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PubMed1997

Factors that influence effect size in 15O PET studies: a meta-analytic review.

The PET literature is growing exponentially, creating a need and an opportunity to perform a meta-analytic review consolidating the published information. This study describes the use of effect size as an index in PET studies and discusses how this measure can be used for comparing findings across studies, laboratories, and paradigms. In comparing studies across laboratories it is essential to know how the methods employed affect the results and conclusions drawn. This study also compared effect size for two different methods of tracer delivery in 15O PET studies ([15O]H2O bolus injection versus inhalation of [15O]CO2), whether averaged versus single-scan conditions were used, and the data analytic strategy employed. The effect sizes observed across studies were consistently large with a median effect size of 8.55, indicating that the phenomena investigated in 15O PET studies are strong. The largest peak activation reported in a study was found to be affected by variability in sample size, data analytic strategy, and repeat versus single-scan conditions. However, the impact of these factors was not examined on smaller or less intense peaks. Minimal standards for reporting statistical results are discussed.

Data Interpretation, Statistical↗
PubMed1990

[Contents and batch-dependent variations of mineral substances in milk formula for premature infants and possible effects on renal acid burden].

The mineral contents of Na, K, Ca, Mg, Cl and P was determined in different batches of 5 preterm formulas. The purpose of this study was 1st to investigate whether the analytical data are in agreement with the specifications of the manufactures and 2nd whether there are large variations between different batches of the same formula. For each analyzed mineral we found marked differences between the specifications and our measurements in at least one of the formulas. In these cases the differences between the labels and the medians of the analytical data were larger than half of the range of all determinations of the respective formula. Without exception the mean values for K were all clearly lower than the specifications of the producers. In 4 of the 5 premature formulas variation coefficients greater than 10% were observed for at least one mineral. The results show that coincidental variations of mineral contents in different batches can result in a disadvantageous mineral composition because of synergistic effects on metabolism. In this context the importance of the sum of Na and K over Cl in premature formulas is stressed with regard to renal acid excretion. The introduction of more stringent quality standards is proposed.

Acid-Base Equilibrium↗
PubMed2002

Fitting of tissue tolerance data to analytic function: improving the therapeutic ratio.

Response of human tissues to ionizing radiation is a complex process. It is influenced by many factors, such as use of chemotherapy drugs and underlying diseases such as diabetes and/or lung emphysema. A phenomenological model such as Lyman's is an attempt to predict the complication, for a variety of tissues, in the absence of these factors. The use of the model requires the knowledge of the parameters to predict the response for a specific endpoint. Clinical response data are needed to determine these parameters. Emami et al. [6] have provided some data, based on pre-CT and pre-3-D information, for some of the most serious complications. Based on this information the parameters were determined [4]. However, to validate and further improve the predictive power of the model, improved clinical response data are needed. With CT-based 3-D treatment planning systems the dose-volume information is routinely produced. Efforts by the radiation oncology community are needed to collect this information and correlate it with the clinical outcomes in a uniform and systematic way, not only for the most serious complications but also for less severe radiation-induced complications that are routinely considered in radiation therapy. Also, the information about the tissue response with underlying disease and drugs will be useful. The use of NTCP for plan comparison is useful. However, the incorporation of TCP and NTCP for designing the plan is remarkable. A plan can be optimized for the best outcome for the patient. It is hoped that as the models and parameters are refined and predictive power of the model increases, better plans will be produced, significantly improving the therapeutic ratio.

Humans↗
PubMed1981

[Comparison of analytical methods for the estimation of glycosylated haemoglobins (author's transl)].

The glycosylated haemoglobins of 26 different blood samples were analysed by six different methods; the regression lines and the correlation coefficients were calculated from the analytical data. The best separation and estimation of the fast haemoglobin fractions were achieved by high performance liquid chromatography (HPLC). Therefore HPLC is regarded as the reference method for the analysis of fast haemoglobin fractions. Microcolumn chromatography or the thiobarbituric acid method are recommended for routine analysis in clinical laboratories. Since the labile aldimine (Schiff's base) can be calculated from the analytical data or destroyed by appropriate methods, this glycosylated haemoglobin fraction does not interfere with the results.

Chromatography, Gel↗
PubMedDate not supplied

Decomposition and plant-available nitrogen in biosolids: laboratory studies, field studies, and computer simulation.

