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PubMed1995

The efficiency of patch sampling for determination of relative tick burdens in comparison with total tick counts.

Quantitative data on host tick burdens are fundamental for the initiation of control strategies and effective management of wildlife populations, but the methods of live sampling employed for domestic animals are unsuitable for sampling wild animals. Despite advances in the use of destructive methods (the scrub and digestion techniques) to obtain measures of the total tick burden on wildlife, these methods are too involved for many field workers, who often need only measures of relative tick burden. Recently, patch sampling methods have been introduced whereby only certain predilection sites are sampled, the presumption being that the number of ticks collected gives an indication of the relative degree of infestation. We examined the validity of patch sampling as a measure of relative tick burden by comparing adult ticks collected from the ears, head, neck, foreleg and perianal region of impala (Aepyceros melampus) with total tick burdens of the same animals derived from the digestion technique. Adult ticks from patch sampling were positively and significantly correlated with total adults and total ticks (larvae, nymphs, and adults) on impala, with ticks patch sampled from the neck showing the highest correlation with the total tick burden. Comparison of relative tick loads from patch sampling with absolute tick loads from digestion for three classes of impala (females, bachelor males and territorial males) gave qualitatively similar results. We conclude that, when measures of relative tick load are sufficient and destructive sampling is not feasible, patch sampling can provide reliable information on relative tick burdens that are positively correlated with the total tick burden.

Animals↗
PubMed1996

Dislodgeability of chlorpyrifos and fluorescent tracer residues on turf: comparison of wipe and foliar wash sampling techniques.

Residential use of pesticides has increased substantially in the United States over the past twenty years. Contact with pesticide-treated turf may result in dermal exposures, particularly among children. This study evaluated wipe sampling and foliar wash techniques to measure chlorpyrifos on turf following insecticidal treatments with Dursban 4E. Residues of the fluorescent tracer Uvitex OB were also measured as part of a larger study adapting video imaging analysis to children's exposure to pesticides. The wipe technique recovered an average of 0.50 microgram/cm2 of chlorpyrifos, or 1.5% of the initial deposit, and an average of 0.21 microgram/cm2 of tracer, or 6.1% of the initial deposit, from bluegrass turf 1-3 hours after application. The foliar wash technique recovered significantly more chlorpyrifos and tracer (1.3 micrograms/cm2, or 4.0% and 0.36 microgram/cm2, or 10.5%, respectively). The resulting chlorpyrifos/tracer ratio was also significantly greater for the foliar wash technique (4.6) than for the wipe sampling technique (2.6). Variability associated with each technique was similar. Chlorpyrifos dissipation on irrigated and non-irrigated plots was evaluated through collection of wipe and foliar wash samples at six time intervals over a 48 h period. Wipe technique results indicated that irrigated residues were significantly lower than non-irrigated during the first 6.5 h post-application; foliar wash residues were significantly lower on the irrigated plot during the first 3.5 h post-application. No effect of irrigation on dislodgeability of chlorpyrifos residues was observed after 24 h. The findings indicate that foliar wash sampling removes larger amounts of chlorpyrifos and fluorescent tracer residues from turf than wipe sampling, and would therefore produce higher estimates of potential exposure among children if used as a turf contact-transfer factor. They also demonstrate that foliar was sampling produces a higher relative transfer factor for video imaging analysis of skin exposure than does wipe sampling. Wipe sampling was found to be far simpler than foliar wash sampling in regard to both sample collection and analysis. Further investigations are required to determine the accuracy of these two techniques in estimating transfer of pesticides from turf to skin.

Chlorpyrifos↗
PubMed1996

Characteristics of voluntary visual sampling of the environment for safe locomotion over different terrains.

The characteristics of visual sampling required for successful locomotion over various terrains is the focus of this work. In the first experiment we directly address the role of continuous visual monitoring of the environment in guiding locomotion by allowing the subjects to choose when and where to take a visual sample of the terrain and examine the effects of different terrains on characteristics of visual sampling. Young subjects walked over travel paths of varying difficulties while wearing opaque liquid crystal eyeglasses and pressed a hand-held switch to make the glasses transparent when they needed to sample the environment. Travel time and visual sampling characteristics were recorded. Results show that intermittent sampling (less than 50%) of the environment is adequate for safe locomotion, even over a novel travel path. The frequency, duration and timing of visual samples are dependent on terrain characteristics. Visual sampling of the environment is unaffected by preview restriction of the travel path and is increased when specific foot placement is required and there is a potential hazard in the travel path. In the second experiment we dissociated steering control and obstacle avoidance from specific foot placement and examined visual sampling demands prior to the initiation of the swing phase and during the swing phase. The results show that steering control and obstacle avoidance do influence the visual sampling time, which is scaled to the magnitude of change. Vision was used in a feedforward control mode to plan for and initiate appropriate changes in the swing limb trajectory: its use during the swing phase to provide on-line control was minimal.

