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Urine
2nd Exam
| Question | Answer |
|---|---|
| What is the preferred specimen for routine urinalysis? | The first morning specimen, since it is the most concentrated. It also has the lowest pH of the day, so the formed elements are preserved better. Dilute random urines may result in false negative results |
| Ideally, how soon after collection should a urine specimen be tested? | Within 1-2 hours, otherwise it should be refrigerated or chemically preserved. |
| What is the preferred method of preservation of urine for routine urinalysis? | Refrigeration for up to 6-8 hours. This slows the multiplication of bacteria, but does not prevent the lytic effect of low specific gravity or alkaline pH. Refrigeration may induce crystal formation, which can obscure other elements in the urine sedimen |
| What changes occur in a urine specimen at room temperature? | The pH increases as bacteria breakdown urea to ammonia. Glucose decreases due to metabolism by bacteria and cells, Ketones, bilirubin, and urobilinogen are lost. Cells and casts lyse. |
| What is the clinical significance of specific gravity? | It is a measurement of the dissolved solute in the urine and reflects the concentrating ability of the kidneys. |
| Which substances contribute most to specific gravity of normal urine? | Urea and sodium chloride. |
| What is normal specific gravity of a random urine? | 1.001-1.035. |
| What is hyposthenuria and what is its significance? | Urine specific gravity less than 1.010. It indicates that the kidneys have lost their concentrating ability. |
| What is isothenuria and what is its significance? | Urine specific gravity fixed at 1.010.This is the specific gravity of the plasma filtrate and indicates that the kidneys can neither concentrate nor dilute the urine. |
| A urine with a specific gravity reading of 1.035 by refractometer contains 1 g/dL of glucose and 1 g/dL of protein. What is the corrected specific gravity? | For each gram/dL of glucose, 0.0004 is subtracted and for each gram/dL of protein, 0.0003 is subtracted. |
| How is the accuracy of the refractometer checked? | It is checked daily with distilled water (1.000) and commercial controls or solutions of known specific gravity such as 5%NaCl (1.022). |
| A urine specific gravity is off the scale of the refractometer. The technologist dilutes the urine 1:2 and reads the result as 1.020.What value should be reported? | 1.040. The last two digits must be multiplied by the reciprocal of the dilution (2). (Some feel that a dilution is not necessary and that the specific gravity should just be reported as "greater than 1.035".) |
| How does the refractometer measure specific gravity? | By refractive index, a comparison of the velocity of light in air with the velocity of light in a solution. |
| A urine has a specific gravity of 1.040 by refractometer. What might be the cause of the high specific gravity? | Since a specific gravity of 1.040is physiologically impossible, it indicates the presence of an iatrogenic (medically administered) high-molecular-weight solute, such as radiopaque dyes (radiographic contrast media, x-ray dye). Although large quantities |
| What is the principle of the specific gravity determination by reagent strips? | It is based on a change in pK (dissociation constant) of a polyelectrolyte on the reagent strip. The polyelectrolyte ionizes in proportion to the number of ions in solution, causing a color change in the indicator. An advantage of this method is that it |
| How does urine pH affect specific gravity by reagent strip? | Specimens with a pH of 6.5 or higher have decreased readings because of interference with the color indicator. Reagent strip manufacturers recommend adding 0.005 to specific gravity readings when the pH is 6.5 or higher. |
| What is responsible for the color of normal urine? | Primarily urochrome, a yellow pigment, and to a lesser extent, uroerythrin (red) and urobilin (orange-red) |
| What might cause the urine to be almost colorless (straw)? | Dilute urine. |
| What are some causes of amber urine? | Urine with high specific gravity, bilirubin, large doses of vitamin A, pyridium, and nitrofurantoin. |
| If a urine develops a yellow foam on top when it is shaken, what abnormal test result would be expected on the reagent strip? | A positive bilirubin. |
| What might cause the urine to be yellow-green? | Bilirubin oxidized to biliverdin. |
| What are some causes of red urine? | Blood, hemoglobin, myoglobin, porphyrins, and beets. |
| What might cause the urine to be black or brown? | Melanin, homogentisic acid, and RBCs oxidized to methemoglobin. |
| When is melanin present in the urine? | With metastatic melanoma. It turns the urine dark brown or black. |
| When is homogentisic acid present in the urine? | With alkaptonuria, an inborn error of metabolism. An enzyme deficiency prevents the phenylalanine-tyrosine pathway from going to completion and homogentisic acid accumulates in the blood, tissues, and urine. Homogentisic acid turns the urine black on s |
| What might cause the urine to be port wine colored? | Porphyrins. |
| What might cause the urine to be smoky in appearance? | Red blood cells. |
| What might cause the urine to be cloudy? | White blood cells, red blood cells, epithelial cells, bacteria, and crystals. |
| What would cause a strong ammonia odor in a urine specimen? | Urinary tract infection or an old specimen. The odor is due to ammonia from the breakdown of urea. |
| What causes a fruity odor in urine? | Ketones. |
| Which chemical urinalysis (dipstick) tests require microscopic analysis? | The sediment must be looked at if any of the following is positive on the dip stick or abnormal appearance. . Any urine sample with clarity other than clear, dipstick positive for Leukocyte esterase, Nitrate, Blood and Protein |
| What are glitter cells? | They are WBCs whose granules demonstrate Brownian movement. They are seen in hypotonic urine and stain faintly or not at all with the Sternheimer-Malbin (Crystal Violet and Safranin) stain. |
| What are clue cells? | Clue cells are epithelial cells cover with bacteria, associated with Gardenerella vaginalis Infections |
| At what pH are the formed elements best preserved in the urine? | Acid. Which stain can be used for urine sediment examination? |
| Interpret the following urine sediment findings: 0-5 WBCs/HPF, 0-2 RBC/HPF, 0-2 hyaline casts/LPF, few epithelial cells, few uric acid crystals, rare calcium oxalate crystals. | These findings are normal. |
| What is the significance of epithelial cells in the urine sediment? | Squamous and transitional epithelial cells are seldom important Renal epithelial cells are a sign of renal tubular necrosis. |
| A urine sediment contains many squamous epithelial cells and 4+ bacteria. What is the significance of these findings? | The results are not significant. These findings are frequently seen in the urine of females when the urine is not a clean catch. Many squamous epithelial cells are a sign of vaginal contamination. |
| What is pyuria? | The presence of white blood cells in the urine. It is a sign of infection or inflammation of the urinary tract. |
| What is the significance of clumped WBCs in the urine sediment? | They are a sign of an active infection. |
| What might cause degranulation and lysis of WBCs in the urine sediment? | Prolonged standing at room temperature. |
| What is the clinical significance of oval fat bodies in the urine sediment? | Oval fat bodies are fat-filled renal tubular epithelial cells. They are a sign of tubular necrosis and are seen with nephrotic syndrome. Oval fat bodies can be confirmed with polarized light or Sudan stains. With polarized light, the lipids will demonst |
| What are dysmorphic RBCs? | They are RBCs that vary in size, have bizarre shapes, or are fragmented. They are a sign of glomerular bleeding. |
| What are casts? | Protein molds of the renal tubules. They are characterized by parallel sides and rounded ends. |
| What protein is found in all casts? | Uromodulin or Tamm Horsfall protein. Pathological casts (granular, cellular, or waxy) contain albumin as well. Hyaline casts have Uromodulin or Tamm Horsfall only. |
| Where are casts formed? | In the distal convoluted tubules and collecting ducts. Their formation is favored by low pH; high specific gravity; urinary stasis; and the presence of sodium, calcium, and protein. |
| List the order of progression in the aging of casts. | Cellular, granular, waxy. |
| Highly refractile structures with blunt ends are observed in an infant's urine sediment and identified as waxy casts. Upon review of the results, the supervisor notes that there was no protein in the urine. What might explain these findings? | Because there is no protein in the urine, the structures must be something other than casts. Since the patient is an infant, disposable diaper fibers should be suspected. Examination with polarized light may be helpful. Paper fibers polarize light; cast |
| What might cause casts to dissolve? | Alkaline urine. |
| How can the presence of large numbers of yeast affect reagent strip results? | If the urine is not tested promptly or refrigerated, the yeast could metabolize any glucose present and cause a false negative result |
| How can the presence of bacteria in the urine affect the urine chemistry results? | If the urine is not tested promptly or refrigerated, bacteria multiply, break down urea, and metabolize glucose. This can cause turbidity, increased pH, decreased glucose, and false positive protein and nitrite. |
| Name the normal crystals found in acid urine. | Amorphous urates, uric acid, and calcium oxalate. |
| Name the abnormal crystals found in acid urine. | Leucine, tyrosine, cystine, cholesterol, and bilirubin. |