This research combines laboratory and field studies with computer simulation to characterize the amount of plant-available nitrogen (PAN) released when municipal biosolids are land-applied to agronomic crops. In the laboratory studies, biosolids were incubated in or on soil from the land application sites. Mean biosolids total C, organic N, and C to N ratio were 292 g kg(-1), 41.7 g kg(-1), and 7.5, respectively. Based on CO2 evolution at 25 degrees C and optimum soil moisture, 27 of the 37 biosolids-soil combinations had two decomposition phases. The mean rapid and slow fraction rate constants were 0.021 and 0.0015 d(-1), respectively, and the rapid fraction contained 23% of the total C assuming sequential decomposition. Where only one decomposition phase existed, the mean first order rate constant was 0.0046 d(-1). The mean rate constant for biosolids stored in lagoons for an extended time was 0.00097 d(-1). The only treatment process that was related to biosolids treatment was stabilization by storage in a lagoon. Biosolids addition rates (dry basis) ranged from 1.3 to 33.8 Mg ha(-1) with a mean value of 10.6 Mg ha(-1). A relationship between fertilizer N rate and crop response was used to estimate observed PAN at each site. Mean observed PAN during the growing season was 18.9 kg N Mg(-1) or 37% of the biosolids total N. Observed PAN was linearly related to biosolids total N. Predicted PAN using the computer model Decomposition, actual growing-season weather, actual analytical data, and laboratory decomposition kinetics compared well with observed PAN. The mean computer model prediction of growing-season PAN was 19.2 kg N Mg(-1) and the slope of the regression between predicted and observed PAN was not significantly different from unity. Predicted PAN obtained using mean decomposition kinetics was related to predicted PAN using actual decomposition kinetics suggesting that mean rate constants, actual weather, and actual analytical data could be used in estimation of PAN. There was a linear relationship between predicted N mineralization for the growing season and for the first year. For this study, the mean values for the growing season and year were 27 and 37% of the organic N, respectively.

Agriculture↗
PubMed2002

Improved reliability of pH measurements.

Measurements of pH are performed on a large scale at laboratory level, and in industry. To meet the quality-control requirements and other technical specifications there is a need for traceability in measurement results. The prerequisite for the international acceptance of analytical data is reliability. To measure means to compare. Comparability entails use of recognised references to which the standard buffer solutions used for calibration of pH meter-electrode assemblies can be traced. The new recommendation on the measurement of pH recently published as a provisional document by the International Union on Pure and Applied Chemistry (IUPAC) enables traceability for measured pH values to a conventional reference frame which is recognised world-wide. The primary method for pH will be described. If analytical data are to be accepted internationally it is necessary to demonstrate the equivalence of the national traceability structures, including national measurement standards. For the first time key comparisons for pH have been performed by the Consultative Committee for Amount of Substance (CCQM, set up by the International Bureau of Weights and Measures, BIPM) to assess the equivalence of the national measurement procedures used to determine the pH of primary standard buffer solutions. The results of the first key comparison on pH CCQM-K9, and other international initiatives to improve the consistency of the results of measurement for pH, are reported.

Journal Article↗
PubMed1986

Statistical approaches to suicidal risk factor analysis.

Suicide research is a particularly difficult area primarily because of the base rate problem and inadequate case finding. Traditional item-analytic and multiple regression or discriminant function data-analytic methods in suicide research are criticized on several technical grounds, including capitalization on chance, failure to cross-validate, and confusion of the degree of relationship with its statistical significance. These errors are further confounded when the research data base misrepresents the very low true base rate. However, the most serious defect in item-analytic and both conventional and stepwise multiple regression procedures is their failure to take into account the causal structure of suicide risk factors. Setwise hierarchical multiple regression/correlation analysis is offered as an effective tool for suicide research. It capitalizes on the powerful general data-analytic features of regression analysis, but does so in a way that represents the causal structure of the putative risk factors. The more complex methods of causal models analysis are also recommended. I do not believe, however, that progress in the understanding of suicide lies mainly in the improvement of the statistical procedures employed. Even with optimal procedures, the amount by which we can expect to increase the predictability of suicidality using psychosocial risk factors is not likely to be large. Recent research in the biochemistry of suicide offers some hope. If to the psychosocial factors now employed we can add relevant biological factors and their interactions with psychosocial factors, we may be able to develop the causal models necessary for the understanding, prediction, and prevention of suicide.