Adult↗
PubMedDate not supplied

Evaluation of the detection of Borrelia burgdorferi DNA in urine samples by polymerase chain reaction.

It is difficult in some cases to identify an infection caused by Borrelia burgdorferi and to monitor the effect of therapy. Seropositivity will persist even after successful treatment and therefore may suggest ongoing infection. For direct detection of B. burgdorferi DNA in human urine samples, the polymerase chain reaction (PCR) was evaluated. A published primer system was selected, which amplifies a 259 bp fragment from the gene encoding the 23S rRNA. The lower detection limit of the primer system was 10 fg of extracted B. burgdorferi DNA. Several methods for the pretreatment of urine samples were tested. Of these, the Geneclean kit (Bio 101, USA) showed the best results. A total of 114 urine samples from 74 patients belonging to three clinical groups was investigated: (i) 51 samples from 26 patients with active Lyme disease, (ii) 36 samples from 27 patients with previous infection but no symptoms at the time the urine was collected, and (iii) 27 samples from 21 seronegative control patients without Lyme disease. B. burgdorferi DNA was detected in 25 urine samples of 17 patients with active disease, whereas 26 samples from this group of patients were negative. Only one asymptomatic case with previous infection showed a positive result, and the urine samples of the patients without Lyme disease were uniformly negative. Two of four patients from whom samples before and directly after onset of therapy were available converted from negative to positive PCR results after initiation of therapy, accompanied by the symptoms of a Jarisch-Herxheimer reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Comparison between a two-layer discontinuous Percoll gradient and swim-up for sperm preparation on normal and abnormal semen samples.

PURPOSE: This work was to compare the effects of Percoll gradient and swim-up treatments for sperm preparation on the percentage of progressive motility, recovery of motile sperm, removal of debris, percentage of normal forms according to strict criteria, and movement characteristics of sperm using computer-assisted velocity analysis. RESULTS: In total, 50 semen samples from 50 patients were tested and divided into two groups: a normal group (n = 27) with normal parameters and an abnormal group (n = 23) with abnormal parameters. The results in both the normal and abnormal groups revealed that the sperm concentration in the Percoll samples was significantly greater than that in the swim-up samples. Although the percentage of progressive motility was greater in the swim-up samples than in the Percoll samples, the number of motile sperm, reflecting the percentage of motile sperm recovery, was till greater in the Percoll samples. The debris of semen was equally removed by both methods and the percentage of normal forms was also similar in the samples treated according to these two procedures. Both curvilinear velocity (VCL) and straight-line velocity (VSL) of sperm were significantly greater in the swim-up samples than in the Percoll samples. Sperm from the swim-up procedure also showed a greater mean amplitude of lateral head displacement than that from the Percoll gradient procedure, but the distinction was insignificant. CONCLUSION: The Percoll gradient technique, by recovering more motile sperm, may be applied to prepare oligospermic samples. The swim-up method may become the standard choice to prepare normal semen which could obtain sufficiently motile sperm, due to its simplicity and recovered sperm with superior motility.

Centrifugation, Density Gradient↗
PubMed2002

Use of SAMPL for a study of DNA polymorphism, genetic diversity and possible gene tagging in bread wheat.

Selective Amplification of Microsatellite Polymorphic Loci (SAMPL) technology was used in bread wheat for the first time for a study of genetic diversity, genotype identification and gene tagging. The diversity studies involved 55 wheat genotypes and two SAMPL primer pairs (SAMPL-6 and SAMPL-7, each with a M-CAG primer), which together gave 43 polymorphic bands out of a total of 87 SAMPL bands. The average polymorphic information content (PIC) of SAMPL primers was 0.221 and that of SAMPL markers was 0.264. The marker index of SAMPL markers was 9.61. The genetic similarity (GS) coefficients for 1,485 pairs of genotypes ranged from 0.35 to 0.96 with an average of 0.65. A dendrogram was prepared on the basis of a similarity matrix using the UPGMA algorithm, which corresponded well with the results of principal component analysis (PCA). From a total of 55 genotypes, 54 could be distinguished using the SAMPL banding patterns of both primers. For gene tagging, 568 bands from a total of 1,185 SAMPL bands detected polymorphism between each of the three pairs of parents differing for grain protein content (GPC), pre-harvest sprouting tolerance (PHST) and grain weight (GW). An association of six bands with GPC, of seven bands with PHST and four bands with GW was observed using bulked segregant analysis (BSA).

