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At least 1,603 records · Page 89Linked to original sources
PubMed2001

Development of an ELISA for the diagnosis of Corynebacterium pseudotuberculosis infections in goats.

An ELISA was developed for the diagnosis of Corynebacterium pseudotuberculosis infections in goats. A bacterial whole cell extract was used as solid-phase antigen, and serum from a culture-positive animal served as the internal reference standard. The well-to-well and assay-to-assay variations were determined to be 12.7 and 33.0%, respectively. A cut off value was determined by parallel testing of 142 sera (112 ELISA-positive, 30 ELISA-negative) in a Western blot, and the correlation between both tests was highly significant (K=0, 93). In addition, the reliability of the ELISA for the detection of infected herds was proven in a double blind study testing 910 sera from 74 goat herds.

Animals↗
PubMed2003

Blood pressure nomograms for school children in Iran.

Currently there are no blood pressure (BP) nomograms based on local data available in Iran. In order to obtain data on BP distribution in Iranian school children, 8848 children aged 7-12 years were studied in Tehran. BP was found to increase with age. Both systolic and diastolic BP showed a positive correlation with height and weight in both sexes. The systolic and diastolic BP in boys and girls were not significantly different. As the sample was representative of Iranian school children, reference standard curves were constructed by modeling data using fractional polynomial. The 50th and 95th percentiles of systolic and diastolic BP of Iranian children were compared for each age with the results reported in the study of the Second Task Force. These percentiles were different from the Second Task Force study. Environmental and genetic determinants are likely to be responsible for the differences. The differences show that the use of local BP nomograms is necessary for assessing the BP levels in Iranian children.

Aging↗
PubMed1982

Interpretation of arm circumference as an indicator of nutritional status.

Data from a longitudinal study of 1342 Zambian children aged between 0 and 60 months are used to derive reference standards for mid-upper arm circumference. To determine the sensitivity, specificity, and predictive value of the arm circumference measurement as an indicator of nutritional status, associations between arm circumference and other anthropometric and clinical indicators of nutritional status are presented. Although none of the anthropometric indices accurately reflects the clinical judgement of nutritional status, arm circumference is shown to be similar in accuracy to weight for age and to weight for length as an indicator of clinical malnutrition; it provides a viable alternative to these more cumbersome measurements for use in field surveys.

Anthropometry↗
PubMed1990

Calibration errors in digital subtraction radiography.

Two methods for the measurements of osseous change detected by digital subtraction radiography have been evaluated. Estimates of errors introduced by soft and hard tissues that overlay the region of interest (ROI) or by soft tissue that replaced the bone are made. All estimates are made assuming that the radiation source is a 40 keV monoenergetic beam and the reference standard is equivalent to compact bone. These assumptions facilitate a theoretical analysis of calibration errors on a relative scale. The radiographic image method uses a calibration wedge on each of the two films. The mean gray value of the ROI on each film is converted into an equivalent thickness of bone by matching the ROI mean gray value to a gray value along the wedge. These thickness values are then subtracted to obtain a measurement of the amount of change. The subtraction image method makes use of a wedge on only one of the two films. The image of the subtraction of the two radiographs is used for detection of the area of change and the mean gray value of the ROI is matched to a gray value along the wedge. The thickness of the wedge at this point is the measured change. The errors introduced by inclusion of the cheek over the ROI and the replacement of bone by soft tissue are estimated for the radiographic image method. The influence of unequal beam attenuation between the reference ramp and the ROI is estimated for the subtraction image method. Other factors influencing the accuracy of estimates of osseous change which are nonlinear in their effects are also considered.(ABSTRACT TRUNCATED AT 250 WORDS)

Calibration↗
PubMed2000

A systematic approach to the validation of process control parameters for monoclonal antibody production in fed-batch culture of a murine myeloma.

A systematic approach to the validation of control ranges of control parameters for a cell culture process producing a monoclonal antibody is described. Specifically, the structure and functional activity of a monoclonal IgG1 antibody produced at the outer limits of numerical ranges of fed-batch culture control parameters such as pH and temperature were examined, with the aim of providing assurance that antibody produced under varying culture conditions was of consistent quality based on a carefully defined set of specifications. An experimental design was created using a half-fractional factorial design for fed-batch culture incorporating half of the thirty two possible combinations of five selected control parameters at high and low levels. Statistical analysis of all data gathered from the study allowed an assessment of the effects of the process control parameters at either high or low outer limits on fed-batch culture response variables such as growth rate and specific antibody productivity. Measured values for the responses of growth rate and specific antibody productivity throughout this study ranged from 0.22-0.44 d(-1) and 6.4-32 microg monoclonal antibody/10(6) cells/d respectively. Analytical characterisation of monoclonal antibody purified from each fed-batch culture considered the purity, structure and biological activity of the glycoprotein. All antibody preparations were identical to each other and to the current antibody reference standard or control. Glycosylation analysis of certain samples from the study demonstrated that the distribution of glycoforms of the antibody was not affected by the varying process control conditions of the fed-batch cultures.

