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PubMed1981

Chemosorption sampling and analysis of formaldehyde in air. Influence on recovery during the simultaneous sampling of formaldehyde, phenol, furfural and furfuryl alcohol.

A method based on trapping formaldehyde on a 2,4-dinitrodinitrophenylhydrazine-coated porous polymer (Amberlite XAD-2) was evaluated for air sampling in occupational environments. The aldehyde is converted to its 2,4-dinitrophenylhydrazone on the adsorbent. The influence of some organic compounds which often occur together with formaldehyde-furfural, phenol and furfuryl alcohol--was studied. The results show that the method allows the sampling of formaldehyde in the range 0.01--1.0 mg/m3 of air, based on a 3-1 (15 min) sample and a coating of 1%. Furfural, phenol, and furfuryl alcohol do not interfere and may be conveniently sampled at the same time. Formaldehyde and furfural hydrazones were analyzed by high-performance liquid chromatography, phenol and furfuryl alcohol by gas chromatography.

Air Pollution↗
PubMed1975

[A new method for sampling and sample application in the ultra-trace of air by gas chromatography-mass spectrometry (author's transl)].

A new method is described for sampling and sample application in the ultra-trace analysis of air by gas chromatography-mass spectrometry. In this new technique, a preseparation occurs on the gas chromatographic column during sample application, since the atmospheric constituents that are co-condensed during sample application we call this method "Druckaufgabe" (pressure application). The method is not only of theoretical value. It has a potentially wide application to occupational and environmental problems.

Acetates↗
PubMed2005

A duplex real-time qPCR assay for the quantification of human nuclear and mitochondrial DNA in forensic samples: implications for quantifying DNA in degraded samples.

A duplex real-time qPCR assay was developed for quantifying human nuclear and mitochondrial DNA in forensic samples. The nuclear portion of the assay utilized amplification of a approximately 170-190 bp target sequence that spans the repeat region of the TH01 STR locus, and the mitochondrial portion of the assay utilized amplification of a 69 bp target sequence in the ND1 region. Validation studies, performed on an ABI 7000 SDS instrument using TaqMan detection, demonstrated that both portions of the duplex assay provide suitable quantification sensitivity and precision down to 10-15 copies of each genome of interest and that neither portion shows cross-reactivity to commonly encountered non-human genomes. As part of the validation studies, a series of DNase-degraded samples were quantified using three different methods: the duplex nuclear-mitochondrial qPCR assay, the ABI Quantifiler Human DNA Quantification Kit qPCR assay, which amplifies and detects a 62 bp nuclear target sequence, and slot blot hybridization. For non-degraded and moderately degraded samples in the series, all three methods were suitably accurate for quantifying nuclear DNA to achieve successful STR amplifications to yield complete profiles using the ABI AmpFlSTR Identifiler kit. However, for highly degraded samples, the duplex qPCR assay provided better estimates of nuclear template for STR amplification than did either the commercial qPCR assay, which overestimated the quantity of STR-sized DNA fragments, leading to an increased proportion of undetected alleles at the larger STR loci, or slot blot hybridization, which underestimated the quantity of nuclear DNA, leading to an increased proportion of STR amplification artifacts due to amplification of excess template.

DNA↗
PubMed2006

[Determination of trace lead in water samples and salt samples by graphite furnace atomic absorption spectrometry after cloud point extraction].

A method was developed for the determination of trace lead in water samples and salt samples by GFAAS after cloud point extraction. The parameters of extraction system such as pH, the concentrations of the extractant and the surfactant, and the time for cloud point extraction were optimized. Under the optimized conditions, the detection limits of lead were 0.000 5 microg x g(-1) for salt, and 0.01 microg x L(-1) for water, respectively. The proposed method was applied to the determination of lead in water samples and salt samples, and satisfactory results were obtained.

Lead↗
PubMed1989

Test statistic and sample size for a two-sample McNemar test.

McNemar's (1947, Psychometrika 12, 153-157) test of marginal homogeneity is generalized to a two-sample situation where the hypothesis of interest is that the marginal changes in each of two independently sampled tables are equal. This situation is especially applicable to two cohorts (a control and an intervention cohort), each measured at baseline and after the intervention on a binary outcome variable. Some assumptions often realistic in this situation simplify the calculation of sample size. The calculation of sample size in a study designed to increase utilization of breast cancer screening is demonstrated.

