Prealbumin in Clinical Practice
Low prealbumin levels (<30 mg/dL) indicate protein-energy malnutrition and predict increased mortality risk, requiring immediate nutritional evaluation and intervention, though interpretation must account for inflammation and renal function. 1
Understanding Prealbumin as a Nutritional Marker
Prealbumin (transthyretin) responds more rapidly to nutritional changes than albumin due to its shorter half-life of 2-3 days versus albumin's 20-day half-life. 1 However, prealbumin is not superior to albumin as a nutritional marker—there is insufficient evidence to conclude it is more sensitive or accurate than serum albumin for assessing malnutrition. 1
Critical Threshold and Mortality Risk
Target prealbumin levels ≥30 mg/dL when monitoring nutritional status. 1, 2 Values below this threshold are associated with:
- Increased mortality risk in dialysis patients 1
- Higher all-cause 180-day mortality (hazard ratio 1.59) in hospitalized patients at nutritional risk 3
- Threefold increased risk of refeeding hypophosphatemia and twofold increased risk of hypoglycemia in severe anorexia nervosa 4
Major Confounding Factors That Limit Interpretation
Inflammation and Acute Illness
Prealbumin is a negative acute-phase reactant, meaning levels decline during inflammation or infection regardless of nutritional status. 1, 2 This severely limits its specificity as a pure nutritional marker. 2 You cannot interpret low prealbumin in isolation without assessing inflammatory status. 2, 5
Renal Failure
Prealbumin levels are artificially elevated in renal failure due to impaired kidney degradation. 1, 2 This makes interpretation particularly challenging in chronic kidney disease patients, though the 30 mg/dL threshold still applies for dialysis patients. 1
Management Algorithm for Low Prealbumin
Step 1: Confirm True Malnutrition vs. Inflammation
- Check inflammatory markers (CRP, ESR) to exclude acute-phase response 5
- Assess hydration status and protein losses 5
- In renal failure patients, recognize baseline elevation but still use 30 mg/dL threshold 1
Step 2: Comprehensive Nutritional Assessment
Do not rely on prealbumin alone. Combine with: 5
- Body weight trends and BMI
- Dietary intake assessment
- Physical examination for muscle wasting
- Serum albumin (though also affected by inflammation) 5
Step 3: Initiate Nutritional Intervention
When prealbumin <30 mg/dL (or <18 mg/dL in critically ill) with confirmed malnutrition: 1, 6
- Implement individualized nutrition support rather than usual care 3
- In cirrhotic patients, oral nutritional products with relatively high carbohydrate and lower protein content may improve MELD scores 7
- Monitor for refeeding complications in severely malnourished patients (BMI <13 kg/m²), particularly hypophosphatemia and hypoglycemia 4
Step 4: Serial Monitoring
- Recheck prealbumin approximately weekly during nutritional intervention 4
- Expect normalization in 77% of patients by discharge with adequate support 4
- Monthly monitoring in dialysis patients 5
Common Pitfalls to Avoid
Never interpret low prealbumin without considering inflammatory status—you will misdiagnose inflammation as malnutrition. 2, 5
Do not assume prealbumin is more sensitive than albumin—the evidence does not support this claim despite the shorter half-life. 1
In renal failure patients, do not dismiss elevated prealbumin as meaningless—the 30 mg/dL threshold still predicts outcomes in dialysis populations. 1
Do not use prealbumin as the sole nutritional marker—it must be part of comprehensive assessment including clinical history, physical examination, and other biochemical markers. 5, 8