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Biomedical subjects

B S Bull

Publications and source records attributed to B S Bull.

At least 19 recordsLinked to original sources
PubMed2003

International Council for Standardization in Haematology (ICSH) recommendations for "surrogate reference" method for the packed cell volume.

The spun packed cell volume (PCV, hematocrit) is a key measurement on which are based hematology instrument calibration, reference range determination, and assignment of values to calibrators/controls. In 2001, the International Council for Standardization in Haematology (ICSH) recommended a Reference PCV method, which is fully traceable to the ICSH reference hemoglobin method. Because of its complexity, however, this method is impractical for occasional use in routine laboratories and is therefore intended primarily for use by manufacturers of capillary microhematocrit tubes, liquid calibrators, and multichannel analyzers. In response to the need for a simpler method--accessible to all routine laboratories--the ICSH offers this "Surrogate Reference" PCV procedure. It is traceable to the original ICSH Reference PCV method and is based on spun PCVs obtained using borosilicate capillary tubes with an already-known relationship to this reference procedure. This ICSH "Surrogate Reference" PCV method is substantially simpler, thus putting it within the reach of most routine hematology laboratories.

Blood Specimen Collection↗
PubMed1998

Guidelines for organisation and management of external quality assessment using proficiency testing. Expert Panel on Cytometry of the International Council for Standardization in Haematology.

This document is intended to assist towards the WHO objective that external quality assessment (EQA) schemes be established at national and/or regional levels world-wide. Quality assurance is defined as all steps taken by the director of a laboratory to ensure reliability of laboratory results and to increase accuracy, reproducibility and between-laboratory comparability. This includes the use of internal quality control procedures and participation in external quality assessment. Internal quality control provides the means for evaluation of analytic test results at the time of testing in order to decide whether they are reliable enough to be released to the requesting clinicians. EQA, on the other hand, refers to a system of retrospective and objective comparison of results from different laboratories by means of proficiency testing (PT) organised by an external agency. The main purpose is to establish between-laboratory and between-method (including between-instrument) comparability, and agreement with a reference standard where one exists. Internal quality control and EQA complement each other and must never be considered as alternatives.

Animals↗
PubMed1994

Hypothesis: disseminated intravascular inflammation as the inflammatory counterpart to disseminated intravascular coagulation.

We have identified a leukocyte activation syndrome that is occasionally associated with the transfusion of intraoperatively recovered erythrocytes. This syndrome appears to result from intravascular damage caused by leukocytes activated during the erythrocyte salvage process. We hypothesize that this syndrome is part of a larger disease grouping: disseminated intravascular inflammation (DII). DII is the analog of the coagulation disorder disseminated intravascular coagulation. In disseminated intravascular coagulation, the organ damage results from uncontrolled activation of the clotting pathway; in DII the damage is caused by leukocytes that have become activated by direct contact with bacteria or in rare instances--such as erythrocyte salvage--in the absence of bacteria and bacterial products. Recent studies of the hazards associated with intraoperative blood salvage indicate that activation of leukocytes can be achieved by exposure to activated platelets alone. If such activated leukocytes are reinfused along with the washed erythrocytes, widespread organ damage may result. The lung is the organ most severely affected by activated leukocytes. Adult respiratory distress syndrome is one outcome. It is likely that DII is a presently unrecognized pathophysiological process that complicates a variety of primary disease states and increases their lethality.

Adolescent↗
PubMed1994

Population variability in the effect of aspirin on platelet function. Implications for clinical trials and therapy.

Little or nothing is known about how the inhibitory effect of aspirin on platelets distributes in the general population. We describe a simple whole-blood assay for the extent of aspirin-induced inhibition of platelet aggregation and its application to 31 aspirin-treated subjects. Platelet inhibition to two or more 325-mg aspirin tablets was measured using a newly developed method in 31 healthy, young adults. These subjects showed a wide range of variation in their response to aspirin, which in subsequent studies was found to be stable over time. The effect persisted even when the steps of gut absorption and liver metabolism were bypassed. We conclude that the response of platelets to aspirin varies to the extent that a significant proportion of the population may be nonresponsive and that this variability may be intrinsic to platelets and/or their blood environment.

