4.8 NITRITE, LEUKOCYTE ESTERASE, SPECIFIC GRAVITY

Question 1

Identify the primary clinical use of the nitrite test in urine analysis

Answer 1

Rapid screening for urinary tract infections (UTIs)

Question 2

Identify the type of bacteria most commonly responsible for causing UTIs detected by the nitrite test.

Answer 2

Gram-negative bacteria, such as E. coli, Proteus, Enterobacter, and Klebsiella species.

Question 3

Identify the condition that the nitrite test helps to detect to prevent complications such as renal tissue damage

Answer 3

Cystitis (bladder infection).

Question 4

Identify the key chemical reaction responsible for detecting nitrite in urine.

Answer 4

The Greiss reaction, where nitrite reacts with an aromatic amine to form a pink azo dye.

Question 5

Identify the type of specimen most reliable for performing the nitrite test to avoid false negatives

Answer 5

First-morning specimens or those collected after at least 4 hours of bladder retention.

Question 6

Identify the major interference factor that can lead to false-negative nitrite test results.

Answer 6

Large quantities of ascorbic acid

Question 7

Identify the bacteria that cannot be detected by the nitrite test due to the lack of the reductase enzyme.

Answer 7

Non–nitrate-reducing gram-positive bacteria and yeasts

Question 8

Identify the specific urinary condition characterized by increased urinary leukocytes, which is detected by the LE test.

Answer 8

Urinary tract infections (UTIs).

Question 9

Identify the main leukocyte type detected by the leukocyte esterase (LE) test.

Answer 9

Neutrophils

Question 10

Identify the type of infections that may produce leukocyturia without bacteriuria, detectable by the LE test

Answer 10

Infections caused by Trichomonas, Chlamydia, or yeast, and inflammation of renal tissues (e.g., interstitial nephritis).

Question 11

Identify the interfering factor that can cause a false-positive result in the LE test

Answer 11

The presence of strong oxidizing agents or formalin.

Question 12

Identify the chemical reaction involved in the LE test that produces a purple azo dye.

Answer 12

The hydrolysis of an acid ester by leukocyte esterase, followed by a reaction with a diazonium salt.

Question 13

Identify the condition where the LE test reaction may produce a false-negative result due to high concentrations of a certain substance.

Answer 13

High concentrations of protein, glucose, or ascorbic acid.

Question 14

Identify the condition indicated by a low specific gravity reading (below 1.010) on a reagent strip.

Answer 14

Dilute urine, potentially caused by conditions such as diabetes insipidus or excessive fluid intake.

Question 15

Identify the method used in the reagent strip test for specific gravity to measure urine concentration.

Answer 15

The change in pKa (dissociation constant) of a polyelectrolyte in an alkaline medium

Question 16

Identify the condition in which the specific gravity reagent strip reading may be falsely elevated.

Answer 16

Elevated concentrations of protein in the urine.

Question 17

Identify the clinical significance of specific gravity testing.

Answer 17

Monitoring hydration status, detecting loss of renal tubular concentrating ability, and determining unsatisfactory specimens

Question 18

Identify the substance whose presence in urine could lead to a false-negative result in the nitrite test due to interference

Answer 18

Ascorbic acid.

Question 19

Identify the compound that bilirubin is conjugated with in the liver to make it water-soluble.

Answer 19

Glucuronic acid

Question 20

Identify the primary source of bilirubin in the body.

Answer 20

The breakdown of hemoglobin from aged red blood cells in the reticuloendothelial system.

Question 21

Identify the type of bacteria that are most likely to cause false-negative nitrite test results due to a lack of nitrate reductase.

Answer 21

Non–nitrate-reducing gram-positive bacteria

Question 22

Identify the method used to detect nitrite in the urine sample on a reagent strip

Answer 22

The Greiss reaction

Question 23

Identify the reason why nitrite tests are most effective on first-morning urine specimens.

Answer 23

Longer contact time between bacteria and urinary nitrate, increasing nitrite production

Question 24

Identify the urine condition that can cause a false-negative result in the nitrite test due to bacterial reduction of nitrite to nitrogen

Answer 24

large number of bacteria present in the urine.

Question 25

Identify the main clinical significance of the specific gravity test in relation to patient hydration.

Answer 25

Monitoring hydration and dehydration status

Question 26

Identify the factor that can lead to a false-negative result in the LE test due to the inability of leukocytes to release esterases

Answer 26

Crenation of leukocytes caused by a high specific gravity.

Question 27

Identify the type of leukocytes that contain esterases, which are detected by the LE test.

Answer 27

Granulocytic white blood cells, including neutrophils, eosinophils, and basophils.

Question 28

Identify the chemical substance present in the reagent strip for specific gravity that reacts with ions in urine to indicate urine concentration

Answer 28

Bromothymol blue.

Question 29

Identify the primary use of the nitrite test in evaluating patients with recurrent UTIs

Answer 29

To evaluate the effectiveness of antibiotic therapy and to screen for ongoing or future infections

Question 30

Identify the reason why the LE test may be more reliable than the nitrite test for screening UTIs

Answer 30

The LE test detects leukocytes regardless of the presence of bacteria, while the nitrite test only detects nitrate-reducing bacteria.

Question 31

Identify the substance that interferes with the LE test by obscuring the color reaction, leading to a false positive.

Answer 31

Nitrofurantoin

Question 32

Identify the condition that can cause the formation of bilirubin in urine, detectable with a reagent strip.

Answer 32

Hemolysis or liver dysfunction leading to increased unconjugated bilirubin.

Question 33

Identify the key reaction involved in the production of bilirubin from hemoglobin

Answer 33

breakdown of protoporphyrin to bilirubin by reticuloendothelial system cells.

Question 34

Identify the condition that would cause an elevated specific gravity reading due to high concentrations of organic substances in the urine.

Answer 34

Proteinuria or high glucose levels

Question 35

Identify the urinary condition that can cause a falsely low specific gravity reading due to a high pH in the sample.

Answer 35

Alkaline urine (pH greater than 6.5).

Question 36

dentify the organ responsible for conjugating bilirubin to make it water-soluble.

Answer 36

liver

Question 37

Identify the urine condition that may be identified by a positive LE test but without positive nitrite results, indicating an infection with Trichomonas or Chlamydia

Answer 37

Nonbacterial urinary tract infections (UTIs

Question 38

Identify the test that is used in combination with the nitrite test to help determine the necessity of performing a urine culture

Answer 38

The leukocyte esterase (LE) test

Question 39

Identify the condition indicated by the presence of conjugated bilirubin in urine.

Answer 39

Liver disease or bile duct obstruction