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PubMedDate not supplied

A field comparison of two methods for sampling lead in household dust.

Comparability of dust lead measurements has been a difficult problem due to different sampling and analysis techniques. This paper compares two dust sampling techniques, the U.S. Department of Housing and Urban Development (HUD) dust wipe method and the Lioy, Wainman, Weisel (LWW) sampler. The HUD method specifies using a moist towelette to pick up as much dust as possible in a specified area and estimates total lead loading. The LWW sampler collects the dust on preweighed wetted filter media, and provides greater standardization of the sampling path and pressure applied. LWW samples were analyzed using inductively coupled plasma mass spectronomy (no samples below minimum detection limit), while HUD samples were analyzed using flame atomic absorption (32% of samples below minimum detection limit). A bootstrapping technique was used in the analysis to contend with those HUD samples below the minimum detection limit. Mixed model equations were generated to predict HUD values from LWW results, and to examine the effects of sampling location, time, and method. The results indicate that the two samplers performed similarly under field conditions, although the LWW sampler produced consistently lower lead loading estimates. LWW values that predicted HUD lead clearance values of 100 micrograms/ft2 for floors and 500 micrograms/ft2 for window sills were 72 micrograms/ft2 and 275 micrograms/ft2, respectively. To examine internal reproducibility, duplicate samples were taken using both the HUD and LWW methods. Correlation results within paired samples indicated a statistically significantly higher (p < 0.001) internal reproducibility for lead loading, for the LWW sampler (r = 0.87), than for the HUD method (r = 0.71). Some of the differences appeared to be related to the analytical methods.

Child, Preschool↗
PubMed1997

Effect of sample volume on quantitative analysis by solid-phase microextraction. Part 1. Theoretical considerations.

This paper discusses the effect of sample volume on the amount of analyte extracted from a sample by solid-phase microextraction (SPME) in two-phase (sample-fiber coating) and three-phase (sample-headspace-fiber coating) systems. Up-to-date knowledge is summarized, and new concepts are introduced. The effect of sample volume on quantification and precision of results can be neglected only in rare cases. The minimum sample volume which ensures that the amount extracted, n, is lower than 1% of the initial amount of the analyte present in the sample, as well as the volume for which exactly half of the initial amount of the analyte is extracted, have been calculated for both two- and three-phase systems. It is critical that the volumes of samples and standards are the same during analysis by SPME. Extraction kinetics in headspace analysis is dependent on the headspace capacity. If it is sufficiently large, the analyte is extracted almost exclusively from the gaseous phase, and equilibration can be very fast. On the other hand, this causes a significant loss of sensitivity. The effect of sample volume on the determination of the value of the partition coefficient, K, is also discussed. If the change in concentration of the analyte in the sample at equilibrium is not taken into account, erroneous results are obtained. Even when a proper procedure is used, there are practical limitations to the accuracy of the K value determination. Large sample volumes should always be used for K value determination, as they enable broader ranges of K values to be covered with good accuracy.

Chemical Phenomena↗
PubMed2002

Diffusive uptake in passive and active adsorbent sampling using thermal desorption tubes.

