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PubMed2003

Research design, organization, and sample characteristics of the Maternal PKU Collaborative Study.

OBJECTIVE: The Maternal PKU Collaborative Study (MPKUCS) was initiated in 1984 by the National Institute of Child Health and Human Development (NICHD). The purpose was to assess the efficacy of dietary restriction of phenylalanine in reducing morbidity in offspring of women with hyperphenylalaninemia (HPA). A contract was awarded to Childrens Hospital Los Angeles as the Coordinating Center to provide implementation of the research protocol, data collection, and analysis. METHODS: The Study included four regional contributing centers: Childrens Hospital Los Angeles (Western Region), Boston Children's Hospital (Northeast Region), University of Illinois (Midwest Region), and University of Texas Medical Branch, Galveston (Southeast Region). Within each region, many participating clinics were responsible for obstetric care, treatment, and monitoring protocols. In 1985, Canada joined the MPKUCS, and in 1992, Germany entered. They were selected because they provided dietary supplies and strong professional services. Acquisition began in 1984 and ended in October 1995. The study included 574 pregnancies in women with HPA and 100 control subjects matched on age, race, parity, and weeks of gestation. The sample included women with blood phenylalanine values >240 micromol/L, 66% of whom had classical PKU, 22% had atypical PKU, and 12% had mild HPA. Informed consents were obtained on all participants. The women ranged in age from 15 to 36 years of age, with a mean age at conception of 23 years. Teenage pregnancies accounted for 19%. Seventy-five percent graduated from high school. Offspring included 416 newborns, 317 of whom were evaluated at 4 years of age and 289 at 6 to 7 years. Follow-up involved medical, nutritional, psychosocial, and psychological assessments. CONCLUSION: Women with PKU treated before conception and in control of their blood phenylalanine levels between 120 and 360 micromol/L (2-6 mg) exhibited normal pregnancies and neonatal outcome. Surprisingly, women who achieved control in the recommended range by 8 weeks of pregnancy also had a normal fetal outcome.

Adolescent↗
PubMed2000

Cytologic features of proliferative breast disease: a study designed to minimize sampling error.

BACKGROUND: Assessment of cytologic features that allow accurate classification of proliferative breast disease has been hampered by sampling errors when fine-needle aspirations have been compared with their corresponding histologic sections. METHODS: To allow for optimal cytohistologic correlation, 2 smears (1 hematoxylin and eosin-stained and 1 Diff-Quik-stained) were prepared from each of 98 breast biopsies without mass lesions and compared with the corresponding histologic sections of the scraped area. Each smear was reviewed in a blinded fashion and assessed for cellularity, background elements, cytoarchitectural features of cell groups, and nuclear features by 2 reviewers. Smears were then classified as nonproliferative breast disease (NPBD), proliferative breast disease without atypia (PBD) or with atypia (PBDA), or DCIS, based on review of the corresponding histologic sections. RESULTS: When comparing NPBD/PBD (n = 86) with PBDA/DCIS (n = 12), smears from PBDA/DCIS were significantly (by the Fisher exact test or Wilcoxon rank sum P values with adjustment for multiple comparisons) more likely to be cellular; contain single cells and necrosis; exhibit nuclear overlap and cytoplasmic vacuoles; have large nuclei, macronucleoli, pleomorphism, clumped chromatin, and hyperchromasia; and were less likely to have complex cell groups, monolayers, swirling, cohesion, and myoepithelial cells in epithelial sheets and the smear background. When NPBD (n = 53) and PBD (n = 33) were similarly compared, smears from PBD were more likely to exhibit larger and more complex cell groups, but they were otherwise similar to smears from NPBD. CONCLUSIONS: There are many cytologic features that will allow a distinction of NPBD/PBD from PBDA/DCIS, but relatively few that can aid in separating NPBD from PBD.

Biopsy↗
PubMed1998

Determination of glucose by capillary electrophoresis/laser-induced fluorescence in transdermally collected samples.

Capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection has been used for the determination of glucose in samples collected by noninvasive means. The method uses an enzymatic reaction scheme that provides for the determination of small quantities of glucose with detection limits of 80 nM. This approach is used to evaluate passive transdermal diffusion as a noninvasive means to sample glucose in vivo. A simple sampling cell design is presented. Sample collection was performed on volunteer human subjects. Our experiments show that fluctuations in blood glucose concentration are reflected in the samples obtained by passive transdermal diffusion after glucose intake. The results indicate that glucose from the subcutaneous fluid can be accessed by passive diffusion.

Blood Glucose↗
PubMed1995

Methodological issues in adolescent health surveys: the case of the Swiss Multicenter-adolescent Survey on Health.

In many countries, health care and prevention professionals face serious lack of data regarding health status, health care utilisation and lifestyles of adolescents. With reference to a survey on health and lifestyles of Swiss teenagers 15-20 years old, this paper reviews the different methodological issues linked with the conception and the realization of such a study. The main objective of the so-called "SMASH" project (Swiss Multicentric Adolescent Survey on Health) is, like other similar researches, to gather health indicators; that is, to measure attitudes and behaviour regarding different aspects of health and lifestyles, to identify the perceived health needs of the respondents and to describe their utilisation of health care services. The main issues which are addressed in the paper are related to: 1) the choice of the channel and the instrument to be used (telephone, vs. face-to-face interview vs. self-administered questionnaire; 2) the sampling procedures (pure random vs. cluster school-based samples; size of the sample); 3) the design and the content of the questionnaire (choice of the areas to be covered, selection and wording of the questions); 4) the ethical considerations linked with the collection of data. One of the specificities of SMASH is the inclusion of youth participation at various steps and levels: the design of the questionnaire, the strategies used to gather the data, and the analysis of the results. Two important issues emerge from this review. First, the importance in the future of being able to rely on common indicators that could be used in different countries and settings through the construction of a validated instrument. Second, the fact that most of the surveys conducted in this field neglect several sub-populations of adolescents with special and important needs: handicapped adolescents, drop-outs and recent immigrants coming either as unskilled workers or as refugees. Surveys in such special in-need groups will have to be planned with specific designs, both in terms of content and of approach.

Adolescent↗
PubMed2002

Polymer-coated synthetic fibers designed for miniaturized sample preparation process.

Miniaturized sample preparation technique for complex sample matrices has been developed with a polymer-coated fibrous extraction medium. Several hundreds of fine fibrous materials were packed longitudinally into a fused-silica capillary followed by a polymeric coating on it to prepare the extraction capillary. The extraction capillary was installed in a liquid chromatograph as a sample loop of the injection valve. The on-line coupled sample preparation/separation system demonstrated a good validity for the analysis of phthalates in real river and wastewater samples. The lowest limits of quantification for several phthalates were less than 1 ng/ml. The effect of polymeric coating to the filaments on the extraction power was also investigated.

Chromatography, High Pressure Liquid↗
PubMed1993

An introduction to the use of interim data analyses in clinical trials.

During a controlled clinical trial, data accumulate that contain information on the relative efficacy of the two treatments, yet these data often are not inspected or analyzed until the planned sample size has been reached and the trial has been terminated. This type of fixed-sample-size trial design, with a single terminal data analysis, has the ethical disadvantage that more patients than are necessary to obtain a reliable result may be randomized to the less efficacious treatment, whichever one that turns out to be. Thus, it often is desirable to schedule one or more analyses of the data, to be conducted before planned termination, to see if a reliable conclusion may be drawn from the data and the trial terminated early. Such analyses are called interim analyses. When interim analyses occur after each of severe relatively large groups of patients, the trial is called a group-sequential trial. Interim data analyses must be planned in advance to avoid increasing the risk of committing a Type I error and to achieve adequate power. This article introduces the statistical issues involved in the planning of interim data analyses and the design of group-sequential clinical trials.

Bias↗
PubMed2002

Multiplex short tandem repeat typing in degraded samples using newly designed primers for the TH01, TPOX, CSF1PO, and vWA loci.

