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PubMed1997

The use of benzo[a]pyrene diolepoxide-modified DNA standards for adduct quantification in 32P-postlabelling to assess exposure to polycyclic aromatic hydrocarbons: application in a biomonitoring study.

The 32P-postlabelling assay is one of the most sensitive methods for detection of DNA adducts induced by exposure to genotoxic chemicals. Under optimal conditions, detection limits of one adduct per 10(9)-10(10) nucleotides have been reported. This sensitivity now allows monitoring of occupational and even environmental exposure of humans to certain classes of chemicals, mainly polycyclic aromatic hydrocarbons (PAH). Despite its widespread use, 3P-postlabelling is still not a standardized method. Rigorous interlaboratory comparisons are scarce, and those that have been undertaken often show rather different results, both in relative and in absolute values, for the amounts of DNA adducts in the same samples. Furthermore, the optimization of many steps in the procedure has still not been given adequate attention. This paper deals with some technical aspects of detection of PAH-DNA adducts by 32P-postlabelling, in particular with assay calibration and adduct quantification. For this purpose, benzo[a]pyrene (BP)-modified DNA standards were prepared, the adduct contents of which were determined by use of an independent fluorometric method, viz. synchronous fluorescence spectrophotometry (SFS). These BP-DNA standards are processed along with the test samples throughout the entire 32P-postlabelling procedure, from the enzymic digestion up to and including the determination of radioactivity in adduct spots on the chromatogram. As such, these reference samples can be considered as external standards for inter-assay calibration. This method for adduct quantification was compared with the commonly used relative adduct labelling (RAL) and comparative dAMP labelling, which appeared to give rise to an underestimation of adduct levels. The method was applied in a biomonitoring study among workers in a carbon-electrode manufacturing plant, exposed to PAH. Although DNA adduct levels in peripheral blood lymphocytes of exposed workers, as determined by 32P-postlabelling, were not significantly different from those of controls, a significant difference was seen when smokers and non-smokers were compared.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2004

Aerosol profile extracted from spacers as a determinant of actual dose.

PURPOSE: We propose a novel method to evaluate the efficacy of a pressurized metered dose inhaler (pMDI) in combination with a spacer, by not only considering the total dose extractable from the spacer but also the dependence of dose on the volume available for aerosol inhalation. METHODS: We studied volume-dependence of aerosol concentration during extraction from two commonly used plastic spacers (150 ml AerochamberPlus; 750 ml Volumatic) after a single puff of a 100 microg salbutamol pMDI (HFA-Ventolin), using laser photometric measurements. RESULTS: After a delay of is in each spacer, the aerosol peak dose for AerochamberPlus was 2-fold that for Volumatic (p < 0.001), with the peak appearing well within the first 0.5 L even for the largest spacer. The opposite dose relationship is reached when considering total cumulative dose, which was 2-fold higher for Volumatic than for AerochamberPlus (p < 0.001); >95% of total cumulative dose was extracted well within 3 L for the largest spacer. The 2-fold cumulative dose relationship was confirmed by chemical assay on an absolute filter [AerochamberPlus: 21.4+/-3.2 (SD) microg; Volumatic: 43.8+/-9.1 (SD) microg]. CONCLUSIONS: Actual aerosol dose available to patients during inhalation via spacers can only be done on the basis of a quantification of aerosol peak dose and cumulative dose as a function of extracted volume.

Administration, Inhalation↗

PubMed1995

[Nuclear magnetic resonance spectroscopy: methodology and applications to the study of asphyxia neonatorum].

Cerebral metabolism has been extensively studied by magnetic resonance spectroscopy (MRS). MRS allows the study of neonates brain maturation as well as the onset and the evolution of brain injury. The use of phosphorous spectroscopy allows the quantification of phosphorylated metabolites. Thus, the measurement of the relative concentrations of creatine-phosphate and inorganic-phosphate is a prognostic factor of the outcome of a neonate after birth asphyxia. Absolute concentrations have more recently been studied and seem to be more significant. Proton MRS gives access to brain metabolites such as choline, lactate, N-acetyl aspartate and taurine. Its use is more recent than the phosphorous spectroscopy but first results already show its potential in neonatology.

Asphyxia Neonatorum↗

PubMed2005

Extraction and determination of sulfonamides, macrolides, and trimethoprim in sewage sludge.