Low flow active sampling techniques collecting vapors and gases using thermally desorbable adsorbents are now feasible and desirable in many applications as they permit long integration times, the potential for miniaturized sampling configurations, and other advantages. At very low air flow rates (< 1 ml min(-1)), diffusive uptake on adsorbents in conventional sorbent tubes may equal or exceed the active (pumped) uptake rate, and even at low flow rates (1-4 ml min(-1)), diffusive uptake may significantly bias measurements. Thus, corrections to account for the diffusive flux or means to limit the diffusive uptake are needed in low flow applications. This paper presents (1) a theoretical analysis of the role of diffusive and advective uptake for several sampling geometries of tube-type samplers; (2) experimental confirmation using both laboratory and field studies; (3) estimates of the tortuosity and porosity of the glass wool packing used to retain the adsorbent, parameters needed to estimate diffusive fluxes in passive and active sampling; (4) a demonstration that orifice-equipped low flow active samplers can reduce diffusive uptake and improve precision, and (5) a model predicting the saturated adsorbent layer that helps to account for the gradual decline in uptake rates seen in passive sampling. Diffusive uptake will depend on the tube configuration and diffusion coefficient of the substance of interest, but for conventional sampling tubes (0.4-0.5 cm id, 1.5 cm air gap), sample flow rates should be maintained above 1 to 4 ml min(-1) to keep errors below 5%. Laboratory experiments showed close agreement with theoretical calculations, and the field study using 1 to 4 d sampling periods and 0.3 ml min(-1) flows demonstrated that the orifice-equipped samplers essentially eliminated diffusive uptake. No significant practical difficulties are encountered using orifices, e.g., pressure drop is minimal. Experimental estimates of tortuosity (0.79 +/- 0.02) and porosity (0.92 +/- 0.10) of the glass wool packing (0.3 cm length) represent relatively little resistance to diffusion; however, variation in the packing and adsorbent placement can degrade the precision achievable by passive samplers. Diffusion barriers, consisting most simply of an orifice, may be used to lower the diffusive uptake. A needle-type orifice permits flows below 0.1 ml min(-1) and is suitable for sampling periods as long as several weeks, and it provided greater precision than conventional open-ended sampling tubes (8% compared to 13%). Finally, the gradual decrease in diffusive fluxes often seen in passive sampling is attributed to additional resistance posed by a saturated adsorbent layer, in agreement with a simple model based on total VOCs and specific adsorptivity of the adsorbent.

Adsorption↗
PubMed2003

A simple calibration procedure for volatile organic compounds sampling in air with adsorptive solid-phase microextraction fibres.

Adsorptive solid-phase microextraction (SPME) fibres have proven to be a reliable means of sampling volatile organic compounds (VOCs) in air. In this work, polydimethylsiloxane/carboxen (PDMS/CAR) fibres were used to test a new approach of air sampling strategy with SPME in the lab which could lighten calibration procedure and enhance the use of this already rapid, simple, convenient and cost effective sampling technique. Indeed, only one curve can be used whatever the extraction time chosen by the analyst under constant conditions of air velocity and temperature. Ficks' law of diffusion was used to model SPME grab sampling when the fibre was totally exposed to the air sample. Experimental sampling rates were then determined by GC-FID for different sampling conditions, i.e. in a flowing air stream of known velocity ("dynamic mode") and in a stagnant air ("static mode"). These sampling rates were found to be 3.50 and 17.80 mL min(-1) for acetone, 4.06 and 21.20 mL min(-1) for 1,2-dichloroethane, 5.10 and 27.80 mL min(-1) for toluene and 5.36 and 30.80 mL min(-1) for butyl acetate, for static and dynamic sampling modes respectively. Deviation from linearity of the calibration curves, indicating that a significant fraction of the adsorption sites are occupied, were determined. They were found to be approximately equal to 0.9, 1.57, 3.82 and 4.37 nmol for acetone, dichloroethane, toluene and butyl acetate, respectively. Experimentally determined sampling rates of these isolated compounds were also valid when a complex equimolar gaseous mixture was investigated, but deviation from linearity appears earlier. Then, for a given application, sampling times should be chosen very carefully to avoid competitive adsorption and hence, bad quantitative analysis results.

Air Pollutants↗
PubMed2002

Thermophilic Campylobacter spp. in turkey samples: evaluation of two automated enzyme immunoassays and conventional microbiological techniques.

