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PubMed2000

Quantitative comparison of static perimetric strategies in early glaucoma: test-retest variability.

PURPOSE: The aim of this study is to describe and compare test-retest variability of threshold-related suprathreshold and threshold examination strategies. METHODS: Threshold-related suprathreshold and FASTPAC threshold central visual field examinations were performed twice (test and retest) within a 4-week period on 322 subjects with early to moderate primary open-angle glaucoma and glaucoma suspects. For both strategies, defects were quantified by a count, or score, of the number of defective locations within the field as a whole and by hemifield, thereby providing a simple measure of defect extent. This quantification was obtained for the suprathreshold strategy at three suprathreshold increments (5, 8, and 12 dB) and for the full threshold strategy at two levels of pattern deviation probability, although absolute full threshold defect depth was not considered. Mean test-retest score differences and spread of score differences were used to describe variability. An index of relative variability was used to compare the two visual field examination strategies. RESULTS: Marked degrees of defect extent variability were found to exist in both suprathreshold and FASTPAC examination strategies. In general, the suprathreshold strategy exhibited lower test-retest variability of defect extent than the FASTPAC strategy. Suprathreshold test variability was dependent on the suprathreshold increment. FASTPAC examination variability was independent of defect depth when analyzed on the basis of pattern deviation probability values and was also found to be independent of the area of visual field loss. CONCLUSIONS: Suprathreshold examination techniques may provide a reliable perimetric alternative to thresholding strategies for monitoring individuals with early and moderate glaucoma, although they may not be suitable for individuals with advanced glaucomatous visual field loss.

Glaucoma, Open-Angle↗

PubMed1993

Similar alterations of lymphocyte subpopulations in type I and type II diabetes.

Peripheral blood lymphocytes of diabetes mellitus patients were analyzed by flow-cytometry using monoclonal antibodies directed against cell surface markers present in T- and B-cells, monocytes and natural killer cells. The lymphocyte subsets were quantified and expressed in an absolute amount. The study included 17 patients with type I (insulin-dependent), 21 patients with type II (non-insulin-dependent) diabetes and 40 age-matched control subjects. Quantification of the cells present within different lymphocyte subsets revealed a general increase in both patient groups compared to their controls, with the exception of activated T-cells. However, no significant difference was found in the relative amount of T-helper cells and T-suppressor/cytotoxic cells of the diabetes patients when they were compared with their control groups. The fact that we found similar changes in lymphocyte subsets in both type I and type II diabetes suggests that the altered immunological state is secondary to the diabetes mellitus in general.

Adolescent↗

PubMed1998

Absolute organ activity estimated by five different methods of background correction.

UNLABELLED: Accurate absorbed dose estimates in radionuclide therapy require patient-specific dosimetry. In patient-based dosimetry, estimation of absolute organ uptake is essential. The methods used should be reasonably accurate as well as easy to perform in routine clinical practice. One of the major sources of uncertainty in quantification of organ or tumor activity from planar images is the activity present in the tissue surrounding the source. METHODS: To estimate organ activity as a function of organ-to-background activity concentration ratio, a cylindrical phantom, filled with 5.6 liters of water was used to simulate the abdomen of a patient. Two other cylinders of 150 ml each, representing the kidneys, were each filled with 19 MBq 99mTC and were positioned in the abdomen phantom. The phantom was imaged with a dual-head gamma camera with the kidneys placed at posterior depths of 1-, 5- and 10-cm at kidney-to-background activity concentration ratios of infinity, 10:1, 5:1 and 2:1. The conjugate view geometric mean counting method was used to quantify activity. Five methods for background correction were applied: (1) no correction; (2) conventional background correction (simple subtraction of the background counting rate from the source region counting rate); (3) Kojima method (background corrected for organ thickness and depth); (4) Thomas method (analytical solution); and (5) Buijs method (background corrected for organ and total-body thickness). RESULTS: Since the results were identical for both kidneys, only the left kidney activity measurements are presented. The accuracy of the five background correction methods is given as the percentage difference between the actual and measured activity in the left kidney. For Method 1, the percentage difference ranged from 2% with an infinite kidney-to-background activity concentration ratio to +413% with a 2:1 ratio. For Method 2, these values ranged from -1% to -80%, for Method 3 from +11% to -18%, for Method 4 from -2% to +120% and for Method 5 from -4% to +39%. CONCLUSION: Even though quantitative SPECT is the most rigorous method for activity quantification in conditions of low organ-to-background activity concentration ratio, planar scintigraphy can be applied accurately if appropriate attention is paid to background correction. Using relatively simple background subtraction methods, the quantitative planar imaging technique can result in reasonably accurate activity estimates (Methods 3 and 5). The use of Kojima's method is preferable, especially at very low source-to-background activity concentration ratios.

