Lecture 3 Flashcards
Glucose
Glucose present in the urine when blood glucose exceeds 10mmol/L
Blood glucose exceeds the renal threshold and cannot be absorbed by the tubules
Read at 30 seconds
RR: Negative
Glucose Normal
Normal urine is negative for glucose. Glucose results semi-quantitative
If present – Glycosuria or glucosuria
Indicate diabetes that’s not under control
Color reaction must be read in the prescribed time, as it will continue react, giving a false result
Significance of Glucose
Diabetes mellitus.
Renal glycosuria.
Limitation of Glucose
Interference: Javex, Ascorbic acid, temperature
Only measures glucose and not other sugars.
Renal threshold must be passed in order for glucose to spill into the urine.
Other Tests for glucose
CuSO4 test for reducing sugars. (Clinitest)Drop of urine to CuSO4 tablet, colour reaction occurs
Maltose
Reducing Sugars
Malt sugar, starch fermented yeast e.g. corn syrup, beer, breads
Fructose
Reducing Sugars
fruit sugar found in pops, candy bars, fruit juices, junk food, sweetened yogurt
Galactose:
Reducing Sugars
Dairy products – milk, cheese, butter. The breakdown of milk is lactose and finally glucose
Sucrose
Non-reducing Sugar
Added to processed foods to increase the flavour e.g. table sugar, jams, chewing gum
Protein normal
What does presence mean
interfered by
- Normal urine is negative or sometimes a trace in concentrated urine (mostly albumin)
- Presence of protein – Proteinuria and the nephrotic syndrome.
- Renal diseases, urinary tract infection, Multiple Myeloma
Interference: highly alkaline urine.
- Much more sensitive to albumin than other proteins (e.g., immunoglobulins, light chains, Bence Jones).
Protein Other Tests
Sulfosalicylic acid (SSA) turbidity test.
- Urine protein electrophoresis (UPEP) - Bence Jones protein
Bilirubin; Urobilinogen
The liver destroys old red blood cells and bilirubin is the by-product.
In the liver, the bilirubin is conjugated with glucuronic acid (direct bilirubin) excreted by the liver through the bile duct into the duodenum
In intestine, bacteria convert bilirubin into several compounds referred to as urobilinogen
An oxidized form of urobilinogen is excreted in the feces and small amount is excreted by the kidneys
Bilirubin normal
what does increased bilirubin means
and what can interfere with it / its limitations
Normal urine is negative for bilirubin
If present - Liver disease, bile duct obstruction, hepatitis
Bilirubin reacts with a diazonium salt and colour develops
Increased direct bilirubin (correlates with urobilinogen and serum bilirubin)
Interference: prolonged exposure of sample to light, bilirubin will disappear
- Only measures direct bilirubin–will not pick up indirect bilirubin
Bilirubin Other Tests
Ictotest (more sensitive tablet version of same assay)
- Serum test for total and direct bilirubin is more informative
Urobilinogen Normal
what happens if too high or too low
results can be interfered by?
Bilirubin degradation product by intestinal bacteria
Normal: 0.2 – 1 mg/dl
Increased in liver and hemolytic diseases
High: increased hepatic processing of bilirubin
- Low: bile obstruction
- Interference: prolonged exposure of specimen to oxygen (urobilinogen —> urobilin)
- Cannot detect low levels of urobilinogen
Other Tests Urobilinogen
Serum total and direct bilirubin
Ketones normal
what happens if present
caused by?
results can be interfered by how can false positives happen?
Normal urine is negative for ketone
If present – Ketonuria – Incomplete fat metabolism
Ketone bodies are acetoacetic acid B-hydroxybutyric acid, acetone
Diabetes, starvation, fasting state, alcoholism, Diabetic ketoacidosis
- Interference: expired reagents (degradation with exposure to moisture in air)
- Only measures acetoacetate not other ketone bodies
- False positive when urine is highly pigmented
Other Tests Ketones
Ketostix (more sensitive tablet version of same assay)
- Acetest
Blood
Occult blood means “hidden”
Dipstick can detect small amounts of blood
Detects intact RBCs, free hemoglobin from lysed RBCs and myoglobin
Myoglobin is the heme protein from muscle and facilitates movement of oxygen within the muscles. Injury to cardiac or skeletal muscle releases myoglobin
Hemoglobin oxidizes a chromogen in the pad to cause a colour change
False positives – menstrual blood