Laboratory Urine Flashcards
What is included in a urinalysis ?
Inspection of the gross appearance.
Dipstick analysis.
Urine sediment.
What is a dipstick analysis and how do you perform one ?
Pour 5-10 mL of urine into a centrifuge and spin the capped sample. Immerse briefly (1s) but completely the test strip into the sample. Remove the excess urine but sliding it against the test tube or using a paper napkin, then wait for 30-60 s (excepté leucocytes) to avoid error before comparing it with the coloured scale.
How do you perform a urine sediment ?
Decant the sample and discard the supernatant (the top liquid to nobly keep the solide bottom). Mix the sediment and put it on microscope slide. Examine at x10 then x40.
What do you look for in a urine sediment ?
At x10 : epithelial cells, cast, crystal, mucus.
At x40 : epithelial cells, crystal, red blood cells, white blood cells, bacterias, parasites.
What do you look at in the gross inspection of an urine sample ?
Color, turbidity/transparency, odor.
What are the normal values of a dipstick test ?
pH : 4.6-8.0, average sample of 6.0
Trace of urobilinogen
RBC : 0-3/hpf for male and 0-5/hpf for women (hpf = high power field)
WBC : 0-4/hpf
Negative for : bilirubin, blood, acetone, glucose, protein, nitrite, leucocytes.
What are normal findings in an urine sediment ?
Only occasionally epithelial cells but a large amount could be due to contamination of the specimen.
Sometimes hyaline casts. Some crystal based on the pH. No bacteria.
What is the meaning and cause of different urine color ?
Pale yellow : normal
Colorless : Polyuria or diabetes
Pink to dark red : hematuria (bleeding), myoglobinuria, hemoglobinuria (acute haemolytic reaction).
Red to black : porphyrinuria and alkaptonuria.
Red/brown/black : UTI
White milky urine : cholurie (presence of bile element)
Dark yellow : dehydratation
What indicate the presence of bilirubin in urine ?
It’s an early indication of a liver disease.
What are the different meaning of positive dipstick for blood ?
If there’s no erythrocytes then it could be free hemoglobin or myoglobin present. Or a high dose of vitamin C.
If there are erythrocytes present then : glomerular hematuria, renal or urologic causes, drug, trauma, menses, vaginal bleeding.
What is the clinical significance of glucose in the urine ?
Beware the dipstick only react to glucose not other sugar.
It could indicate : diabetes, steroids, SGLT2 inhibitors (medication to reduce the glycemia), RTA (renal tubular acidosis)
What is the clinical significances of ketones bodies in urine ?
Trace = 5mg/dL
It can indicate : starvation, DKA (diabetic ketoacidosis), vomiting, alcohol, hyperthyroidism, carbohydrate free diet.
What is the meaning of leucocytes in urine ?
How are they detected ?
Positive UTI signs.
Detected by leucocytes esterase activity.
What is the clinical significance of nitrite in urine ?
Some bacteria can turn nitrate into nitrite. It can then be a sign of an infection.
What is the clinical significance of pH in urine?
Acidic : high protein diet, ammonium chloride, mandolin acid, medication.
Alkaline : UTI, renal tubular acidosis, diet.
What is the clinical significances of proteinuria ?
Can be a sign of glomerulonephritis or nephrotic syndrome.
What does the odor of the urine can tell you ?
Almost no smell : normal
Strong ammonia smell : possibly UTI, presence of bacteria that can transform urea, high level of waste product
Acetone (sweet smell) : diabetes because of ketones body
Rotten egg : presence of sulfite because of cystinuria, diet, UTI, necrosis of tissue
What is the clinical relevance of specific gravity ?
Normal values : osmolarity
Increased values (concentrated urine) : decreased volume, CHF (congestive heart failure), adrenal insufficiency
- possibility of false positive
Decreased values (diluted urine) : diabetes, pyelonephritis, glomerulonephritis.
- possibility of false negative
For what particule is the collection of mid stream urine not necessary ?
For glucose
What does the pH level influence ?
If the pH level is too high (alkaline solution) it is difficult to trust the values of test (false positive = make illusion of the presence of other components).
What does the presence of ascorbic acid signify ?
It comes from vitamin C.
Its presence may interfere with the other parameter like glucose level (false neg = mask the presence of others)
Which technique of collection is best for the presence of blood in urine ?
A test strip with the first morning urine.
What are the best collection methods in general ?
First morning urine = more concentrated
Mid stream urine = less contamination of the external world
Test less than 2 hours after collection = waiting too long affect the protein level
How long should you wait to read the result of a dipstick test ?
30-60s except for leucocytes for which you should wait 60-120s