Humans↗

PubMed1997

Quantification of carbohydrate-deficient transferrin by ion-exchange chromatography with an enzymatically prepared calibrator.

The current HPLC method for the determination of carbohydrate-deficient transferrin (CDT) yields ratios of CDT isoforms in relation to total transferrin, whereas the use of absolute concentrations obtainable in routine analysis by RIA and the reference ranges based here-upon is more convenient. We describe a modified HPLC method that likewise gives absolute CDT concentrations by using a calibrator prepared by treatment of transferrin with neuraminidase. Separation of isoforms could be improved and analysis time reduced to approximately 2 h. Iron saturation proved stable during chromatography. In contrast to a commercial RIA, the cheaper and more time-saving HPLC method excludes erroneous results caused by aged samples or genetic transferrin variants and enables the determination of asialo- and disialotransferrin. Both methods showed comparable precision and correlated with each other (y = 1.76 + 0.27x; Sy[symbol: see text]x = 5.38); for the HPLC method precision was 1.3-9.8% (within assay) and 6.2-10.6% (between assay). The clinical evaluation with a cutoff concentration of 80 mg/L resulted in a diagnostic specificity of 100% and a sensitivity of 82.5%.

Alcoholism↗

PubMed2006

Cerebral vascular response to hypercapnia: determination with perfusion MRI at 1.5 and 3.0 Tesla using a pulsed arterial spin labeling technique.

PURPOSE: To compare the quantification of cerebral blood flow (CBF) at 1.5 and 3.0 Tesla, under normo- and hypercapnia, and to determine the cerebral vascular response (CVR) of gray matter (GM) to hypercapnia, a pulsed arterial spin labeling technique was used. Additionally, to improve GM CBF quantification a high-resolution GM-mask was applied. MATERIALS AND METHODS: CBF was determined with the QUIPSS II with thin slice TI1 periodic saturation (Q2TIPS) sequence at 1.5 and 3.0 Tesla in the same group of eight subjects, both under normocapnia and hypercapnia. Absolute GM-CBF maps were calculated using a GM-mask obtained from a high-resolution structural scan by segmentation. The CVR to hypercapnia was derived from the quantitative GM-CBF maps. RESULTS: For both field strengths, the GM-CBF was significantly higher under hypercapnia compared to normocapnia. For both conditions, there was no significant difference of GM-CBF for 1.5 and 3.0 Tesla; the same applies to the CVR, which was 4.3 and 4.5%/mmHg at 1.5 and 3.0 Tesla, respectively. CONCLUSION: The method presented allows for the quantification of CBF and CVR in GM at the common clinical field strengths of 1.5 and 3.0 Tesla and could therefore be a useful tool to study these parameters under physiological and pathophysiological conditions.

Adult↗

PubMed1984

Quantification of cutaneous oedema in patch test reactions by measurement of skin thickness with high-frequency pulsed ultrasound.

