AHG must be added immediately after washing to prevent the possibility of a false negative; a false negative can occur in this situation because previously bound globulins may dissociate from red cells, leaving insufficient antibody coating on the red cells to produce a reaction, or free antibody may directly neutralize antiglobulin reagent.
Blood bank
A false-negative reaction while performing the DAT technique may be the result of:
Cryoglobulin testing can be used to:
The lactophenol blue mount reveals tiny, ovoid microconidia, arranged in a daisy-head pattern at the tip of a straight conidiophore. This appearance is characteristic of the mold form of Sporothrix schenckii. By moving the focus up and down in a microscopic preparation, delicate hair-like attachments may be observed for each conidium.
The mold form of Coccidioides immitis produces delicate hyphae that break up into arthroconidia separated by empty cells, giving an alternatively staining appearance.
The mold form of Blastomyces dermatitidis is characterized by the production of single, smooth microconidia, each borne on a single, thin conidiophore ("lollipops").
The mold form of Histoplasma capsulatum is recognized by the production of large, echinulate macroconidia, appearing as a prickly surface.
The ovoid microconidia arranged in a daisy-head pattern at the tip of a a straight conidiophore, observed in the photomicrograph on the right, is characteristic of which of the following dimorphic molds?
A negative glucose oxidase test and a positive test for reducing sugars in urine indicates the presence of a non-glucose reducing sugar such as galactose, fructose, glyceraldehyde, etc. This is the reason that certain patient populations require additional confirmatory sugar testing on their urine samples.
A negative glucose oxidase test and a positive test for reducing sugars in urine indicates:
Hives and rash usually indicate an allergic reaction. Hematuria is due to a variety of causes. Fever and chills usually indicate a febrile reaction. Positive DAT due to conditions other than sensitization to red cell alloantigens is not uncommon. Therefore a positive DAT in the posttransfusion specimen with a negative DAT in the pretransfusion specimen is more likely to indicate alloimmunization.
The most definite indication that a patient has been sensitized to a specific red cell antigen is:
If a drug is given at intervals that are the same as its half-life, it will take about 5 half-lives to reach steady state.
If a drug is given at intervals that are the same as its half-life, approximately how long will it take the drug to reach steady state?
The dematiaceous molds can be broadly separated into two major groups: the agents of chromomycosis that grow more slowly, maturing only after 7 days or more of incubation, and the more rapidly growing species that most commonly are clinically insignificant commensals or contaminants when recovered from clinical specimens, but in rare situations may cause opportunistic infections called phaeohyphomycosis.
Dematiaceous molds can be broadly separated into two major groups; the agents of chromomycosis and clinically insignificant commensals or contaminants. The agents of chromomycosis grow: more slowly than; more rapidly than; or generally at the same rate as the clinically insignificant commensals or contaminants?
Thin-layer chromatography has the advantage of being able to test for a large number of drugs at the same time.
Thin-layer chromatography is particularly useful as a tool in the identification of:
The deposition of plaques containing cholesterol and lipids on the innermost layer of the walls of large and medium-sized arteries is the defintion of atherosclerosis.
Arteriosclerosis is a more general term that describes a thickening and loss of elasticity of the walls of the arteries (hardening of the arteries). Atherosclerosis is a type of arteriosclerosis but is not synonymous with it.
Atherosclerosis is not the most common outcome for risk marker studies because it can be hard to measure. Infarcts, cardiac procedures, death, and 'events' are more common. Most humans have visible or measureable atherosclerosis by early middle age.
Chemistry
Which of the following is true concerning atherosclerosis?
Lavender stopper tubes can be used for all of the following except:
Hemoglobin F has a high affinity for oxygen. When Hb F is elevated, cells containing Hb S are more oxygenated and do not sickle as readily as they would if Hb F were not present or present in small quantities.
Which hemoglobin, when elevated, acts as a protection against sickling in patients with HbS?
A patient with influenza would be placed in:
A normal hemoglobin molecule consists of a tetramer, of four heme and four globin chains, with a molecular weight of 64,500 daltons. Each of the four units can bind a molecule of oxygen for transport to the body's tissues. In the image shown below, there are four monomers (2 red globin chains and 2 blue globin chains) which form the entire hemoglobin tetramer structure. The green portions represent the 4 heme groups.
A normal hemoglobin molecule is comprised of the following:
Hemoglobin electrophoresis uses an electric field to separate hemoglobin molecules based on differences in net electrical charge. The rate of electrophoretic migration is also dependent on the ionic radius of the molecule, the viscosity of the solution through which it is migrating, the electrical field strength, temperature, and the type of supporting medium used.
Electrophoretic separation of hemoglobin fundamentally relies on:
Immunology
The immunoglobulin molecule is made up of both heavy and light chains - the light chains can be comprised of which of the following:
