Significance of Prealbumin Values in Nutritional Assessment
Serum prealbumin is a valid and clinically useful measure of protein-energy nutritional status, with levels below 30 mg/dL indicating a need for evaluation of protein-energy malnutrition, particularly in patients with chronic conditions such as renal failure. 1
What is Prealbumin?
- Prealbumin (transthyretin) is a hepatic secretory protein that serves as a marker of visceral protein pool size 1
- It has a shorter half-life (2-3 days) compared to albumin (20 days), which theoretically makes it more responsive to acute changes in nutritional status 1
- Normal prealbumin levels should be ≥30 mg/dL, with values below this threshold warranting nutritional evaluation 1
Clinical Utility in Nutritional Assessment
Advantages of Prealbumin Measurement:
- Functions as an early indicator of protein-energy malnutrition due to its shorter half-life 1, 2
- Prealbumin levels at initiation of dialysis or during maintenance dialysis predict future mortality risk 1, 3
- Lower prealbumin concentrations are independently associated with mortality and hospitalization due to infection, even after adjusting for serum albumin and other clinical characteristics 3
Limitations and Confounding Factors:
- Prealbumin is a negative acute-phase reactant, meaning levels decline during inflammation or infection, limiting its specificity as a pure nutritional marker 1
- Levels are artificially elevated in renal failure due to impaired degradation by the kidney 1
- There is insufficient evidence to conclude that prealbumin is more sensitive than albumin as a nutritional marker 1
Clinical Applications
Risk Stratification:
- Among patients at nutritional risk, low prealbumin levels (<0.17 g/L) are associated with significantly higher mortality at 180 days (adjusted HR=1.59) 4
- In hemodialysis patients, the risk of death is inversely related to serum prealbumin concentration, with adjusted RRs of 2.41,1.85,1.49, and 1.23 for prealbumin <15-20-25, and 25-30 mg/dL respectively 3
Monitoring Nutritional Support:
- Dynamic changes in prealbumin during ICU stay correlate with cumulative energy and protein intakes, particularly in high-risk patients (elderly, malnourished, or those with increased inflammation) 5
- Prealbumin deficiency may predict the risk of malnutrition associated with inflammation in cancer patients 6
Specific Populations:
- In pediatric cancer patients, prealbumin deficiency is more common than albumin deficiency both before and after treatment 6
- In critically ill patients, both initial prealbumin values and dynamic changes over the first week are negatively associated with ICU mortality 5
Practical Recommendations
- Use prealbumin as part of a comprehensive nutritional assessment, not as a standalone marker 2
- Target prealbumin levels ≥30 mg/dL when monitoring nutritional status in patients 1
- Consider inflammatory status when interpreting prealbumin values, as inflammation will artificially lower levels independent of nutritional status 1
- Monitor prealbumin dynamically rather than relying on single measurements, especially when evaluating response to nutritional interventions 5
- Be aware that hypoalbuminemia may predict an unfavorable course of treatment complicated by frequent infections in cancer patients 6
Common Pitfalls to Avoid
- Interpreting low prealbumin in isolation without considering inflammatory status may lead to overdiagnosis of malnutrition 1
- Failing to recognize that prealbumin levels are artificially elevated in renal failure patients 1
- Assuming prealbumin is always superior to albumin as a nutritional marker (current evidence does not support this) 1
- Neglecting to establish baseline prealbumin levels before initiating nutritional support, making it difficult to assess response 5