69 doubtful and positive patch test readings (?+21, +23, ++18, 7) in 15 contact dermatitis patients were studied by measurement of skin thickness as an expression of allergic oedema. Exposed skin was compared with a regional control. Skin thickness was measured by 15 MHz pulsed ultrasound (A-scan) to 0.1 mm accuracy. The ?+, +, ++, and reactions could be separated by measurements of absolute difference in thickness (p less than 0.001, p less than 0.001, p less than 0.02) between exposed and non-exposed skin; the mean increases were 0.14, 0.49, 0.93, and 1.37 mm. The ?+, +, and ++ reactions, but not the reactions, could also be separated by measurements of relative increase in skin thickness (p less than 0.001, p less than 0.001, n.s.); the mean increases were 7%, 25%, 50% and 55%. The normal thickness of the skin of the back was shown to have increased (p less than 0.02) in patients with reactions only. It is concluded that the high-frequency ultrasound method is suitable for quantification of doubtful and positive patch test reactions. The reactions are probably explained by the normal thick skin of the back, and they need no separate recording in patch testing. Standards of increase in skin thickness in doubtful and positive patch tests are defined: absolute increase (mm) was ?+ less than or equal to 0.2; +0.3-0.7; ++0.8-1.3 ( greater than or equal to 1.4); relative increases were ?+ less than 15%; +15-45%, ++ ( included) greater than 45%.

Adult↗

PubMed1997

Quantification of CD34+ cells: comparison of methods.

BACKGROUND: Quantification of CD34+ stem and progenitor cells is predominantly performed by flow cytometric analysis of cells prepared by whole blood staining and red cell lysis. This method also includes cell washing, which is thought to cause the destruction and loss of some of the nucleated cells (NCs). To address this cell loss and its influence on the outcome of enumeration, three techniques for preparing cells for quantification of CD34+ cells were compared. STUDY DESIGN AND METHODS: Blood (n = 179), bone marrow (n = 60), and leukapheresis components (n = 64) were examined by the use of density separation of mononuclear cells (MNCs) and two red cell-lysis procedures (wash and no-wash). Cell counts were determined in the original materials and after cell preparation. Absolute CD34+ cell counts were calculated using the flow cytometry-analyzed proportions of CD34+ cells and the various white cell counts. RESULTS: Depending on the cell source and the cell preparation chosen, the loss of NCs ranged between 12 percent and 89 percent of the original white cell number. This loss of NCs was exclusively due to cell washing and predominantly affected granulocytic cells. Analysis of the flow cytometry data revealed that the relative CD34+ values in blood and bone marrow were roughly threefold higher in density separated MNCs than in those that underwent the lyse-and-wash procedure. Calculation of absolute CD34+ cell counts confirmed that the MNC procedure underestimated the CD34+ cell content by a median of 26 percent (blood), 21 percent (bone marrow), and 5 percent (leukapheresis component) when compared with the median yield from analysis and cell counting performed after the lyse-and-wash procedure. On the other hand, the conventional lysis procedure, which applies the original white cell counts for CD34+ quantification, was shown to overestimate the CD34+ cell content by a median of 1.2-fold, 1.33-fold, and 1.13-fold, respectively. CONCLUSION: Neither density separation nor the whole-blood lysis procedure seems appropriate for optimal CD34+ quantification.

Ammonium Chloride↗

PubMed1993

A new quantitative method for the analysis of cardiac perfusion tomography (SPET): validation in post-infarct patients treated with thrombolytic therapy.

In this study a new method for assessment of perfusion defects (PDs) derived from myocardial perfusion tomograms was evaluated in patients treated with thrombolytic therapy. Using global constraints and dynamic programming, a model-based delineation algorithm defined myocardial borders, the basal plane and absolute and relative PD size in 49 thallium-201 chloride (201TL CL) and 60 technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) tomograms. Tomographic (single-photon emission tomography: SPET) and planar quantification of PDs was compared to enzymatic infarct size as well as to global (LVEF) and regional ventricular function (RWM) obtained by contrast angiography. The algorithm delineated the myocardium and the valve plane in most cases, even when large PDs were present. Manual correction of the automatic delineation of the basal plane was necessary in less than 20% of the studies. Using 201Tl Cl, LVEF correlated better with tomographic PD (r = -0.67) than with planar PD (r = -0.54). Comparing planar to tomographic imaging using 99mTc-MIBI, a higher correlation with enzymatic infarct size (r = 0.73 vs 0.57) and with global ventricular function (r = 0.64 vs -0.52) was found when tomographic techniques were used. No close correlation between PD and RWM was found. The beneficial effect of thrombolysis was shown by a significant difference of PD in patients with open versus occluded infarct-related vessels. It can be concluded that this new automated algorithm for quantification of SPET perfusion defect size provides a useful tool in evaluating thrombolytic therapy.