Adolescent↗
PubMed1993

Effect of patient age on tests of the acute-phase response.

Tests of the acute-phase response are used to screen for occult disease in the elderly, but there is little consensus as to their diagnostic value because of uncertainty as to the effect of age on reference ranges. We have therefore measured, as a function of age, the blood concentration of acute-phase proteins (C-reactive protein, alpha 1-acid glycoprotein, fibrinogen, albumin, and globulin) in parallel with three screening tests of the acute-phase response (erythrocyte sedimentation rate, plasma viscosity, and zeta sedimentation ratio). The study included 164 healthy individuals (age range, 25 to 84 years) plus 91 elderly ill but ambulant patients (age range, 65 to 84 years) from a family practitioner screening clinic. Reference ranges for the erythrocyte sedimentation rate, plasma viscosity, and zeta sedimentation ratio rose with age, with the erythrocyte sedimentation rate showing a particularly wide reference range. Healthy individuals aged 75 to 84 years, compared with those aged 65 to 74 years, showed a trend to a lower reference range for all three screening tests that may have reflected survival of the fittest individuals to the higher decade. Precise reference ranges are therefore required in the elderly; when these were used, the three screening tests showed a significant difference between elderly well and ill individuals.

Acute-Phase Proteins↗
PubMed1993

Calibration and validation for erythrocyte sedimentation tests. Role of the International Committee on Standardization in Hematology reference procedure.

The Westergren erythrocyte sedimentation rate (ESR) has been used for many years without any formal procedure for method validation or for quality assurance. In 1988, the International Committee on Standardization in Hematology (ICSH) (Leuven, Belgium) described an ESR validation procedure as well as a method for producing ESR reference material (ICSH reference method) in the laboratory where it is to be used. The ICSH proposal was tested in our laboratory during a consecutive period of 36 months. In this article, a new mathematical relationship between the ICSH recommendation and the Westergren method is developed, which can be easily used for method validation and/or quality assurance. A table has been made that establishes 95% action limits for Westergren ESRs based on ICSH reference ESRs from 5 through 105 mm/h. The table, derived from 36 months of data, has been tested against two new data sets and used to validate two commercial ESR methods. Analysis of outliers was performed with special attention to the mixing of whole blood samples with sodium citrate necessary for the Westergren ESR. This mixing process is best performed in a large-bore test tube as opposed to the use of the Westergren ESR tube as an aliquoting and mixing device.

Blood Sedimentation↗
PubMed1992

Passive blood/contrast agent exchange in angiographic catheters and its effects on platelets.

A static column of contrast agent or saline in an angiographic catheter will passively exchange with blood during angiography. The authors investigated the time course of this exchange in 5.5- and 7-F polyethylene catheters inclined at various angles. Passive blood exchange occurred 2 cm into the catheters within 7-15 seconds at most catheter tip angles, except for those catheters oriented so that their tips were nearly horizontal. In a separate series of experiments, the effect of contrast agent on platelet function and blood clotting was analyzed. The agent was sufficiently diluted in blood so as to simulate an angiographic procedure. The studies were performed in 60 cylindrical polyethylene containers with both unheparinized and heparinized blood. Use of an ionic contrast agent, more than a nonionic agent, lengthened the time for platelet aggregation (mean increases for ionic vs nonionic agents were 46.4 and 37.1 seconds, for unheparinized and heparinized blood, respectively), platelet adhesion to polyethylene surfaces (mean increases, 46.0 and 64.2 seconds), and platelet-stimulated coagulation (mean increases, 38.5 and 43.9 seconds). Conventional, intermittent flushing with saline or filling the catheter with contrast agent may be insufficient to prevent blood from rapidly back-filling the catheter tips. Contrast agents (ionic more than nonionic) distributed in the patient's blood volume inhibit platelet coating of catheter lumens and/or blood clotting under such circumstances.

Angiography↗
PubMed1992

A method for the independent assessment of the accuracy of hematology whole-blood calibrators.

