the tables flashcards

All 49 cards

1. Card 1

   Why is it important for a requisition form to accompany specimens delivered to the laboratory?

   A requisition form ensures that the information on the form matches the information on the specimen label, providing crucial details such as the method of collection, possible interfering medications, and the patient's clinical information, which are essential for accurate testing and diagnosis.

2. Card 2

   Define the conditions under which a urine specimen should be rejected by the laboratory.

   A urine specimen should be rejected if it is in an unlabeled container, if the labels and requisition forms do not match, if it is contaminated with feces or toilet paper, if the container's exterior is contaminated, if the quantity is insufficient, or if it has been improperly transported.

3. Card 3

   How does improper handling of a urine specimen after collection affect its composition?

   Improper handling, such as delays in delivery or testing without preservation, can lead to significant changes in urine composition due to in vitro processes. These changes, often related to bacterial growth, can seriously affect the results of a routine urinalysis.

4. Card 4

   Why should urine specimens be delivered to the laboratory promptly and tested within 2 hours of collection?

   Urine specimens should be delivered and tested promptly to maintain specimen integrity. If left unpreserved at room temperature for longer than 2 hours, significant changes can occur in various analytes, primarily due to bacterial growth and metabolism, which can alter test results.

5. Card 5

   How does refrigeration at 2°C to 8°C preserve a urine specimen?

   Refrigeration at 2°C to 8°C is the most routinely used preservation method because it effectively decreases bacterial growth and metabolism. This helps to maintain the specimen's integrity and prevents changes in its composition that would otherwise occur at room temperature.

6. Card 6

   Explain why a refrigerated urine specimen must return to room temperature before chemical testing by reagent strips.

   A refrigerated urine specimen must return to room temperature before chemical testing by reagent strips because the chemical reactions on the strips are temperature-dependent. Testing a cold specimen could lead to inaccurate or falsely low results.

7. Card 7

   What are the ideal characteristics of a chemical preservative for urine specimens?

   The ideal chemical preservative for urine specimens should be bactericidal, inhibit urease activity, and preserve formed elements in the sediment. Additionally, it should not interfere with chemical tests, although such an ideal preservative does not currently exist.

8. Card 8

   Why does the color of unpreserved urine become modified or darkened?

   The color of unpreserved urine becomes modified or darkened primarily due to the oxidation or reduction of metabolites present in the specimen over time. This chemical change alters the visual appearance of the urine.

9. Card 9

   How does bacterial growth affect the clarity of an unpreserved urine specimen?

   Bacterial growth in an unpreserved urine specimen leads to a decrease in clarity. This is because the multiplication of bacteria, along with the precipitation of amorphous material, makes the urine appear cloudier.

10. Card 10

    Explain the cause of increased odor in unpreserved urine.

    The increased odor in unpreserved urine is caused by bacterial multiplication. These bacteria break down urea into ammonia, which has a distinct, strong odor, leading to the noticeable change in the specimen's smell.

11. Card 11

    Why does the pH of unpreserved urine tend to increase?

    The pH of unpreserved urine tends to increase due to the breakdown of urea to ammonia by urease-producing bacteria and the loss of carbon dioxide. Ammonia is alkaline, which raises the pH of the urine.

12. Card 12

    What causes the decrease in glucose levels in unpreserved urine?

    Glucose levels decrease in unpreserved urine due to glycolysis and the utilization of glucose by bacteria present in the specimen. Bacteria metabolize glucose as a food source, leading to its reduction over time.

13. Card 13

    Explain why bilirubin levels decrease in unpreserved urine.

    Bilirubin levels decrease in unpreserved urine primarily due to exposure to light, which causes photo-oxidation of bilirubin to biliverdin. This chemical change reduces the detectable amount of bilirubin in the specimen.

14. Card 14

    What causes the decrease in urobilinogen levels in unpreserved urine?

    Urobilinogen levels decrease in unpreserved urine because it oxidizes to urobilin when exposed to air. This chemical transformation reduces the concentration of urobilinogen detectable in the specimen.

15. Card 15

    How does bacterial activity lead to an increase in nitrite levels in unpreserved urine?

    Bacterial activity leads to an increase in nitrite levels in unpreserved urine through the multiplication of nitrate-reducing bacteria. These bacteria convert nitrates, naturally present in urine, into nitrites.

16. Card 16

    Why do red and white blood cells and casts decrease in unpreserved urine?

    Red and white blood cells and casts decrease in unpreserved urine because they disintegrate, particularly in dilute alkaline urine. The cellular structures break down over time, making them less detectable.