Algorithms↗

PubMed2001

Endocrine-disrupting nonylphenols--ultra-trace analysis and time-dependent trend in mussels from the German bight.

A very sensitive and efficient analytical procedure is presented for the determination of 4-nonylphenols (NP) in blue mussels by use of off-line coupling of high-performance liquid chromatography (HPLC) and gas chromatography with mass spectrometric detection (GC-MS). Combined steam distillation and solvent extraction were used to extract the analytes from the mussel samples. Before quantification by GC-MS the raw extracts were purified by normal-phase HPLC. 4-n-Nonylphenol was used as internal standard. The detection limit was 15 ng NP absolute, calculated from the blank value. The method was applied to the determination of NP in blue mussel samples from the German North Sea sampled over a period of 10 years. Collection, homogenization, and storage of the mussels were performed according to the Standard Operating Procedures of the German Environmental Specimen Bank since 1985. The total NP concentrations in the mussels decreased significantly from 1985 (4 microgram kg (-1)) to 1995 (1.1 microgram kg (-1)).

Animals↗

PubMed2006

Quantitative measurement of cerebral haemodynamics in early vascular dementia and Alzheimer's disease.

Alzheimer's disease (AD) and vascular dementia (VaD) both share significant vascular risk factors. The present study measures the haemodynamics of these diseases in absolute rather than relative terms. Twenty-four patients were classified as either early AD or VaD and were compared with 12 non-cognitively impaired subjects. Magnetic resonance imaging flow quantification was used to measure arterial inflow and arterial pulse volume. Mean vascular resistance and compliance were calculated. In AD, the arterial inflow was lower by 18%, resistance was higher by 23% and compliance of the arterial tree was lower by 20% compared with normal (p=0.01, 0.02 and 0.05, respectively). In VaD, the arterial pulse volume was higher by 24% and compliance was higher by 35% compared with normal (p=0.05 for both). Early VaD is characterized by normal blood flow, but increased pulsation. Reduced blood flow and an incompliant arterial tree characterize early AD.

Aged↗

PubMed2003

The age-related decline in resting energy expenditure in humans is due to the loss of fat-free mass and to alterations in its metabolically active components.

There is conflicting evidence as to whether the age-related decline in resting energy expenditure (REE) can be attributed to i) absolute changes in fat-free mass (FFM), ii) alterations in the composition of FFM or iii) decreasing organ metabolic rates. This study directly addressed the first and second hypotheses by quantification of metabolically active components of FFM assuming constant tissue respiration rates to calculate REE (REEc). REE was measured (REEm) in 26 young (13 females, 13 males, age 22-31 y) and 26 elderly subjects (15 females, 11 males, age 60-82 y) by indirect calorimetry and detailed body composition analysis was obtained using bioelectrical impedance analysis (BIA), dual energy X-ray absorptiometry (DXA), and MRI. Specific organ metabolic rates were taken from the literature. REEm adjusted for differences in FFM was lower in older subjects than in younger control subjects (5.43 +/- 0.61 MJ/d compared with 6.37 +/- 0.48 MJ/d; P < 0.001). Skeletal muscle mass plus liver mass accounted for 86% and 48% of the variance in REE in young and elderly subjects, respectively. The difference between REEm and REEc was 0.03 +/- 0.40 MJ/d and -0.36 +/- 0.70 MJ/d in young and elderly subjects, respectively. In the elderly 58% of the difference in variance was attributed to heart mass. REEm - REEc was -1.40 +/- 0.44 MJ/d in subjects with hypertensive cardiac hypertrophy, i.e., heart mass > 500 g, suggesting a decrease in heart metabolic rate with increasing heart mass. Excluding five elderly subjects with cardiac hypertrophy resulted in agreement between REEm and REEc in the elderly (-0.10 +/- 0.48 MJ/d). We concluded that the age-related decline in REE is attributed to a reduction in FFM as well as in proportional changes in its metabolically active components. There is no evidence for a decreasing organ metabolic rate in healthy aging.

