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.

The effectiveness of the clinical self-assessment (MHAQ) compared with other clinical and laboratory tests used to monitor the activity of rheumatoid arthritis by consensus analysis.

Disease activity in rheumatoid arthritis (RA) is difficult to measure objectively. Both clinical and laboratory measures were evaluated by the statistical method of consensus analysis. In the literature, laboratory tests as a group have proved more effective; however, studies did not include self-assessment questionnaires. We evaluated the effectiveness of a Modified Health Assessment Questionnaire (MHAQ) relative to other clinical and laboratory tests measuring disease activity in 100 patients with RA. Hemoglobin, hematocrit, mean corpuscular volume, fibrinogen level, Wes-tergren erythrocyte sedimentation rate and C-reactive protein tests, along with tests of morning stiffness, visual analog pain scale, Ritchie index, total joint count, and MHAQ, were evaluated simultaneously. The erythrocyte sedimentation rate was confirmed as a highly effective test to follow disease activity. The MHAQ was the best clinical test; in the methotrexate-treated subgroup it ranked as highly as the most effective laboratory assays. MHAQ is a more effective tool than many laboratory tests currently ordered for monitoring RA disease activity and should be a part of the record of each visit of an arthritis patient.

Approximate standard errors and confidence intervals for indices of positive and negative agreement.

Indices of positive and negative agreement for observer reliability studies, in which neither observer can be regarded as the standard, have been proposed. In this article, it is demonstrated by means of an example and a small simulation study that a recently published method for constructing confidence intervals for these indices leads to intervals that are too wide. Appropriate asymptotic (i.e., large sample) variance estimates and confidence intervals for the positive and negative agreement indices are presented and compared with bootstrap confidence intervals. We also discuss an alternative method of interval estimation motivated from a Bayesian viewpoint. The asymptotic intervals performed adequately for sample sizes of 200 or more. For smaller samples, alternative confidence intervals such as bootstrap intervals or Bayesian intervals should be considered.

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.

Factors influencing the activation of platelets by nonionic contrast medium.

PURPOSE: To determine why nonionic, low-osmolality contrast media (LOCM) at high concentrations (> 30%) induce almost immediate platelet activation and to explore preventive measures. MATERIALS AND METHODS: Nonionic LOCM, when added to blood, activates platelets, raises the osmolality, and lowers the ionic strength. To clarify the mechanisms involved, platelet activation was studied in sodium chloride-sucrose solutions of varying osmolalities and varying ionic strengths. Several salts and Iloprost were evaluated as potential inhibitors of platelet activation. RESULTS: Platelets are activated by both osmolality and ionic strength changes. The salts most inhibitory to platelet activation were magnesium sulfate and sodium citrate. Iloprost lowered platelet activation to control levels at 4.3 ng/mL of nonionic LOCM and completely eliminated it at 8.6 ng/mL. CONCLUSION: Three-quarters of nonionic LOCM-induced platelet activation appeared to be due to increased osmolality-the remainder to the decrease in ionic strength. Magnesium sulfate and Iloprost are potent inhibitors of this type of platelet activation.

An analysis of platelet activation and aggregation produced by three classes of contrast media.

PURPOSE: To evaluate the platelet activation and aggregation produced by ionic high-osmolality contrast media (HOCM) and both ionic and nonionic low-osmolality contrast media (LOCM). MATERIALS AND METHODS: After each agent was mixed with heparinized blood, sequential platelet counts were used to monitor platelet aggregation, and flow cytometry was used to monitor both aggregation and activation. Aggregation was measured with CD41a-FITC (specific for glycoprotein IIb-IIIa) and activation was measured with CD62-PE (specific for P-selectin). RESULTS: High concentrations of the nonionic LOCM (> 31% by volume in whole blood) induced more than 90% platelet activation within 2 minutes of exposure to freshly drawn heparinized whole blood. Aggregation followed immediately after activation and was somewhat reversible. High concentrations of the ionic HOCM (> 31%) induced prominent activation, although it occurred at a much slower rate and to a lesser degree than with the nonionic media. There was approximately 70% activation after 45 minutes of exposure. Ionic HOCM inhibited platelet aggregation, however. The ionic LOCM ioxaglate produced minimal or no platelet aggregation or activation. CONCLUSION: There is likely to be an agent-related difference in the risk of platelet activation and aggregation in the catheter lumen and in the immediate environment of the catheter tip, where high concentrations of contrast media are known to exist.

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.

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.

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.

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.

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.

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.

Coping with cancer in remission: stressors and strategies reported by children and adolescents.

Thirty-nine school-age children and adolescents with cancer in remission completed the Children's Stress Inventory (CSI) and a cancer-related stress and coping measure (McCabe & Weisz, 1988) that elicited information about their life stressors and coping strategies. Children identified a range of stressors including general life and cancer-related stress, but general life stressors accounted for the majority of their perceived stress. Children were not consistent across cancer-related and non-cancer-related stressful situations, except for their use of intrapsychic coping strategies. Compared with school-age children, adolescents used more emotion-management and less problem-solving coping strategies when faced with cancer-related stressors, but not when dealing with non-cancer-related stress. When coping with cancer-related stress, females used more emotion-management and less problem-solving strategies than males. Findings have implications for refinement of measures and future research.

A national profile of school-based transition programs for deaf adolescents.

In this study, the transition programs of 326 secondary educational programs for deaf and severely hearing-impaired adolescents were surveyed. Three types of programs were surveyed: residential, mainstream, and "other" (a combination of the first two programs). Sixty-four items depicting desirable transition characteristics were included in the survey, and each item was rated by the programs on a value scale and an implementation scale. Analyses of variance were calculated to determine if there were statistically significant differences among the three program types for each individual survey item on the two rating scales. Based on the data, it appears that the residential schools had higher implementation rates than the mainstream and other programs. All three respondent groups valued the transition items more than they had implemented them (i.e., the value scores were higher than the implementation scores). The data point out the need for researchers and educators to develop and implement more effective transition programs for deaf and severely hearing-impaired students.

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.

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.

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.