An indirect colorimetric method for

An indirect colorimetric method for estimating specific gravity is available on reagent strips ("urine dipsticks"). This method uses a pad that contains a complex, pre-treated electrolyte that undergoes a pH change based on the ionic concentration of the urine. This change results in a change of color of the pad. For the Multistix SG-10, specific gravity is measured using an apparent pKachange in the presence of an indicator (dyes) whose colors vary from deep blue-green at low ionic strength to green and yellow-green at higher ionic concentration. This estimate of specific gravity is rapid, simple, and requires no special equipment.
The falling drop method is a direct method of measuring specific gravity that is usually used with automated instruments, such as the Clinitek Auto 2000 (Ames Division, Miles Laboratories, Inc., Elkhart , IN). The CliniTek2000 uses a specially designed column containing silicone oil. Specific gravity is calculated from the time it takes for a drop of urine to fall between two optical gates.
Osmolality—Osmolality is usually measured by an osmometer, most frequently by a freezing point osmometer. Osmolalityis a measure of the number of particles per unit mass, whereas the specific gravity is a reflection of the density (mass per unit volume) of the suspended particles.
Clinical Significance—Primary kidney function includes the ability to produce, in the appropriate circumstances, either a concentrated urine (osmolality>850 mOsm/kg) or a dilute urine (osmolality600 mOsm/kg is presumptive evidence of an ability to concentrate urine. The urine osmolality thus is part of the mechanism of maintaining water balance. In the presence of excess free water, the kidneys will produce a dilute urine, while in periods of water lack, a concentrated urine is produced.
Loss of concentrating ability is often one of the earliest signs of kidney disease, clinically evidenced as nocturia (needing to void at night) and polyuria (increased volume of [usually dilute] urine).

Chemical Testing
Reagent-strip Testing
A plastic strip is used, which contains pads that have incorporated within them the reagents for chemical reactions for the detection of a number of urine constituents. Urine is added to the pads for reaction by dipping the plastic strip into the urine and then slowly withdrawing it. The subsequent colorimetric reactions are timed to an endpoint; the extent of colors formation is directly related to the level of the urine constituent. The colors can be read manually by comparison with color charts or with the use of automated reflectance meters.
The following are four general rules to be followed when performing urine reagent strip testing.
1. Test urine promptly; use properly timed test readings only.
2. Beware of interfering substances.
3. Understand the advantages and limitations of the test.
4. Employ controls at least once per day, documenting the results.
Positive results from reagent-strip testing may require confirmation with chemical and microscopic methods.
Manufacturers' information on sources of inhibitors and false-positive and false-negative results can be identified from the package inserts of the test strips. For example, ascorbic acid in urine can interfere with reagent-strip reactions for glucose, hemoglobin, bilirubin, and nitrite.
Manufacturers have been encouraged to minimize or eliminate this interference when possible because ingestion of vitamin C supplements is so common. Some reagent test strips have an additional test reaction that measures the levels of urinary ascorbic acid, and serve as a reminder of the possibility of interference from this source.
Test Principles, Significance, and Normal
1.pH 2. Proteins
3.Sugars 4. Ketones
5.Blood and myoglobin 6.Bilirubin
7.Urobilinogen 8.Nitrities
9.Leukocyte esterase


1. pH
Most urinalysis laboratories use multi-test reagent strips containing two pH indicators, methyl red and bromthymol blue. These provide a range of sensitivity to pH from 5.0 to 9.0; the pH is reflected by a color which can change from orange (acid) to green to blue (alkaline).
Fresh urine specimens can have pH values ranging from acidic to alkaline. Upon standing the decomposition of urea into ammonia causes the urine to become more alkaline. Lower pH values are observed in cases of diabetes and in patients with fever. Urine retention by some patients can result in more alkaline urine. The standard method for pH measurements uses glass electrodes. Urinary pH measured with indicator paper is more than accurate enough for clinical purposes, since small changes in urinary pH are of little clinical significance. There is no confirmatory testing for urine pH.
Clinical significance—Common clinical causes of acidic and alkaline urine are listed in the following table. The normal American diet is high in protein that results in acidic urine (pH 5.0 to 6.5). Alkaline urines (pH 8.0 to 8.5) are more often associated with an unpreserved or old specimen, which turns alkaline as the result of urease-producing ammonia bacteria, such as Proteus species. Patients with renal tubular acidosis, a clinical syndrome characterized by an inability to excrete an acidic urine, may produce urine with a much higher pH than would be expected on the basis of the acidosis.
Normal—The urinary pH range is usually 4.7 to 7.8. Extremely acidic or alkaline urine usually indicates a poorly collected specimen.


2. Proteins
Reagent-strip test for protein is a semi-quantitative screening procedure for proteinuria. Reagent strips contain a pH sensitive dye; tetrabromphenol blue and 31, 35, 51, 55 tetrachlorophenol-3,4,5,6-tetrabromosulfophthalein. The presence of protein on the strip changes the pH environment of the dye embedded in the pad, resulting in a change in color.
pH 3
Tetrabromphenol blue Positive results (green-blue)
Protein


pH 3
Tetrabromphenol blue Negative results (yellow)
No protein

Strip tests are more sensitive for albumin and can detect other proteins at higher concentrations. Thus, because there is a risk for false-negative results, it is recommended that the laboratory consider simultaneously performing both a reagent-strip test and an acid precipitation test for the detection of all types of proteinuria. A faintly positive result should be confirmed with a more specific test such as the trichloroacetic acid or the sulfosalicylic acid tests. A grossly positive SSA or TCA turbidity test result may indicate the presence of drugs or Bence Jones proteins.
False positive results maybe caused by alkaline or buffered urine as well as by quarternary ammonium compounds found in detergents.
Clinical significance—Most of the urine protein is albumin, which has crossed the glomerular membrane. Smaller-molecular-weight proteins such as globulins may also be present in urine. Once filtered at the glomerulus, proteins are almost completely reabsorbed in the proximal tubule. Proteinuria, therefore, can be the result of either increased filtration at the glomerulus or decreased tubular reabsorption. Glomerular proteinuria is associated with the presence of larger molecular weight proteins and larger protein losses, usually > 2 g/day. The nephrotic syndrome is associated with very large losses of protein, usually >2-3 g/day. Tubular proteinuria is associated with smaller amounts (1-3 g/day) of lower molecular weight protein molecules. Small losses of protein in urine can be seen with vigorous exercise and pregnancy.
Measurement of urinary pH is also useful for managing patients with renal stones or crystals. Uric acid stones form in acidic urine and are more soluble in alkaline urines. However, alkaline urine will precipitate calcium or calcium phosphate crystals, while an acidic urine will tend to dissolve them. Inducing an alkaline urine during sulfonamide and streptomycin therapy is done to prevent precipitation of these drugs in the kidneys and to prevent the formation of uric acid, cystine, and oxalate stones. Alkaline urines are also desirable during treatment of transfusion reactions and salicylate intoxication. An acidic pH is used to combat bacteriuria in patients with cystitis and to prevent formation of alkaline stones. Technologists should be aware that alkaline urine interferes with the determination of proteins by the reagent strip technology and may alter the urine sediment examination.
Normal—A healthy person will excrete up to approximately 100 mg/day, a very small fraction of the plasma protein that is filtered at the glomerulus.

3. Sugars
Enzymatic testing—The reagent-strip tests are highly specific for glucose. They detect the oxidation of glucose to gluconic acid:
Glucose oxidase
Glucose + Oxygen in room air Gluconic acid + Hydrogen peroxide


Peroxidase
Hydrogen peroxide + Chromogen Oxidized chromogen (blue) + H2O

Tetramethylbenzidine and o-toluidine have been used as the chromogen for the indicator reaction.
Copper reduction (Clinitest, Benedict's test)—The Clinitest tablet (Ames Division, Miles Laboratories, Inc., Elkhart, IN) usually serves as a confirmatory test for sugar. Using the principle of the reduction of cupric salts by reducing sugars; including glucose, galactose, lactose, and pentoses; the copper reduction test measures total reducing substances in urine.
Heat
Cupric ions + Glucose
(or other reducing substances) Cuprous
oxide + Cuprous
hydroxide
Alkali (red) (yellow)