Adult↗

PubMed2002

Comparison of quantitative competitive PCR with LightCycler-based PCR for measuring Epstein-Barr virus DNA load in clinical specimens.

The aim of this study was to develop a LightCycler-based real-time PCR assay for monitoring the Epstein-Barr virus (EBV) DNA load in unfractionated whole blood. This assay was compared with quantitative competitive PCR (Q-PCR) for EBV. The LightCycler-based assay was highly sensitive and reproducible when quantifying plasmid DNA in either the presence or absence of healthy donor blood DNA. Amplifying plasmid DNA in DNA backgrounds from different donors slightly increased the variation of quantification, indicating that clinical specimen DNA has an influence on quantification. In most transplant recipients, a good correlation was observed between EBV DNA load dynamics determined by LightCycler and Q-PCR in follow-up samples, although the correlation between absolute values of EBV DNA loads was weak and occasional samples were false negative in the LightCycler assay. In 253 cross-sectional blood samples from patients with Burkitt's lymphoma, infectious mononucleosis, or human immunodeficiency virus infection, a weak but significant correlation between the two methods was found (r(2) = 0.37, P < 0.001). Our results indicate that the clinical specimen DNA background may influence the absolute values of EBV DNA load in LightCycler analyses but that this effect is rare. LightCycler PCR is very well suited for monitoring of EBV DNA load dynamics, and its diagnostic value is comparable to that of Q-PCR. To avoid false negativity or underestimation of viral load, future internal calibration of the LightCycler is recommended. This would also enhance EBV load assay standardization and interinstitute comparisons.

DNA, Viral↗

PubMed2004

[Examination of exhaled breath condensate in patients with asthma and chronic obstructive pulmonary diseases].

Considerable interest of specialists all over the world has focused on the measurement of the markers of inflammation and oxidative stress in the exhaled breath condensate in patients with asthma or chronic obstructive pulmonary diseases recently. Use of exhaled condensate is based on the hypothesis that aerosol particles exhaled in human breath reflect the composition of the bronchoalveolar extracellular lining fluid. The standard collection of the material requires condensation of exhaled air and the samples have to be kept in biologically inert containers. Measurement of the very low concentrations of selected substances requires very sensitive analytical methods. The examination of exhaled breath condensate is absolutely non-invasive method, which can be repeated as often as needed and it is extremely well tolerated both by children and seniors. Markers in the condensate enable detection and quantification of the inflammation process, the disease monitoring, and assessment of the response to the treatment. The breath condensate diagnostics is a new progressive method and in the patients with asthma and chronic obstructive pulmonary disease it can bring complementary information to the very sensitive method of determination of exhaled nitric oxide.

Asthma↗

PubMed2006

Rapid dual-injection single-scan 13N-ammonia PET for quantification of rest and stress myocardial blood flows.

Quantification of myocardial blood flows at rest and stress using 13N-ammonia PET is an established method; however, current techniques require a waiting period of about 1 h between scans. The objective of this study was to test a rapid dual-injection single-scan approach, where 13N-ammonia injections are administered 10 min apart during rest and adenosine stress. Dynamic PET data were acquired in six human subjects using imaging protocols that provided separate single-injection scans as gold standards. Rest and stress data were combined to emulate rapid dual-injection data so that the underlying activity from each injection was known exactly. Regional blood flow estimates were computed from the dual-injection data using two methods: background subtraction and combined modelling. The rapid dual-injection approach provided blood flow estimates very similar to the conventional single-injection standards. Rest blood flow estimates were affected very little by the dual-injection approach, and stress estimates correlated strongly with separate single-injection values (r=0.998, mean absolute difference=0.06 ml min-1 g-1). An actual rapid dual-injection scan was successfully acquired in one subject and further demonstrates feasibility of the method. This study with a limited dataset demonstrates that blood flow quantification can be obtained in only 20 min by the rapid dual-injection approach with accuracy similar to that of conventional separate rest and stress scans. The rapid dual-injection approach merits further development and additional evaluation for potential clinical use.