17. Card 17

    What is the effect of unpreserved conditions on bacteria in a urine specimen?

    In unpreserved urine specimens, bacteria will multiply significantly. This increase in bacterial count can lead to various changes in the urine's composition and affect the accuracy of test results.

18. Card 18

    How does improper preservation affect the presence of Trichomonas in a urine specimen?

    Improper preservation leads to a decrease in Trichomonas in a urine specimen because these organisms lose their motility and eventually die. This makes them undetectable or difficult to identify in the specimen.

19. Card 19

    What specific information, beyond patient details, can be included on a requisition form for a urine specimen?

    Beyond patient details, a requisition form can include specific information such as the method of collection or type of specimen, any possible interfering medications the patient is taking, and relevant clinical information about the patient's condition.

20. Card 20

    Why is it important to record the time a specimen is received in the laboratory?

    It is important to record the time a specimen is received in the laboratory to track the specimen's handling timeline. This information helps ensure that the specimen is tested within the recommended timeframe (e.g., 2 hours) or properly preserved, maintaining its integrity for accurate results.

21. Card 21

    How can laxity in the treatment of a urine specimen after collection impact urinalysis results?

    Laxity in treating a urine specimen after collection can significantly impact urinalysis results because changes in urine composition occur in vitro. This can lead to inaccurate readings for various analytes, potentially resulting in misdiagnosis or incorrect treatment decisions.

22. Card 22

    Why is it crucial for laboratories to have a written policy detailing conditions for specimen rejection?

    It is crucial for laboratories to have a written policy for specimen rejection to ensure consistency, maintain quality control, and prevent the testing of compromised specimens. This policy guides personnel on when to reject a specimen and ensures appropriate action is taken, such as collecting a new one.

23. Card 23

    What is the primary reason for adding a chemical preservative to a urine specimen when refrigeration is not possible for long-distance transport?

    The primary reason for adding a chemical preservative when refrigeration is not possible for long-distance transport is to prevent changes in urine composition. The preservative aims to be bactericidal, inhibit urease, and preserve formed elements, thus maintaining specimen integrity during transit.

24. Card 24

    Why is it advised never to discard a specimen before checking with a supervisor?

    It is advised never to discard a specimen before checking with a supervisor because a supervisor can provide guidance on whether a specimen is truly unsuitable or if there are alternative handling or testing protocols that can be applied, preventing unnecessary loss of a patient sample.

25. Card 25

    Why is it important to choose a suitable preservative for urine specimens, and what is a key challenge in this selection?

    It is important to choose a suitable preservative to prevent analyte changes caused by bacterial growth, metabolism, or disintegration. A key challenge is that an ideal preservative that does not interfere with chemical tests does not exist, so the choice depends on the specific analysis required.

26. Card 26

    Define the term 'random specimen' in the context of urine collection.

    A random specimen is the most commonly received urine specimen due to its ease of collection and convenience. It can be collected at any time, but the exact time of voiding should be recorded on the container.

27. Card 27

    How does refrigeration act as a urine preservative, and what is its primary disadvantage?

    Refrigeration preserves urine by preventing bacterial growth and metabolism. Its primary disadvantage is that it precipitates amorphous phosphates and urates, which can interfere with analysis.

28. Card 28

    Explain the advantages of using boric acid as a urine preservative.

    Boric acid prevents bacterial growth and metabolism, keeps the pH at about 6.0, and can be used for urine culture transport. It also does not interfere with chemical tests.

29. Card 29

    What are the disadvantages of using formalin (formaldehyde) as a urine preservative?

    Formalin acts as a reducing agent, which interferes with chemical tests for glucose, blood, leukocyte esterase, and copper reduction. It also inhibits reagent strip tests for glucose, blood, and leukocytes.

30. Card 30

    How does sodium fluoride function as a urine preservative, and what are its drawbacks?

    Sodium fluoride is a good preservative for drug analyses. However, its drawbacks include interfering with drug and hormone analyses and inhibiting reagent strip tests for glucose, blood, and leukocytes.

31. Card 31

    What are the benefits of using commercial preservative tablets for urine specimens?

    Commercial preservative tablets are convenient when refrigeration is not possible and have controlled concentrations to minimize interference with tests. Their composition needs to be checked to determine possible effects on desired tests.

32. Card 32

    Why is the first morning specimen considered the ideal screening specimen for urinalysis?

    The first morning specimen is considered ideal because it is a concentrated specimen, which assures the detection of chemicals and formed elements that might not be present in a dilute random specimen. It is also essential for preventing false-negative pregnancy tests and evaluating orthostatic proteinuria.

