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The aim of this practical is to develop further knowledge of the composition of urine and how it may change in disease

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Introduction The aim of this practical is to develop further knowledge of the composition of urine and how it may change in disease. Urinalysis is the analysis of several properties of urine such as the volume, physical, chemical and microscopic properties of urine and reveals a significant amount about the state of the body. The volume of urine voided by an adult human body can vary considerably depending on several factors such as fluid intake, blood pressure, blood osmolality, diet, body temperature, diuretics, mental state of the subject and general health. The normal range for volume of urine voided is 1-2 litres/day. The depth of the colour of urine gives an indication of how concentrated it is although the usual colour is amber. Unusual colours such as red may indicate the presence of blood, drugs or other colour pigments. Urine voided freshly is transparent and warm but in time as the temperature cools down it can appear cloudy owing to the precipitates of urates or phosphated depending on whether the urine is acid or alkali respectively. When normal urine is allowed to stand a deposit can usually form which can then be examined under the microscope. Deposits may be of such things like phosphate, urate, oxalate crystals, epithelial cells from the urinary tract, fibres from clothing or in the case of kidney disease red blood cells and casts can form. In this practical we will be testing the urine samples for the presence of abnormal constituents, such as the presence of protein, glucose, ketones, blood and bilirubin. Methods We have been given five pairs of sample tubes each containing urine. Each urine sample comes from an individual female subject and has been obtained via a 'clean-catch' midstream collection method. To obtain a clean catch sample the women subjects must first clean the area around their genitals with medicated wipes or swabs. The subject should then begin to urinate for a few seconds, using the container provided place the container mid stream into the flow of the urine and collect about 1-2 ounces of urine and then remove the container from the urine steam. ...read more.


There are no risks associated with the presence of glucose in urine. There are some drugs, which may increase urine glucose measurements including aminosalicyclic acid, chloral hydrate, diazoxide, diuretics, estrogens and nicotinic acid. This test is most commonly performed as a screening test for possible diabetes mellitus or to monitor the control of blood glucose in diabetes. Drugs that may give false positive results include acetylsalcyclic acid. Ascorbic acid and sulfonamides. Drugs which may give false negative results include ascorbic acid, levodopa and phenothiazines. If ketone bodies were also present in the urine sample this can cause the reagent area to have a decreased sensitivity to glucose therefore affecting the reaction. If ketone bodies are present in significant amounts (greater than 4.0mmol/L) then they can cause false negative results for specimens containing small amounts of glucose. If the specific gravity of the urine increases the reactivity of the glucose test will decrease therefore this will affect the result measured. The reactivity also varies with temperature. Normally small amounts of glucose are excreted by the kidney and may be found in the urine sample but this is below the sensitivity level of the test however on occasions the test will produce a colour change between negative and the 5.5mmol/L concentration giving a false positive result. If glucose is found in the urine then the patient must undergo further investigation including testing for ketone bodies in the urine in case the patient has diabetes. Other techniques such as x-ray and a complete urinalysis may complement this in order to come to a diagnosis. Sample pair three was tested using ketostix. Sample A gave a measurement of 4 (see table 1) which shows that ketones are present in moderate levels. Sample B gave a negative result (see table 1), which is normal for this test. Results showing the presence of ketones may be listed as small, moderate or large. ...read more.


These techniques accompanied with injecting coloured dyes to produce contrast may reveal the underlying problem such as gallstones. There are some limitations and errors may have affected all of the dipstick tests carried out. If any of the test strips where tampered with before use this may have caused a reaction with the reagent area and therefore cannot be entirely accurate if accidentally used again. In all the tests there where specific timing instruction given for when to observe the colour on the reagent area, if the timing was inaccurate due to a delay in starting/stopping the stop clock then this can lead to a reaction proceeding for longer than it should and the colour observed will be incorrect. If the reagent test kits where not thoroughly checked before use some of the bottles may have passed their expiry date therefore will not be of any use and give unreliable results. Specifically dipsticks should not have been used from a bottle, which was opened more than 6 months ago, it should be discarded and a fresh set used. If the urine samples used where left uncovered for a period of time before tested then cross contamination may have occurs therefore the urine sample will give inaccurate results. The reagent area on the dipstick or the Ictotest tablet must not be touched because moisture can affect the out come of the results. When attempting to read the result of the dipsticks lighting conditions may influence the colour observed. Heat and light may hve caused the reagent areas of dipsticks to become unstable and therefore cannot give an accurate result. In all tests exact agreement between visual results and instrumental results might not be found because of the inherent differences between perception of the human eye and the optical system of the instruments. Finally as with all laboratory testing, a definitive diagnostic decision should not be made on a single method or result. The tests should be repeated a minimum of three times and further diagnostic tests carried out to confirm diagnosis. ...read more.

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