Glucose in Urine
Clinitest
(Reducing Sugars)
-
Dipstick
(Glucose
Oxidase)
+
+
+
+
(without gluc)
-
+
(with gluc)
-
-
+
Clinitest
(Reducing Sugars)
-
Dipstick
(Glucose
Oxidase)
+
+
+
+
(without glucose)
-
+
(with glucose)
-
-
+
Notes
Explanation
Explanation
Small amount of glucose is present
Dipstick is sensitive to lower conc. of glucose than
Clinitest
Glucose present
Glucose is not present
Pos Clinitest is do to presence of some other reducing
substance like galactose, ascorbic acid or cephlosporin
False Neg dipstick
Enzyme may have been destroyed by large amount of
ascorbic acid
False positive dipstick No glucose or other reducing
substance is present
Bleach
There are no false positive Clinitest results
No natural False positive Dipstick results but presence of Bleach, peroxide Strong oxidizers will
give false positive results
False Negative Enzymatic dipstick results due to large amounts of Ascorbic Acid
Nitrite
Nitrite is an indirect means used to determine the presence of bacteria in urine
Gram neg bacteria convert Nitrate to Nitrite (Citrobacter Klebsiella Proteus E. Coli)
Dipstick Reaction
Method Diazotization reaction followed by Azo coupling
Aromatic Amine(p-arsanilic acid) + nitrite(NO2)  Diazonium salt
Diazonium salt + 1,2,3,4-tetrahydrobenzoquinolin-3-ol  pink color
Notes
Urine must remain in bladder for at least 4 hours to enable the bacteria to convert nitrate to
nitrite.
False Positives
If urine with a small amount of bacteria from contamination is allowed to sit at RT long
enough for the bacteria to grow and multiply and convert nitrate to nitrite
Colored urine
False Negatives
May have a pathogen that does not convert nitrate to nitrite such as Strep and Staph
Urine may not have been in bladder long enough
Pathogens may be present but no nitrate in urine for conversion to nitrite.
(nitrate is taken in by diet)
Pathogens may convert the nitrite to nitrogen
Ascorbic Acid (Ascorbic Acid reacts with the diazonium salt produced in the
diazotization reaction to a colorless end product)
Medications which inhibit nitrate conversion
Sensitivity is reduced in specimens with a high SG
Leukocyte Esterase
Clinical Significance
Inflammation Most likely due to bacterial infection of the kidneys or lower
urinary tract infection. Pyelonephritis cystitis or urethritis
Also could be due to trichomonads, yeast, chlamydia, mycoplasms, viruses and tuberculosis
Method
Ester hydrolysis reaction
Ester
leukocyte esterase
Aromatic Compound
Azo-coupling reaction
Diazonium salt
+
Aromatic Compound 
False Positives
Contamination
Drugs or foods like phenazopyridine,
nitrofurantoin, beets
Azodye
False Negatives
Strong oxidizing agents interfere with pH of
reaction
Drugs which reduce sensitivity such as
gentamycin and cephlosporin
Increased protein, glucose and specific gravity
may reduce sensitivity
Note
The leukocyte esterase pad will give a positive reaction even when microscopic
examination may not reveal WBC due to lysis of the WBC particularly in hypotonic or alkaline
urines
Lymphocytes do not react because they lack leukocyte esterase