Purpose of Urine Chemistry Examination

URINE CHEMICAL EXAMINATION Urine chemical examination based on biochemical reactions, also called the dry chemical method or dip strip test, is widely used in clinical laboratories. This dip strip method is also practical because the reagent is available in ready-to-use tape form, the reagent is relatively stable, cheap, the volume of urine required is small, it is disposable, and does not require reagent preparation. The procedure is simple and easy, does not require any expertise in taking the test and the results are fast. How to use the dip strip Before carrying out a urine examination, the dipstick must be controlled with a urine control agent. Examination with urine control material is intended to assess the dipstick, the examination tools, namely pipettes and reading tools, as well as the examiner/person who does the work. After examination with control materials according to the expected results, the patient's urine is then examined.The material for chemical examination using a dipstick must be fresh urine and have a minimum amount of 10-12 ml. After mixing it by turning the urine tube upside down to make it homogeneous, it is examined using a dipstick. The dipstick is inserted into the urine in less than 1 second, then removed and the excess urine is cleaned by placing the dipstick horizontally on its side on the filter paper so that the excess urine that flows is absorbed by the absorbent paper, aiming to prevent carry over between the reagent bands.After30-60 secondsThe color that occurs can be compared with the color on the dye bottle visually. The test results are based on the color changes that occur. Purpose of urine chemistry examination Aims to support the diagnosis of disorders outside the kidneys such as disorders of carbohydrate metabolism, liver function, acid base balance disorders, kidney and urinary tract disorders such as urinary tract infections. A type of chemical examination of urine with a dipstick The most complete dipstick can test 10 urine chemical examination parameters at once consisting of pH, specific gravity, glucose, bilirubin, urobilinogen, ketones, protein, blood, leukocyte esterase, and nitrite. 1) Check urine pH Urine pH examination is based on the presence of dual indicators (methyl red and bromthymol blue), where there will be a change in color according to the pH ranging from orange to greenish yellow and bluish green. The pH testing range includes pH 5.0 to 8.5. 2) Examination of Urine Specific Gravity Examination of specific gravity in urine is based on changes in pKa (dissociation constant) of polyelectrolytes (methylvinyl ether/maleic anhydride). The polyelectrolyte contained in the dye strip will undergo ionization, producing hydrogen ions (H+). H ion+produced depends on the number of ions contained in the urine. In urine with low specific gravity, H ions+little is produced so the pH is more towards alkaline. This pH change will be detected by the bromthymol blue indicator. Bromthymol blue will be dark blue to green in urine with a low specific gravity and yellowish green if the urine has a high specific gravity. 3) Urine Glucose Examination Examination of glucose in urine is based on glucose oxidase which will break down glucose into gluconic acid and hydrogen peroxide. Then this hydrogen peroxide in the presence of peroxidase will catalyze the reaction between potassium iodide and hydrogen peroxide to produce H2O and On (O nascens). O nascens will oxidize the potassium iodide dye within 10 seconds to form light blue, green to brown colors. In this method, urine glucose levels are reported as negative, trace (100 mg/dl), +1 (250 mg/dl), +2 (500 mg/dl), +3 (1000 mg/dl), +4 (> 2000 mg/dl). The sensitivity of this test is 100 mg/dl, and this test is specific for glucose.False negative results in this examination can be caused by reducing agents in the urine such as vitamin C (more than 40 mg/dl), homogentisic acid, aspirin andingredients that interfere with enzymatic reactions such as levodova, gluthation, and drugs such as diphyrone Apart from using a dipstick, urine glucose examination can use: a. Fehling Method Principles:By heating urine in an alkaline atmosphere, glucose will reduce cupric sulfate to cuprous oxide. Precipitation of cupric hydroxide is prevented by the addition of potassium sodium tartrate. b.Benedict's Principle Method:Glucose in urine will reduce the complex salts contained in Benedict's reagent (cupric ions are reduced to cupro) and precipitate in the form of CuO and Cu2O. Interpretation of results using the Fehling and Benedict method: (-) : remains blue, greenish blue. (+1) : yellowish green and cloudy (corresponds to 0.5 – 1 % glucose) (+2) : cloudy yellow (1 – 1.5 % glucose) (+3) : orange or cloudy mud color (2 – 3.5 % glucose) (+4): brick red (more than 3.5 % glucose).