When encountering a patient with a sodium level of 130 mmol/L, what is the most appropriate next step assuming quality control is acceptable?

The most appropriate next step after finding a sodium level of 130 mmol/L, which indicates hyponatremia, is to check the albumin, total protein, calcium, phosphorus, and magnesium results, and if those results are normal, proceed to repeat the sodium test.

This approach is essential because hyponatremia can be influenced by a range of factors, including changes in volume status and the presence of other electrolyte imbalances. By evaluating the levels of other proteins and electrolytes, you can determine whether the low sodium level may be a spurious result, particularly in the case of serum samples, where changes in protein levels or other electrolytes can lead to misinterpretation of sodium concentrations. For example, a low sodium reading could be seen in the context of hyperlipidemia or hyperproteinemia due to an interference with the sodium measurement.

If those other results are found to be normal, it reinforces the need to repeat the sodium test to confirm the initial finding, ensuring that there are no laboratory errors influencing the results. This step is crucial before making any clinical decisions or interventions based on the sodium reading.