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Biomedical subjects

B Wenz

Publications and source records attributed to B Wenz.

At least 37 records · Page 2Linked to original sources
PubMed1991

Improvement in transfusion safety using a new blood unit and patient identification system as part of safe transfusion practice.

A new patient and blood unit identification system designed to confirm the identity of crossmatched blood products and that of the intended recipient was evaluated. Six hundred seventy-two red cell concentrates were transfused to 312 patients. Participating hospital personnel and patients were interviewed regarding the use and benefit of this unique system, which incorporates a "lock-box" approach to the identification process. The product and procedure were accepted unanimously and enthusiastically, and three potential mistransfusions were avoided by use of the system during the limited period of observation. This type of approach to the identification process affords greater security than conventional practices and minimally burdens staff.

Blood Transfusion↗
PubMed1991

Rapid removal of heparin from plasma by affinity filtration.

Coagulation test abnormalities caused by the presence of heparin are not uncommon and frequently result in additional laboratory investigation and unwarranted therapy. Methods to neutralize the effect of heparin include the addition of polyanions, enzymes, or resins to the clinical samples. These techniques are time consuming and cumbersome and produce inconsistent results. As an alternative, use of a positively charged porous filtration medium to remove heparin from the sample is described. The filtration procedure requires less than one minute and provides a consistent and total removal of heparin at plasma concentrations in excess of therapeutic levels. Chromogenic substrate analysis for residual heparin activity confirms total removal of the drug at levels greater than one unit/mL of plasma. In clinical trials, filtration normalized the activated partial thromboplastin time (APTT) of all patient specimens containing heparin (n = 41). Filtration did not shorten the coagulation assay times of patients receiving warfarin (n = 36) or of those with a variety of acquired coagulopathies (n = 14). The level of coagulation factors adsorbed to the filter medium compares favorably to that adsorbed by other commercially available heparin-binding resins. Routine use of the filter in the clinical laboratory allows for the rapid and definitive identification of heparin in specimens with prolonged coagulation times and provides clinically meaningful data.

Blood Coagulation Factors↗
PubMed1990

Removal of white cells from red cells by transfusion through a new filter.

The effectiveness of a new filter (RC100) for the preparation of white cell-depleted red cells (RBCs) at the bedside was evaluated in vitro and in vivo using three RBC products: standard RBC concentrate (CPDA units), RBCs suspended in saline-adenine-glucose-mannitol additive solution after the removal of plasma (SAGM units), and RBCs suspended in SAGM after the removal of plasma and buffy coat (SAGM-BC units). Median RBC recovery was at least 92 percent when 2 units were administered through one filter; median values for residual white cells and platelets were less than or equal to 20 x 10(6) and less than or equal to 2.5 x 10(9) per 2 units, respectively. The in vivo study was carried out in 80 multiply transfused patients with thalassemia, 35 of whom had experienced frequent nonhemolytic transfusion reactions when given standard or buffy coat-free RBCs. During the 6-month study, each patient was given two transfusions of each type of RBC product One febrile nonhemolytic transfusion reaction occurred in each of two patients receiving SAGM-BC units, but in no other case. If the flow rate is not reduced, the median transfusion time is 35 minutes per CPDA unit and 15 minutes per SAGM and SAGM-BC unit. It is concluded that the transfusion of RBCs through the RC100 is a simple and effective procedure to administer white cell-depleted RBCs prepared at the bedside.

Blood Transfusion↗
PubMed1990

Evaluation of the polyethylene glycol-potentiated indirect antiglobulin test.

Results of the indirect antiglobulin test (IAT) potentiated by the addition of polyethylene glycol (PEG) were compared with those of the IAT performed with bovine serum albumin (BSA). This retrospective study, which encompasses 3 years, confirms that use of PEG-IAT increases the rate of detection of clinically significant red cell (RBC) antibodies, decreases the detection of insignificant antibodies, reduces the need to use other serologic enhancement techniques (such as enzyme modification of RBCs), and has a positive impact on the laboratory's workload. These advantages are provided with no diminution in the quality of service provided by the blood bank.