Amidohydrolases↗
PubMed1987

Comparison of measurement of glomerular filtration rate by single sample, plasma disappearance slope/intercept and other methods.

Various in vitro methods employing radioactive indicators have been presented for the determination of glomerular filtration rate (GFR) including slope/intercept (S/I) and single sample (SS) methods. The S/I technique utilizes the analysis of the slope of a certain segment of the plasma disappearance curve of a suitable radioactive indicator and its intercept on the y axis. The SS method is based on the theoretical volumes of distribution derived from a single plasma concentration at some specific time after intravenous injection of the indicator. Using GFRs estimated from the compartmental analysis of the entire plasma disappearance curve as a reference standard, we have compared the errors of GFR estimation calculated from 12 S/I methods, 3 SS methods and 2 techniques in which original formulae were derived. The errors of the SS method of Tauxe et al. gave the lowest standard error of estimate (Sy X x) of all the methods. The S/I methods gave lowest errors when sampling times were taken between 60 min and 240 min. Almost all the errors observed here were significantly less than those observed using scintillation camera techniques. The SS method seems to be the method of choice for estimation of GFR by single injection techniques. The use of the scintillation camera in conjunction with the SS technique would provide a useful right to left ratio so that individual kidney GFR could be calculated.

Adolescent↗
PubMed1998

Is intrasound vibration useful in the diagnosis of occult scaphoid fractures?

This study was designed to confirm the results of Finkenberg et al. (J Hand Surg 1993;18A: 4-7), who found a high sensitivity (100%) and specificity (95%) of the intrasound vibration method in diagnosing occult scaphoid fractures. These occult scaphoid fractures are not visible on x-ray films, but clinically the patients are suspected of having a scaphoid fracture. A vibratory apparatus is placed over the anatomical snuff-box and a vibration of 100 mW is emitted; a painful sensation is produced if the scaphoid is fractured. Thirty-seven consecutive patients with a clinically suspected scaphoid fracture were evaluated. In 6 patients, a scaphoid fracture was radiographically identified; in the remaining 31 patients, a 3-phase bone scan was obtained. Eleven wrists showed increased uptake over the scaphoid and were considered to have an occult scaphoid fracture. In this group, bone scintigraphy was used as the reference standard. The vibration test was painful in 1 of 6 patients with a proven scaphoid fracture and in 3 of the 11 patients with a positive bone scan. In contrast to the results of Finkenberg et al, the intrasound vibration method shows a sensitivity of 24%, a specificity of 85%, a positive predictive value of 40%, and a negative predictive value of 65%. We conclude that the accuracy of intrasound vibration is low and that it is not useful in the diagnosis of scaphoid fractures.

Adolescent↗
PubMed2006

Concentric-needle single-fiber electromyography for the diagnosis of myasthenia gravis.

The goal of this study was to estimate the accuracy of concentric-needle single-fiber electromyography (CN-SFEMG) for the diagnosis of myasthenia gravis (MG). A consecutive series of patients referred for CN-SFEMG was evaluated by an investigator blinded to the results of CN-SFEMG in order to determine the presence or absence of MG using an independent reference standard. Sensitivity, specificity, predictive values, and likelihood ratios were calculated. The study population included 51 patients (21 with MG). CN-SFEMG was normal in 34 patients (67%) and abnormal in 17 (33%). The sensitivity of CN-SFEMG for the diagnosis of MG was 0.67 and the specificity was 0.96. The positive likelihood ratio was 16.8 and the negative likelihood ratio was 0.34. The positive and negative predictive values were 0.93 and 0.76, respectively. These results indicate that CN-SFEMG showing abnormal jiggle is extremely useful for confirming the diagnosis of MG, but that CN-SFEMG showing normal jiggle has limited utility in excluding the diagnosis.

Action Potentials↗
PubMed1995

Quantitative RT-PCR for measuring gene expression.