| Name the normal crystals found in alkaline urine. | Amorphous phosphates, triple phosphates, ammonium biurate, calcium phosphate, and calcium carbonate. |
| Name the abnormal crystals found in alkaline urine. | None. |
| At which pH are abnormal urinary crystals most likely to be seen? | Acid. |
| Stair steps or notch glass | cholesterol |
| Thorn apples | ammonium biurate |
| Envelopes | calcium oxalate |
| Coffin lids | triple phosphate |
| Silky needles | tyrosine |
| Oily spheres | leucine |
| Dumb-bells | calcium carbonate |
| Hexagon | cystine |
| Which crystal is the only needle found in alkaline urine? | Calcium phosphate. It may appear as rosettes and “pointing fingers". |
| In what other forms does calcium oxalate appear besides the "envelope"? | Less commonly, it can be dumb-bell shaped or ovoid. When ovoid, it may be mistaken for RBCs. Polarized light can help in the differentiation. Calcium oxalate crystals are strongly birefringent; RBCs are not |
| What is the clinical significance of calcium oxalate crystals? | Calcium oxalate crystals are usually not significant. Large crystals in clusters may be associated with stone formation. Calcium oxalate is the most common constituent of renal calculi. |
| What is the clinical significance of triple phosphate crystals? | Usually none. |
| What other crystal may be mistaken for cystine? | Uric acid may also be six-sided. It is important to differentiate the uric acid and cystine because cystine is pathologic and uric acid usually is not. Patients with cystinuria may form cystine stones which can cause kidney damage. Cystine can be confir |
| Name two crystals that are seen in the urine with severe liver disease. | Leucine and tyrosine. |
| What is the clinical significance of cholesterol crystals in the urine sediment? | They are associated with the nephrotic syndrome. |
| Which urinary crystals are birefringent? | Calcium oxalate, cholesterol, uric acid, triple phosphate, and calcium carbonate. Starch, diaper fibers, and radiographic contrast media are also birefringent. |
| An MLT student observed that several of the urine sediments he examined had irregularly round granules with central slits. What were they? | Starch granules. They are a common contaminant in the laboratory if powdered latex gloves are worn. With polarized light, starch granules produce irregular, fuzzy Maltese crosses. |
| A urine sediment shows 10-20 RBCs/HPF, but the reagent strip is negative for blood. Controls on the reagent strips gave expected results and the patient's urine was tested again, with the same results. What might account for this apparent discrepancy? | The patient might have ingested large quantities of vitamin-C. Vitamin-C may cause false negative or delayed results with tests that depend on the release of oxygen and oxidation of a chromogen. This includes not only the blood test on the reagent strip |
| The technologist in charge of the MT students' urinalysis training places morning specimens with abnormal sediment in the refrigerator for examination in the afternoon student lab. When comparing student results with his, he notes that all of the stude | The technologist examined the urine while it was fresh. Crystals often precipitate when urine is refrigerated. |
| What is hemosiderin? | A form of stored iron. Hemosiderin, formed from hemoglobin by the renal tubular epithelial cells, is seen in the urine with severe intravascular hemolysis and hemochromatosis. Unstained, it appears as coarse yellow-brown granules, It stains blue with t |
| A urine specimen for routine urinalysis has been refrigerated overnight. Prior to testing, what two things should be done to the specimen? | It should be brought to room temperature and thoroughly mixed. The enzymatic reactions on the strips may be inhibited if the urine is cold and false negative results may be obtained if RBCs and WBCs have settled to the bottom of the specimen container. |
| A technologist notices that a urine specimen is intensely colored. Why is this an important observation? | Intensely colored urines may result in false positive reagent strip reactions |
| What are the normal values for the tests on the urine reagent strip? pH: | random urine 4.5-8, first AM specimen 5-6 |
| What are the normal values for the tests on the urine reagent strip? Protein: | negative or trace |
| What are the normal values for the tests on the urine reagent strip? Blood: | negative |
| What are the normal values for the tests on the urine reagent strip? Nitrite: | negative |
| What are the normal values for the tests on the urine reagent strip? Leukocyte esterase: | negative |
| What are the normal values for the tests on the urine reagent strip? Glucose: | negative |
| What are the normal values for the tests on the urine reagent strip? Ketones: | negative |