Antibodies↗
PubMed1990

Clinical utility of serum tests for iron deficiency in hospitalized patients.

Serum iron and ferritin measurements lack the requisite sensitivity and/or specificity to accurately diagnose iron deficiency. To determine their utility in hospitalized patients, the authors compared the results of these tests with the presence of stainable iron in bone marrow aspirates of 301 patients. Forty (13.3%) had absent marrow iron. The serum diagnosis of iron deficiency was accepted on the basis of the following: iron less than 11 mumol/L, total iron-binding capacity (TIBC) greater than 45 mumol/L, transferrin saturation (%Sat) less than 0.20, and ferritin less than 13 micrograms/L for females and less than 25 micrograms/L for males. Using these criteria, iron deficiency was correctly diagnosed by serum iron in 41%, TIBC in 84%, %Sat in 50%, and ferritin in 90% of the patients. The serum ferritin is clearly the only useful serum test for diagnosing iron deficiency in hospitalized patients but is limited by a low sensitivity. The bone marrow examination is the most sensitive test for diagnosing iron deficiency in hospitalized patients.

Anemia, Hypochromic↗
PubMed1989

Eliminating unnecessary urine microscopy. Results and performance characteristics of an algorithm based on chemical reagent strip testing.

The ability of a urinalysis reagent strip to predict the presence of formed elements in the sediment was evaluated. The sensitivity of individual biochemical analytes varies from 0.51 to 0.85; however, the combined sensitivity of positive reactions for either protein, nitrite, leukocyte esterase, and/or hemoglobin is 0.95. Leukocyte esterase activity becomes detectable at a concentration of 15 white blood cells per high-power field (WBCs/HPF). Proteinuria is nonspecifically related to pyuria and detects a minimum concentration of 6 WBCs/HPF, and the hemoglobin reaction detects 6 red blood cells/HPF. Most false negative reactions are associated with bacteriuria. A positive chemical reagent strip test can be safely and effectively used as a prerequisite for routine urine microscopic examination.

Adolescent↗
PubMed1987

Studies on the mechanism of decreased NMR-measured free magnesium in stored erythrocytes.

31P-NMR spectra have been recorded on erythrocytes stored at 4 degrees C in various preservation media. Storage was always associated with an upfield shift of the inorganic phosphate (Pi) resonance and a pronounced upfield shift of the ATP beta resonance, indicating decreased intracellular pH (pHi) and decreased intracellular free magnesium ([Mg2+]i). The decreased [Mg2+]i occurred in preservation media not containing citrate and even in media supplemented with Mg2+. It could not be attributed to the changes in pHi, Na+, K+, lactate, Pi or 2,3-diphosphoglycerate, that occur with storage. The decrease in [Mg2+]i was largely reversed when stored cells were incubated for 1 h at 37 degrees C in fresh plasma. Stored cells were found to contain significant amounts of inorganic pyrophosphate, up to about 200 mumol per liter cell water. Being a tight binder of Mg2+, pyrophosphate could account for some of the observed decrease in [Mg2+]i. Additional mechanisms may involve precipitation of some other Mg2+ complex during cold storage or enhancement of Mg2+ binding to membrane components.

Blood Preservation↗
PubMed1987

A new assay for quantifying human reticulocytes.

The authors describe a new method for quantitative reticulocyte analysis. The assay uses a conventional clinical blood cell analyzer to size a patient's red blood cell neocyte population, which relates to the reticulocyte fraction in a linear fashion. Blood is layered atop Stractan (arabino-galactan polysaccharide) and centrifuged for 30 minutes at 1,500 X g. This density medium fractionation process enriches the Stractan layer with neocytes by up to 20-fold as determined by G6PD enzyme analysis. The mean corpuscular volume (MCV) of the red blood cells partitioning in the Stractan layer and the starting whole blood is then measured. The ratio of the two MCV measurements is then related to the reticulocyte percentage by a standard curve. In 93 patients, the derived MCV ratio was linearly correlated with manual reticulocyte counts (r = 0.96/slope = 0.99). Agreement of results obtained for single samples was within 0.2%. The assay's within-run and between-run precision is excellent (coefficient of variation less than 1%). The assay provides data on the percentage of reticulocytes in whole blood with an accuracy and precision that is at least 20 times greater than conventional microscopic technics.