AIMS: To determine the sensitivity and specificity of two automated enzyme immunoassays (EIA), EiaFoss and Minividas, and a conventional microbiological culture technique for detecting thermophilic Campylobacter spp. in turkey samples. METHODS AND RESULTS: A total of 286 samples (faecal, meat, neckskin and environmental samples) were collected over a period of 4 months at a turkey slaughterhouse and meat-cutting plant in Denmark. Faecal and environmental samples were tested by the conventional culture method and by the two EIAs, whereas meat and neckskin samples were tested by the two EIAs only. Two enrichment broths were used, Campylobacter Enrichment Broth (CEB) and Preston Broth (PB). Verification of positive test results was carried out by conventional culture on selective solid media. The specificities of all methods were high. The sensitivities of the EIAs were higher than that of the conventional culture technique but varied depending on the type of sample and enrichment broth. For neckskin samples, the Minividas had a significantly higher sensitivity than the EiaFoss and using PB instead of CEB as the enrichment broth significantly improved the sensitivity for both EIAs. CONCLUSIONS: Both EIAs provided more accurate results than the conventional culture technique. Furthermore, neckskin samples enriched in PB resulted in more positive test results and Campylobacter growth than samples enriched in CEB. SIGNIFICANCE AND IMPACT OF THE STUDY: The Eiafoss and Minividas proved to be reliable methods for detecting Campylobacter spp. in various samples. However, the results emphasize the need for the development of specific enrichment protocols for specific samples.

Animals↗
PubMed2002

Optimization of a culture technique for the isolation of Listeria monocytogenes from faecal samples.

A culture technique employing cold enrichment at 4 degrees C followed by selective enrichment and plating at higher temperatures (30 degrees C) was used to isolate Listeria monocytogenes from faecal samples. The samples were held at 4 degrees C for 15 weeks and cultured weekly to assess the sensitivity of the culture after cold storage for different lengths of time. No media, Listeria selective enrichment broth (LSEB), nutrient broth (NB) and saline were used as cold storage medium. Cold storage increased the frequency of Listeria positive samples. The sensitivity of the culture for Listeria spp. and L. monocytogenes was 72 and 94%, and 56 and 61% after third and seventh week of cold storage, respectively. When the results of third and seventh week of cold storage were combined, the sensitivity was 100% for Listeria spp. and 94% for L. monocytogenes. LSEB and NB as storage medium increased Listeria positive samples after the first week of cold storage but did not maintain the increase thereafter while saline had an adverse effect on the growth of the bacteria. However, samples held in no media in a pilot study involving monthly sampling of a herd revealed better results. Detection limit of the culture media was also investigated. The lowest concentration detected by culture media was 3.17 organisms/ml. This was seven organisms/g for known Listeria positive sample. The faecal samples spiked with 10-fold dilutions of L. monocytogenes and held at 4 degrees C revealed that the sample spiked with 3.17 x 10-1 cfu/ml organisms resulted in growth after the second week of cold storage. The results suggest that the culture technique employing cold enrichment followed by selective enrichment and plating is more sensitive, the storage of faecal samples in no media when compared with the samples in storage medium, LSEB, NB and saline, during cold enrichment is a better application and culture of faeces, immediately after collection, at third and seventh week of cold enrichment produce more satisfactory results.

Animals↗
PubMedDate not supplied

Effect of milk sampling techniques on milk composition, bacterial contamination, viability and functions of resident cells in milk.

Three different milk sampling techniques were evaluated during milk sampling: a direct aseptic collection from the udder through a sterile cannula was used as the reference technique, compared with either a manual or a mechanical sampling method. In this study 30 high-yielding Holstein-Friesian dairy cows at different stages of lactation and free of udder infection were used. For each milk sample, the influence of milk sampling techniques was determined for the following parameters: somatic cell count, milk composition, bacterial contamination, viability, in vitro phagocytosis and overall killing of Staphylococcus aureus Newbould 305, and cellular chemiluminescence. Because milk sampling occurred throughout lactation, the differences between early, mid- and late lactation were estimated. It was concluded that bacterial contamination was not significantly different in manual milking samples and the reference technique; bacterial contamination was, however, significantly (P < 0.001) higher in machine milking samples than in the reference technique. Among the different sampling techniques, no significant effects on SCC, milk composition, viability and functions of the cells isolated from milk were observed. It was found that viability, intracellular killing and cellular chemiluminescence of milk PMN were significantly lower (P < 0.05) in early lactation compared to mid-lactation. Phagocytosis was significantly (P < 0.05) higher in early lactation compared to mid- and late lactation, and no significant differences were observed between mid- and late lactation. From this study, it can be concluded that despite a higher bacterial contamination obtained with the mechanical sampling method, the 3 milk sampling techniques described in this study can be used for the evaluation of milk cell functions.

