CAP Pro Course - Chemistry - Laboratory Evaluation of Serum/Plasma Electrolytes and Acid-Base Balance (2025 & 2026)

Author: Kevin F. Foley, PhD, DABCC, MT, SC, TC(NRCC)
Reviewer: Laurie Bjerklie, MA, MLS(ASCP)CM

Continuing Education Credits

Objectives

  • List and describe the major electrolytes, their functions, associated conditions, and how they are regulated.
  • Describe the mechanisms for controlling acid-base balance in the body and identify disorders associated with acid-base imbalance.
  • Define anion gap in relation to measured and unmeasured cations and measured and unmeasured anions.
  • Discuss conditions associated with low and high anion gap and the importance of anion gap in the differential diagnosis of metabolic acidosis.

Course Outline

  • List and describe the major electrolytes, their functions, associated conditions, and how they are regulated.
      • Serum Electrolytes
      • Serum Electrolytes, continued
      • Sodium (Na+)
      • Hyponatremia
      • Hypernatremia
      • Potassium (K+)
      • Hypokalemia
      • Hyperkalemia
      • Chloride (Cl-)
      • Hypochloremia and Hyperchloremia
      • Calcium (Ca2+)
      • Ionized Calcium
      • Bicarbonate (HCO3–)
      • Bicarbonate, continued
      • Metabolic Acidosis: Decreased Bicarbonate
      • Metabolic Alkalosis: Increased Bicarbonate
      • Measurement of Electrolytes
      • Testing Methodologies
      • Testing Methodologies, continued
      • Assessment Checks for Validity
      • A patient presents with primary hyperaldosteronism. Serum sodium and potassium tests are ordered. Which of the following results would be the most con...
      • Which alternative methodology can be used for electrolyte determination that is not susceptible to interference caused by hyperlipidemic samples?
      • The following results were obtained on a non-hemolyzed plasma sample collected in a green-top tube containing lithium heparin as an anticoagulant. The...
      • An arterial blood gas syringe drawn on the patient in the emergency department was loosely capped, put in a biohazard bag, and delivered to the clinic...
      • Which electrolyte has the primary function of maintaining acid-base balance?
      • What is the main form of carbon dioxide (CO2) in the blood, normally accounting for more than 90% of the total CO2?
      • Which electrolyte has the largest influence on normal distribution of water and regulating the osmotic pressure in the extracellular fluid (ECF)?
      • Which of the following statements is not true concerning chloride (Cl-)?
  • Describe the mechanisms for controlling acid-base balance in the body and identify disorders associated with acid-base imbalance.
      • Acid-Base Balance
      • Acid-Base Balance, continued
      • Regulation of Acid-Base Balance
      • Buffer Systems
      • Bicarbonate Buffer System
      • Respiratory Regulation of Acid-Base Balance
      • Renal Regulation of Acid-Base Balance
      • Acid-Base Disorders
      • Respiratory Acidosis and Respiratory Alkalosis
      • Metabolic Acidosis and Metabolic Alkalosis
      • Compensation Mechanisms
      • Metabolic Compensation
      • Measurement of Acid-Base Balance Parameters
      • Measurement of Acid-Base Balance Parameters, continued
      • Ion Selective Electrodes Used for the Measurement of Arterial Blood Gas Parameters
      • How will the body respond if the ratio of HCO3- to H2CO3 in the plasma is greater than 20:1?
      • Which of the following conditions is consistent with hypercapnia?
      • A sample is sent to the laboratory for blood gas analysis. The sample sat on the counter with the cap on for two hours before testing. What are the po...
      • Which of the following is not true concerning partially compensated respiratory alkalosis?
      • A blood gas specimen has a pH of 7.56. The normal range for blood pH is 7.35–7.45. Which of the following conditions is indicated by this pH res...
      • A 74-year-old patient suffering from pneumonia has been admitted for treatment. An arterial blood gas sample was sent to the laboratory. Which of the ...
      • A 64-year-old patient with a history of alcoholism was admitted to the ER for possible ingestion of methanol. An arterial blood gas sample was sent to...
  • Define anion gap in relation to measured and unmeasured cations and measured and unmeasured anions. Discuss conditions associated with low and high anion gap and the importance of anion gap in the differential diagnosis of metabolic acidosis.
      • Anion Gap
      • Anion Gap, continued
      • Anion Gap, continued
      • Increased Anion Gap
      • Decreased Anion Gap
      • Laboratory Error
      • Use of Anion Gap for Determining Causes of Metabolic Acidosis
      • Normal Anion Gap Metabolic Acidosis
      • Which of the following statements is true?
      • What is the predominant unmeasured anion contributing to the "gap" in a normal anion gap?
      • A 58-year-old patient with a history of diabetes is brought to the emergency department. A glucose test and electrolytes test are ordered. Accumulatio...
      • A patient with a high anion gap and metabolic acidosis is being cared for in your hospital. Follow-up laboratory testing is being ordered. Which of th...
      • A medical laboratory scientist performing electrolyte panel testing notices that several patients have decreased anion gaps (values consistently below...
      • Which of the following conditions is most consistent with the following laboratory results?TestResultReference RangeNa+ 137 mEq/L135–145 mEq/LK+...
      • A patient visits their physician with abdominal discomfort, muscle pain, and cramping symptoms. The physician orders an electrolyte panel.TestResultRe...
      • An electrolyte panel is performed on a patient with the following results.TestResultReference RangeNa+ 126 mEq/L135–145 mEq/LK+ 4.8 mEq/L 3.5...
  • References
      • References

Additional Information

Level of Instruction: Intermediate
Intended Audience: This program is designed as an educational and training tool for medical laboratory scientists, medical laboratory technicians, laboratory supervisors, and laboratory managers. This course is also appropriate for MLS and MLT students and pathology residents.
Author Information: Kevin F. Foley, PhD, DABCC, MT, SC, TC(NRCC), is the director of clinical pathology for the Kaiser Permanente Northwest region. He also instructs clinical chemistry at Oregon Health Sciences University. Dr. Foley earned his PhD in clinical pharmacology and toxicology at the East Carolina School of Medicine in North Carolina.
Reviewer Information: Laurie Bjerklie, MA, MLS(ASCP)CM, is currently an Education Developer. She earned a B.S. in Medical Laboratory Science from the University of North Dakota and an M.A. in Curriculum and Instruction from Saint Xavier University. She has over 15 years of experience in higher education and has held program director and faculty positions in both MLT and MLS programs.

This course is part of the CAP Competency Assessment Hub.

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