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Factitious hypophosphatemia related to mannitol therapy
Clinical Chemistry
|October 1, 1981
Summary
Intravenous mannitol can interfere with phosphorus lab tests, causing falsely low results. A specific Dupont method was affected, but kinetic methods were not, highlighting the need for method-specific considerations.
Area of Science:
- Clinical Chemistry
- Analytical Chemistry
- Biochemistry
Background:
- Accurate phosphorus measurement is crucial for diagnosing and managing various medical conditions.
- Intravenous mannitol is a commonly used osmotic diuretic with potential to affect laboratory assays.
Observation:
- A patient receiving intravenous mannitol presented with factitious hypophosphatemia.
- Phosphorus measurements using the Dupont aca endpoint method were inhibited by mannitol concentrations as low as 25 mmol/L.
Findings:
- The interference mechanism involves mannitol binding to molybdate, reducing color development and endpoint measurements in the Dupont method.
- Kinetic phosphorus measurement methods remained unaffected by mannitol interference.
- The molybdate concentration in the Dupont method is suboptimal for accurate phosphorus determination in the presence of mannitol.
Implications:
- Clinicians should be aware of potential interferences when interpreting phosphorus results in patients receiving mannitol.
- Laboratory methods for phosphorus measurement should be evaluated for interference from common intravenous solutions like mannitol.
- Further optimization of analytical methods may be necessary to ensure accurate phosphorus measurements in complex patient samples.