Animals↗
PubMed2002

A limited sampling strategy for pharmacokinetic directed therapy with intravenous busulfan.

High-dose busulfan is widely used in allogeneic and autologous marrow transplantation preparative regimens. Variation in the area under the concentration/time curve (AUC) for oral busulfan results in substantial risk of over or under treatment with excess risk of toxicity or relapse. Use of the IV formulation reduces this variability by eliminating variability in absorption. Variability due to drug metabolism remains, but simplified pharmacokinetic study may be employed to achieve a specific target AUC. In conventional sampling strategies for determining AUC after oral administration, 12 samples are used over 6 hours to assure accurate tracking of erratic absorption. With IV busulfan there is no necessity for measuring plasma levels during the infusion because busulfan pharmacokinetics are well described with a single-compartment, first-order elimination model. In theory, only peak and trough levels should be necessary, but for assurance of reliability in clinical decision making, it must be possible to identify outlier values. This process requires at least 4 samples. We studied a total of 59 adult patients receiving a 2-hour IV busulfan infusion to develop a limited sampling strategy (LSS). At the end of a 2-hour infusion, we collected 11 samples from 18 patients and compared the AUC obtained when all samples were used with the AUC obtained when samples were collected only hourly. The mean AUC calculation was 5% higher (1002 versus 956 microM-min) and the coefficient of variation (CV) was substantially better (4.6% versus 8.2%) when only the postinfusion samples were used. A follow-up study of 41 consecutive patients demonstrated that all patients were easily evaluable with a coefficient of variation (CV) for the AUC of 2.6%. To validate this approach, we analyzed pharmacokinetic data on 60 patients in the phase II clinical trial of the IV formulation described by Anderson et al. Data on an additional 36 patients from a companion study also were analyzed. The AUC based on all 11 samples from each patient were compared with the AUC based on the 5 postinfusion samples. The results of this analysis confirmed comparable reliability and possibly superior precision of the University of Alabama at Birmingham 5-sample LSS. These results validated that LSS for IV busulfan will make possible meaningful and accurate comparisons of busulfan versus TBI-based preparative regimens and comparison of dose intensity of busulfan-containing preparative regimens in trials of submyeloablative transplantation.

Antineoplastic Agents, Alkylating↗
PubMed2002

Randomized clinical trial of PCR-determined human papillomavirus detection methods: self-sampling versus clinician-directed--biologic concordance and women's preferences.

OBJECTIVE: The purpose of this study was to compare the high-risk human papillomavirus detection rates from self-sampled swabs and tampons with standard clinician-directed speculum sampling and to assess women's acceptance of self-sampling methods. STUDY DESIGN: One hundred three women who required a colposcopy underwent order randomization of the human papillomavirus sampling technique. Kappa and McNemar test statistical results were used to measure the agreement between clinician-directed and self-sampling techniques for high-risk types of human papillomavirus and the acceptance of self-sampling techniques. RESULTS: All self-directed samplings were equivalent to clinician sampling for all cervical intraepithelial neoplasia disease states. High-risk human papillomavirus was detected by self- and clinician-directed methods in 83% of the women with cervical intraepithelial neoplasia, grade 2/3. The 2 sequential swabs trend toward better detection of high-risk types of human papillomavirus than all other techniques for women with normal histologic factors (P =.0736, by McNemar's chi2 test). Ninety-four percent of women would accept self-sampling for their yearly cervical screen. CONCLUSION: Self-sampling is equivalent to clinician sampling for the detection of high-risk human papillomavirus and is acceptable to women as a yearly screen.