| What are the normal values for the tests on the urine reagent strip? Bilirubin: | negative |
| What are the normal values for the tests on the urine reagent strip? Urobilinogen: | ≤ 1 EU/dL |
| How does a vegetarian diet affect the urine pH? | It results in an alkaline urine. |
| What is the principle of the protein test on the reagent strip? | It is based on the protein error of indicator. A buffer in the reagent pad maintains the pH at 3, a pH at which the indicator should be yellow; however, if protein is present, the indicator changes to green or blue. |
| How could the protein reaction be adversely affected by dipping the reagent strip in the urine too long? | If the citrate buffer is washed out, a false positive occurs because the pH of the Urine causes a color change in the indicator. |
| Which protein(s) does the reagent strip detect? | Albumin. |
| Which proteins are detected by the acid precipitation tests for protein? | Albumin, globulins, and Bence Jones proteins. |
| Which acid is commonly used to precipitate urine protein? | Sulfosalicylic acid (SSA). The protein precipitation test should be performed on the supernatant of a centrifuged urine to avoid false positive reactions. Before automated reagent strip readers, it was common practice to confirm all positive protein res |
| Why is the test for protein included in a routine urinalysis? | It is an early indicator of renal disease. |
| 1What are some causes of false positive results in protein precipitation tests? | Turbidity, radiographic contrast media, and some drugs such as penicillin, sulfonamides, cephalosporins, and tolbutamide. |
| What might account for a positive protein precipitation test with a negative reagent strip protein? | A protein other than albumin, such as Bence-Jones protein. The discrepancy could also be due to a false positive precipitation test due to factors listed above. |
| How can a highly buffered alkaline urine cause erroneous protein results? | It can cause a false-negative precipitation test by neutralization of the acid reagent. It can also cause a false-positive protein on the reagent strip if the citrate buffer is overcome and the pH of the reagent square increased. The increased pH would |
| What are Bence Jones proteins? | Free immunoglobulin light chains, either kappa or lambda. They may be present in the urine of patients with multiple myeloma and Waldenstrom's macroglobulinemia. |
| What is orthostatic proteinuria? | A benign proteinuria most commonly seen in young adults. It is characterized by protein in the urine after standing. The first morning urine is negative for protein. |
| What reagents are used in the glucose test on the reagent strip? | Glucose oxidase / peroxidase. |
| Which sugar(s) does the reagent strip detect? | The reagent strip is specific for glucose. |
| What is the significance of a positive urine glucose? | It usually indicates an elevated blood glucose and is commonly seen in uncontrolled diabetics. |
| If a patient has glucose in his urine, what is probably true about his blood glucose level? | It is probably above 160- 180mg/dL, the average renal threshold for glucose. |
| What is the name of the condition in which glucose is excreted in the urine when the blood sugar is within the normal range? | Renal glucosuria, a defect in the renal tubules' ability to reabsorb glucose. |
| What effect would contamination of the urine container with oxidizing detergents or bleach have on the glucose test results by reagent strip? | It would result in a false positive glucose. The blood reaction would also be a false positive. |
| Which is more specific for glucose, the reagent strip or the copper reduction test? | The reagent strip. The copper reduction test reacts with all reducing sugars (glucose, galactose, fructose, lactose, and pentose). Uric acid, creatinine, homogentisic acid, ascorbic acid, chloroform, and formaldehyde are non-sugar reducing substances th |
| Which is more sensitive for glucose, the reagent strip or copper reduction test? | The reagent strip. |
| What is "pass through" with the copper reduction test? | When the glucoses greater than2 g/dl, the color changes to bright orange and then back to dark greenish-brown. Unless the reaction is watched, the result will be mistakenly recorded as negative. The test should be repeated using the 2-drop method. |
| Which specimens should routinely be tested by the copper reduction test? | Urine from pediatric patients (up to at least 2 years of age), to screen for galactosemia. |
| What might cause a positive urine glucose oxidase test and a negative test for reducing sugars? | Since glucoses a reducing sugar, it should be detected by both methods. In this case, the glucose level must be below the sensitivity of the copper reduction test. |
| Name the three ketones . | Acetone, acetoacetic acid (diacetic acid), and beta-hydroxybutyric acid (betahydroxybutyrate). |