We performed multiplex polymerase chain reaction (PCR) for the TH01, TPOX, CSF1PO, and vWA loci using a newly designed pair of primers that yield smaller fragments than reported previously [Fujii et al., J Hum Genet 45 (2000) 303; Lederer et al., Int J Legal Med 114 (2000) 87]. These loci can be detected in the range of 74-143 bp amplifying products. This system required genomic DNA in a range of 80 pg to 2 ng, and proved to be a sensitive typing method. We compared our system against the GenePrint Fluorescent STR Multiplex Systems CTTv (Promega, Madison, WI, USA), using DNA extracted from old bloodstains left to stand for 17-26 years at room temperature. With our designed system, all allele-typing efforts were successful in the range of 1-5 ng DNA, while no signal peaks were detected, even with when using 10 ng of DNA GenePrint Fluorescent STR Multiplex Systems CTTv.

Journal Article↗
PubMed2002

Comparative pharmacokinetic studies in haemophilia.

The general rules of pharmacokinetics have been applied to the study of the behaviour of clotting factor concentrates in patients with haemophilia. Since 1980, the continuous development of innovative plasma- and rDNA-derived concentrates and the implementation of new virucidal methods in manufacturing processes has prompted us to define a standard approach to this issue. Model-based methods, based upon one or two open compartment models, were available when this work was initiated. Unfortunately, these methods are supported by very little biological data and are profoundly affected by the goodness-of-fit of the data. In contrast, the model-independent method, which is not affected by errors in fitting, provides reproducible and reliable estimates of the behaviour of clotting factor concentrates in patients with haemophilia. Further, the calculations required for the model-independent method are quite simple and can be computed using a pocket minicomputer. The need for an accurate standardization has been recognized by the Factor VIII/IX Sub-Committee which, in 1991, issued the first recommendations on the pharmacokinetic evaluation of Factor VIII/IX concentrates. A recent revision of the recommendations has been made available on the web site of the International Society on Thrombosis and Haemostasis. The most crucial changes - sample size, study design, dosages in single-dose studies, potency assessment, need for well-defined standards, optimal number of points, and most important outcomes - are discussed in this report. In addition, the model-independent and compartmental methods are described.

Area Under Curve↗
PubMed2006

Statistical modelling as an aid to the design of retail sampling plans for mycotoxins in food.

A study has been carried out to assess appropriate statistical models for use in evaluating retail sampling plans for the determination of mycotoxins in food. A compound gamma model was found to be a suitable fit. A simulation model based on the compound gamma model was used to produce operating characteristic curves for a range of parameters relevant to retail sampling. The model was also used to estimate the minimum number of increments necessary to minimize the overall measurement uncertainty. Simulation results showed that measurements based on retail samples (for which the maximum number of increments is constrained by cost) may produce fit-for-purpose results for the measurement of ochratoxin A in dried fruit, but are unlikely to do so for the measurement of aflatoxin B1 in pistachio nuts. In order to produce a more accurate simulation, further work is required to determine the degree of heterogeneity associated with batches of food products. With appropriate parameterization in terms of physical and biological characteristics, the systems developed in this study could be applied to other analyte/matrix combinations.

Aflatoxin B1↗
PubMed1997

Designing better adaptive sampling algorithms for ECG Holter systems.

Let psi be any adaptive sampling algorithm that can run in real time on a tapeless multichannel electrocardiogram (ECG) Holter system. Simple methods which can significantly improve psi's fidelity are described and their results are compared in this paper. It is shown that by adding some simple tests to psi, the signals reconstructed by psi can be improved as much as 5.45 dB. It is also shown that under the same data rate, a good data compressor with slowly sampled input ECG is preferable to a bad data compressor with highly sampled input ECG.

Algorithms↗
PubMedDate not supplied

Talking circles: Northern Plains tribes American Indian women's views of cancer as a health issue.

OBJECTIVE: The purpose of this research was to understand the cultural meanings of cancer among American Indian women from Northern Plains tribes living in western South Dakota and their experiential view of breast and cervical cancer screening. DESIGN AND SAMPLE: Using an exploratory design, a purposive sample of 28 women, 35-75 years of age, were recruited into three Talking Circles. MEASUREMENT: Talking Circle and focus group methodology, combined with Affonso's Focus Groups Analytic Schema, were used to generate contextual data sets including thematic findings. RESULTS: Ten themes emerged indicating interrelationships between cultural traditions and health structures of care. The themes provided a unique perspective for conceptualizing women's experiences with breast and cervical cancer screening. CONCLUSIONS: Incorporating women's cultural experiences into screening services is necessary to address clinical and policy challenges for reducing breast and cervical cancer mortality among American Indian women. Findings from this research will be used to guide a future study investigating breast-screening patterns related to mammography adherence and development of interventions specific to American Indian women.

