4.8 NITRITE, LEUKOCYTE ESTERASE, SPECIFIC GRAVITY Flashcards
Identify the primary clinical use of the nitrite test in urine analysis
Rapid screening for urinary tract infections (UTIs)
Identify the type of bacteria most commonly responsible for causing UTIs detected by the nitrite test.
Gram-negative bacteria, such as E. coli, Proteus, Enterobacter, and Klebsiella species.
Identify the condition that the nitrite test helps to detect to prevent complications such as renal tissue damage
Cystitis (bladder infection).
Identify the key chemical reaction responsible for detecting nitrite in urine.
The Greiss reaction, where nitrite reacts with an aromatic amine to form a pink azo dye.
Identify the type of specimen most reliable for performing the nitrite test to avoid false negatives
First-morning specimens or those collected after at least 4 hours of bladder retention.
Identify the major interference factor that can lead to false-negative nitrite test results.
Large quantities of ascorbic acid
Identify the bacteria that cannot be detected by the nitrite test due to the lack of the reductase enzyme.
Non–nitrate-reducing gram-positive bacteria and yeasts
Identify the specific urinary condition characterized by increased urinary leukocytes, which is detected by the LE test.
Urinary tract infections (UTIs).
Identify the main leukocyte type detected by the leukocyte esterase (LE) test.
Neutrophils
Identify the type of infections that may produce leukocyturia without bacteriuria, detectable by the LE test
Infections caused by Trichomonas, Chlamydia, or yeast, and inflammation of renal tissues (e.g., interstitial nephritis).
Identify the interfering factor that can cause a false-positive result in the LE test
The presence of strong oxidizing agents or formalin.
Identify the chemical reaction involved in the LE test that produces a purple azo dye.
The hydrolysis of an acid ester by leukocyte esterase, followed by a reaction with a diazonium salt.
Identify the condition where the LE test reaction may produce a false-negative result due to high concentrations of a certain substance.
High concentrations of protein, glucose, or ascorbic acid.
Identify the condition indicated by a low specific gravity reading (below 1.010) on a reagent strip.
Dilute urine, potentially caused by conditions such as diabetes insipidus or excessive fluid intake.
Identify the method used in the reagent strip test for specific gravity to measure urine concentration.
The change in pKa (dissociation constant) of a polyelectrolyte in an alkaline medium
Identify the condition in which the specific gravity reagent strip reading may be falsely elevated.
Elevated concentrations of protein in the urine.
Identify the clinical significance of specific gravity testing.
Monitoring hydration status, detecting loss of renal tubular concentrating ability, and determining unsatisfactory specimens
Identify the substance whose presence in urine could lead to a false-negative result in the nitrite test due to interference
Ascorbic acid.
Identify the compound that bilirubin is conjugated with in the liver to make it water-soluble.
Glucuronic acid
Identify the primary source of bilirubin in the body.
The breakdown of hemoglobin from aged red blood cells in the reticuloendothelial system.
Identify the type of bacteria that are most likely to cause false-negative nitrite test results due to a lack of nitrate reductase.
Non–nitrate-reducing gram-positive bacteria
Identify the method used to detect nitrite in the urine sample on a reagent strip
The Greiss reaction
Identify the reason why nitrite tests are most effective on first-morning urine specimens.
Longer contact time between bacteria and urinary nitrate, increasing nitrite production
Identify the urine condition that can cause a false-negative result in the nitrite test due to bacterial reduction of nitrite to nitrogen
large number of bacteria present in the urine.