Journal Article↗
PubMed2003

Determination of phosphorus in small amounts of protein samples by ICP-MS.

Inductively coupled plasma mass spectrometry (ICP-MS) is used for phosphorus determination in protein samples. A small amount of solid protein sample (down to 1 micro g) or digest (1-10 micro L) protein solution was denatured in nitric acid and hydrogen peroxide by closed-microvessel microwave digestion. Phosphorus determination was performed with an optimized analytical method using a double-focusing sector field inductively coupled plasma mass spectrometer (ICP-SFMS) and quadrupole-based ICP-MS (ICP-QMS). For quality control of phosphorus determination a certified reference material (CRM), single cell proteins (BCR 273) with a high phosphorus content of 26.8+/-0.4 mg g(-1), was analyzed. For studies on phosphorus determination in proteins while reducing the sample amount as low as possible the homogeneity of CRM BCR 273 was investigated. Relative standard deviation and measurement accuracy in ICP-QMS was within 2%, 3.5%, 11% and 12% when using CRM BCR 273 sample weights of 40 mg, 5 mg, 1 mg and 0.3 mg, respectively. The lowest possible sample weight for an accurate phosphorus analysis in protein samples by ICP-MS is discussed. The analytical method developed was applied for the analysis of homogeneous protein samples in very low amounts [1-100 micro g of solid protein sample, e.g. beta-casein or down to 1 micro L of protein or digest in solution (e.g., tau protein)]. A further reduction of the diluted protein solution volume was achieved by the application of flow injection in ICP-SFMS, which is discussed with reference to real protein digests after protein separation using 2D gel electrophoresis.The detection limits for phosphorus in biological samples were determined by ICP-SFMS down to the ng g(-1) level. The present work discusses the figure of merit for the determination of phosphorus in a small amount of protein sample with ICP-SFMS in comparison to ICP-QMS.

Animals↗
PubMed2004

Validation of a simplified field-adapted procedure for routine determinations of methyl mercury at trace levels in natural water samples using species-specific isotope dilution mass spectrometry.

A field-adapted procedure based on species-specific isotope dilution (SSID) methodology for trace-level determinations of methyl mercury (CH(3)Hg(+)) in mire, fresh and sea water samples was developed, validated and applied in a field study. In the field study, mire water samples were filtered, standardised volumetrically with isotopically enriched CH(3) (200)Hg(+), and frozen on dry ice. The samples were derivatised in the laboratory without further pre-treatment using sodium tetraethyl borate (NaB(C(2)H(5))(4)) and the ethylated methyl mercury was purge-trapped on Tenax columns. The analyte was thermo-desorbed onto a GC-ICP-MS system for analysis. Investigations preceding field application of the method showed that when using SSID, for all tested matrices, identical results were obtained between samples that were freeze-preserved or analysed unpreserved. For DOC-rich samples (mire water) additional experiments showed no difference in CH(3)Hg(+) concentration between samples that were derivatised without pre-treatment or after liquid extraction. Extractions of samples for matrix-analyte separation prior to derivatisation are therefore not necessary. No formation of CH(3)Hg(+) was observed during sample storage and treatment when spiking samples with (198)Hg(2+). Total uncertainty budgets for the field application of the method showed that for analyte concentrations higher than 1.5 pg g(-1) (as Hg) the relative expanded uncertainty (REU) was approximately 5% and dominated by the uncertainty in the isotope standard concentration. Below 0.5 pg g(-1) (as Hg), the REU was >10% and dominated by variations in the field blank. The uncertainty of the method is sufficiently low to accurately determine CH(3)Hg(+) concentrations at trace levels. The detection limit was determined to be 4 fg g(-1) (as Hg) based on replicate analyses of laboratory blanks. The described procedure is reliable, considerably faster and simplified compared to non-SSID methods and thereby very suitable for routine applications of CH(3)Hg(+) speciation analysis in a wide range of water samples.

