CHEM EXAMINATION - Nitrite, leukocyte Esterase

Rapid, indirect method for the detection of bacteria capable of reducing nitrate to nitrite

Nitrite

Screening of urine culture specimens

Nitrite

Nitrite Reagent Strip Principle:

Greiss Reaction

Nitrite Reagent Strip positive result

Pink azo dye

In Nitrite Reagent Strip, ___________ reacts with nitrite in an acid medium to produce diazonium salt which in turn reacts with ________________ to produce a pink azo dye

p-arsanilic acid , tetrahydrobenzoquinolin

Nitrite Reagent Strip Sensitivity

Multistix: 0.06 to 0.1 mg/dL

Chemstrip: 0.05 mg/dL

 Multistix: 0.06 to 0.1 mg/dL

 Chemstrip: 0.05 mg/dL

Detects the presence of esterase in WBCs that function as the body’s defense against microorganisms

Leukocyte esterase

Leukocyte esterase Reagent Strip Principle

Hydrolysis of Acid Ester

Leukocyte esterase Reagent Strip Reagent:

acid ester and diazonium salt

LE reagent strip positive result

purple azo dye

Leukocyte esterase Reagent Strip Sensitivity

Multistix:

Chemstrip:

Multistix: 5 to 15 WBC/hpf

Chemstrip: 10 to 25 WBC/hpf

Leukocyte esterase Reagent Interferences that causes False positive

strong oxidizing agent, formalin, highly pigmented urine, nitrofurantoin

Leukocyte esterase Reagent Interferences that causes False negative

high specific gravity, protein (>500mg/dL), glucose (>3g/dL), oxalic acid, ascorbic acid, gentamicin, cephalin, cephalothin, tetracycline

Has a strong reducing property leading to false-negative results on several reagent strip parameters

Ascorbic acid

Incorporated in some reagent strips as the 11th reaction pad

Ascorbic acid