5. CHEM CLS

1. What specimen is used for most chemistry tests?

Serum, usually from a red-top tube.

2. What specimen is generally better than oxalate, EDTA, or citrate for chemistry testing?

Plasma.

3. What additive is used for ammonia, blood gases, and lactic acid specimens?

Heparin, often collected on ice.

4. What additive tube is used for glucose testing?

Sodium fluoride, gray-top tube.

5. What enzyme does sodium fluoride inhibit?

Enolase, an enzyme in glycolysis.

6. Why does sodium fluoride help preserve glucose?

It inhibits enolase and slows glycolysis, preventing glucose from being consumed by cells.

7. How does acid phosphatase affect specimen pH?

Acid phosphatase decreases pH.

8. Why should EDTA not be used for sodium or potassium testing?

EDTA contains Na+ or K+ and can falsely increase those results.

9. Why should EDTA not be used for calcium testing?

EDTA chelates calcium, making the calcium result falsely low.

10. What is hemolysis?

RBC rupture that releases intracellular contents into serum or plasma.

11. Which chemistry analyte is increased by hemolysis because RBCs release it?

Potassium.

12. Which enzyme is increased by hemolysis and is abbreviated LD?

Lactate dehydrogenase.

13. Which enzyme abbreviated ALD is increased by hemolysis?

Aldolase.

14. Which enzyme abbreviated ACP is increased by hemolysis?

Acid phosphatase.

15. Which mineral abbreviated Mg is increased by hemolysis?

Magnesium.

16. Which ion abbreviated PO4 is increased by hemolysis?

Phosphate.

17. What can hemolysis cause on protein electrophoresis?

An extra band from released hemoglobin.

18. How can hemolysis affect iron results?

It can increase iron.

19. How can hemolysis affect bilirubin results?

It can decrease or increase bilirubin depending on hemoglobin and bilirubin concentration.

20. What is the end product of carbohydrate digestion?

Glucose.

21. What body process keeps blood glucose at a maintained level?

Hormonal regulation.

22. Why is blood glucose tightly maintained?

Glucose is the preferred energy source for life processes.

23. How much can glucose decrease per hour in whole blood?

About 10 mg/dL per hour due to cellular glycolysis.

24. What happens to glucose stability if the sample is refrigerated?

Glucose remains stable longer because cell metabolism slows.

25. What anticoagulant helps slow glycolysis in glucose testing?

Sodium fluoride.

26. How do arterial and capillary glucose values compare with venous glucose values?

They are about 2 to 3 mg/dL higher than venous values.

27. What is the usual relationship between CSF glucose and plasma glucose?

CSF glucose is about 60 to 65 percent of plasma glucose.

28. What hormone lowers serum glucose?

Insulin.

29. Where is insulin produced?

Beta cells of the islets of Langerhans in the pancreas.

30. What is the main action of insulin?

It decreases serum glucose by stimulating cellular glucose uptake.

31. What hormone from pancreatic alpha cells increases serum glucose?

Glucagon.

32. What is the main action of glucagon?

It increases serum glucose by stimulating glycogenolysis, the breakdown of glycogen to glucose.

33. What pituitary hormone increases serum glucose and opposes insulin?

ACTH.

34. What hormone from the anterior pituitary increases serum glucose and opposes insulin?

Growth hormone.

35. What adrenal cortex hormone increases serum glucose?

Cortisol.

36. How does cortisol increase glucose?

It stimulates gluconeogenesis, the production of glucose from non-carbohydrate sources.

37. What placental hormone increases serum glucose and opposes insulin?

Human placental lactogen.

38. What adrenal medulla hormone increases serum glucose?

Epinephrine.

39. How does epinephrine increase glucose?

It stimulates glycogenolysis and sympathetic activity.

40. Which thyroid hormones increase serum glucose?

T3 and T4.

41. How do T3 and T4 affect glucose?

They increase serum glucose by stimulating glycogenolysis.

42. Which hormones in the GAG CHET memory aid increase serum glucose?

Glucagon, ACTH, growth hormone, cortisol, human placental lactogen, epinephrine, T3, and T4.

43. What causes diabetes mellitus?

Decreased insulin production or ineffective insulin action.

44. What symptom in diabetes is related to excess urination?

Polyuria.

45. What symptom in diabetes is related to excess thirst?

Polydipsia.

46. What symptom in diabetes is related to increased hunger?

Polyphagia.

47. What common wound-related symptom occurs in diabetes?

Poor wound healing.

48. What body weight change may occur in uncontrolled diabetes?

Weight loss.

49. Which blood test is commonly increased in diabetes?

Glucose.

50. Which urine test is commonly positive in diabetes?

Urine glucose.

51. Which long-term glycemic marker is increased in diabetes?

A1c.

52. Which lipid result may be increased in diabetes?

Cholesterol.