An independent assessment of the accuracy with which a large manufacturer assigned values to hematologic calibrators was performed. Data were collected from 1,767 hospitals and clinics distributed over North America. Statistical analysis of the mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration of these patient data confirmed the accuracy of the values for hemoglobin, erythrocyte count, hematocrit, and erythrocyte indices for the calibrators manufactured and released during a 9-month period. This approach proved both workable and effective in detecting inaccuracies of less than 1%. Few technologist-users have the time or the equipment to verify independently the accuracy of hematologic calibrators. The manufacturers should perform ongoing, independent assessments of the accuracy of their products. The statistical analysis of patient data provides manufacturers with a suitable method.

Calibration↗
PubMed1991

Heparin supplementation of nonionic contrast agents.

Diatrizoate has been widely used clinically for many years and has been effective in inhibiting clot formation in catheters and syringes. The authors attempted to determine the amount of heparin required to raise the anticoagulant potency of ioversol, iohexol, or iopamidol to that of diatrizoate. The anticoagulant potency of ioxaglate was also examined. One hundred eighty glass syringes containing unmodified diatrizoate, unmodified ioxaglate, or a nonionic contrast agent mixed with incremental amounts of heparin were contaminated with venous blood from 10 healthy volunteers. The syringes were then repeatedly disturbed to simulate the frequent handling that occurs during an angiographic procedure. The weights of the clots in the syringes at 30 minutes were plotted against heparin levels and indicated that, for the average sample studied, the "diatrizoate-equivalent" heparin level for ioversol, iohexol, or iopamidol was less than 1.5 U (USP) of heparin per milliliter. An additional margin of anticoagulation is probably desirable. The 97.5 percentile of the distribution of the diatrizoate equivalents in the population was estimated to require a heparin dose of 3.5 U/mL.

Anticoagulants↗
PubMed1990

Thrombin generation in nonclottable mixtures of blood and nonionic contrast agents.

The four newly introduced contrast agents--iopamidol, iohexol, ioversol, and ioxaglate--are of much lower osmolality than conventional agents, and claims have been made that they are substantially safer. A chromogenic assay for thrombin was applied to 1:1 (50%), 2:1 (67%), and 4:1 (80%) contrast agent-whole blood mixtures, each containing enough contrast agent to render them unclottable. Thrombin generation occurred in the nonionic-whole blood mixtures and increased with time. No thrombin could be detected in any ioxaglate-whole blood mixtures. The authors conclude that this difference presents a novel hazard in that iopamidol, iohexol, and ioversol permit thrombin generation to occur while inhibiting the fibrin polymerization step of blood coagulation, thus posing a significant, albeit theoretical, threat to patient well-being.

Adult↗
PubMed1990

A proposed reference haematocrit derived from multiple MCHC determinations via haemoglobin measurements.

An easily performed reference haematocrit would be useful in quality control, in the preparation of whole-blood calibrators and in the evaluation of automated, whole-blood analysers. Available techniques are complex, time-consuming and require radiolabelled reagents that are difficult to obtain. They have largely been directed towards correction of 'trapped plasma' errors. Other errors which affect haematocrit measurement but which have not yet been addressed include those due to white-cell contamination, those due to defects in tube plugging and those resulting from red-cell dehydration. We propose a simple, rapid and reliable reference haematocrit procedure which relies on the fact that haematocrit equals haemoglobin/MCHC and that MCHC determinations via haemoglobin analyses can be performed accurately on as little as 6 microliters of packed red cells (CV less than 0.5%). Selection of the cells to be analysed from the mid portion of a packed red-cell column eliminates interference from white-cell contamination/red-cell dehydration. The absence of trapped plasma in this portion of the red cell column after centrifugation for 4 min at 10,000 r.c.f. can be documented by a second cycle of centrifugation.

Erythrocyte Indices↗
PubMed1990

The salvaged blood syndrome: a sequel to mechanochemical activation of platelets and leukocytes?