Ammonia↗

PubMed1998

Comparison of seven immunoassays for the quantification of CA 125 antigen in serum.

Seven CA 125 immunoassays were compared for their clinical performance. CA 125 concentrations were determined in 289 serum samples obtained from women with benign pelvic tumors (samples from 98 patients) and patients with various cancers (samples from 111 patients). In the range of 0-1000 kilounits/L, all assays tested were linearly correlated, with correlation coefficients ranging from 0.89 to 0.99. In relation to the original Centocor CA 125 assay, there was an overall tendency to measure higher absolute values in the lower CA 125 value range. This was not seen in relation to the Centocor CA 125 II assay. ROC curves (benign vs pretreatment ovarian cancer patients) were nearly identical for all assays, and the areas under the ROC curves were not markedly different. We conclude that the CA 125 assays tested are strongly related to each other and are clinically reliable for the quantification of serum CA 125 and that none of the assays offers higher diagnostic accuracy or better discrimination between patient groups, especially not in the lower ranges.

Adenocarcinoma↗

PubMed2006

Simultaneous determination of protein aggregation, degradation, and absolute molecular weight by size exclusion chromatography-multiangle laser light scattering.

The feasibility of size exclusion chromotography (SEC)-multiangle laser-light scattering as a technique to investigate aggregation and degradation of glycosylated and nonglycosylated proteins, and antibodies under various conditions such as addition of detergent, changes in pH, and variation of protein concentration and heat stress temperature was examined. Separation of proteins and their aggregates was performed using SEC-high-performance liquid chromatography. Detection of analytes was carried out with on-line UV, refractive index, and multiangle laser light-scattering detectors. Quantification and molecular weight determination were performed using commercial software. Aggregation and degradation were examined under various conditions and quantitative results are presented for bovine serum albumin, choriogonadotropin, glyceraldehyde-3-phosphate dehydrogenase, Herceptin, and ReoPro. This method can simultaneously determine both the quantities and the molecular weights of macromolecules from a single injection. The determination of molecular weight is absolute which avoids misleading results caused by molecular shape or interactions with the column matrix. This technique is valuable not only for assessing the extent of aggregation but also for effectively monitoring molecule degradation as evidenced by molecular weight reduction and change in monomer amount.

Abciximab↗

PubMed1991

Quantification of water content in biological tissues by proton nuclear magnetic resonance.

We have made quantitative measurements of water content in biological tissue using proton nuclear magnetic resonance (NMR). We evaluated the factors which affect the NMR signal intensity measurements in order to quantify the absolute water content of the tissue. It can be said that there is an optimum sample length to achieve the absolute value of water content using NMR. The integrated NMR water signal intensity was determined in the frequency domain. The absolute water content was measured gravimetrically. The NMR detectable water in brain and lung tissue was determined using the signal intensity of the analyzed tissue compared with the signal intensity for the same weight of distilled water. The NMR detectable water was 99% by weight for brain and 60% by weight for peripheral lung tissue. The NMR detectability of water in biological tissues varied for different tissues.

Animals↗

PubMed1983

A quantification of the risk of trypanosomiasis infection to cattle on the south Kenya coast.

The number of trypanosome-infected bites received by cattle grazed around an 8 ha area of forest harbouring a semi-isolated population of Glossina pallidipes Austen was estimated. The absolute size of the tsetse population was determined by mark-release-recapture techniques, the tsetse host range by the identification of blood-meals, and trypanosome infection rates by dissection of samples of tsetse. Feeding frequency was estimated and the number of cattle present was known. It was estimated that each cow received, from G. pallidipes, one infective inoculum of T. congolense every 5.8 days during the first experiment and 5.0 days in the second. For T. vivax results were 3.2 and 79.1 days, respectively.

Animals↗