Adult↗
PubMed1993

Development of a population pharmacokinetic model and optimal sampling strategies for intravenous ciprofloxacin.

Data obtained from 74 acutely ill patients treated in two clinical efficacy trials were used to develop a population model of the pharmacokinetics of intravenous (i.v.) ciprofloxacin. Dosage regimens ranged between 200 mg every 12 h and 400 mg every 8 h. Plasma samples (2 to 19 per patient; mean +/- standard deviation = 7 +/- 5) were obtained and assayed (by high-performance liquid chromatography) for ciprofloxacin. These data and patient covariates were modelled by iterative two-stage analysis, an approach which generates pharmacokinetic parameter values for both the population and each individual patient. The final model was used to implement a maximum a posteriori-Bayesian pharmacokinetic parameter value estimator. Optimal sampling theory was used to determine the best (maximally informative) two-, three-, four-, five-, and six-sample study designs (e.g., optimal sampling strategy 2 [OSS2] was the two-sample strategy) for identifying a patient's pharmacokinetic parameter values. These OSSs and the population model were evaluated by selecting the relatively rich data sets, those with 7 to 10 samples obtained in a single dose interval (n = 29), and comparing the parameter estimates (obtained by the maximum a posteriori-Bayesian estimator) based on each of the OSSs with those obtained by fitting all of the available data from each patient. Distributional clearance and apparent volumes were significantly related to body size (e.g., weight in kilograms or body surface area in meters squared); plasma clearance (CLT in liters per hour) was related to body size and renal function (creatinine clearance [CLCR] in milliliters per minute per 1.73 m2) by the equation CLT = (0.00145.CLCR + 0.167).weight. However, only 30% of the variance in CLT was explained by this relationship, and no other patient covariates were significant. Compared with previously published data, this target population had smaller distribution volumes (by 30%; P < 0.01) and CLT (by 44%; P < 0.001) than weight- and CLCR- matched stable volunteers. OSSs provided parameter estimates that showed good to excellent estimates of CLT (or area under the concentrations-time curve [AUC]) were unbiased and precise (e.g., r2 for AUC for all data versus AUC for OSS2 was > 0.99) and concentration-time profiles were accurately reconstructed. These results will be used to model the pharmacodynamic relationships between ciprofloxacin exposure and response and to aid in developing algorithms for individual optimization of ciprofloxacin dosage regimens.

Adult↗
PubMed2000

Stomatopod antennule design: the asymmetry, sampling efficiency and ontogeny of olfactory flicking.

Many crustaceans detect odors from distant sources using chemosensory sensilla (aesthetascs) on their antennules. The greater the flow of water through arrays of aesthetascs, the faster the access of odorant to receptors inside the aesthetascs. Stomatopods facilitate odorant access by flicking their antennules, thus increasing the relative velocity of the water reaching their aesthetascs. We used dynamically scaled physical models to investigate how aesthetasc size and spacing and antennule flicking velocity affect flow penetration into the simple aesthetasc arrays of the stomatopod Gonodactylaceus mutatus. Particle image velocimetry of flow fields near models of juvenile and adult antennules revealed that velocity gradients around the aesthetascs are steeper during the outward part of the flick than during the return stroke and that the velocity gradients are steeper at the aesthetasc tips than at their bases. More fluid per unit time flows between aesthetasc rows during the outward stroke than during the return stroke, ensuring that odor sampling is pulsatile. During flicking, velocity gradients are steeper near adult aesthetascs than near juvenile aesthetascs, and adults process more fluid per unit time than juveniles. The resulting differences in odorant access can be related to size- and age-dependent changes in stomatopod ecology.

Aging↗
PubMed2006

Evaluation of cost-effectiveness of targeted sampling methods for detection of Mycobacterium avium subsp paratuberculosis infection in dairy herds.