Adult↗
PubMed1987

The H*1 hematology analyzer. Its performance characteristics and value in the diagnosis of infectious disease.

The performance characteristics and the value of data provided by the H*1 Automated Blood Cell Analyzer in the diagnosis of infectious disease are assessed. Data produced by the machine are precise over a wide range of complete blood cell counts and differential white blood cell (WBC) parameters. It is capable of accurately quantifying WBCs greater than 4000/mm3 (4 X 10(9)/L); red blood cells (RBCs), greater than 2.5 X 10(6)/mm3 (2.5 X 10(12)/L); and platelets greater than 1 X 10(3)/mm3 (1 X 10(9)/L). There is good agreement between the neutrophils and lymphocytes quantified by the standard microscopic count and the automated system; however, cells that are generally present in low incidence, namely, monocytes, basophils, and eosinophils, are less well correlated. The microscopic band cell count provides the greatest test efficiency in the diagnosis of infection. None of the unique parameters generated by the H*1 differential analyzer proved to have neither a test efficiency nor a diagnostic index greater than that of the absolute WBC count in the diagnosis of infection. The "left shift" in the leukocyte differential count as detected by the H*1 relates poorly to the presence of band neutrophils in the specimen. It is concluded that the state-of-the-art automated leukocyte differential count can dramatically reduce workload, but offers no advantage over the traditional differential WBC count in the diagnosis of infectious disease. Its potential value in the diagnosis of other conditions, particularly hematologic diseases, and in the sequential monitoring of infections in individual patients were not addressed by the present study.

Evaluation Studies as Topic↗
PubMed1987

Survival rates and properties of sickle cell anemia red cells treated with nitrogen mustard.

A machine for the extracorporeal delivery of covalent anti-sickling agents has been described by Babb and coworkers and this therapeutic modality has been found feasible by others. We report here, further evaluation of nitrogen mustard (HN2), for possible use in the extracorporeal therapy of sickle cell anemia. Heparinized aliquots of whole blood from three patients with sickle cell disease were treated extra-corporeally with HN2 (0.65 mg/ml); the excess HN2 was neutralized with thiosulfate, and the blood was returned to the donor after labelling with 51Cr. HN2 produced an average 51Cr T1/2 which was 160% of control values. Fractionation of labelled red cells into different densities (ages) revealed that the main effect of HN2 was on the younger cell population which was characterized by a 51Cr T1/2 increase of 300% over the untreated blood. Further, "in vitro" studies were conducted to establish the effects on the SS red cells that could be expected from the treatment with HN2 at the concentrations used. Solubility determination (Csat) of deoxy hemoglobin S gels demonstrated that HN2 markedly inhibited the polymerization of HbS, was significantly more effective than potassium cyanate, and is among the most potent anti-sickling agents thus far reported. The viscosity of deoxygenated sickle red cells in a cone plate viscometer was markedly reduced by HN2, and hemodynamic studies using the microvasculature of an isolated rat mesoappendix demonstrated a reduction of peripheral resistance and an increase in flow rate when deoxygenated sickle cells pre-treated with HN2 were tested. At the highest concentration of HN2 (2 mg/ml), the peripheral resistance and the flow rates of deoxygenated cells attained levels found with oxygenated sickle blood. O2 affinity was partially corrected in the HN2 treated HbSS red cells. -SH reactivity of the red cell membrane was not affected by HN2. Among the added advantages of HN2 for extra-corporeal use is its rapid reaction rate, the lack of significant change of the O2 equilibrium at the concentration tested and the fact that the unreacted compound can be readily detected and neutralized. For these reasons HN2 is well suited for extra-corporeal treatment of sickle cell anemia for those patients with a severe form of the disease.