Clinical significance—Glucose is the predominant sugar in urine. It is not detectable by reagent strips in the urine of healthy individuals. Temporary elevation of glucose excretion measurable by test strips can occur after treatment with some drugs, cases of shock and during pregnancy. Repeated positive testing is almost always diagnostic for diabetes.
Reagent strips will detect glucose at a concentration of 400 to 750 mg/L (2.2 to 3.85 mmol/L), while the Clinitest will detect

ผลลัพธ์ (ไทย) 1:

วิธีการเทียบเคียงทางอ้อมสำหรับการประเมินความถ่วงจำเพาะอยู่ในแถบรีเอเจนต์ ("ปัสสาวะ dipsticks") วิธีนี้ใช้แผ่นที่ประกอบด้วยอิเล็กโทรซับซ้อน บำบัดก่อนการที่ผ่านการเปลี่ยนแปลง pH ตาม ionic ความเข้มข้นของปัสสาวะ การเปลี่ยนแปลงนี้ส่งผลในการเปลี่ยนแปลงของสีของแผ่น สำหรับ SG Multistix-10 ถ่วงถูกวัดโดยใช้การ pKachange ชัดเจนในต่อหน้าของตัวบ่งชี้ (สี) ที่มีสีแตกต่างกันจากลึกสีฟ้า-เขียวที่แรงต่ำ ionic จะสีเขียว และสีเหลืองอมเขียวที่ความเข้มข้นสูง ionic ความถ่วงจำเพาะประมาณนี้คือรวดเร็ว ง่าย และต้องมีอุปกรณ์พิเศษไม่วิธีการปล่อยตกโดยตรงวิธีการวัดความถ่วงจำเพาะที่มักจะใช้กับเครื่องอัตโนมัติ เช่น Clinitek อัตโนมัติ 2000 (เอมส์หาร ไมล์ห้องปฏิบัติการ Inc., Elkhart, IN) ได้ CliniTek2000 ใช้คอลัมน์ที่ออกแบบมาโดยประกอบด้วยน้ำมันซิลิโคน ความถ่วงจำเพาะคำนวณเวลาใช้สำหรับหยดปัสสาวะลงระหว่างประตูสองแสงOsmolality — Osmolality มักจะวัด โดยการ osmometer บ่อยที่สุดโดย osmometer จุดเยือกแข็ง Osmolalityis การวัดจำนวนอนุภาคต่อหน่วยมวล แรงโน้มถ่วงเฉพาะเป็น ภาพสะท้อนของความหนาแน่น (มวลต่อหน่วยปริมาตร) ของอนุภาคระงับความสำคัญทางคลินิกซึ่งฟังก์ชันหลักไตมีความสามารถในการผลิต ในสถานการณ์ที่เหมาะสม การปัสสาวะที่เข้มข้น (osmolality > 850 mOsm/kg) หรือปัสสาวะ dilute (osmolality < 100 mOsm/kg) ปัสสาวะสุ่มมี osmolality > 600 mOsm/kg คือ presumptive สามารถปัสสาวะเข้มข้น Osmolality ปัสสาวะจึงเป็นส่วนหนึ่งของกลไกในการรักษาสมดุลน้ำ ในต่อหน้าของน้ำส่วนเกิน ไตจะผลิตปัสสาวะ dilute ในรอบระยะเวลาของการขาดน้ำ ผลิตปัสสาวะเข้มข้นConcentrating ความสูญเสียมักจะเป็นสัญญาณเริ่มแรกของโรคไต เป็นหลักฐานทางคลินิก nocturia (จำเป็นต้องยกเลิกในเวลากลางคืน) และ polyuria (เพิ่มปริมาณของปัสสาวะ [มักจะ dilute]) อย่างใดอย่างหนึ่ง การทดสอบสารเคมีรีเอเจนต์แถบทดสอบแถบพลาสติกไว้ ประกอบด้วยแผ่นที่มีรวมอยู่ใน reagents สำหรับปฏิกิริยาเคมีตรวจจำนวนปัสสาวะ constituents ปัสสาวะจะถูกเพิ่มลงแผ่นสำหรับปฏิกิริยา โดยการจุ่มแถบพลาสติกเป็นปัสสาวะแล้ว ช้าถอนมัน ปฏิกิริยาเทียบเคียงตามมาคือเวลาปลายทาง ขอบเขตของผู้แต่งสีโดยตรงที่เกี่ยวข้องกับระดับของวิภาคปัสสาวะ สีสามารถอ่านด้วยตนเอง by comparison with สีแผนภูมิ หรือ โดยการใช้ตารางเมตรแบบสะท้อนแสงแบบอัตโนมัติต่อไปนี้เป็นกฎทั่วไปสี่หลังการปัสสาวะรีเอเจนต์แถบทดสอบ1. ทดสอบปัสสาวะทันที ใช้ทดสอบได้อย่างถูกต้องเวลาอ่านเท่านั้น2. ระวังของสารรบกวน3. เข้าใจข้อดีและข้อจำกัดของการทดสอบ4. ใช้ควบคุมอย่างน้อยหนึ่งครั้งต่อวัน เอกสารผลผลบวกจากรีเอเจนต์แถบทดสอบอาจต้องยืนยัน ด้วยวิธีการทางเคมี และกล้องจุลทรรศน์สามารถระบุข้อมูลของผู้ผลิตแหล่ง inhibitors และผล บวกปลอม และ ลบเท็จจากแทรกชุดของแถบทดสอบ ตัวอย่าง กรดแอสคอร์บิคในปัสสาวะสามารถรบกวนปฏิกิริยาที่รีเอเจนต์แถบกลูโคส ฮีโมโกลบิน bilirubin และไนไตรต์ผู้ผลิตได้รับสนับสนุนให้ลด หรือขจัดสัญญาณรบกวนนี้เมื่อเป็นไปได้เนื่องจากกินอาหารเสริมวิตามินซีทั่วไปดังนั้น บางรีเอเจนต์ทดสอบแถบมีปฏิกิริยาการทดสอบเพิ่มเติมที่วัดระดับของกรดแอสคอร์บิคท่อปัสสาวะ และทำหน้าที่เป็นตัวเตือนของสัญญาณรบกวนจากแหล่งนี้หลักการทดสอบ ความสำคัญ และปกติ1. pH 2 โปรตีน3.