Pressurized liquid extraction (PLE) was optimized and validated for the determination of sulfonamide and macrolide antimicrobials and trimethoprim in sewage sludge samples. A mixture of water/methanol (50:50, v/v) was found as the most efficient extraction solvent. A temperature of 100 degrees C and a pressure of 100 bar were chosen for extraction. Two cycles of 5 min each efficiently extracted at least 97% of the total extractable amount of all studied analytes from activated sludge. The limits of quantification (S/N= 10) varied between 3 and 41 microg/kg dry weight (dw) and the relative recoveries ranged between 78 and 142%. Additionally, the influence of pH and different LC/MS/MS systems on the absolute recoveries was assessed. Of the investigated antimicrobials sulfapyridin, sulfamethoxazole, trimethoprim, azithromycin, clarithromycin and roxithromycin were detected in municipal sewage sludge samples. Concentrations in activated sludge ranged up to 197 microg/kgdw. In comparison, results obtained by ultrasonic solvent extraction were significantly lower for sulfonamides and in tendency lower for macrolides.

Chromatography, Liquid↗

PubMed2003

Simple determination of cyclosporine in human whole blood by high-performance liquid chromatography.

A simple and reproducible high-performance liquid chromatography (HPLC) method was developed for determination of cyclosporine (CyA, also known as cyclosporin A) in human whole blood. The method entailed direct injection of the blood samples after deproteination using acetonitrile. Chromatography was carried out using an ODS column under isocratic elution with acetonitrile-5mM disodium hydrogen phosphate (75:25, v/v), pH 5.1 at 70 degrees C and a detector set at 210 nm. The mean absolute recovery of cyclosporine from blood was 97%, and the linearity was assessed in the range of 100-3000 ng/ml blood, with a correlation coefficient of greater than 0.999. The limit of quantification and detection of the present method were 100 and 50 ng/ml, respectively. This method has been used to analyze several hundred human blood samples for bioavailability studies.

Chromatography, High Pressure Liquid↗

PubMed2005

Desorption electrospray ionization of explosives on surfaces: sensitivity and selectivity enhancement by reactive desorption electrospray ionization.

Desorption electrospray ionization (DESI), an ambient mass spectrometry technique, is used for trace detection of the explosives trinitrohexahydro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 2,4,6-trinitrotoluene (TNT), Pentaerythritol tetranitrate (PETN), and their plastic compositions (Composition C-4, Semtex-H, Detasheet) directly from a wide variety of surfaces (metal, plastic, paper, polymer) without sample preparation or pretreatment. Analysis of the explosives is performed under ambient conditions from virtually any surface in very short times (<5 s) including confirmatory tandem mass spectrometry (MS/MS) experiments, while retaining the sensitivity and specificity that mass spectrometry offers. Increased selectivity is obtained both by MS/MS and by performing additional experiments in which additives are included in the spray solvent. These reactive DESI experiments (reactions accompanying desorption) produce such ions as the chloride and trifluoroacetate adducts of RDX and HMX or the Meisenheimer complex of TNT. Desorption atmospheric pressure chemical ionization, a variant of DESI that uses gas-phase ions generated by atmospheric pressure corona discharges of toluene or other organic compounds, provides evidence for a heterogeneous-phase (gaseous ion/absorbed analyte) charge-transfer mechanism of DESI ionization in the case of explosives. Plastic explosives on surfaces were analyzed directly as fingerprints, without sample preparation, to test DESI as a possible method for in situ detection of explosives-contaminated surfaces. DESI also allowed detection of explosives in complex matrixes, including lubricants, household cleaners, vinegar, and diesel fuel. Absolute limits of detection for the neat explosives were subnanogram in all cases and subpicogram in the case of TNT. The DESI response was linear over 3 orders of magnitude for TNT. Quantification of RDX on paper gave a precision (RSD) of 2.3%. Pure water could be used as the spray solution for DESI, and it showed ionization efficiencies for RDX in the negative ion mode similar to that given by methanol/water. DESI represents a simple and rapid way to detect explosives in situ with high sensitivity and specificity and is especially useful when they are present in complex mixtures or in trace amounts on ordinary environmental surfaces.

Journal Article↗

PubMed1998

Precision and reliability for measurement of change in MRI lesion volume in multiple sclerosis: a comparison of two computer assisted techniques.