Classical Northern blot analysis for measuring mRNA requires too many cells to be practical for cell sorting. Yet, measurement of gene expression in small subsets within a heterogeneous population of cells is often desired. The PCR in combination with prior reverse transcription (RT-PCR) of the mRNA of interest provides a means for measuring gene expression using as few as one cell. When RT-PCR is performed, the reliability of the data can be highly subjective due to the efficiency of both RT and PCR steps. This subjectivity can be eliminated by a technique for quantitating specific RNA molecules using an internal RNA competitive reference standard (RNA-CRS), which is identical to the sequence of interest except for a deletion of 80 bases. Here we illustrate a strategy for quantitative PCR using a RNA-CRS, synthesized solely using nonplasmid-based PCR techniques. The competitive reaction consists of a constant quantity of wild-type mRNA (from 100-1000 cells) added individually to tubes containing a serially decreasing amount of RNA-CRS. The RT-PCR is performed on these samples, then the resulting product is analyzed by gel electrophoresis and densitometry. The procedure for preparing the RNA-CRS and subsequent RT-PCR steps are described in detail.

Animals↗
PubMed1994

Comparison of vitamin A status assessment techniques in children from two Indonesian villages.

The vitamin A statuses of preschool-aged children without clinical eye signs of vitamin A deficiency in two villages near Bogor, West Java, Indonesia, were studied by the modified-relative-dose-response (MRDR) test and the conjunctival impression cytology (CIC) method. In the second village the relative-dose-response (RDR) test was also applied. Of the children examined, 71% in the first village (group 1, n = 75) and 36% in the second village (group 2, n = 83) fell below the third percentile of the WHO reference standard of weight-for-age. The following provisional cutoff values for inadequate vitamin A status in Indonesia were used: MRDR (> or = 0.06), RDR (> or = 20%), CIC (an abnormal impression in one eye). The percent abnormal values were as follows: group 1--MRDR 48%, CIC 51%; group 2--MRDR 12%, RDR 11%, CIC 5%. Thus, the indicators gave concordant results for the two populations but did not necessarily identify the same individuals at risk. The consistency of the RDR test was much improved by increasing the oral dose of 3.5 mumol and by retesting only after a 3-wk interval.

Administration, Oral↗
PubMed2004

Inter-laboratory comparison of qualitative and quantitative detection of hepatitis C (HCV) virus RNA in diagnostic virology: a multicentre study (MS) in Italy.

BACKGROUND: The importance of the standardisation of nucleic acid amplification technology (NAT) assays for the detection of hepatitis C virus RNA is well known today, as many studies carried out in different European countries attest. The results of a previous study performed in Italy (J. Clin. Virol. 1 (2003) 83) by the Italian Society of Clinical Microbiology (AMCLI) showed that the use of external reference standards and of multicentre collaborative studies significantly improves laboratory performance for the qualitative evaluation of HCV RNA. OBJECTIVES: the AMCLI organised a new study on the standardisation of both the qualitative and the quantitative evaluation of HCV RNA with NAT in order to improve the implementation of the diagnostic methods for HCV RNA detection. STUDY DESIGN: seventeen diagnostic centres of major Italian Hospitals participated in this quality control study. The study consisted of testing three panels, each made up of 10 coded samples including negative and positive samples. Positive samples contained four levels of HCV RNA (genotype 1). RESULTS AND CONCLUSION: Seven out of 510 qualitative results obtained were incorrect (1.4%), two false negative and five false positive. The results gave a sensitivity of 99.5% and a specificity of 95.8%. Regarding quantitative tests, the geometric mean (GM) and standard deviation (S.D.) could be calculated only for the three highest HCV RNA levels. The percentage of results within the range of GM +/- 0.5 log(10) varied from 91% to 100%. Some laboratories had some difficulty in the exact quantification of the lowest (3.00 log IU/ml) as well as of the highest viral levels (6.35 log IU/ml) values, very near to the limits of the dynamic range of the assays. The comparison of the results of this study with that previously carried out one confirms that a regular participation in external quality assessment (EQA) assures the achievement of a high proficiency level in the diagnosis of HCV infection.

Hepacivirus↗
PubMed2006

Characterization of two phase I metabolites of bendamustine in human liver microsomes and in cancer patients treated with bendamustine hydrochloride.