Adult↗
PubMed2006

CO2 concentrations and delta13C (CO2) values in monthly sets of air samples from downtown Parma and the Parma and Taro river valleys, Emilia-Romagna, Italy.

Monthly sets of discrete air samples were collected from September 2004 to June 2005 in the town of Parma, along North-South and East-West runs (8 plus 8 samples), using four-litre Pyrex flasks. The CO2 concentrations and delta13C values were determined on these samples with the aim of evaluating quantitatively the contribution of domestic heating to the winter atmospheric CO2 pollution in downtown Parma by comparing autumn and spring atmospheric values with winter values. After separation of CO2 from the other air gases in the laboratory, the CO2 concentrations were calculated from the intensity of the 12C16O2+ ion beam in the mass spectrometer, after calibration with artificial air samples whose CO2 concentration was very carefully determined by the Monte Cimone Observatory (Sestola, Modena, Italy). The reproducibility of these measurements was of approximately +/-0.4 % and, consequently, the most probable error is not higher than+/-2-3 ppmv and does not affect the magnitude of the gradients between different samples. The standard deviation of delta13C measurements ranges from+/-0.02 to +/-0.04 per thousand (1sigma). The results suggest that the contribution of domestic heating to atmospheric CO2 pollution is almost negligible in the case of ground level atmosphere, where the main CO2 pollution is essentially related to the heavy car traffic. This is probably because of the fact that the gases from the domestic heating systems are discharged tens of metres above ground level at a relatively high temperature so that they rise quickly to the upper atmospheric layers and are then displaced by air masses dynamics. Monthly sets of discrete air samples were also collected from October 2004 to June 2005 along North-South runs from the town of Parma to the Apennine ridge following the Parma and the Taro river valleys (8 samples and 7 samples per set, respectively) and measured using the same technique. The aim of this study was the comparison between the town samples, the plain country samples and the samples collected on the northern slope of the Apennines. The results reveal huge variations of both CO2 concentration and delta13C through space and time, some of which can be reasonably explained whereas others are rather difficult to understand. The sets of values are discussed and various hypotheses are suggested.

Air Pollution↗
PubMed1987

Environmental sampling and analysis for zeranol.

Due to concern over health effects associated with the use of zeranol, a sampling and analytical method to monitor zeranol in the work environment was developed. The collection strategy included air samples on FHLP filters, area samples on gauze pads, hand/dermal samples on gauze pads and bulk samples. The sampling method evaluation included choice of media, flow rate and duration for air samples, sample preparation, extraction efficiencies and sample stability. Analysis of the samples was accomplished by high performance liquid chromatography with identification and quantification by UV and fluorescence detection. The analytical method evaluation included separation of possible interfering compounds, calibration curves, limits of detection (LOD), limits of quantitation (LOQ), precision and accuracy. The tested analytical range was 0.01 to 150 micrograms/mL with a LOD of 0.007 microgram/mL and a LOQ of 0.02 microgram/mL using UV detection. For the fluorescence detector, the LOD was 0.05 microgram/mL and the LOQ was 0.15 microgram/mL. Peak confirmation was achieved by retention time and comparing the two detector responses. Use of this method provided the sensitivity and specificity to analyze environmental samples for zeranol in the workplace environment.

Air Pollutants, Occupational↗
PubMed2004

Determination of amorphous content of lactose samples by solution calorimetry.