| What is the significance of positive urine ketones? | Ketones in the urine are a sign of impaired carbohydrate metabolism and an indication that fats are being used as the primary source of energy. Ketones are seen in the urine with uncontrolled diabetes mellitus, low carbohydrate diets, vomiting, and star |
| What reagent is used to detect ketones on reagent strips? | Sodium nitroprusside. |
| Laboratory tests for ketones are usually most sensitive to which ketone? | Acetoacetic acid. |
| A patient's urine is positive for glucose and ketones. What further testing should be performed? | Blood glucose. The urine results are suggestive of uncontrolled diabetes mellitus. |
| What can result in a false negative urine ketone test? | An improperly stored specimen. Acetoacetic acid is converted to acetone, which is lost through evaporation. |
| What reagent is used to detect bilirubin on reagent strips? | Diazonium salts. |
| Atypical color reactions are observed on the bilirubin pad on the reagent strip. What should be done? | An Ictotest. The Ictotest is less subject to interference and is more sensitive than the reagent strip. |
| What reagent is used to detect urobilinogen in the quantitative test? | Ehrlich's reagent, para-dimethylamino-benzaldehyde. This reagent also reacts with porphobilinogen. The urine should be at room temperature to avoid false positives caused by the warm aldehyde reaction. |
| A physician suspects that his patient is in the early stage of liver disease. The urinalysis shows slightly increased urobilinogen, but the bilirubin is negative. What might cause these results? What further urine testing should be performed? | Urobilinogen is a more sensitive indicator of liver disease than bilirubin. An Ictotest should be performed on the urine since it is more sensitive to bilirubin than the reagent strip test. A serum bilirubin and liver enzymes should be ordered. |
| Which substances in the urine are light sensitive? | Bilirubin and urobilinogen. |
| What reagents are used in the blood test on the reagent strip? | The test is based on the peroxidase-like activity of hemoglobin. The reagents on the strip are peroxide and a chromogen. The second step in this reaction is similar to that of the glucose oxidase test. |
| What substances will cause a positive blood test on the reagent strip? | Red blood cells, hemoglobin, and myoglobin. |
| What does a speckled reaction on the blood square of the reagent strip indicate? | Hematuria. The speckled reaction is due to the lysis of RBCs on the reagent pad. |
| What might cause a positive urine blood test with no RBCs seen in the microscopic examination? | Lysis of the RBCs, hemoglobinuria, or myoglobinuria. |
| What is the significance of a positive urine nitrite? | Urinary tract infection by nitrate-reducing bacteria. |
| What are some factors that can cause false negative nitrite tests? | Less than four hours incubation time in the bladder, insufficient dietary nitrate, large quantities of ascorbic acid. And degradation of nitrite to nitrogen. |
| What is the significance of a positive urine leukocyte esterase test? | Urinary tract infection. The advantage of the chemical test is its ability to detect leukocyte enzymes even if the cells have lysed and are not visible by microscopy. |
| Which tests on the reagent strip are inhibited by large amounts of vitamin C (ascorbic acid)? | Blood, glucose, bilirubin. nitrites, and leukocyte esterase reactions may be inhibited. This varies from brand to brand so the manufacturer's package insert should be consulted. |
| Which other chemical urinalysis test might be a false positive due to large amounts of ascorbic acid in the urine? | The copper reduction test. Vitamin-C (ascorbic acid) is a reducing substance. |
| Which chemical urinalysis tests require confirmation? | The routine use of confirmatory testing for glucose, bilirubin, ketones, and protein has been eliminated in most laboratories. |
| What are porphyrins? | Porphyrins (uroporphyrin, coproporphyrin, and protoporphyrin) are precursors in the synthesis of heme. Porphyrinuria can be due to an inherited inborn error of metabolism or acquired through metabolic disease or exposure to toxic substances. Lead poison |
| How are porphyrins detected? | The presence of porphyrins can be suspected when the urine has a red or port-wine color. Porphyrins can be identified based on their fluorescence with UV light. |
| How is porphobilinogen detected? | porphobilinogen is colorless and does not fluoresce. It is identified by Watson Schwartz test using Ehrlich's aldehyde reagent, the same reagent used for urobilinogen. To differentiate between porphobilinogen and urobilinogen, extractions with chlorofo |
| In what is Urobilinogen soluble? | chloroform and butanol |
| porphobilinogen is insoluble in ? | chloroform and butanol. |
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