PURPOSE: The metabolism of bendamustine (BM) hydrochloride, a bifunctional alkylator containing a heterocyclic ring, was investigated in vitro and in vivo for identification of cytochromes P450 (CYP) involved in the formation of two phase I metabolites, structural confirmation of these previously unidentified metabolites and assessment of their cytotoxic effect in relation to the parent compound. METHODS: Potential metabolites of BM were synthesized and structurally characterized by nuclear magnetic resonance (NMR) and liquid chromatography-mass spectrometry (LC-MS) analysis. In vitro metabolism of BM hydrochloride in human hepatic microsomes was conducted to identify the CYP450 isoenzymes involved in the oxidative metabolism of BM. Samples from cancer patients after treatment with BM hydrochloride and microsomal preparations were analyzed by LC-MS and HPLC with fluorescence detection. The cytotoxic effect of the metabolites was analyzed in several lymphoma cell lines and peripheral blood lymphocytes and compared with that of the parent compound using an MTT assay. RESULTS: LC-MS as well as HPLC with fluorescence detection revealed hydroxylation of the methylene carbon at the C-4 position of the butanoic acid side chain and N-demethylation of the benzimidazole skeleton as the main metabolic pathways in human liver microsomes. Isoform-specific chemical inhibitors and correlation analysis pointed to CYP1A2 as the prominent enzyme in BM oxidation. The rate of formation for both metabolites correlated (r=0.931 and 0.933) with the activity of CYP1A2 and there were no other notable correlations with any of the other CYPs. In addition, both metabolites were identified in plasma, urine, and bile samples from cancer patients under BM hydrochloride therapy as shown by comparison with chromatograms obtained from the authentic reference standards. Cytotoxic activity observed for gamma-hydroxy BM was approximately equivalent to that obtained for the parental compound BM. N-demethyl BM displays five to tenfold less cytotoxic activity than BM. CONCLUSION: The results indicate that CYP1A2-catalyzed N-dealkylation and gamma hydroxylation are the major routes for BM phase I metabolism producing two metabolites less or similarly toxic than the parent compound. In contrast to the metabolic pathways of the structurally related chlorambucil, no beta-oxidation of the butanoic acid side chain leading to enhanced toxicity was detected for BM.

Aged↗
PubMed1986

The concentration, physical state, and purity of bacterial endotoxin affect its detoxification by ionizing radiation.

Increasing concentrations of a highly purified bacterial lipopolysaccharide preparation, the U.S. Reference Standard Endotoxin, were exposed to increasing doses of ionizing radiation from a 60Co source. At identical radiation doses both the structural change and Limulus amebocyte lysate (LAL) reactivity were progressively smaller with increasing concentrations of the lipopolysaccharide in an aqueous medium. Under the experimental conditions used, there was a linear relationship between the endotoxin concentration and radiation dose for the structural changes. In contrast to endotoxin in aqueous medium, endotoxin irradiated in its dry state showed no decrease in LAL reactivity and rabbit pyrogenicity. Endotoxin exposed to radiation in water in the presence of albumin showed a much smaller decrease in LAL and pyrogenic activities than expected. The results show that the concentration, physical state, and purity of endotoxin influence its structural and functional alteration by ionizing radiation.

Chemical Phenomena↗
PubMed2004

CT colonography: effect of experience and training on reader performance.

The purpose of this paper was to investigate the effect of radiologist experience and increasing exposure to CT colonography on reader performance. Three radiologists of differing general experience (consultant, research fellow, trainee) independently analysed 100 CT colonographic datasets. Readers had no prior experience of CT colonography and received feedback and training after the first 50 cases from an independent experienced radiologist. Diagnostic performance and reporting times were compared for the first and second 50 datasets and compared with the results of a radiologist experienced in CT colonography. Before training only the consultant reader achieved statistical equivalence with the reference standard for detection of larger polyps. After training, detection rates ranged between 25 and 58% for larger polyps. Only the trainee significantly improved after training ( P=0.007), with performance of other readers unchanged or even worse. Reporting times following training were reduced significantly for the consultant and fellow ( P<0.001 and P=0.03, respectively), but increased for the trainee ( P<0.001). In comparison to the consultant reader, the odds of detection of larger polyps was 0.36 (CI 0.16, 0.82) for the fellow and 0.36 (CI 0.14, 0.91) for the trainee. There is considerable variation in the ability to report CT colonography. Prior experience in gastrointestinal radiology is a distinct advantage. Competence cannot be assumed even after directed training via a database of 50 cases.

Clinical Competence↗
PubMed1990

Quantitation of IgG subclass antibodies to pneumococcal capsular polysaccharides by ELISA, using Pneumovax-specific antibodies as a reference.

A quantitative enzyme-linked immunosorbent assay (ELISA) method has been developed to assay the levels of IgG subclasses to pneumococcal capsular polysaccharides (PCP) by using a reference standard. This standard solution containing specific antibodies to a polyvalent pneumococcal vaccine (Pneumovax) was purified from the serum of an immunized healthy adult by affinity chromatography. In order to determine the predominant response to Pneumovax in the four IgG subclasses, specific IgG subclasses in preimmune and postimmune sera from six healthy adults were assessed quantitatively by the ELISA. With regard to peak concentrations after immunization, there was a marked increase in the IgG2 subclass, compared with those of IgG1 and IgG3. Such a quantitative assay of Pneumovax-specific IgG subclass antibodies is useful for the direct evaluation of immune responses to immunization with a polyvalent pneumococcal vaccine, and at the same time, for estimating the IgG2 response to PCP antigens in individuals.