33. Card 33

    How does exposure to light affect bilirubin and urobilinogen levels in a urine specimen?

    Exposure to light and leaving the specimen at room temperature can cause bilirubin and urobilinogen levels to decrease due to photo-oxidation to biliverdin and oxidation to urobilin, respectively.

34. Card 34

    What is the primary cause of the multiplication of nitrate-reducing bacteria in a urine specimen?

    The primary cause of the multiplication of nitrate-reducing bacteria in a urine specimen is not explicitly stated in the provided text, but it is listed as an 'Analyte Change Cause'.

35. Card 35

    What specific instructions should be given to a patient regarding the collection and delivery of a first morning urine specimen?

    The patient should be instructed to collect the specimen immediately upon arising and to deliver it to the laboratory within 2 hours or keep it refrigerated until delivery.

36. Card 36

    What are the potential drawbacks of a random urine specimen, despite its convenience?

    Despite its convenience, a random urine specimen may show erroneous results due to dietary intake or physical activity just before collection, potentially leading to a request for an additional specimen under more controlled conditions.

37. Card 37

    How does a light gray and gray C&S tube preserve a urine sample, and for how long is it stable?

    A light gray and gray C&S tube contains a preservative (boric acid, sodium borate, and sodium formate) that prevents bacterial growth and metabolism. The sample is stable at room temperature for 48 hours.

38. Card 38

    What are the components of the preservative in the yellow UA Plus tube, and what is its stability?

    The yellow UA Plus tube contains no preservative. It is designed for use on automated instruments and must be refrigerated within 2 hours.

39. Card 39

    Describe the preservative and stability features of the cherry red/yellow Preservative Plus tube.

    The cherry red/yellow Preservative Plus tube contains sodium propionate, ethyl paraben, and chlorhexidine. It prevents bacterial growth for 24 hours and is stable for 72 hours at room temperature, making it instrument-compatible.

40. Card 40

    What additional information is provided regarding the use of formalin as a preservative for cells and casts?

    To preserve cells and casts, the specimen container should be rinsed with formalin. However, it's important to remember its interference with chemical tests.

41. Card 41

    When preserving samples for transport to another laboratory, what crucial step should be taken?

    When preserving samples for transport to another laboratory, it is crucial to check with that laboratory concerning the appropriate preservative to ensure compatibility and accurate testing.

42. Card 42

    What specific conditions might be necessary to regulate when collecting a urine specimen that is representative of a patient's metabolic state?

    Regulation of certain aspects like time, length, and method of collection, as well as the patient's dietary and medicinal intake, may be necessary to obtain a representative specimen of a patient's metabolic state.

43. Card 43

    What happens to a urine specimen if it undergoes disintegration in dilute alkaline urine?

    The specific analyte change caused by disintegration in dilute alkaline urine is not detailed in the provided text, but it is listed as an 'Analyte Change Cause'.

44. Card 44

    How does the loss of motility and death of microorganisms affect a urine specimen?

    The loss of motility and death of microorganisms are listed as 'Analyte Change Cause' and would typically indicate a change in the viability or presence of certain elements in the urine, potentially affecting culture results.

45. Card 45

    What is the consequence if a urine specimen is below the minimum fill line in a light gray and gray C&S tube?

    If a urine specimen is below the minimum fill line in a light gray and gray C&S tube, it should not be used, as the preservative concentration may not be effective or accurate.

46. Card 46

    Why is it important to instruct patients about special collection procedures for urine specimens?

    It is important to instruct patients about special collection procedures because these conditions, such as time, length, and method of collection, and dietary intake, are necessary to obtain a specimen representative of their metabolic state.

47. Card 47

    What is the primary advantage of the light gray and gray C&S tube regarding pH?

    The primary advantage of the light gray and gray C&S tube is that its preservative (boric acid, sodium borate, and sodium formate) keeps the pH at about 6.0, which is beneficial for urine culture transport.

48. Card 48

    How does the yellow UA Plus tube differ from other collection tubes in terms of preservatives and usage?

    The yellow UA Plus tube has no preservative and is specifically designed for use on automated instruments. It requires refrigeration within 2 hours of collection, unlike some other tubes that offer longer room temperature stability with preservatives.

49. Card 49

    Why is a 24-hour urine specimen often necessary for quantitative chemical tests?

    A 24-hour urine specimen is necessary because many solutes, such as catecholamines, 17-hydroxysteroids, and electrolytes, exhibit diurnal variations, with concentrations changing throughout the day. Additionally, daily activities like exercise, meals, and body metabolism can affect the concentration of substances, making a timed collection essential for accurate quantitative results.

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