Question

How does a rapid/dipstick test work (either pregnancy or for influenza)? You can either draw this or describe it. When searching on Google, use image search AND the word reagent.

Answer 1

Diptest is a coloured strip made of paper or plastic used in urine analysis. It is about 5mm wide and consist of 10 different reagents impregnated within to give 10 different test results. Can be used to acess the presence of proteins,glucose,ketones,haemoglobin,bilirubin,urobilinogen,leukocytes, pH ,specific gravity and nitrate which serves as the primary indicator for detecting any physiological condition of the body.

Procedure: Through mixing of the urine sample done after collection. Strip is completely dipped into the collected sample and allowed to dry for 1 to 2 min. The colour change of the strip is compared with the given manufacturer referance.

Identification of various parameters:

pH:

• Kiney being an acid base regulator variation in pH can be due to any disturbance in the acid base homeostasis. Can also be indication of certain diseases like urinary tract infection, kidneystone etc.
• Reagent used:Methyl blue and Bromothymol blue used for the indication. Strip vary in colour according to the urine pH.

Specific gravity

• Specific gravity depends on the solute concentration. As blood flow through the filtration cup the glomerular filtrate is formed, which then undego reabsorption and secretions to finally form the concentrated urine. Presence of any disease can affect this function. Hence determing specific gravity is important
• Reagent: Based on change in dissociation constent.( Hyderogen released by the dissociation of an electrolyte in a basic medium withrespect to the numer of actions present) . presence of more hydrogen ion decrease the pH , hence pH indicator Bromothymol blue used.

Hemoglobin

• Blood in urine can be Hemoglobinuria. Presence of hemoglobin inblood. Caused mainly due to hemolytic anemia and burns.
• Reagent:Based on pseudoperoxidase activity of hemoglobin. Chemical used in strip is tetramethylbenzidine.

Protein

• Very little protein is usually found in urine as protein cannot pass through the filtration membrane in the kidney. Therefor glomerular filtrate dosent contain any protein, protein in urine indicate renel disease.
• Reagent: Chemical present in the strip are tetrabromophenol blue,tetrachlorophenol,tetrabromosulfonphthalein. Uses principle of protein error of indicators.

Glucose

• Normal condition all the glucose will be resorbed in the tubules. During diabetes the blood concentration of glucose is high resulting in high glucose level in the glomerular filtrate making it unabe to resorb all of them.
• Reagent: Detection by oxidation of glucose by enzyme glucose oxidase, enzyme peroxidase.

Ketone

• Intermediate product of fatty acid metabolism. Metabolic imbalance, Diabetes mellitus type 1 lead to presence of ketone in urine.
• Reagent: Based on reaction of sodium nitroprusside.

Bilirubin

• byproduct of haemoglobin degradation, mainly excreted by the intestine not seen in urine.Can occur in urine either due to impared degradation or renal damage
• Reagent:diazotization reaction. Bilirubin react with diazodium salt in acidic medium to produce colured dye.

Urobilinogen

• Its a byproduct of hemoglobin degradation manily excreted by intestine. Liver disfunction causes presence of excress urobilinogen.
• Reagent: uses Ehrlich's reagent and 4 methoxybenzene- diazonium tetrafluoroborate in the strip.

Nitrate

• Seen in the presence of bacteria causing urinary tract infection, as they are produced by thse bacteria.
• Reagent:Greiss reaction. Nitrate react with aromatic amine in acidic medium to form diazonium salt.

Leckocyte

• Increase in number indicate urinary infection, inflamation of renal tissue.
• Reagent:Leukocyte esterase. lyberating indoxyl by the hydrolysis of indolecarboxylic acid.