Environmental Monitoring↗
PubMed2006

Sampling of water, soil and sediment to trace organic pollutants at a river-basin scale.

Sampling is considered a crucial step in the analysis of organic compounds in the environment. This review describes field sampling techniques and provides detailed step-by-step procedures for collection and preservation of all major environmental matrices (water, sediment and soil) integrated as part of the river-basin water cycle. Attention is given to the prerequisites for obtaining reliable samples, and the practical issues of sample collection (planning, field sampling, sampling strategies and equipment and data quality assessment) are considered. Considering the heterogeneity of environmental matrices, special considerations for each matrix are given to solve typical problems and to find the most appropriate solutions to ensure the quality of the sample. The procedures described in the next sections are commonly used protocols that reflect true field conditions and current state-of-the-art techniques used in the sampling of organic compounds. The aim is to signify the importance of sampling to the overall analytical procedure. Finally, quality control issues to be considered in environmental sampling are given.

Geologic Sediments↗
PubMed2006

Determination of NSAIDs in river sediment samples.

Consumption of non-steroidal anti-inflammatory drugs (NSAIDs) is increasing and with it the danger of environmental pollution by pharmaceutical residues. Publications regarding NSAIDs in the environment not only show that they are toxic to many animal species, but also highlight the need for robust analytical methods for monitoring the level of such contaminants in environmental matrices. In our study we selected the four most widely used NSAIDs in Slovenia and Central Europe, ibuprofen, naproxen, ketoprofen and diclofenac, and studied their extraction from sediment samples. We examined several extraction techniques (ultrasonic extraction, Soxhlet extraction, pressurized liquid extraction, supercritical fluid extraction and microwave-assisted extraction) using a spiked sediment sample and determined optimal extraction conditions. After extraction we applied a clean-up step, derivatisation of the analytes and gas chromatography with mass spectrometric detection (GC-MSD) and selected the most appropriate extraction procedure. The optimised analytical method chosen for analysis of sediment samples consisted of microwave-assisted extraction, clean-up of the extract with SPE, derivatisation with MSTFA and determination with GC-MSD. The optimised procedure was applied to the analysis of two environmental river samples taken from the vicinity of Novo mesto, the biggest town in the south eastern part of Slovenia with 62,000 inhabitants, a hospital and a pharmaceutical factory in its vicinity. While analysis of the sample taken upstream of the town showed no detectable amounts of NSAIDs, analysis of samples taken downstream showed quantifiable levels of two of the studied NSAIDs (naproxen and ketoprofen). Besides these two NSAIDs, river water samples sampled at the same time and location on the River Krka also showed the presence of diclofenac. Sampling on the River Krka and other Slovene rivers will in the future be repeated at different sampling points in order to track down the main sources of pollution.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2007

Evaluation of a serological method for the detection of Taenia saginata cysticercosis using serum and meat juice samples.

Two peptides, HP6-2 and Ts45S-10, were used as antigens for the detection of antibodies against Taenia saginata cysticercosis in serum and meat juice samples using enzyme-linked immunosorbent assay (ELISA). Positive control samples were obtained from animals experimentally infected (serum) and from animals naturally infected (meat juice). The two peptides and a pooled preparation of both peptides were evaluated, and their cut-off points with both sample categories were calculated. ELISA results from these different peptides were compared. Sensitivity and specificity of HP6-2 using serum were calculated as being 100 and 98%, respectively, showing to be higher than the values for the other antigens used. The average optical density (OD) value for negative samples was 0.646, whereas it was 1.702 for the positive control samples. This peptide was used to examine serum samples from animals with cysts and random field serum samples. For meat juice samples the pooled peptides showed the highest sensitivity and specificity, as they were 100 and 95%, respectively. The average OD values for the negative and the positive reference meat juice samples were 0.379 and 1.291, respectively. The optimal dilution of the meat juice samples for the ELISA was very low, as it was 1:20 using the pooled peptides, compared with 1:800 serum dilution using HP6-2. To the authors' knowledge, this is the first report of a successful testing for T. saginata cysticercosis using meat juice.

Animals↗
PubMed2005

Feasibility of flow cytometry for the detection of bacteria from body fluid samples.

The detection of microorganisms in body fluids is indispensable for identifying the source of infection and is one of the important examinations that influence subsequent treatment. In order to quickly detect bacteria in body fluid samples, a flow cytometry-based experimental automated bacteria counter (BF-FCM), was tested to determine its clinical value. The results for detectability obtained with the BF-FCM were compared with those obtained by conventional culture and Gram-staining techniques. We evaluated a total of 318 body fluid samples, excluding bile samples from which fungus alone was isolated. The samples consisted of 176 bile, 64 ascites, 42 pleural fluid, and 36 cerebrospinal fluid samples. Among the 318 samples, 154 (48.4%) were culture-positive. Of these 154, the BF-FCM identified 130 as positive (sensitivity, 84.4%). Of the 164 samples that were culture-negative, 141 were negative by the BF-FCM (specificity, 86.0%). Based on the culture results, the BF-FCM detected bacteria with a positive predictive value of 85.0% (130 of 153 samples), a negative predictive value of 85.5% (141 of 165 samples), and percent agreement of 85.2%. Although there were 23/164 (14.0%) false-positive samples, we consider that the BF-FCM, in combination with Gram staining and conventional cultures, would be helpful in the diagnosis and management of patients with diseases such as bacterial meningitis that present emergently.

Bacteria↗
PubMed2006

Wild chimpanzee infant urine and saliva sampled noninvasively usable for DNA analyses.

In many genetic studies on the great apes, fecal or hair samples have been used as sources of DNA. However, feces and hairs are difficult to collect from chimpanzee infants under 3 years of age. As alternative DNA sources, we investigated the efficiency of collecting urine samples from infants compared with fecal samples, as well as the validity of the DNA extracted from urine and saliva samples of well-habituated M group chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania. We collected 40 urine and 3 fecal samples from 10 infants under 3 years. Compared with feces, the urine samples were relatively easy to collect. The saliva of infants, which remained on the twigs sucked by them, was collected using cotton swabs. The average amounts of DNA extracted from the 40 urine and 6 saliva samples were 3,920 and 458 pg/mul, respectively. The rate of positive PCR was low and the allelic dropout rate was high when using less than 25 pg of template DNA in the PCR mixtures. Based on the amounts of DNA, 50% of the urine samples and 100% of the saliva samples were judged usable for accurate microsatellite genotyping. For infant chimpanzees in particular, collecting urine and saliva as an alternative to fecal and hair samples can reduce the effort invested in collection in the field.

Animals↗
PubMed2006

Influence of riffle and snag habitat specific sampling on stream macroinvertebrate assemblage measures in bioassessment.

Stream macroinvertebrate communities vary naturally among types of habitats where they are sampled, which affects the results of environmental assessment. We analyzed macroinvertebrates collected from riffle and snag habitats to evaluate influences of habitat-specific sampling on taxon occurrence, assemblage measures, and biotic indices. We found considerably more macroinvertebrate taxa unique to snags (143 taxa) than to riffles (75 taxa), and the numbers of taxa found in both riffles and snags (149 taxa) were similar to that found in snags. About 64% of the 47 macroinvertebrate measures we tested differed significantly between riffles and snags. Eighty percent intercepts of regressions between biotic indices and urban or agricultural land uses differed significantly between riffles and snags. The Hilsenhoff biotic index calculated from snag samples explained 69% of the variance of riffle samples and classified 66% of the sites into the same stream health group as the riffle samples. However, four multimetric indices for snag samples explained less than 50% of the variance of riffle samples and classified less than 50% of the sites into the same health group as the riffle samples. We concluded that macroinvertebrate indices developed for riffle/run habitat should not be used for snag samples to assess stream impairment. We recommend developing an index of biotic integrity specifically for snags and using snags as an alternate sampling substrate for streams that naturally lack riffles.

Animals↗
PubMed2006

Comparative study of two vitreous humor sampling methods in rabbits.

To compare and evaluate two methodologies, entire-sampling and micro-sampling for the harvesting of vitreous humor, the vitreous humor of rabbits were sampled with the two methods respectively, and the concentrations of calcium, chlorine, potassium, sodium and phosphorus of the were measured. The results showed that the differences in the variance coefficient and two-eye concentrations of micro-sampled specimens were less than those of the entire-sampled specimens. In the micro-sampling group, the concentrations of repeated micro-sampling showed no differences among different groups (P > 0.05) and the intra-ocular fluid dynamics did not have significant influence on post-mortem sampling. The sampling technique may affect the concentrations of specimen collected. Our study suggests that micro-sampling is less influenced by the human factor and is reliable, reproducible, and more suitable for forensic investigation.

