interval, 8.8-20.2) per 1000 patient-years among older persons. Age, male sex, number of medical conditions, and number of medications from different classes were associated with an increased rate of indicator positives. CONCLUSIONS: Indicators of potential drug-related morbidities can be fully automated and used to search through medical and pharmacy claims. The indicators investigated in this study show promise as a quality improvement tool and should be further developed and evaluated.

Adolescent↗
PubMed2005

National differences in reporting 'pneumonia' and 'pneumonia interstitial': an analysis of the WHO International Drug Monitoring Database on 15 drugs in nine countries for seven pulmonary conditions.

PURPOSE: Increased post-marketing reports of 'interstitial pneumonia' as an adverse drug reaction (ADR) from the use of gefitinib, irinotecan, or leflunomide among patients in Japan have not been noted in other countries. The WHO International Drug Monitoring Database was analyzed to examine Japan's pattern of reporting the term 'pneumonia interstitial' for 15 selected drugs with a mixed history of association with pulmonary ADRs. METHODS: ADR counts from the WHO Database for 1992-2001 were obtained for 15 disparate drugs (three androgen blockers, eight cytotoxics, one proton pump inhibitor, one monoclonal antibody, and two anti-epileptics) from nine countries (Australia, France, Germany, Italy, Japan, Spain, Thailand, U.K., and U.S.A.) for seven pulmonary ADR terms (alveolitis fibrosing, pneumonia, pulmonary fibrosis, lung fibrosis interstitial, pulmonary infiltration, interstitial lung disease, and pneumonia interstitial). Statistical analyses included estimating Poisson-distributed expected rates, observed/expected (O/E) ratios, and 95% confidence intervals (CI). The overlapping nature and changes in definition over time of these terms in medical texts and in the WHO-ART, COSTART, J-ART, and MedDRA coding systems is also noted. RESULTS: Compared to other countries, both Japan and France did not have higher O/E reporting ratios for all seven pulmonary ADRs combined, but did have higher O/E ratios for 'pneumonia interstitial' and lower O/E ratios for 'pneumonia' for the same drugs. CONCLUSIONS: Japan and France were found to preferentially use the term 'pneumonia interstitial' for ADR where other countries used 'pneumonia.' This cultural pattern coincides with the fact that 'pneumonia interstitial' in older versions of COSTART, J-ART, and MedDRA were subsumed under infectious pulmonary diseases.

Adverse Drug Reaction Reporting Systems↗
PubMed2005

Sampling strategies for detecting rare impurities: an application in gene therapy products.

Detection of rare impurities in drug products presents special challenges. Replication competent adenovirus (RCA) is a rare impurity found in adenovirus-based gene therapy products. Various methods are used for detection of RCAs. We primarily focus on qualitative assays. Acceptance sampling plans for detecting RCAs in batches of gene therapy products are discussed. Assuming that the number of RCA units per patient dose follows a Poisson distribution, operating characteristics (OC) of these sampling plans can be studied. The OC curves display the acceptance probabilities for batches with specific true but unknown level of RCA and can be used to assess the specificity and sensitivity of the test strategies. Application of Bayesian methodologies in the assessment of RCA levels in drug batches is also discussed. Using observed data and prior belief, a 95% credible region for the number of RCA units per patient dose can be constructed. Both classical and Bayesian calculations display the impact of sample size, sampling fraction, and assay quality on the detection of RCA. For better sensitivity, the largest possible sampling fraction that does not interfere with the logistics and the performance of the assay should be used. The choice of sample size will depend on the upper limit of the biologically safe level of RCA, the testing strategy, the desired level of sensitivity and specificity, and also on practical issues.

Adenoviridae↗
PubMed1994

False-positives in spontaneous reporting: should we worry about them?

Spontaneous reporting remains the most used and, undoubtedly, the most cost-effective approach for the identification of adverse drug reactions (ADRs). Most of the limitations of this method are well recognised but the possibility of receiving false-positive reports of coincidental drug-event associations has received little attention. In this paper we propose a method based on the Poisson distribution for computing the maximum number of reports of an ADR that could be expected to be reported coincidentally. Three parameters are required: (i) the background risk of the event in the reference population, (ii) the total number of patients treated with the drug considered and, (iii) the proportion of cases that have been reported to the pharmacovigilance system. For most empirical situations occurring in the post-marketing surveillance setting, the expected number remains low and only a maximum of one to three cases could be accepted as possibly coincidental. For rare adverse events such as agranulocytosis or toxic epidermal necrolysis, coincidental associations are so unlikely that a number of reports greater than three constitutes a strong warning and requires further investigation. These findings suggest that for rare events, reports of coincidental drug-event associations are too unlikely to be considered as an important limitation of spontaneous reporting.

Drug-Related Side Effects and Adverse Reactions↗