Biometry↗
PubMed1987

Sample size for testing differences in proportions for the paired-sample design.

Miettinen (1968, Biometrics 24, 339-352) presented an approximation for power and sample size for testing the differences between proportions in the matched-pair case. Duffy (1984, Biometrics 40, 1005-1015) gave the exact power for this case and showed that Miettinen's approximation tends to slightly overestimate the power or underestimate the sample size necessary for the design power. A simple alternative approximation that is more conservative is presented here. In many cases, the sample size for the independent-sample case provides a conservative approximation for the matched-pair design.

Research Design↗
PubMed1979

Elemental composition of platelets. Part I. Sampling and sample preparation of platelets for trace-element analysis.

Sampling of platelets for trace-element analysis poses special problems: obtaining adequate sample material, achieving a sufficient cell purity, preserving viability (integrity), correcting for trapped plasma, and controlling contamination. We used a blood-cell separator for the primary isolation of platelets from blood, and differential centrifugation in natural plasma to further isolate them. The pyrimidopyrimidine RA233 was used as a stabilizer to maintain viability. 131I-labeled human serum albumin was used to estimate trapped plasma. Contamination was controlled by using five-times-distilled water to simulate donor's blood in the system and by comparing three fractions: the serum, the first portion of the platelet-rich plasma, and the supernatant plasma after the final centrifugation. Neutron activation analysis was used for the elemental analysis. A single differential centrifugation of the platelet-rich plasma from the blood-cell separator at 400 x g for 8 min was optimum (mean mass fractions:erythrocytes/platelets less than 5 mg/g and leukocytes/platelets less than 20 mg/g). The trapped plasma in the wet platelet samples amounted to about 0.40 g/g. No appreciable contamination from the sampling system was found for the elements Ag, Cd, Co, Cr, Cs, Cu, Fe, Mo, Rb, Sb, Se, and Zn.

Blood Platelets↗
PubMedDate not supplied

Factors significant in the diagnostic accuracy of lung cytology in bronchial washing and sputum samples. II. Sputum samples.

Some factors influencing the detection of malignant cells in sputum samples were evaluated in 449 consecutive cases of primary lung carcinoma seen between 1959 and 1974. Diagnostic accuracy increased during the years under study; the reasons are discussed. The overall accuracy was 82.8%. Detection of malignant cells was 85% for small-cell carcinoma, squamous-cell carcinoma and large-cell carcinoma, 75% for adenocarcinoma, bronchioloalveolar carcinoma and adenosquamous carcinoma and 64% for the uncommon tumors. Accuracy was 87% for central tumors and 42% for peripheral lesions. Tumors less than 2 cm in diameter yielded only 39% accuracy as compared to 90% for larger tumors. The specificity of diagnosis of cell type in those specimens with malignant cells was 95% for small-cell carcinoma and squamous-cell carcinoma, more than 80% for adenocarcinoma and large-cell carcinoma, 65% for bronchioloalveolar-cell carcinoma and adenosquamous carcinoma and less than 30% for the uncommon tumors. Diagnostic accuracy was optimal in those cases with three or more sputum samples: 83% for those with three samples and 90% for those with five or more samples per case. The use of both sputum and bronchial specimens was complementary and increased the accuracy further. Reasons for unsatisfactory specimens included no deep cough, limited cellular material, excessive blood or leukocytes and drying artifacts; the first two were the most common causes.

Adenocarcinoma↗
PubMed1980

Sampling and preparation of samples of peanut butter for aflatoxin analysis.

Procedures are discussed for sampling peanut butter and preparing those samples for alatoxin analysis. Special emphasis is placed on sampling the product from shipping pallets and comminuting chunk stype peanut butter in order to reduce the variability in the analysis associated with the nonuniform distribution of aflatoxin in the product. The slurry method of preparation is a convenient means of obtaining a sample which is representative of a nonhomogeneous product.

Aflatoxins↗
PubMed2001

Gibbs sampling-based segregation analysis of asthma-associated quantitative traits in a population-based sample of nuclear families.

