What is the role of testing for albumin or prealbumin in patients with hyponatremia (low sodium levels)?

From the Guidelines

Testing for albumin is recommended in the evaluation of hyponatremia, particularly when assessing for pseudohyponatremia or determining the underlying cause, as it can provide valuable information about the patient's volume status and liver synthetic function 1.

Importance of Albumin Testing

The measurement of serum albumin levels is crucial in the initial workup of hyponatremia, as low albumin levels (hypoalbuminemia) can contribute to hyponatremia through decreased effective arterial blood volume and activation of baroreceptors, leading to increased ADH secretion 1.

Normal Values and Interpretation

Normal albumin values range from 3.5-5.0 g/dL, and low albumin levels should prompt investigation for underlying conditions such as liver disease, nephrotic syndrome, malnutrition, or protein-losing enteropathy, which may be the primary drivers of the hyponatremic state 1.

Prealbumin Testing

Prealbumin (transthyretin) testing, while less commonly used specifically for hyponatremia, may provide additional information about nutritional status and liver synthetic function, with normal values ranging from 15-36 mg/dL 1.

Clinical Implications

The presence of hypoalbuminemia should prompt investigation for underlying conditions, and corrected sodium calculations may be necessary when interpreting sodium levels in patients with abnormal protein states 1.

• Key points to consider when testing for albumin or prealbumin in hyponatremia include:
  • Measuring serum albumin levels as part of the initial workup
  • Investigating underlying conditions that may be contributing to hypoalbuminemia
  • Considering corrected sodium calculations in patients with abnormal protein states
  • Using prealbumin testing to provide additional information about nutritional status and liver synthetic function
• In clinical practice, albumin infusion appears to improve serum sodium concentration, but more information is needed 1.

From the Research

Testing for Albumin or Prealbumin in Hyponatremia

• The use of albumin in clinical practice is largely accepted for specific indications such as resuscitation in shock states, liver disease, and fluid replacement in certain conditions 2.
• In the context of hyponatremia, albumin administration may be considered in cases of severe hyponatremia in cirrhosis, although the evidence is limited and the recommendation is weak 2.
• Prealbumin has been evaluated as a nutritional and prognostic marker, but its routine use in clinical practice remains debatable 3.
• There is no direct evidence to support the use of prealbumin as a diagnostic tool for hyponatremia, but it may be used to assess malnutrition in patients with hyponatremia 3.
• The diagnosis and management of hyponatremia should be based on the underlying cause, fluid volume status, and symptom severity, rather than relying solely on albumin or prealbumin levels 4, 5, 6.

Diagnostic Approach to Hyponatremia

• The initial step in diagnosing hyponatremia is to differentiate between hypotonic and non-hypotonic hyponatremia 6.
• Further differentiation is based on urine osmolality, urine sodium level, and volume status 6.
• Recently identified parameters, such as fractional uric acid excretion and plasma copeptin concentration, may improve the diagnostic approach 6.

Treatment of Hyponatremia

• The treatment of hyponatremia depends on the duration and symptoms, with acute or severely symptomatic hyponatremia requiring bolus hypertonic saline 4, 6.
• Fluid restriction remains the first-line treatment for most forms of chronic hyponatremia, with therapy to increase renal free water excretion often necessary 6.
• Vasopressin receptor antagonists, urea, and loop diuretics may be used to increase renal free water excretion, but the recommendations vary between guidelines 6.