น้ำตาล 4 คีโตน5.เลือดและไมโยโกลบิน 6 Bilirubin7. Nitrities Urobilinogen 89. leukocyte esterase1. pHส่วนใหญ่ปฏิบัติ urinalysis ใช้รีเอเจนต์ทดสอบหลายแถบที่ประกอบด้วย pH 2 ตัวบ่งชี้ methyl สีแดง และสีฟ้า bromthymol เหล่านี้ให้ช่วงของความไวต่อค่า pH จาก 5.0 การ 9.0 pH อยู่เป็นประจำ โดยสีที่สามารถเปลี่ยนจากสีส้ม (กรด) ให้สีเขียวเป็นสีน้ำเงิน (ด่าง)Fresh urine specimens can have pH values ranging from acidic to alkaline. Upon standing the decomposition of urea into ammonia causes the urine to become more alkaline. Lower pH values are observed in cases of diabetes and in patients with fever. Urine retention by some patients can result in more alkaline urine. The standard method for pH measurements uses glass electrodes. Urinary pH measured with indicator paper is more than accurate enough for clinical purposes, since small changes in urinary pH are of little clinical significance. There is no confirmatory testing for urine pH.Clinical significance—Common clinical causes of acidic and alkaline urine are listed in the following table. The normal American diet is high in protein that results in acidic urine (pH 5.0 to 6.5). Alkaline urines (pH 8.0 to 8.5) are more often associated with an unpreserved or old specimen, which turns alkaline as the result of urease-producing ammonia bacteria, such as Proteus species. Patients with renal tubular acidosis, a clinical syndrome characterized by an inability to excrete an acidic urine, may produce urine with a much higher pH than would be expected on the basis of the acidosis.Normal—The urinary pH range is usually 4.7 to 7.8. Extremely acidic or alkaline urine usually indicates a poorly collected specimen.2. ProteinsReagent-strip test for protein is a semi-quantitative screening procedure for proteinuria. Reagent strips contain a pH sensitive dye; tetrabromphenol blue and 31, 35, 51, 55 tetrachlorophenol-3,4,5,6-tetrabromosulfophthalein. The presence of protein on the strip changes the pH environment of the dye embedded in the pad, resulting in a change in color. pH 3 Tetrabromphenol blue Positive results (green-blue) Protein pH 3 Tetrabromphenol blue Negative results (yellow) No protein Strip tests are more sensitive for albumin and can detect other proteins at higher concentrations. Thus, because there is a risk for false-negative results, it is recommended that the laboratory consider simultaneously performing both a reagent-strip test and an acid precipitation test for the detection of all types of proteinuria. A faintly positive result should be confirmed with a more specific test such as the trichloroacetic acid or the sulfosalicylic acid tests. A grossly positive SSA or TCA turbidity test result may indicate the presence of drugs or Bence Jones proteins.False positive results maybe caused by alkaline or buffered urine as well as by quarternary ammonium compounds found in detergents.Clinical significance—Most of the urine protein is albumin, which has crossed the glomerular