Clinical chemistry

1. Concepts of Biochemical
Reference Values
Dr. Cynthia C. Chemonges

2. Outline
• Normal and abnormal values
• Quality control in Biochemical analysis
• Water and Electrolyte balance
• Acid-Base Balance and imbalance
• Fluid and Electrolyte balance in clinical disorders

3. Normal and Abnormal Values
Normal Values:
Definition:
Established standards representing the typical range of biochemical parameters in
healthy individuals.
Significance:
Serve as benchmarks for health assessments and diagnostic comparisons.
Abnormal Values:
Definition:
Deviations from the established normal ranges.
Indicators:
Suggest potential health issues or underlying medical conditions.

4. Factors affecting interpretation
Age and Gender:
Variability:
Reference values may differ based on age and gender.
Considerations:
Pediatric and geriatric populations may have distinct reference ranges.
Physiological State:
Influence:
Pregnancy, exercise, and fasting can impact biochemical values.
Adjustments:
Interpretation should account for these physiological states

5. Time of Day:
Diurnal Variations:
Some parameters show fluctuations throughout the day.
Timing Significance:
Consideration for accurate interpretation based on when the sample is
collected.
Biological Variations

6. Individual Differences:
Genetic Factors:
Genetic variations contribute to individual differences.
Customized Care:
Understanding genetic influences aids personalized healthcare.
Environmental Factors:
Geographic Influence:
Dietary and lifestyle differences based on location affect reference values.
Adaptation:
Consideration for regional variations in interpreting results.

7. Quality Control in Biochemical Analysis
Internal Quality Control
Routine Monitoring:
Frequency:
Regular checks within the laboratory to ensure precision and accuracy.
Prevention:
Early identification of issues to prevent errors.
Calibration:
Standardization:
Regular calibration of equipment for accuracy.
Reliability:
Ensures consistency in measurement tools

8. External Quality Control
Inter-laboratory Comparisons:
Proficiency Programs:
Participation in external proficiency testing to ensure competency.
Benchmarking:
Comparison with other laboratories for standardized practices.
Certification:
Accreditation:
Obtaining certifications and accreditations to meet industry standards.
Continuous Improvement:
Commitment to maintaining high-quality standards.

9. Water and Electrolyte Balance
Fluid Balance
Importance:
Cellular Function:
Essential for cellular activities and metabolic processes.
Homeostasis:
Critical for maintaining overall internal balance.

10. Regulation:
Hormonal Control:
Controlled by hormones such as antidiuretic hormone (ADH).
Renal Mechanisms:
Kidneys play a key role in fluid balance through filtration and reabsorption.
Electrolyte Balance

11. Essential Ions:
Sodium (Na+), Potassium (K+), Chloride (Cl-), etc.:
Critical for nerve conduction, muscle contraction, and osmotic balance.
Role in Homeostasis:
Maintaining proper levels is crucial for physiological function.

12. Acid-Base Balance and Imbalance
Blood pH
Normal Range:
Definition:
Blood pH typically ranges between 7.35 to 7.45.
Importance:
Maintaining this range is vital for enzymatic and metabolic processes.
Equation:
pH = pKa + log([HCO3-]/[CO2]).
Significance:
Utilized to calculate and understand factors influencing blood pH.

13. Maintained by Buffers:
Bicarbonate (HCO3-), Phosphate, Proteins:
Buffering systems prevent rapid changes in pH.
Stability:
These buffers act as stabilizers against shifts in acidity or alkalinity.
Henderson-Hasselbalch (H-H) Equation
pH Calculation:

14. Buffering Mechanism
Neutralize Acids or Bases:
Prevention of pH Fluctuations:
Buffers act as a defense mechanism against sudden changes.
Respiratory and Renal Buffers:
Lungs regulate CO2, and kidneys regulate bicarbonate.

15. Renal Handling of Hydrogen Ion:
Excretion of H+ Ions:
Role of Kidneys:
Kidneys regulate acid-base balance by excreting or reabsorbing hydrogen ions.
Urine pH Regulation:
Acidic or alkaline urine reflects renal adjustments.
Compensatory Mechanisms

16. Respiratory Compensation:
Ventilation Adjustment:
Lungs alter breathing rate to regulate CO2 levels.
Immediate Response:
Rapid adjustments to maintain acid-base equilibrium.
Renal Compensation:
Bicarbonate Regulation:
Kidneys alter bicarbonate reabsorption to stabilize pH.
Slower Response:
Longer-term adjustments to maintain homeostasis.

17. Fluid and Electrolyte Balance in Clinical Disorders
Clinical Disorders
Dehydration:
Definition:
Insufficient fluid intake or excessive fluid loss.
Manifestations:
Thirst, dry mucous membranes, concentrated urine.

18. Hyponatremia/Hypernatremia:
Sodium Imbalances:
Affect osmotic balance and cellular function.
Symptoms:
Neurological manifestations, fluid retention, or dehydration.
Acidosis/Alkalosis:
Imbalances in Blood pH:
Acidosis (low pH) or alkalosis (high pH).
Consequences:
Disruption of enzyme function, potential organ failure.

19. References
1. Carl A. Burtis, David E. Bruns (2023) Tietz Fundamentals of Clinical
Chemistry, 9th Ed.
2. Lawrence A. Kaplan, Amadeo J. Pesce (2009) Clinical Chemistry:
Theory, Analysis,Correlation, 5 th Ed.
3. Robert L. Sunheimer (2010) Clinical Laboratory Chemistry.