Animals↗
PubMed2005

Prevalence of Clostridium difficile toxins A and B and Clostridium perfringens enterotoxin A in stool samples of patients with antibiotic-associated diarrhea.

BACKGROUND: Antibiotic-associated diarrhea (AAD) is a major nosocomial as well as a community health problem. Clostridium difficile toxins (CDT) can be detected in only 10-25% of patients with AAD. The role of Clostridium perfringens enterotoxin A (CPEnt) as a cause of AAD remains to be elucidated. We, therefore, prospectively investigated the prevalences of both CPEnt and CDT in stool samples of patients with AAD. MATERIALS AND METHODS: A total of 693 stool samples consecutively submitted to our department from patients with AAD were screened for CDT and CPEnt using commercially available enzyme-linked immunoassays (ELISA). C. difficile and C. perfringens were detected by standard culture techniques. In addition, samples being CPEnt positive and/ or harboring C. perfringens were screened for the CPEnt gene by duplex PCR. RESULTS: CDT was detected in 79 (11.4%) of 693 stool samples. Of these, 49 (62.0%) harbored C. difficile. In one (0.14%) of 693 samples, CPEnt could be detected by ELISA. This respective CPEnt-positive stool sample also harbored C. perfringens. 147 (21.2%) of all stool samples were culture positive for C. perfringens. We did not detect samples positive for both CPEnt and CDT. In five (3.4%) of 147 C. perfringens isolates, the CPEnt gene could be detected by duplex PCR. PCR was positive in two (40%) of the five stool samples harboring CPEnt gene-positive C. perfringens isolates. CONCLUSION: The present prospective study revealed a prevalence of CDT of 11.4%, whereas the prevalence of CPEnt was less than 1%. Routine screening of stool samples for CPEnt does not appear to be justified in patients with AAD.

Anti-Bacterial Agents↗
PubMed1989

Optimal sampling interval to estimate heart rate at rest and during exercise in atrial fibrillation.

To investigate the ideal sampling interval for the estimation of heart rate (HR) at rest and during exercise in atrial fibrillation (AF), maximal exercise testing with continuous electrocardiographic acquisition was performed in 10 patients with chronic AF (mean age 66 +/- 4 years) and 10 subjects in normal sinus rhythm (mean age 31 +/- 6 years). Measurements of HR were obtained at 9 different sampling intervals (1, 2, 3, 6, 10, 15, 20, 30 and 60 seconds) at rest and 7 different sampling intervals (1, 2, 3, 6, 10, 15 and 20 seconds) during the last 30 seconds of each minute during exercise. The HR obtained from each interval was compared with true HR (determined by a 4-minute sample at rest and by the last 30 seconds of each minute during exercise). Among patients with AF, large differences were observed between the HR obtained and true HR, both at rest and during exercise, using small sampling intervals. The mean of these differences ranged between 16 +/- 11 beats/min (range 14 to 22) using 1-second sampling intervals and 2.2 +/- 2.0 beats/min (range 1.6 to 4.4) using 20-second sampling intervals during progressive exercise. Variability of the HR obtained from a given random sample was also high when short sampling intervals were used among patients with AF. These observations were contrasted by subjects in normal sinus rhythm, among whom neither variability nor measurement error were influenced remarkably by changing the sampling interval or increasing HR.

Adult↗
PubMed1983

Reproducibility of expired breath hydrogen levels in the neonate: a comparison of two methods for sample collection.

We have compared a nasopharyngeal catheter method for breath sampling and a valved collection device. Sample quality was assessed by simultaneous oxygen measurement and reproducibility was checked by the analysis of 50 pairs of samples from four premature neonates. Both collection methods produced samples of highly variable quality suggesting a variable mixture of alveolar and non-alveolar air as well as differences in expired oxygen levels between babies. The mean oxygen levels were similar for both sampling techniques. Linear regression analysis of paired hydrogen results showed a highly significant correlation coefficient r = 0.73. This was improved markedly to r = 0.94 by normalization of hydrogen values based on observed oxygen levels, and so supports the earlier article by Robb and Davidson [1]. All breath hydrogen analyses require a measure of sample quality. Reproducible results and meaningful changes in hydrogen concentration in breath samples can only be achieved by correction according to sample quality. Correction to a common oxygen value should allow quantitative comparisons between patients. Samples were best collected from neonates by the nasopharyngeal catheter method, which least disturbed the patient, allowed multiple sample collection and gave lower oxygen and higher hydrogen values where large differences between pairs occurred.

Autoanalysis↗