Earlies studies suggest that solution calorimetry can be used to determine the extent of amorphous content of drug and excipient, when the solubility and dissolution rate of the compound in the chosen solvent are reasonably high. In the present study, the use of solution calorimetry for assessment of amorphous content of a sample that is not completely dissolved in a solvent was evaluated. Physical mixtures of lactose and spray-dried lactose samples were analysed. The amorphous content of the physical mixtures and the spray-dried samples varied from 0% to 100% determined by isothermal microcalorimetry. The enthalpy of solution (delta(sol)H) was determined in water. The lactose samples were dissolved quickly in water. In addition, the enthalpy accompanied with an addition of a lactose sample in an over saturated aqueous solution (delta(sat)H) (prepared from the corresponding lactose sample) was determined. The lactose sample did not completely dissolve in the over saturated aqueous solution. An excellent correlation was observed between delta(sol)H and the amorphous content of the samples. Interestingly, there was a linear correlation also between delta(sat)H and the amorphous content of the samples. Further, a linear relationship was observed between the delta(sat)H and the delta(sol)H of the samples. Therefore, solution calorimetry may represent a rapid and simple method for determining the amorphous content also in samples that are not completely dissolved in the solvent.

Calorimetry↗
PubMed2002

Quality evaluation of samples obtained by spontaneous or induced sputum: comparison between two methods of processing and relationship with clinical and functional findings.

The aim of the study was to assess, on a large group of spontaneous or induced sputum samples, the difference in quality between slides processed by two different methods, and the relationship between quality assessment and some clinical and functional characteristics of the examined subjects. We examined 631 sputum samples obtained from 337 subjects with proven (n = 291) or suspected bronchial asthma. Of these, 467 samples were processed using the whole-sample method (Group I), while 164 samples were processed using the plug method (Group II). Salivary contamination, cell distribution on the slide, and cell borders were evaluated, and samples were classified as inadequate, adequate, or good. Inadequate samples were equally represented in both groups, while good samples were represented more in Group II. No significant difference in most clinical and functional findings was observed between the different quality categories of both groups. A higher proportion of inadequate samples was observed in Group I samples spontaneously collected. Mild intermittent asthmatics produced a better quality of slides in comparison with other groups of asthma severity. In conclusion, sputum quality partially depends on the different methods of sputum collection and/or processing, although the percentage of inadequate samples is similar for the two methods of processing. Sputum quality is only marginally affected by clinical and functional characteristics of asthma, or by asthma severity.

Adrenal Cortex Hormones↗
PubMed2004

Comparison between LightCycler Real-Time Polymerase Chain Reaction (PCR) assay with serum and PCR-enzyme-linked immunosorbent assay with whole blood samples for the diagnosis of human brucellosis.

BACKGROUND: To overcome some of the limitations of conventional microbiological techniques, polymerase chain reaction (PCR)-based assays have been proposed as a useful tool for the diagnosis of human brucellosis. METHODS: A single-blinded comparative study was undertaken that compared 2 different PCR assays: a SYBR Green I LightCycler-based Real-Time PCR assay (LC-PCR; Roche Diagnostic) with serum samples and a PCR-enzyme-linked immunosorbent assay (ELISA) with whole blood samples. Both assays amplify a 223-bp sequence of a gene that codes for the synthesis of an immunogenetic membrane protein specific for Brucella genus (BCSP31). We analyzed the diagnostic yield of these assays with 60 samples obtained from patients with active brucellosis and 37 samples obtained from a control group composed of patients with febrile syndromes of other defined etiologies, asymptomatic subjects with past brucellosis or exposure to Brucella infection who had persistently high titers of anti-Brucella antibodies, and healthy subjects. RESULTS: The sensitivities of LC-PCR with serum samples, PCR-ELISA with whole blood samples, and blood cultures were 93.3%, 90%, and 65%, respectively. Three control samples (8.1%) had a positive PCR-ELISA result, and 2 of these samples (5.4%) also had positive LC-PCR results. The specificity and positive likelihood ratios were 94.6% and 17.3, respectively, for LC-PCR and 91.9% and 11.1, respectively, for PCR-ELISA. CONCLUSIONS: The diagnostic yield of LC-PCR with serum samples was higher than that of PCR-ELISA with whole blood samples. The speed and technical simplicity of LC-PCR in serum samples make it a useful alternative to blood cultures for patients with suspected brucellosis and negative or doubtful serological test results.

Adolescent↗
PubMed2005

Laboratory and field evaluation of a new personal sampling system for assessing the protection provided by the N95 filtering facepiece respirators against particles.