OBJECTIVE: The serial quantification of MRI lesion load in multiple sclerosis provides an effective tool for monitoring disease progression and this has led to its increasing use as an outcome measure in treatment trials. Segmentation techniques must display a high degree of precision and reliability if they are to be responsive to small changes over time. This study has evaluated the performance of two such techniques, the manual outlining and contour methods, in serial lesion load quantification. METHODS: Sixteen patients with clinically definite multiple sclerosis were scanned at baseline and after two years. Scan analysis was performed twice, independently by three observers using each technique. RESULTS: For the absolute lesion volumes the median intrarater coefficient of variation (CV) was 3.2% for the contour technique and 7.6% for the manual outlining method (p < 0.005), the interrater CVs were 3.8% and 6.1% respectively (p < 0.01) and the reliability of both techniques was very high. For the change in lesion volume the intrarater and interrater repeatability coefficients were respectively 2.6 cm3 and 2.8 cm3 for the contour technique, and 3.3 cm3 and 3.7 cm3 for the manual outlining method (lower values reflect higher precision). The values for intrarater and interrater reliability for measuring change in lesion volume were respectively, 0.945 and 0.944 for the contour technique, and 0.939 and 0.921 for the manual outline method (perfect reliability = 1.0). CONCLUSIONS: With such high values for reliability, the impact of measurement error in lesion segmentation on sample size requirements in multiple sclerosis treatment trials is minor. This study shows that a change in lesion volume can be measured with a higher level of precision and reliability with the contour technique and this supports its further application in serial studies.

Adjuvants, Immunologic↗

PubMed1993

Single dose of filgrastim (rhG-CSF) increases the number of hematopoietic progenitors in the peripheral blood of adult volunteers.

Hematopoietic progenitor cell levels were monitored in the peripheral blood of ten healthy adults receiving a single dose of recombinant human granulocyte colony-stimulating factor (rhG-CSF). The objective was to determine the time and number of progenitor cells released into the peripheral blood, induced by a single dose of 15 micrograms/kg rhG-CSF administered intravenously. In all cases the absolute number of circulating progenitor cells including granulocyte-macrophage and erythroid lineages increased up to 12-fold (median 9.4-fold) 4 days after treatment. These findings were based on flow cytometric quantification of CD34+ cells and on progenitor assays. The relative distribution of granulocyte/macrophage and erythroid progenitors remained unchanged. rhG-CSF was well tolerated; mild to moderate bone pain was the most common side-effect and was noted in 6 of 10 subjects. Thus a single dose of rhG-CSF is effective in mobilizing progenitor cells into the peripheral blood in healthy adults. If these progenitors are capable of reconstituting bone marrow, peripheral progenitor cell separation following rhG-CSF administration could be a reasonable alternative to conventional bone marrow harvest in healthy adults.

Adult↗

PubMed1996

Analytical instruments for stable isotopic tracers in mineral metabolism.

Thermal ionization mass spectrometry (TIMS) is the best of four currently used techniques for obtaining results of high accuracy and precision in studies of metal metabolism. TIMS is also the most general technique because it allows measurements of all the metallic elements of interest. The highest absolute sensitivity as well as the ability to determine multiple elements are simultaneously obtained with inductively coupled plasma mass spectrometry (ICP-MS). Current results with this technique show that, although element quantification may be done with acceptable accuracy and precision, use of ICP-MS in metabolic studies at low levels of isotopic labels may be limited. The most favorable elements for study using ICP-MS in metabolic studies appear to be Mg, Zn and possibly Fe. Use of this technique is limited further by isobaric interferences from plasma jet ion molecule reactions, and metabolic studies of Ca are particularly limited. Acceptable levels of accuracy and precision have been obtained from fast atom bombardment-secondary ion mass spectrometry (FAB-SIMS), which has allowed these approaches to be used in metabolic studies of ZN, Fe and Ca, but the approaches are ultimately limited by hydride isobaric interferences. Both FAB-SIMS and gas chromatography-mass spectrometry of metal chelates have the advantage of using widely available instrumentation. GC-MS of metal chelates has been shown to be useful in studies of Cr and Se metabolism and for the determination of a number of other metals. Values of accuracy and precision from use of this approach have been satisfactory.

Calcium↗

PubMed1998

Quantification of thyroid hormone receptor isoforms, 9-cis retinoic acid receptor gamma, and nuclear receptor co-repressor by reverse-transcriptase PCR in maturing and adult skeletal muscles of rat.