Animals↗
PubMed1998

The performance of CA-125 measurement in the detection of endometriosis: a meta-analysis.

OBJECTIVE: To assess the diagnostic performance of serum CA-125 measurement in the detection of endometriosis. DESIGN: Meta-analysis. SETTING AND PATIENT(S): Twenty-three studies comparing serum CA-125 levels and laparoscopically confirmed endometriosis. INTERVENTION(S): Serum CA-125 measurement and laparoscopy. MAIN OUTCOME MEASURE(S): Sensitivity and specificity of serum CA-125 measurement in the diagnosis of endometriosis with laparoscopy as the reference standard. RESULT(S): The estimated summary receiver operating characteristic curves showed that the performance of serum CA-125 measurement in the diagnosis of endometriosis grade I/IV is limited, whereas its performance in the diagnosis of endometriosis grade III/IV is better. CONCLUSION(S): Despite its limited diagnostic performance, we believe that the routine use of serum CA-125 measurement in patients with infertility might be justified. In contrast to laparoscopy, serum CA-125 measurement is an inexpensive test that is not a burden for the patient. It could identify a subgroup of patients who are more likely to benefit from early laparoscopy. Studies reporting on the mutual dependence between serum CA-125 measurement and data from the history and physical examination are needed.

CA-125 Antigen↗
PubMed1997

Analysis of drug/plasma protein interactions by means of asymmetrical flow field-flow fractionation.

PURPOSE: The applicability of Asymmetrical Flow Field-Flow Fractionation (Asymmetrical Flow FFF) as an alternative tool to examine the distribution of a lipophilic drug (N-Benzoyl-staurosporine) within human plasma protein fractions was investigated with respect to high separation speed and loss of material on surfaces due to adsorption. METHODS: Field-Flow Fractionation is defined as a group of pseudochromatographic separation methods, where compounds are separated under the influence of an externally applied force based on differences in their physicochemical properties. This method was used to separate human plasma in its protein fractions. The drug distribution in the fractions was investigated by monitoring the fractionated eluate for drug content by fluorescence spectroscopy. RESULTS: Human plasma was separated into human serum albumin (HSA), high density lipoprotein (HDL), alpha 2-macroglobulin and low density lipoprotein (LDL) fractions in less than ten minutes. Calibration of the system and identification of the individual fractions was performed using commercially available protein reference standards. The influence of membrane type and carrier solution composition on the absolute recovery of N-Benzoyl-staurosporine and fluorescein-isothiocyanate-albumin (FITC-albumin) was found to be quite significant. Both factors were optimized during the course of the investigations. N-Benzoyl-staurosporine was found to be enriched in the fraction containing HSA. CONCLUSIONS: If experimental conditions are thoroughly selected and controlled to suppress drug and plasma protein adsorption at the separation membrane, Asymmetrical Flow FFF shows high recoveries and fast separation of human plasma proteins, and can be a reliable tool to characterize drug/plasma protein interactions. For analytical purposes it has the potential to rival established technologies like ultracentrifugation in terms of ease-of-use, precision, and separation time.

Adsorption↗
PubMed2000

Clinical trials of cost effectiveness in technology evaluation.

This article discusses models of efficacy, design of clinical trials and the role of mathematical modeling in diagnostic technology evaluation and determination of cost-effectiveness. A multi-tiered model of efficacy, which views diagnostic imaging as part of a global process of patient management and outcome, has been described. The first tier involves imaging efficacy, which must be determined by clinical trial. Direct comparison of new and established modalities in a single study population has major advantages over randomized controlled trials, which are extremely costly and time-consuming and are not appropriate for most evaluations of diagnostic modalities. Selection of patients for inclusion in the trial, interpretation and verification of results, and determination of a reference standard are all possible sources of bias, which need to be identified and controlled. Decision analysis modeling can be used to assess diagnostic, therapeutic, patient-outcome and cost efficacy, once imaging efficacy has been evaluated by clinical trial. Decision analysis is easier and less expensive to perform than clinical trials, and results are easily generalizable to other settings. Disadvantages arise from the nondescriptive nature of modeling and lack of transparency, which make it difficult to evaluate the appropriateness of decision tree structures and input data. Modeling is an unavoidable fact of life in technology evaluation, since the resources that would be required for full evaluation of imaging modalities by clinical trial are not available.

Bias↗