Posted in Checkpoint Notes, Lecture Notes

Clinical Microscopy – REAGENT STRIPS

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TEST PRINCIPLE TIMEREAGENTSFALSE (+)FALSE (-)
Glucose (correlated with ketones)  
Double sequential enzyme reaction  

ENZYMES: Glucose oxidase Peroxidase  

30 s
M – glucose oxidase, peroxidase, potassium iodide  
C – glucose oxidase, peroxidase, tetramethylbenzidine  

CHROMOGENS:
O-toluidine (pink to purple) Potassium iodide (blue to brown) Aminopropryl-carbazol (yellow to orange-brown) Tetramethylbenzidine (yellow to green)
Contamination by oxidizing agents and detergentsHigh levels of ascorbic acid, ketones, specific gravity
Low temperature   Improperly preserved specimens
Ketones (correlated with glucose)  

Sodium nitroprusside reaction  

40 s
M – sodium nitroprusside (acetoacetic acid)  

C – sodium nitroprusside + glycine (acetoacetic acid & acetone)
Phthalein dyes, highly pigmented red urine, levodopa   Medications containing free sulfhydryl groups (MESNA)Improperly preserved specimens
Specific Gravity  

pKa change of polyelectrolyte

pKa = dissociation constant

45 s
M – poly (methy lvinyl ether/maleic anhydride) bromthymol blue

C – ethyleneglycol-Bis (aminoethylether) bromthymol blue
High concentrations of proteins because of protein anionsHighly alkaline urines (>6.5) Add 0.005 to S.G. readings
pH
(correlated with Nitrite, LE, microscopic)  

Double-indicator system

60 s
Methyl red
Bromthymol blue
NoneRunover from the adjacent CHON pad may lower pH
Protein (correlated with blood, nitrite, LE, microscopic)

Protein error of indicators  

60 s
M – tetrabromphenol blue

C – tetrachloropenol tetrabromosulfonphthalein

ACID BUFFER: Citrate
Highly buffered alkaline urine High specific gravity   pigmented specimens, phenazopyridine quaternary ammonium compounds (detergents)   antiseptics, chlorhexidine   loss of buffer from prolonged exposure of reagent strip to the specimenProteins other than albumin
Blood (correlated with protein and microscopic)  

Pseudo-peroxidase activity of hemoglobin  

60 s
M – diisopropylbenzenedehydroperoxide tetramethylbenzidine

C – dimethyldihyroperoxide- tetramethylbenzidine    

spotted blue for intact RBCs uniform blue for Hb and myoglobin
Strong oxidizing agents, bacterial peroxidases   menstrual contaminationHigh specific gravity/ crenated cells   high concentration of nitrite   formalin, captopril, ascorbic acid > 25mg/dl   unmixed specimens
Bilirubin (correlated with urobilinogen)  

Diazo reaction

60 s
M – 2,4-dichloro-analine diazonium salt

C -2,6-dichorobenzene-diazonium-tetrafluoroborate  
Highly pigmented urines, phenazopyridine, indican metabolites of LodineSpecimen exposure to light, ascorbic acid >25 mg/dL, high concentration of nitrite
Urobilinogen (correlated with bilirubin)  

Ehrlich’s reaction

60 s
M – para-dimethylaminobenzaldehyde
C – 4-methoxybenzenediazonium-tetrafluroborate  
M – Porphobilinogen, indican, p-aminosalicyclic acid, sulfonamides, methyldopa, procaine, chlorpromazine, highly pigmented urine

C – highly pigmented urine
M – old specimens, preservation in formalin

C – old specimens, preservation in formalin, high concentration of nitrite
Nitrite (correlated with protein, LE and microscopic)  

Greiss reaction

60 s
M – p-arsanilic acid Tetrahydrobenzo(h)-quinolin-3-ol

C – Sulfanilamide, hydroxytetrahydro benzoquinoline      
Improperly preserved specimens  


Highly pigmented urine
Nonreductase-containing bacteria insufficient contact between bacteria and urinary nitrate (should be 4 hours) lack of urinary nitrate, large quantities of bacteria converting nitrite to nitrogen, presence of antibiotics, high concentration of ascorbic acid high specific gravity
Leukocytes (correlated with protein, nitrite and microscopic)  

Leukocyte esterase  

120 s
M – derivatized pyerole amino acid ester, diazonium salt  

C – indoxylcarbonic acid ester diazonium salt  
Strong oxidizing agents, Formalin, highly pigmented urine, nitrofurantoinHigh concentration of protein, glucose, oxalic acid, ascorbic acid, gentamicin, cephalosporins, tetracyclines

Author:

Hi! I am an anime-loving registered medical technologist turned doctor of medicine. Oh yeah, I teach medtech and life. Hihi. ^o^ Yoroshiku.

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