Quantitative competitive reverse-transcriptase polymerase chain reaction (qcRT-PCR) was established for determining absolute molecule numbers of the thyroid hormone receptor (T3R) isoforms T3Ralpha1, T3Ralpha2, T3Rbeta1, and the 9-cis retinoic acid receptor gamma (RXRgamma) in developing and adult fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles of rat. Expression levels of the nuclear receptor co-repressor (NCoR) were measured in the same muscles because responses to thyroid hormones during muscle maturation might not only depend on the expression levels of the various receptors but might also be modulated by changes in the expression of NCoR. The qcRT-PCR method was based on the addition of known amounts of homologous competitor RNAs to the reverse transcriptase (RT) reaction. We show that all nuclear receptors under study were expressed in fast and slow muscles. Transcript numbers of T3Rbeta1, which was the most abundant isoform, were higher in SOL than in EDL during all developmental stages. The mRNAs for T3Ralpha1, T3Ralpha2, RXRgamma and the NCoR displayed molecule numbers in similar ranges, but were differentially expressed. T3Ralpha1 mRNA increased in SOL during postnatal development, while T3Ralpha2 mRNA initially decreased, then increased to adult levels. Conversely, pronounced decreases were observed for T3Ralpha1 (10-fold) and T3Ralpha2 (28-fold) mRNAs in the EDL muscle during postnatal maturation. RXRgamma mRNA was 10-fold downregulated during EDL maturation, but unaltered in maturing SOL. NCoR transcript number displayed only minor changes in both muscles.

Aging↗

PubMed2006

Visual field defects and retinal ganglion cell losses in patients with glaucoma.

OBJECTIVE: To determine whether the structure-function relationships for glaucoma in humans and experimental glaucoma in monkeys are similar. METHODS: The study was based on retinal ganglion cell density and visual thresholds in patients with documented glaucoma. Data were analyzed with a model that predicted ganglion cell density from standard clinical perimetry, which was then compared with histologic cell counts. RESULTS: The model, without free parameters, produced accurate and relatively precise quantification of ganglion cell density associated with visual field defects. For 437 sets of data, the unity correlation for predicted vs measured cell density had a coefficient of determination of 0.39. The mean absolute deviation of the predicted vs measured values was 2.59 decibels (dB), and the mean +/- SD of the distribution of residual errors of prediction was -0.26 +/- 3.22 dB. CONCLUSIONS: Visual field defects based on standard clinical perimetry are proportional to neural losses caused by glaucoma. CLINICAL RELEVANCE: The evidence for quantitative structure-function relationships provides a scientific basis for interpreting glaucomatous neuropathy from visual thresholds and supports the application of standard perimetry to establish the stage of the disease.

Aged↗

PubMed2007

Characterization of a three bacteria mixed culture in a chemostat: evaluation and application of a quantitative terminal-restriction fragment length polymorphism (T-RFLP) analysis for absolute and species specific cell enumeration.

Growth dynamics of Pseudomonas aeruginosa, Burkholderia cepacia, and Staphylococcus aureus in a batch and chemostat, were investigated as a laboratory model system for persistent infections in cystic fibrosis. Most species-specific enumeration methods for mixed cultures are laborious or only qualitative, and therefore impede generation of quantitative data required for validation of mathematical models. Here, a quantitative T-RFLP method was evaluated and applied for specific and absolute cell number enumerations. The method was tested to be unbiased by quantitative sample composition and allowed reproducible enumerations of mixed cultures. For assay validation, samples of defined concentration containing one, two or three species were quantified. Logarithmically transformed absolute cell numbers of single-species dilutions were linear within a lower working range of 10(4)-10(6) cfu/mL (species-dependent) and an upper working range of 10(10) cfu/mL. Quantifications of single species (10(6)-10(10) cfu/mL) spiked with one or two other species agreed well with single species controls. Differences between slopes of first order linear regression of spiked and pure dilution series were insignificant. Coefficient of variation of defined mixed replicates was maximum 4.39%, of a three-species chemostat it was maximum 1.76%. T-RFLP monitoring of pure cultures in parallel shake flasks and of a three-species mixed chemostat gave very consistent results. Coexistence of at least two species after a time period equivalent to more than 33 volume exchanges was found. This result was not predicted from pure cultures clearly indicating the need for quantitative mixed culture experiments to better understand microbial growth dynamics and for mathematical model validation.