OBJECTIVES: We have recently developed a new personal sampling system for the real-time measurement of the protection provided by respirators against airborne dust and micro-organisms. The objective of this study was to evaluate the performance characteristics of the new sampling system in both laboratory and field conditions. METHODS: The measurements were conducted using the N95 filtering facepiece respirators and the newly developed personal sampling system put on a manikin (laboratory study) or donned by a human subject (laboratory and field studies). Two inhalation flow rates (0 and 40 l min(-1)) in conjunction with the sampling flow rate (10 l min(-1)) were tested in the manikin-based experiments to investigate the effects of the leak location (nose, cheek and chin) and the depth of the sampling probe (0, 5, 10 and 15 mm) within the respirator. The effect of human activity on the protection factor was evaluated using a variety of head movements and breathing patterns when a human subject wore the respirator in a room-size laboratory test chamber. The field study was conducted during corn harvesting with a respirator worn by a human subject on a combine. RESULTS: There was no significant difference in the protection factors for different leak locations, or for sampling probe depths, when the inhalation rate was 0 l min(-1). For the inhalation rate of 40 l min(-1), the protection factors for nose leaks were higher than those for chin and cheek leaks. Furthermore, the protection factor was the lowest and showed the least variation when the sampling probe depth was equal to 0 mm (imbedded on the respirator surface). Human subject testing showed that the grimace maneuver decreased the protection factor and changed the original respirator fit. The protection factor during breath holding was lower than that found during inhalation and exhalation. Field results showed greater variation than laboratory results. CONCLUSIONS: The newly designed personal sampling system efficiently detected the changes in protection factors in real time. The sampling flow was least affected by the inhalation flow when the sampling probe was imbedded on the respirator surface. Leak location, breathing patterns and exercises did affect the measurement of the protection factors obtained using an N95 filtering facepiece respirator. This can be attributed to the differences in the in-mask airflow dynamics contributed by the leak, filter material, sampling probe and inhalation. In future studies, it would be beneficial if the laboratory data could be integrated with the field database.

Equipment Design↗
PubMed2005

Surface sampling for endotoxin assessment using electrostatic wiping cloths.

OBJECTIVES: Much of the cost of exposure assessment for studies of residential cohorts is in scheduling and travel time for field staff. One way to reduce costs is to simplify methods such that subjects can sample their own residence. Analysis of settled dust is being widely used for assessment of exposures to allergens, lead and pesticides and can also be used for endotoxins. While vacuum sampling is the most common surface sampling method, wipe sampling has the advantage that it can be readily performed by the resident when convenient and samples can then be mailed to researchers. Thus, we evaluated the feasibility of wipe sampling for endotoxin environmental assessment using electrostatic wipes with or without the use of disposable examination gloves. METHODS: Multiple lots of six types of commercial wipes and eight types of gloves were extracted and analyzed for endotoxin content using the kinetic chromogenic Limulus amebocyte lysate assay. Wipes were compared across brands, between lots, within lots, between pairs depending on proximity to cardboard packaging, and in wipe tests with or without gloves. Collected dust samples of known concentration were also tested in spiking assays for endotoxin recovery. RESULTS: The most striking finding was the high variability of endotoxin contamination of both wipes and gloves across brands and between various lots. The content of endotoxin in unused gloves ranged from <1.5 to 5810 endotoxin units (EU). The range for unused wipes was 3.6-87.8 EU. Surfaces of equal loading and area were sampled using three types of cloths that had low initial endotoxin contamination. The cloths were very good at collecting dust and endotoxin could be assayed from aqueous extracts of the wipes. Samples collected using cloths with bare washed hands yielded higher endotoxin loading per mass of collected dust versus samples collected wearing endotoxin-free gloves. This demonstrated additional endotoxin loading from the subject's hand. CONCLUSION: This study shows that wipe sampling while wearing medical gloves can be an effective method for collecting and assessing endotoxin on surfaces, so long as each lot of wipes and gloves have been tested and determined to be low in endotoxin.