OBJECTIVE: To investigate the epidemiologic and financial impacts of targeted sampling of subpopulations of cows, compared with random sampling of all cows, for classification of dairy herd infection status for paratuberculosis. ANIMALS: All cows from 4 infected herds with a low-to-moderate prevalence of paratuberculosis and from 1 noninfected herd in California. PROCEDURE: The infection status of each cow was classified on the basis of results of an ELISA or combined ELISA and fecal culture results. Thirteen sampling schemes designed to randomly sample cows on the basis of lactation number, stage of lactation, and milk production were evaluated. Sampling without replacement was used to obtain a probability of herd detection of paratuberculosis for each evaluated sampling method and for simulated sample sizes between 30 and 150 cows. Marginal cost-effectiveness analysis was used to determine the cost increase relative to the increase in detection probability. RESULTS: Sampling cows in the third or higher lactation and > or = 200 days into lactation yielded the highest detection probability in most instances, resulting in a detection probability that was 1.4 to 2.5 times that obtained by sampling 30 cows in the second or higher lactation. Costs of testing via the alternative method with a 95% detection probability were approximately dollar 300 lower in a high-prevalence herd (31%) and dollar 800 lower in a low-prevalence herd (9%), compared with use of the reference method. CONCLUSIONS AND CLINICAL RELEVANCE: Detection of herds with paratuberculosis could be improved, and costs of testing substantially reduced by sampling targeted groups of cows.

Animals↗
PubMed2000

Cytocentrifugation conditions affecting the differential cell count in bronchoalveolar lavage fluid.

OBJECTIVE: To investigate variations in speed, duration and acceleration rate of the Cytospin 3 cytocentrifuge (Shandon Scientific Ltd., Astmoor, England) on the differential cell count of bronchoalveolar lavage (BAL) fluid samples. STUDY DESIGN: BAL fluid samples (n = 51) were cytocentrifuged at various combinations of speed (500, 1,200 and 2,000 rpm), acceleration rate (low, medium and high) and duration (5, 10, 15 and 20 minutes). The preparations were May-Grünwald-Giemsa stained and differentiated on 500 cells. Data were analyzed by mixed model repeated measurements ANOVA. RESULTS: The mean lymphocyte count was significantly higher at 1,200 rpm than at 500 rpm, whereas the macrophage count decreased. Between 1,200 and 2,000 rpm, the number of both cell types stabilized. Significantly higher numbers of lymphocytes were recorded at 10 and 15 minutes of cytocentrifugation than at 5 minutes. The acceleration rate did not influence the differential cell count. Seventeen BAL fluid samples were selected to test the diagnostic impact of cell damage using a validated computer program. In 1 of 17 samples the predicted diagnosis did not correspond between two different speeds (500 and 2,000 rpm). CONCLUSION: Variations in cytocentrifugation speed and duration affected the mean lymphocyte and macrophage counts of BAL fluid samples.

Bronchoalveolar Lavage Fluid↗
PubMed2003

Comparison of cryopreserved sperm in vaporous and liquid nitrogen.

OBJECTIVE: To evaluate the feasibility of using the vaporous phase of liquid nitrogen as a storage medium for human semen samples. STUDY DESIGN: Human semen samples were used in a 2-armed study. In the first arm, semen samples were rapidly frozen and randomly assigned to storage in either liquid nitrogen (-196 degrees C) or vapor-phase nitrogen (-189 degrees C). In the second arm, sperm specimens were frozen in a controlled, stepwise process and randomly assigned to storage in either the vaporous or liquid phase of liquid nitrogen. The samples were subsequently thawed and analyzed for sperm viability. RESULTS: The rapid freezing technique demonstrated no differences in the examined viability parameters between semen specimens stored in either liquid or vaporous nitrogen. Similarly, semen samples prepared by the slower, controlled freezing process also showed no differences in viability parameters after storage in either the liquid or vaporous phase of liquid nitrogen. The rapid freezing technique was equal to the slow, controlled freezing method in terms of preserving the integrity of the sperm when the specimens were subsequently stored in either liquid or vaporous nitrogen. CONCLUSION: Cryopreservation of human semen in the vapor phase of nitrogen is a viable alternative to storage in liquid-phase nitrogen.

Cryopreservation↗