Pretest Practice

Which of the following analytes would be increased due to delay in centrifugation? a) AST b) Folate c) Glucose d) Ionized Calcium

a) AST The specimen should not be delayed for more than two hours prior to centrifugation because some of the analyte levels (such as glucose, ionized calcium, bicarbonate, folate, etc.) may be falsely decreased due to cellular consumption or falsely increased (such as potassium, ALT, AST, creatinine, etc.) because they are released over time from cells into serum or plasma.

What is the cause of iron overload in hereditary hemochromatosis? a) Absorption of excessive amounts of iron in the small intestine b) Ingestion of excessive amounts of iron from diet or supplements c) Inability of the body to excrete normal amounts of dietary iron d) Failure of developing red blood cells to incorporate iron into protoporphyrin IX

a) Absorption of excessive amounts of iron in the small intestine Hereditary hemochromatosis is a genetic disorder typically involving a deficiency of hepcidin due to a mutation in the hepcidin gene or genes whose products regulate the expression of hepcidin. These mutations cause increased iron absorption in the small intestine, leading to iron overload.

The ketone component that is measured by the nitroprusside reaction is: a) Acetoacetic acid b) Beta-hydroxybutyric acid c) Acetone d) C-Reactive Protein

a) Acetoacetic acid The ketone component that is measured by the nitroprusside reaction is acetoacetic acid. A positive ketone result is demonstrated as a color change from purple to violet. The intensity of the violet color is proportional to the concentration of ketone bodies in the urine.

Acetest® can be used to test for ketones in: a) Urine b) Urine and serum c) Urine, serum, and whole blood d) Urine, serum, whole blood, and CSF Feedback

c) Urine, serum, and whole blood Acetest® is used as a confirmatory test for ketones and can be used to test urine, serum, and whole blood.

Whipworm infection may be diagnosed in stool specimens by microscopic observation of adult worms or barrel-shaped eggs with polar plugs. Which species is known as the whipworm? a) Trichuris trichiura b) Ascaris lumbricoides c) Necator americanus d) Enterobius vermicularis

a) Trichuris trichiura Whipworm infection, or trichuriasis, is caused by Trichuris trichiura. It is a soil-transmitted parasite. Eggs are brown, barrel-shaped, and have a polar plug at each end. Heavy infections may lead to rectal prolaspe.

All of the following are causes of hypernatremia EXCEPT: a) Excess water loss b) Low aldosterone production c) Decreased water intake d) Increased sodium intake or retention

b) Low aldosterone production Excess water loss, decreased water intake, and increased sodium intake and retention are all causes of high levels of sodium (hypernatremia). Hypernatremia is seen in diabetes insipidus due to excess water loss and in hyperaldosteronism (increased retention of sodium).Aldosterone is a hormone produced by the adrenal cortex. Aldosterone stimulates sodium reabsorption in the distal tubules of the nephron. Low levels of aldosterone would not promote increased levels of sodium.

Which of the following tests require a 72 hour stool (fecal) collection? a) Occult blood b) Quantitative fecal fat c) Ova and Parasite (O&P) d) Stool culture

b) Quantitative fecal fat

If a commercial lyophilized reagent is diluted using slightly more distilled water than indicated, what type of error will occur? a) Random error b) Systematic error c) Precision error d) Reagent error

b) Systematic error An error in adding additional distilled water to a reagent would cause each sample to have an abnormal high or low result is an example of a systematic error. Systematic errors typically cause a trend or shift of results above or below the quality control mean.

If detected in antibody screen testing, which of the following antibodies is NOT considered clinically significant in prenatal patients? a) Anti-M b) Anti-N c) Anti-Leb d) Anti-Fya

c) Anti-Leb Anti-Leb may be detected in antibody screen testing of prenatal patients; however, this antibody is considered clinically insignificant. It is not indicated in causing hemolytic disease of the fetus and newborn (HDFN). Although rarely seen, both anti-M and anti-N can potentially cause mild to moderate HDFN. The most common clinically significant antibodies noted in prenatal patients includes the following: anti-Fya, anti-K, anti-D, anti-E, anti-e, anti-C, and anti-c. These IgG antibodies have been determined to cause moderate to severe HDFN.

A tech working on a fungal culture encounters growth of a yeast on the agar plates (hyphae absent). Upon investigation, the tech thinks the yeast may be Cryptococcus species, but is unsure if the organism is Cryptococcus neoformans. What testing can be performed to assist with the differentiation of Cryptococcus species? a) India Ink b) Urease c) Caffeic Acid Test d) Inositol

c) Caffeic Acid Test The caffeic acid test differentiates Cryptococcus neoformans from other Cryptococcus species. This test can be done on bird seed agar, and production of caffeic acid is shown by a maroon-red pigment. The test can also be done directly by inoculating a reagent-impregnated filter paper and observing a black pigment develop. Cryptococcus neoformans is caffeic acid positive, while other Cryptococcus species are negative.

The laboratory test most commonly used to establish a definitive diagnosis of primary syphilis is: a) Rapid plasma reagin (RPR) b) Recovery of spirochetes via culture c) Direct fluorescent antibody test d) Fluorescent treponemal antibody (FTA) with adsorption test

c) Direct fluorescent antibody test The direct fluorescent antibody test is the definitive method for diagnosing early syphilis. The antibodies produced in response to infection with Treponema pallidum are detectable during primary syphilis. Levels will continue to increase as the disease progresses to secondary syphilis.

The number of patients correctly diagnosed for the disease or not having the disease is defined as: a) Positive predictive value b) Negative predictive value c) Efficiency d) Sensitivity

c) Efficiency The efficiency is calculated by the following equation: ((TP + TN) / (TP + FP + FN + TN)) x 100 TP = True Positives TN = True Negatives FP = False Positives FN = False Negatives The efficiency is generally used in addition to the sensitivity and specificity to determine the diagnostic value of a test method.

Which of the following analytes would be increased due to delay in centrifugation? a) Bicarbonate b) Folate c) Ionized Calcium d) ALT

d) ALT The specimen should not be delayed for more than two hours prior to centrifugation because some of the analyte levels (such as glucose, ionized calcium, bicarbonate, folate, etc.) may be falsely decreased due to cellular consumption or falsely increased (such as potassium, ALT, AST, creatinine, etc.) because they are released over time from cells into serum or plasma.

To assess drug concentrations during the trough phase: a) Blood should be drawn about one hour after the administration of an oral dose of the drug. b) Blood should be drawn about half an hour before the next dose is given. c) Blood should be drawn about two hours after the administration of an oral dose of the drug. d) Blood should be drawn immediately before the next dose is given.

d) Blood should be drawn immediately before the next dose is given.

Schistosoma species can be differentiated by the shape and location of a spine located on the egg. Of the following, which species is paired with the correct location of the spine for that species? a) S. mansoni - Small lateral spine b) S. japonicum - Pointed terminal spine c) S. haematobium - Large lateral spine d) S. mansoni - Large lateral spine

d) S. mansoni - Large lateral spine A feature common to the three schistosome eggs is the presence of a spine. This structure is believed to aid in the puncturing of human tissue which results in the mechanism by which the parasite gains its nourishment. S. haematobium has a pointed, terminal spine, while S. mansoni and S, japonicum both have lateral spines, with S. mansoni having a larger, lateral spine.