Depressive Disorder↗
PubMed1999

Volatile nitrosamines and tobacco-specific nitrosamines in the smoke of Thai cigarettes: a risk factor for lung cancer and a suspected risk factor for liver cancer in Thailand.

In Thailand, smoking of commercial cigarettes and of handmade cigarettes has drastically increased in recent decades. Cancer of the lung and of the upper aero-digestive tract have also increased in Thailand as they have in many other countries. It is our working hypothesis that the increase of primary cancer of the liver, especially of cholangiocarcinoma in the north-eastern provinces of Thailand is associated with the use of tobacco in men infested with the liver fluke Opisthorchis viverrini (OV). Bioassays have shown that volatile nitrosamines and tobacco-specific nitrosamines induce cholangiocarcinoma in laboratory animals and that the hepatocarcinogenic action of nitrosodimethylamine in hamsters is significantly increased by infestation with the liver fluke OV. The endogenous formation of nitrosamines is significantly increased by OV infestation. This report presents analytical data on the concentration of volatile nitrosamines and tobacco-specific nitrosamines in mainstream smoke of nine leading brands of commercially produced Thai cigarettes which represent approximately 85% of the market share in Thailand. Observed ranges (ng/cigarette) were 8.5-31.9 for nitrosodimethylamine, 8.8-49.6 for nitrosopyrrolidine and 4.2-18.9 for nitrosodi-n-butylamine. These values are exceptionally high compared with the smoke of light and blended cigarettes from North America and Western Europe. Among the tobacco-specific nitrosamines, the range was 28-730 for nitrosonornicotine and 16-370 for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. There was a correlation between volatile and tobacco-specific nitrosamines, and tar and nicotine deliveries in the mainstream smoke. The analytical data are in line with the rate for lung cancer and support our working hypothesis that nitrosamines, and especially the tobacco-specific nitrosamines, are associated with the increased risk for primary liver cancer among those Thai people who smoke cigarettes and also carry OV infestation.

Bile Duct Neoplasms↗
PubMed1984

[Use of computers in forensic toxicology analysis].

For more than 10 years the analytical data gathered on nearly 600 drugs and other potentially poisonous substances that came up in our own investigations, as well as the pertinent bibliography, were stored in card indexes and lists. For immediate and fast recall via terminal we now store this cumulative data collection on magnetic tapes or disks in our clinic host computer. Extensive software was developed in FORTRAN compiler language to achieve rapid coordination of the data measured to that stored and consequently permit positive identification of unknown substances. The data obtained by different analytical methods such as TLC, GC, ultraviolet and infrared spectra, or HPLC can be evaluated by selective or sequential procedures using variable tolerances. That is also possible to enlarge and complete these data files in an easy manner using the same software.

Computers↗
PubMed1995

[Immunoproliferative small intestinal disease (IPSID): IPSID-like lymphomas, IPSID equivalents?, in 12 Spanish patients].

BACKGROUND: Immunoproliferative small intestine disease (IPSID) encompasses a primary intestinal lymphoma of underpriviliged populations of North Africa, Middle East, etc. This epidemiological feature strongly implicates environmental and host (genetic) factors in its pathogenesis. IPSID can be distinguished on clinicopathological grounds from "Western-type" intestinal lymphomas. "IPSID-like" lymphomas had been sporadically identified, i.e., patients with original clinico-analytical data of IPSID (chronic diarrhoea, malabsortion, clubbing of fingers, diffuse intestinal involvement, etc.) without its conventional histopathologic (lymphoplasmocytic or plasmocytic infiltration) and immunological (alpha-heavy-chain paraprotein) background. PURPOSE: The aim of this study has been: 1) to identify, in a series of small intestine lymphomas, a group of patients with a long-lasting history of chronic diarrhoea and a clinico-biologic pattern of "IPSID-like" lymphoma; 2) to analyze its clinicopathological profile; 3) to search for differences with the pattern of the remaining cases ("Western-type" lymphomas) and 4) To suggest a possible epidemiological significance. PATIENTS AND METHODS: Patients considered were 12 Spanish caucasians with primary intestinal lymphoma and a long-lasting history of chronic diarrhoea vs 31 cases of "Western-type" intestinal lymphomas admitted in our Hospital over a 33-year period. Statistical significance of differences in clinico-biological features (symptoms/signs, analytical data, patterns of involvement, histopathology, immunophenotype and tumor staging) between these two groups was evaluated using X2 test. RESULTS: The results of this retrospective study allow us to delineate a relatively homogeneous "IPSID-like" group (12 cases) among 43 cases of primary small intestine lymphoma diagnosed between 1960 and 1993. The clinico-pathological behavior of these patients was significantly different from that exhibited by the 31 cases of so-called "Western-type" lymphomas. CONCLUSIONS: It is suggested that they may represent a group of patients suffering an evanescent "IPSID-equivalent" disorder (last case diagnosed in 1975), that probably has evolved in similar but not identical epidemiological circumstances to those present in the "Third World" countries of our Mediterranean area.

Adolescent↗
PubMed2002

Tar ball frequency data and analytical results from a long-term beach monitoring program.

Following the spill of fuel oils from the New Carissa in February 1999, approximately 300 km of beaches on the Pacific coast of North America were surveyed. A long-term observation program focused on the documentation of stranded tar balls in the vicinity of the spill site. Systematic beach surveys which were conducted over the period March 1999 to April 2001 and semi-logarithmic scale, time-series plots proved the most useful format for identifying trends. Beach monitoring continued through to August 2001. by which time 212 tar balls had been analyzed by GC/MS for their chemical characteristics. The samples of tar balls collected between February 1999 and August 2001 were qualitatively compared with New Carissa source oils (NCSO) and 101 (48%) were not consistent with NSCO. The presence of tar balls that are not related to an incident can confound attempts to define cleanup or endpoint criteria and to assess possible injury to natural resources.

Accidents↗
PubMed1996

On-line monitoring of benzene air concentrations while driving in traffic by means of isotopic dilution gas chromatography/mass spectrometry.

There is no shortage of information about the average benzene concentrations in urban air, but there is very little about microenvironmental exposure, such as in-vehicle concentrations while driving in various traffic conditions, while refuelling, or while in a parking garage. The main reason for this lack of data is that no analytical instrumentation has been available to measure on-line trace amounts of benzene in such situations. We have recently proposed a highly accurate, high-speed cryofocusing gas chromatography/mass spectrometry (GC/MS) system for monitoring benzene concentrations in air. Accuracy of the analytical data is achieved by enrichment of the air sample before trapping, with a stable isotope permeation tube system. The same principles have been applied to a new instrument, specifically designed for operation on an electric vehicle (Ducato Elettra, Fiat). The zero emission vehicle and the fully transportable, battery-operated GC/MS system provide a unique possibility of monitoring benzene exposure in real everyday situations such as while driving, refuelling, or repairing a car. All power consumptions have been reduced so as to achieve a battery-operated GC/MS system. Liquid nitrogen cryofocusing has been replaced by a packed, inductively heated, graphitized charcoal microtrap. The instrument has been mounted on shock absorbers and installed in the van. The whole system has been tested in both fixed and mobile conditions. The maximum monitoring period without external power supply is 6 h. The full analytical cycle is 4 min, allowing close to real-time monitoring, and the minimum detectable level is 1 microgram/m3 for benzene. In-vehicle monitoring showed that, when recirculation was off and ventilation on, i.e., air from outside the vehicle was blown inside, concentrations varied widely in different driving conditions: moving from a parking lot into normal traffic on an urban traffic condition roadway yielded an increase in benzene concentration from 17 to 62.3 micrograms/m3 even if the actual distance was small. A larger increase was observed when a car was left with the engine running at a distance 2 m from the zero emission vehicle: We measured an increment of benzene concentrations from 15.2 to 174.4 micrograms/m3 with a car equipped with a catalytic converter, and from 19.1 to 386.3 micrograms/m3 with a car without such a converter.

Air Pollutants↗
PubMed1986

On robust partial discriminant analysis as a decision-making tool with clinical and analytical chemical data.

Classification is one of the fundamental goals of science and is basic to the diagnosis of disease. Unfortunately, classifying objects (e.g., patients) on the basis of clinical and/or laboratory experimental observations into various groups can be difficult when the groups overlap or contain outlying points. Recently, Broffitt, Randles, and co-workers proposed a procedure, robust partial discriminant analysis (RPDA) for dealing with such problems, but testing of the procedure was limited to Monte Carlo simulation. In this study, RPDA was applied to real data, in order to compare its effectiveness with ordinary discriminant analysis, as well as to determine if RPDA was a suitable procedure to use to classify chemical compounds on the basis of experimental observations and as a tool in the diagnosis of disease (in particular, multiple sclerosis and thyrotoxicosis), with data based on experimental and clinical observations. The resulting RPDA classifications were an improvement over those obtained from ordinary discriminant analysis.