Anemia, Sickle Cell↗
PubMed1986

Volumetric erythrocyte macrocytosis induced by hydroxyurea.

An atypical form of macrocytosis termed volumetric macrocytosis is described. In contrast to the macrocyte associated with megaloblastic anemia and the pseudomacrocyte caused by viscoelastic defects, the volumetric macrocyte is characterized by an increased mean corpuscular volume and a normal cell diameter. The volumetric macrocyte proves to be thicker than the normocytic red blood cell. This large erythrocyte is overhydrated and contains an increased quantity of hemoglobin. The cell has many characteristics in common with the red blood cells of neonates. Volumetric macrocytosis accompanies sustained hydroxyurea therapy and may represent a drug-induced dyserythropoiesis.

Blood Viscosity↗
PubMed1986

The clinical utility of the leukocyte differential in emergency medicine.

Leukocyte differentials from 468 emergency room patients were assessed for clinical value by determining their associations with diagnosis, disposition, therapy, and prognosis. The test efficiency of an elevated band count as an indicator of infectious or inflammatory disease is 86%. However, all but 2 of the 99 patients in this disease category had additional indicators of inflammation, including elevated temperatures and/or white blood cell (WBC) counts. The band count lacks utility beyond this limited function. The remaining parameters of the differential count correlate poorly with all diagnostic subsets. The use of antibiotics correlates well with fever and WBC count (r = 0.95) and less well with the differential count, bands (r = 0.85), and granulocytes (r = 0.5). Elevations in the total WBC count and the band count are each associated with an increased likelihood of hospitalization. However, in the absence of leukocytosis, an elevated band count was instrumental in suggesting admission for only one patient. The patient's outcome correlates poorly with the total WBC and differential count. It is concluded that most leukocyte differentials performed for emergency room patients provide information that is no more clinically significant than that obtained from the medical history, physical examination, and absolute leukocyte count.

Blood Cell Count↗
PubMed1986

Leukocyte-poor blood.

The conventional techniques used to prepare leukocyte-poor red cell concentrates are described. These techniques conveniently group by their primary processing modalities which are centrifugation, freeze thawing, cell washing, and filtration. Each of these procedures has unique logistical requirements. The complexity, need of dedicated capital equipment, and stringent quality assurance requirements make the use of some of these techniques impractical for the hospital blood bank laboratory. The majority of patients benefit from the receipt of leukocyte-poor blood products prepared by an "in-line" microaggregate filtration technique. Those patients with symptoms which prove to be refractory to microaggregate-filtered blood products and those who require highly purified red cell concentrates to forestall sensitization to transplantation antigens should receive blood prepared either by the cryopreservation/deglycerolization technique or by cotton wool filtration.

Blood Cells↗
PubMed1985

False positive immunometric assays caused by anti-immunoglobulin antibodies: a case report.

A serological phenomenon causing aberrant results with monoclonal immunoenzymetric assays (IEMA's) is reported. Two different commercial IEMA kits detected low levels of choriogonadotropin (hCG) in the serum of a non-pregnant woman. These assays detected between 32 and 55 IU/l of serum hCG over a 3-wk period; however, an RIA for beta-subunit and two monoclonal immunoradiometric assays (IRMA's) detected no hCG (less than 5 IU/l). An IEMA measurement of creatine kinase MB isozyme was also elevated. Antisera to either human immunoglobulin or specifically to human IgM, added to the serum prior to assay, substantially decreased these IEMA reactions. Addition of either mouse serum or purified mouse IgG totally abolished them. It is concluded that these spurious reactions were most likely caused by an IgM antibody which binds to native and enzyme-labelled mouse IgG, but not to iodinated IgG.

Adult↗