Biomass↗

PubMed2004

Use of real-time PCR for determining copy number and zygosity in transgenic plants.

This review examines how real-time PCR can be used to determine copy number and zygosity in transgenic plants. Distinguishing between plants that harbor one and two copies of a transgene or are hemizygous and homozygous requires the ability to routinely distinguish twofold differences, a detection difference which approaches the resolution of PCR-based quantification methods. After explaining the basic principles, especially the threshold cycle (Ct value) as the basic measuring unit in real-time PCR, we introduce three quantitation methods currently in use. While the absolute and relative standard curve approaches are qualitative methods that distinguish high-copy from low-copy transformants, the comparative (2(-DeltaDeltaCt)) method with double-dye oligonucleotides (TaqMan probes) is able to detect twofold differences. In order to obtain reliable results, Ct values for an amplicon should be below 25 and the standard deviation below 0.3. Although real-time PCR can deliver exact copy number determinations, the procedure is not fail-safe. Therefore, real-time PCR should to be viewed as complementary to--rather than as a replacement of--other methods such as Southern analysis, but it is particularly useful as a preliminary screening tool for estimating copy numbers of a large number of transformants.

DNA, Plant↗

PubMed2003

Experimental validation of novel and conventional approaches to quantitative real-time PCR data analysis.

Real-time PCR is being used increasingly as the method of choice for mRNA quantification, allowing rapid analysis of gene expression from low quantities of starting template. Despite a wide range of approaches, the same principles underlie all data analysis, with standard approaches broadly classified as either absolute or relative. In this study we use a variety of absolute and relative approaches of data analysis to investigate nocturnal c-fos expression in wild-type and retinally degenerate mice. In addition, we apply a simple algorithm to calculate the amplification efficiency of every sample from its amplification profile. We confirm that nocturnal c-fos expression in the rodent eye originates from the photoreceptor layer, with around a 5-fold reduction in nocturnal c-fos expression in mice lacking rods and cones. Furthermore, we illustrate that differences in the results obtained from absolute and relative approaches are underpinned by differences in the calculated PCR efficiency. By calculating the amplification efficiency from the samples under analysis, comparable results may be obtained without the need for standard curves. We have automated this method to provide a means of streamlining the real-time PCR process, enabling analysis of experimental samples based upon their own reaction kinetics rather than those of artificial standards.

Actins↗

PubMed1998

Impact on the immune system of undetectable plasma HIV-1 RNA for more than 2 years.

OBJECTIVE: To investigate the impact of prolonged HIV suppression on the immune system by analysing the expression of several lymphocyte surface markers in a group of HIV-1-infected patients who maintained undetectable HIV-1 RNA levels for more than 24 months. PATIENTS AND METHODS: The study included a highly selected group of nine HIV-1-infected asymptomatic subjects and seven HIV-1-seronegative controls. The inclusion criteria of HIV-1-infected patients was to have plasma HIV-1 RNA levels below 20 (1.3 log10) copies/ml for at least 24 months while under antiretroviral treatment with nucleoside analogues. The patient population was retrospectively taken from a cohort of 1418 treated subjects. Mean initial absolute CD4+ T-cell count and percentage were 468+/-234 x 10(6)/l (range, 202-935 x 10(6)/l) and 25+/-6% (range, 16-33%), respectively. Plasma HIV-1 RNA quantification was determined using a standard and ultrasensitive reverse transcriptase polymerase chain reaction assay. Median HIV-1 RNA plasma level before antiretroviral treatment was 3.14 log10 copies/ml (range, 1.74-3.73 log10 copies/ml). Two or three-colour immunophenotyping was performed on whole blood and frozen peripheral blood mononuclear cells by flow cytometry. RESULTS: A significant increase was noted in CD4+ lymphocyte counts at the end of the study in HIV-1-positive patients. In addition, the CD4: CD8 ratio rose significantly with respect to baseline, although it remained lower than in the controls. CD45RA+ and CD45RO+ population percentages did not differ between groups. A significant rise in CD45RA+ T cells was observed. Analysis of T-cell activation measuring the expression of human leukocyte antigen-DR and CD25 did not differ between groups. The proportion of CD8+ lymphocytes that were CD28+ was similar in both groups at the end of the follow-up. T-cell receptor Vbeta subfamily analysis showed that an expansion of the T-cell receptor repertoire might occur in these patients. CONCLUSION: Patients who maintain undetectable viral load for prolonged periods of time with antiretroviral therapy may achieve a partial immune restoration of the immune system. Our results suggest that treatment of patients at early stages of HIV infection is warranted.