Asthma is a common, complex human disease. Elevated serum immunoglobulin E (IgE) levels, elevated blood eosinophil counts, and increased airway responsiveness are physiological traits that are characteristic of asthma. Few studies have investigated major gene effects for these traits in a population-based sample. Further, it is not known if any putative major genes may be common to two or more of these traits. We investigated the existence and nature of major genes modulating asthma-associated quantitative traits in an Australian population-based sample of 210 Caucasian nuclear families. The sharing of these major genes was also investigated. Segregation analysis was based upon a Markov Chain Monte Carlo (Gibbs sampling) approach as implemented in the program BUGS v0.6. All models included adjustment for age, height, tobacco smoke exposure, and gender. The segregation of total IgE levels, blood eosinophil counts, and dose-response slope (DRS) of methacholine challenge were all consistent with major loci at which a recessive allele acted to increase or decrease the phenotype. The respective estimated frequencies of the recessive alleles were 68% (total IgE), 10% (blood eosinophil count), and 27% (DRS). Extensive modelling suggested that the major loci controlling total serum IgE levels, blood eosinophil counts, and airway responsiveness represent different genes. These data provide evidence, for the first time, of the existence of at least 3 distinct genetic pathways involving major gene effects on physiological traits closely associated with asthma. These results have implications for gene discovery programs.

Adolescent↗
PubMed2006

Using random telephone sampling to recruit generalizable samples for family violence studies.

Convenience sampling methods predominate in recruiting for laboratory-based studies within clinical and family psychology. The authors used random digit dialing (RDD) to determine whether they could feasibly recruit generalizable samples for 2 studies (a parenting study and an intimate partner violence study). RDD screen response rate was 42-45%; demographics matched those in the 2000 U.S. Census, with small- to medium-sized differences on race, age, and income variables. RDD respondents who qualified for, but did not participate in, the laboratory study of parents showed small differences on income, couple conflicts, and corporal punishment. Time and cost are detailed, suggesting that RDD may be a feasible, effective method by which to recruit more generalizable samples for in-laboratory studies of family violence when those studies have sufficient resources.

Adult↗
PubMed2001

Comparison of telephone sampling and area sampling: response rates and within-household coverage.

Random digit dialing is used frequently in epidemiologic case-control studies to select population-based controls, even when both cases and controls are interviewed face-to-face. However, concerns persist about the potential biases of random digit dialing, particularly given its generally lower response rates. In an Atlanta, Georgia, case-control study of breast cancer among women aged 20-54 years, all of whom were interviewed face-to-face, two statistically independent control groups were compared: those obtained through random digit dialing (n = 652) and those obtained through area probability sampling (n = 640). The household screening rate was significantly higher for the area sample, by 5.5%. Interview response rates were comparable. The telephone sample estimated a significantly larger percentage (by approximately 7%) of households to have no age-eligible women. Both control groups, appropriately weighted, had characteristics similar to US Census demographic characteristics for Atlanta women, except that respondents in both control groups were more educated and more likely to be married. The authors conclude that households contacted through random digit dialing are somewhat less likely to participate in the household screening process, and if they are cooperative, some households may not disclose that age-eligible women reside therein. Investigators need to develop improved methods for screening and enumerating household members in random digit dialing surveys that target a specific subpopulation, such as women.

Adult↗
PubMed1982

Postcensal estimates for local areas using current samples with census as the source of sampling frame.

"Two techniques for direct postcensal local area estimation are introduced in this paper. Compared with existing techniques for postcensal local area estimation, the proposed techniques are not subject to any bias due to the assumption of constancy of certain statistical relationships between the variable of interest and the symptomatic or associated variables established at a certain point in time (typically a census)." The author notes that "application of the proposed techniques calls for recognition of an integrated design approach at the early planning stage, incorporating considerations of survey designs for the census and the postcensal sample surveys, maintenance and upkeep of the census sampling frame, data analysis and local area estimation requirements simultaneously. When the current samples are continuous and overlap each other, a third technique for postcensal local area estimation is also proposed. An example illustrating these techniques in estimating postcensal district population in Hong Kong is given." (summary in FRE)

Asia↗
PubMed1990

Initiating a chorionic villus sampling program. Relying on placental location as the primary determinant of the sampling route.