Disseminated intravascular coagulopathy (DIC) and/or increased vascular permeability in the lungs (ARDS) or systemic circulation (anasarca) has been seen in an occasional patient following the administration of washed autologous red cells. We have found that platelets and leukocytes, activated by the process of salvage, can contaminate such red cell suspensions. Apparently, activation begins with the mechanical deposition of platelets on the centrifuge bowl wall during the cell-concentration phase of blood salvage if there has been substantial prior dilution of the salvaged blood with saline. Electron microscopy of the deposit reveals activated, degranulated platelets lining the inner surface of the bowl. There is a preferential "homing" of specific leukocyte types to local regions of the deposit. On the basis of morphological evidence, we hypothesize that these mechanically activated platelets release leukoattractant substances, including arachidonate-rich phospholipids which trigger the oxidative burst enzymatic pathway in exposed phagocytic cells. These cells, when reinfused, cause increased vascular permeability. This presents clinically as ARDS or anasarca, whereas DIC results from reinfused platelet phospholipid plus accompanying cellular debris.

Aged↗
PubMed1989

Efficacy of tests used to monitor rheumatoid arthritis.

The relative efficacy of clinical and laboratory tests used to monitor disease activity in rheumatoid arthritis was determined by consensus analysis in a study of 21 patients treated for 6 months. Erythrocyte sedimentation rate (ESR), which is influenced by the anaemia of chronic disease and by variation in the blood concentration of acute-phase proteins, was the most effective single test. ESR was a better guide to disease severity than measurement of plasma viscosity, serum C-reactive protein, and serum orosomucoid--tests that reflect the blood concentration of acute-phase proteins only. Clinical tests performed poorly unless combined with laboratory data in a numerical index. Consensus analysis can be used to assess the efficacy of clinical and laboratory tests and to identify redundant tests.

Adult↗
PubMed1989

Red cell membrane crenation: a macromodel of the echinocyte I.

A physical macromodel of the erythrocyte membrane was constructed to investigate the effect of intrinsic membrane precurvature on a unique non-isotropic, composite material that dissipated shear energy but stored bending energy. The intrinsic precurvature of the material could be modified from strong positive precurvature through neutral to strong negative precurvature. A spherical shell constructed of the negatively precurved variant of this non-isotropic material spontaneously assumed the characteristic shape of the echinocyte I.

Erythrocyte Membrane↗
PubMed1989

Enhancing the safety of intraoperative RBC salvage.

Devices for intraoperative blood salvage remove plasma and, in theory, all of the cellular elements of blood except for rbcs. We have previously shown that complete white cell and platelet removal does not always occur and that the retained platelet-leukocyte deposit is potentially harmful (2). In this study we investigated the hydraulic conditions in the centrifuge bowl that allow activated platelets and leukocytes to adhere, the histology of the resulting cellular deposit, and the effects of reinfusing a saline extract of the deposit. Earlier work had suggested that the addition of calcium, of partially clotted blood, and of excessive saline should be avoided during intraoperative rbc salvage (2). The present observations explain, in part, why such measures would be expected to be beneficial.

Animals↗
PubMed1989

Does tube diameter influence the packed cell volume?

The relationship between observed PCV and PCV tube diameter was investigated and it was found that the PCV decreased as the PCV tube diameter decreased. An equation which predicted the PCV as a function of the PCV tube radius was derived from the hypothesis that red blood cells in contact with the glass wall were partially dehydrated during high-speed centrifugation and that the amount of dehydration was related to the type of glass. PCV determinations were made on five patient blood samples using eight tubes of varying diameters, four made of soda-lime glass and four made of borosilicate glass. The predictions of the equation correlated well with the experimental results. Twice as much dehydration was observed in the soda-lime tubes as in the borosilicate, thus confirming both parts of the hypothesis. Independent confirmation of the hypothesis was obtained by counting the number of spheroechinocytes in the bottom of the PCV tube. There were twice as many in the soda-lime as in the borosilicate glass tubes. We conclude that dehydration errors must be considered along with trapped plasma errors when attempting to perform a reference PCV determination.

Centrifugation↗