53. What acid-base change is associated with diabetic ketoacidosis?

Increased H+ due to metabolic acidosis.

54. What urine and blood finding is associated with diabetic ketoacidosis?

Ketones in blood and urine.

55. What fasting plasma glucose result is normal?

Less than 100 mg/dL.

56. What fasting plasma glucose result is diagnostic for diabetes mellitus?

Greater than or equal to 126 mg/dL.

57. What fasting plasma glucose result indicates impaired fasting glucose?

100 to less than 126 mg/dL.

58. What 2-hour oral glucose tolerance result is normal?

Less than 140 mg/dL.

59. What 2-hour oral glucose tolerance result is diagnostic for diabetes mellitus?

Greater than or equal to 200 mg/dL.

60. What 2-hour oral glucose tolerance result indicates impaired glucose tolerance?

140 to less than 200 mg/dL.

61. What casual plasma glucose result can diagnose diabetes when symptoms are present?

Greater than or equal to 200 mg/dL with unexplained weight loss, polyuria, or polydipsia.

62. What A1c result is considered normal in the source table?

Less than 5.6 percent.

63. What A1c result is diagnostic for diabetes mellitus?

Greater than or equal to 6.5 percent.

64. What A1c result indicates prediabetes?

5.7 to 6.4 percent.

65. What glucose dose is used for a standard oral glucose tolerance test?

75 g glucose.

66. What glucose dose is used for children during an oral glucose tolerance test?

1.75 g per kg, up to a maximum of 75 g.

67. What glucose dose is used for pregnancy glucose tolerance testing?

100 g glucose.

68. Which pregnancy glucose tolerance time points are used for diagnosis?

Fasting, 1 hour, 2 hours, and 3 hours.

69. What fasting glucose value is abnormal in pregnancy glucose tolerance testing?

Greater than 95 mg/dL.

70. What 1-hour glucose value is abnormal in pregnancy glucose tolerance testing?

Greater than 180 mg/dL.

71. What 2-hour glucose value is abnormal in pregnancy glucose tolerance testing?

Greater than 155 mg/dL.

72. What 3-hour glucose value is abnormal in pregnancy glucose tolerance testing?

Greater than 140 mg/dL.

73. What is glycosylated hemoglobin?

Hemoglobin with glucose attached to it, used to estimate average glucose control.

74. What time period does A1c reflect?

About 90 days.

75. What is A1c reported as?

A percent and it can be converted to estimated average glucose.

76. What condition can make A1c interpretation less accurate?

An abnormal hemoglobin pattern.

77. What does fructosamine measure?

Glucose attached to serum proteins, including albumin.

78. What time period does fructosamine reflect?

About 2 to 3 weeks.

79. What did urinary albumin testing used to be called?

Microalbuminuria testing.

80. What is urinary albumin testing used to detect?

Small amounts of albumin in urine to assess early renal damage.

81. What is C-peptide?

A peptide cleaved from proinsulin when insulin is produced.

82. What does C-peptide reflect?

Endogenous insulin production.

83. Why is C-peptide useful in a patient taking insulin?

It helps show how much insulin the patient is producing naturally.

84. What is the formula for estimated average glucose from A1c?

eAG = 28.7 x A1c

85. What does eAG stand for?

Estimated average glucose.

86. What estimated average glucose corresponds to an A1c of 6 percent?

About 126 mg/dL.

87. How much does eAG change for every 1 percent change in A1c?

About 28 mg/dL.

88. What pattern is seen in a diabetic glucose tolerance curve?

A higher glucose peak with delayed return toward baseline.

89. What type of method is the glucose oxidase method?

An enzymatic glucose method.

90. In the glucose oxidase method, what enzyme converts glucose to gluconic acid and hydrogen peroxide?

Glucose oxidase.

91. What enzyme converts hydrogen peroxide into water and oxygen in the glucose oxidase method?

Peroxidase.

92. What can endogenous oxygen consumption by cells do to glucose oxidase results?

It can decrease pO2 and affect oxygen-dependent reactions.

93. Why is the reagent strip glucose method not used for plasma or serum glucose?

It is designed for urine screening and uses a color-strip reaction.

94. What is the hexokinase method for glucose?

An enzymatic reference-type method using hexokinase and NAD/NADP chemistry.

95. What is the first reaction in the hexokinase glucose method?

Glucose + ATP forms glucose-6-phosphate + ADP.

96. What wavelength is used to measure NADPH in the hexokinase method?

340 nm.

97. What is lactose intolerance caused by?

Lactase deficiency in the small bowel.

98. What blood response supports lactose intolerance during a lactose tolerance test?

A mean glucose rise less than 20 mg/dL.

99. What symptoms may occur during lactose intolerance testing?

Vomiting, diarrhea, or intestinal discomfort.

100. What is the purpose of a xylose absorption test?

To evaluate intestinal absorption without needing pancreatic enzymes.