Aldehydes↗
PubMed1994

Determining confidence intervals for parameters derived from analysis of equilibrium analytical ultracentrifugation data.

In the above discussion, we have introduced the profiling approach of Bates and Watts. It is an easy to implement, empirical approach to the determination of confidence intervals for parameters in nonlinear models. We have applied the approach to the analysis of equilibrium sedimentation data and have demonstrated that, although models for analyzing such data are formally nonlinear they are functionally linear. As such, linear approximation confidence intervals for the parameters are adequate for these models and data sets. Further, we have been able to examine the effect of implementing a multiple independent variable approach (in this case, using multiple rotor speeds) on the precision of the analysis. We found that the standard errors of the parameters were reduced and that this is accounted for by either the increase in the number of data points or the decreases in parameter correlation. In this case, profiling helped to visualize the effect on the sum of squares surface of reducing parameter correlation, making the effect of the small decreases in the correlation of some parameters more evident. Using profiling, it should be easy to explore other methods for the improvement of the analysis of ultracentrifugation data and to be able to quantitate the improvement. With the above discussion as an example, it is likely that the profiling approach should be quite useful and broadly applicable in the analysis of data in terms of nonlinear models.

Computer Simulation↗
PubMed1997

Coronary angiography and angioplasty after acute myocardial infarction.

PURPOSE: To assess the data that support the use of coronary angiography and angioplasty after acute myocardial infarction, that identify the risks of these procedures, and that analyze their use and costs. DATA SOURCES: English-language articles published between 1970 and June 1995 identified through a search of the MEDLINE database. STUDY SELECTION: Studies that contained information about benefits, risks, use, and costs of coronary angiography and angioplasty after acute myocardial infarction. DATA EXTRACTION: Descriptive and analytic data from each study were collected. DATA SYNTHESIS: The outcome for patients who have complications of myocardial infarction (such as shock) is poor. Such patients usually undergo angiography, although the evidence that supports this practice is weak. Preliminary data suggest that patients who immediately have angiography and angioplasty after acute myocardial infarction have better outcomes than do patients who receive thrombolytic therapy with angioplasty only for specific indications in experienced centers. After the acute phase of myocardial infarction, patients who have noninvasive evidence of persistent or recurrent ischemia are believed to benefit from angiography. In the remaining patients, however, angiography after myocardial infarction has not been shown to be beneficial. Coronary angiography is done in 30% to 81% of patients after acute myocardial infarction in different settings and regions; for many of these patients, the benefit is questionable. Better outcomes are not always associated with more frequent use of the procedure. In the United States, catheterizations after myocardial infarction cost approximately $1 billion per year. CONCLUSIONS: Although many patients benefit from angiography and angioplasty after myocardial infarction, others probably do not. Substantial resources are at stake.

Angioplasty↗
PubMed1998

Epidemiology of oral contraceptives and cardiovascular disease.

PURPOSE: To review the association between combined oral contraceptives and cardiovascular disease, with emphasis on oral contraceptives containing low doses of estrogen (low-dose oral contraceptives). DATA SOURCES: A systematic search of the MEDLINE database was done for all relevant articles published between 1967 (when low-dose oral contraceptives were introduced in the United States) and June 1997. Textbooks, meeting proceedings, and reference lists were also searched. STUDY SELECTION: All English-language human epidemiology studies of oral contraceptives that used cardiovascular disease as an end point were reviewed. Animal and metabolic studies were reviewed only if they were especially relevant to the mechanism of action of oral contraceptives. DATA EXTRACTION: Descriptive and analytic data from each study were collected. DATA SYNTHESIS: Data were organized by cardiovascular end point, study design, estrogen dose, and type of progestogen. Data on relative and absolute risk are presented to address current prescription guidelines. CONCLUSIONS: The risk for cardiovascular disease is lower with current preparations of oral contraceptives, including those that contain the new progestogens, than with older oral contraceptives containing high doses of estrogen. Among users of low-dose oral contraceptives, cardiovascular diseases occur mainly in smokers and women with predisposing factors. Every effort should be made to encourage smoking cessation among potential users of oral contraceptives.

Animals↗