In initiating a chorionic villus sampling (CVS) protocol, we relied upon placental locations as the determinant in the choice of technique. An anterior or fundal location prompted a transabdominal (TA) CVS, while the transcervical (TC) approach was reserved for posterior placentas. A coaxial needle system was used for TA CVS (18-gauge, 15-cm guide needle and 20-gauge, 20-cm sampling needle), while TC CVS was accomplished with a 5.8-French, 27-cm polyethylene catheter. Between July 1988 and February 1989 our initial 118 procedures were performed for 115 consecutive pregnancies using this protocol. Testing indications and antenatal characteristics of the TA (n = 56) and TC (n = 63) groups were similar. One procedure failure occurred in the TC group, and a single aspiration was sufficient in 59% of the cases (TA, 30/55; TC, 39/63). In TC procedures an increased aggregate sample weight was observed as compared to TA cases (25.8 g vs. 16.9 g, respectively; P less than .001). This difference was not attributable to an increased number of placental aspirations in TC cases. One abnormal karyotype was observed (45X), and four pregnancy losses occurred (TC, 3; TA, 1). Using placental location to determine the choice of CVS technique appears to be feasible and may be associated with a lower failure rate during a facility's initial experience (when compared to reliance upon one technique alone). Trials comparing the safety of these two methods should consider placental location an independent variable before randomization.

Abdomen↗
PubMed1980

More (or less) about interspouse personality similarity: a sample of incompatible samples.

Examined the degree of interspouse similarity in three samples from previous studies. Two of these samples were matched on age, education, and SES. The third sample represented couples who were not matched on these variables. Contrary to prior assumptions, the matched groups differed from each other nearly as much as they did from the unmatched group. This has implications for the ability to generalize from interspousal data even when comparison groups are matched on several traditional variables.

Humans↗
PubMed2001

High-performance liquid chromatography/tandem mass spectrometry for the quantitative analysis of a novel taxane derivative (BAY59-8862) in biological samples and characterisation of its metabolic profile in rat bile samples.

A sensitive, specific, accurate and reproducible high-performance liquid chromatography (HPLC) analytical method was developed and validated for the quantification of the novel oral taxane analogue BAY59-8862 in mouse plasma and tissue samples. A fully automated solid-phase extraction procedure was applied to the plasma after internal standard (IS) addition, with only 0.2 mL volume of the sample loaded on a CN-Sep-pak cartridge. In the case of the tissues a very simple acetonitrile extraction was used to recover BAY59-8862 and its internal standard from liver. The procedure for the quantification of BAY59-8862 and its IS (IDN5127) is based on high-performance liquid chromatography/ion spray-tandem mass spectrometry, operating in selected ion monitoring mode. The retention times of BAY and IS were 7.21 and 10.36 min, respectively. In both plasma and tissue specimens the assay was linear in the range 50-5000 ng/mL (ng/g). The overall precision and accuracy were assessed on three different days. The results for plasma were within 6.1% (precision) and between 99 and 112% (accuracy), and for the liver samples within 7.3% and between 104 and 118%, respectively. The LOD was 5 ng/mL and 20 ng/g in the plasma and liver, respectively. In addition, the biliary excretion of the compound in rats was studied. The study showed that an oxidative chemical reaction was the preferred metabolic pathway for biliary excretion, and two sets of mono- and dihydroxylated metabolites were detected by LC/ISP-MS/MS experiments. With this method, BAY59-8862 pharmacokinetic was determined in mice. The combined results demonstrate that the methodology can be considered a valid approach to conduct pharmacokinetic and metabolic studies during preclinical and clinical investigations.

Animals↗
PubMedDate not supplied

A simple method of sample size calculation for unequal-sample-size designs that use the logrank or t-test.

This paper presents a simple method of calculating sample sizes for unequal-sample-size designs with use of published tables applicable to equal-sample-size design. The method applies to both the logrank test and the t-test. For the power of logrank test, this paper compares the proposed method with existing methods and with the Monte Carlo simulation.

Clinical Trials as Topic↗
PubMed1995

On the use of a pilot sample for sample size determination.

To compute the sample size needed to achieve the planned power for a t-test, one needs an estimate of the population standard deviation sigma. If one uses the sample standard deviation from a small pilot study as an estimate of sigma, it is quite likely that the actual power for the planned study will be less than the planned power. Monte Carlo simulations indicate that using a 100(1-gamma) per cent upper one-sided confidence limit on sigma will provide a sample size sufficient to achieve the planned power in at least 100(1-gamma) per cent of such trials.

Clinical Trials as Topic↗