• Urine Containers :
The containers must be cleaned and thoroughly dried. Disposable containers of plastic or coated paper are available in many sizes and are provided with lids to reduce bacterial and other types of contamination. Special polyethlene bags are available for collection of urine from infants and children who are not toilet trained .
1. First Morning Specimen :
- A specimen obtained during the first urination of the day.
- Most concentrated.
- Bladder incubated.
• Best for :
1.Nitrite.
2.Protein.
3.Microscopic examination.
2. Random Specimen :
- A specimen obtained at any time during examination.
- Most convenient.
- Most common.
• Good for :
1.Chemical Screen.
2.Microscopic examination.
3. Second-voided Specimen :
- In this case first morning specimen is discarded and the second specimen is collected and tested.
• Good for :
1. Reflection of blood glucose.
2. Keeping of formed elements intact.
4. Postprandial :
- A specimen obtained 2 hours after meal.
• Good for :
- Glucose.
5. (24) Hour specimen :
- A specimen obtained within 24 hours.
- Necessary for quantitative tests, especially for quantitative determination of protein .
6. Mid- stream Specimen :
- a specimen obtained from the middle part of the first urine.
- It is commonly used for routine urinalysis.
- It is also important for bacteriological urine culture.
7. Clean Catch Urine Specimen :
- Used for microbial culture and routine urinalysis. When specimens are collected for bacteriological examination they should be collected by the ‘clean catch’ method or by catheterization into sterilized container. Catheterization is the process of passing a tube through the urethra to the bladder for the withdrawal of urine.
• Sources of Errors in the Collection of Urine :
1. Bacteriologically or chemically contaminated specimen.
2. Wrong type/amount of preservative.
3. Partial loss of specimen or inclusion of two-morning specimen in the 24 hr collection.
4. Inadequate mixing of specimen before examination.
5. Careless measuring of the 24 hr volume.
Urine should be examined immediately as much as possible after it is passed, because some urinary components are unstable. If urine specimen can not be examined immediately, it must be refrigerated or preserved by using different chemical preservatives. The maximum time that urinary contents to be maintained in urine specimen is one hour .
• Long standing of urine at room temperature can cause :
1. Growth of bacteria.
2. Break down of urea to ammonia by bacteria leading to an increase in the pH of the urine and this may cause the precipitation of calcium and phosphates.
3. Oxidation of urobilingen to urobilin.
4. Distraction of glucose by bacteria.
5. Lysis of RBCs, WBCs and casts.
• Method of Preservation of Urine :
A. Physical Method :
- Refrigeration.
- Freezing.
B. Chemical Method :
• Use of chemical preservatives such as :
- Thymol.
- Toluene.
- Formaldehyde.
- Hydrochloric acid( HCl).
- Chloroform.
- Boric acid
- Chlorhexidine.
- Sodium carbonate.