Man has curious about urine from earliest times. The Babylonians and Sumerians studied urine and attempted to relate its appearance to various human aliments. Early Hindu literature describes ” Honey urine” as one, which attracted ants. Primitive analysis included testing of urine. The early 19th century marks the start of scientific methods of urine examination. In 1827, Richard Bright studied urine at Guy’s hospital. In 1909, Stanley Benedict described solution for quantitation of glucose in urine. In 1941, Dr Walter Compton created clinitest, for the measurement of reducing sugars. This test was the forerunner of the wide range of convenient urine test to be used all over the world.
Urine testing provides rapid, valuable and reliable information into health status of the patient. Urine is a valuable index to many normal and pathology mechanisms. It is a complicated aqueous solution of various organic and inorganic substances. These substances are products from the body metabolism (either normal or abnormal) or products derived directly from foods.
Many characteristics and components are unstable. The urine is also an excellent culture medium. Therefore examine within 30 minutes of collection or samples should be refrigerated. The delay in testing may result in gross changes, which affect the test result. Bacterial action effects PH, Glucose, Ketones and RBCs. Hydrolysis and oxidation affect bilirubin. Delay and exposure to light result in photo-degradation of urobilinogen to urobilin and volatilisation of acetone. It should be noted that sediments are unstable even at reference temperature if the urine is alkaline.
Major Sources of Error are:
- Bacterial or chemical contamination
- Contamination with menstrual blood
- Contamination with vaginal and urethral discharges
- Inadequate mixing before examination
- Wrong/Inadequate preservatives
Types of Urine Specimen:
1- First Morning Specimen
It it provides concentrated urine as the bladder incubated it the whole night. It is best for nitrite, proteins, good for microscopic examination and culture and sensitivity. The casts may have deteriorated and bacteria may affect to glucose reading.
2- Random Specimen
It is most common type and most convenient sample. It is good for observing physical characteristics, chemical analysis and identification of cast, crystal and cells.
3- Second Voided
The first morning specimen is discarded and second specimen is collected. Formed elements remain intact.
It is collected after meal (usually after 2 hours. It is good for glucose and protein estimation. Urine sugar testing now has limited diagnostic or prognostic value.
5- Timed Specimen
It is a combination of all voiding over a length time. Two-hour specimen is good for urobiliongen and 24-hour specimen is good for quantitative urinary components estimation. Timed urine specimens are collected in dynamic function test.
6- Foley Catheter
Disinfect a portion of the catheter with alcohol, puncturing the tubing directly with a sterile syringe and needle and aspirate the urine. Place urine in a sterile container, it should never be collected from drainage bag.
Apart from these procedures, urine specimen can also be collected by supra-pubic aspiration and cytoscopy.