Air Pollutants↗
PubMed2005

Direct detection in clinical samples of multiple gene mutations causing resistance of Mycobacterium tuberculosis to isoniazid and rifampicin using fluorogenic probes.

BACKGROUND: This study evaluates a method based on real-time PCR for direct detection in clinical samples of the common mutations responsible for isoniazid and rifampicin resistance of Mycobacterium tuberculosis. METHODS: Six pairs of fluorogenic 5' exonuclease probes (Taqman), mutated and wild-type, were designed for six targets: codon 315 of katG, substitution C209T in the regulatory region of inhA, and codons 513, 516, 526 and 531 of rpoB. RESULTS: A total of 98 clinical samples harbouring resistant bacilli from 55 patients and 126 samples harbouring susceptible bacilli from 126 patients were processed. The isolates from samples were tested for drug susceptibility with the radiometric method and sequenced for the same genetic targets. Among the samples, 93 harboured isoniazid-resistant bacilli. According to the sequencing results, 30 had mutations in katG, 30 in inhA and 33 (35.4%) had no mutations in these targets. All 27 clinical specimens harbouring rifampicin-resistant bacilli showed mutations in rpoB. The detection threshold of this method in detecting target genes in serial dilutions of artificial samples was 1.5 x 10(3) cfu/mL. In clinical samples, the sensitivity ranged from 30.4 to 35.3% for smear-negative samples and from 95.1 to 99.2% for smear-positive samples, with a specificity of 100%. In this study, the overall sensitivity in detecting patients having the target mutations was 74.3%. CONCLUSIONS: The main advantage of the described method is the possibility of detecting rifampicin and isoniazid resistance within 48-72 h after sample collection, with a sensitivity of nearly 100% in smear-positive samples if the chosen target is responsible for the resistance.

Antitubercular Agents↗
PubMedDate not supplied

An investigation of the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in authentic urine samples.

Preanalytical stability of a drug and its major metabolites is an important consideration in pharmacokinetic studies or whenever the analyte pattern is used to estimate drug habits. Firstly, the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH, THCCOOglu) in authentic urine samples was investigated. Random urine samples of cannabis users (n = 38) were stored at -20, 4, and 20 degrees C up to 15 days and up to 5 days at 40 degrees C, and alterations of the analyte pattern during storage were followed by liquid chromatography-tandem mass spectrometry. Secondly, the influence of pH (range 5.0-8.0) on the stability of the analytes was studied using spiked urine to elucidate the results obtained from authentic samples. In authentic urine samples, the initial pH ranged from 5.1 to 8.8. The glucuronide was found to be highly labile at a storage temperature of 4 degrees C and above. Initially, 18 urine samples tested positive for THCCOOH. After 2 days storage at 20 degrees C, THCCOOH was detectable in a further 4 samples, and 7 more samples tested positive for THCCOOH (5-81 ng/mL) after 15 days. Depending on time and temperature, the glucuronide concentration decreased, resulting in an increase of THCCOOH concentration. However, a loss in mean total THCCOOH concentration was found, which was significantly higher in deteriorated samples than in samples without signs of deterioration after 15 days of storage at 20 degrees C. In the drug-free urine sample separately spiked with THCCOOglu or THCCOOH, the investigations on the stability of the target analytes at various pH values revealed that THCCOOH was stable at pH 5.0. At higher pH values, its concentration slightly decreased with time, and about 69% of the initial THCCOOH concentration was still present at pH 8.0 on day 5. THCCOOglu concentrations rapidly decreased with increasing pH value. For example, only 72% of the initial THCCOOglu concentration could be detected at pH 5.0 on day 1. Degradation of the glucuronide resulted in formation of THCCOOH, which was observed even at pH 5.0. In light of the present findings, advanced forensic interpretations based on the presence of THCCOOH or the pattern of THCCOOH and THCCOOglu in stored urine samples seems questionable.

Artifacts↗