membrane. Smaller-molecular-weight proteins such as globulins may also be present in urine. Once filtered at the glomerulus, proteins are almost completely reabsorbed in the proximal tubule. Proteinuria, therefore, can be the result of either increased filtration at the glomerulus or decreased tubular reabsorption. Glomerular proteinuria is associated with the presence of larger molecular weight proteins and larger protein losses, usually > 2 g/day. The nephrotic syndrome is associated with very large losses of protein, usually >2-3 g/day. Tubular proteinuria is associated with smaller amounts (1-3 g/day) of lower molecular weight protein molecules. Small losses of protein in urine can be seen with vigorous exercise and pregnancy.Measurement of urinary pH is also useful for managing patients with renal stones or crystals. Uric acid stones form in acidic urine and are more soluble in alkaline urines. However, alkaline urine will precipitate calcium or calcium phosphate crystals, while an acidic urine will tend to dissolve them. Inducing an alkaline urine during sulfonamide and streptomycin therapy is done to prevent precipitation of these drugs in the kidneys and to prevent the formation of uric acid, cystine, and oxalate stones. Alkaline urines are also desirable during treatment of transfusion reactions and salicylate intoxication. An acidic pH is used to combat bacteriuria in patients with cystitis and to prevent formation of alkaline stones. Technologists should be aware that alkaline urine interferes with the determination of proteins by the reagent strip technology and may alter the urine sediment examination.Normal—A healthy person will excrete up to approximately 100 mg/day, a very small fraction of the plasma protein that is filtered at the glomerulus.3. SugarsEnzymatic testing—The reagent-strip tests are highly specific for glucose. They detect the oxidation of glucose to gluconic acid: Glucose oxidase Glucose + Oxygen in room air Gluconic acid + Hydrogen peroxide Peroxidase Hydrogen peroxide + Chromogen Oxidized chromogen (blue) + H2OTetramethylbenzidine and o-toluidine have been used as the chromogen for the indicator reaction.Copper reduction (Clinitest, Benedict's test)—The Clinitest tablet (Ames Division, Miles Laboratories, Inc., Elkhart, IN) usually serves as a confirmatory test for sugar. Using the principle of the reduction of cupric salts by reducing sugars; including glucose, galactose, lactose, and pentoses; the copper reduction test measures total reducing substances in urine. Heat Cupric ions + Glucose (or other reducing substances) Cuprous oxide + Cuprous hydroxide Alkali (red) (yellow)Clinical significance—Glucose is the predominant sugar in urine. It is not detectable by reagent strips in the urine of healthy individuals. Temporary elevation of glucose excretion measurable by test strips can occur after treatment with some drugs, cases of shock and during pregnancy. Repeated positive testing is almost always diagnostic for diabetes.Reagent strips will detect glucose at a concentration of 400 to 750 mg/L (2.2 to 3.85 mmol/L), while the Clinitest will detect