CD4 Lymphocyte Count↗

PubMedDate not supplied

Comparison of two commercial test kits for quantification of serum carbohydrate-deficient transferrin.

Serum levels of carbohydrate-deficient transferrin (CDT) were measured in subjects of two independent studies using two different commercial kits. The kits measure CDT either as a percentage of total transferrin (AXIS %CDT, AXIS Biochemicals AS, Norway), or as the absolute amount (CDTect, Pharmacia, Sweden). In a population of males (mean age 41 years) consisting of alcoholics, heavy, moderate and non-drinkers, a strong correlation was found between AXIS %CDT and CDTect results (r = 0.92, n = 58, P < 0.001). Sensitivity and specificity in detecting chronic alcoholic drinking of over 60 g/day were 78 and 94% for the AXIS assay, and 83 and 88% for the CDTect assay, respectively. In a population from a birth cohort study, consisting of 21-year-old males and females with less excessive alcohol consumption, the correlation between AXIS %CDT and CDTect CDT was weaker but still statistically significant (r = 0.46, n = 212, P < 0.001). In this population, with specificities > 83% in detecting alcohol consumption levels of > or = 6 drinks per week, the sensitivities were low with both CDT assays (< 43% for > or = 6 drinks per week, and < 44% for > or = 16 drinks per week). These results suggest that (a) both assays are equally effective in detecting chronic drinking over 60 g/day in older alcoholic males, and (b) both assays are similarly ineffective in detecting less excessive regular drinking in young males and females.

Adult↗

PubMed1995

Enhanced expression of GM2/GD2 synthase mRNA in human gastrointestinal cancer.

BACKGROUND: The content of the GM2 ganglioside and the activity of UDP-GalNAc: GM3 beta-1,4N-acetylgalactosaminyltransferase (beta-1,4GalNAcT), which synthesizes GM2, increased in gastric cancer tissues and gastric cancer cell lines as compared with that in normal gastric mucosa. METHODS: Expression of beta-1,4GalNAcT mRNA and a concentration of GM2 in the human gastrointestinal tissues were examined. Beta-1,4GalNAcT mRNA in human surgical specimens, which was not detectable with Northern blotting because of the paucity of absolute amounts expressed, was detected with competitive reverse transcription-polymerase chain reaction (PCR) method using an internal standard cRNA that could be amplified by the same primers as target mRNA in PCR. The quantification of GM2 was examined using immunostaining of thin-layer chromatography. RESULTS: In 10 of 10 gastric carcinomas and 6 of 13 colonic carcinomas, mRNA expression was more enhanced than that in the normal mucosa of each patient. The alteration of GM2 content in carcinoma from normal tissue generally was correlated to the change in the expression of beta-1,4GalNAcT mRNA with a few exceptions. One gastric cancer sample had a higher level of mRNA with a lower GM2 content than the corresponding normal tissue, and two colonic carcinoma tissue specimens had a lower level of mRNA with a higher GM2 content. CONCLUSIONS: These results suggest that expression of the beta-1,4GalNAcT gene is a key step in the molecular mechanisms underlying the regulation of cancer-associated GM2 expression in the stomach and the colon.

Adenocarcinoma↗

PubMed1994

Accuracy of quantification of coronary arteriograms with hand-held calipers. A validation study.

This study compares the use of hand-held calipers to automated quantitative coronary arteriography in assessing coronary artery stenosis severity. 48 stenoses in the visually estimated range of 30-90% were evaluated in two orthogonal projections. Absolute stenosis dimensions and calculated transstenotic pressure gradient (PG) were compared. Hand-held calipers were of limited value in assessing absolute stenosis dimensions (SD = 0.32 mm, r = 0.80). However, the correlation found in the assessment of percent diameter stenosis (SD = 7.7%, r = 0.83) and PG (SD = 1.3 mm Hg, r = 0.83) was acceptable. In particular, the allocation into hemodynamically significant (n = 30) and nonsignificant (n = 18) stenoses, according to the criterion of a PG > 30 mm Hg, was accomplished identically by both methods.

Algorithms↗