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Pseudohyperphosphataemia in patients with multiple myeloma
D McClure1, L C Lai, C Cornell
1Department of Clinical Biochemistry, Freeman Hospital, Newcastle upon Tyne.
Journal of Clinical Pathology
|August 1, 1992
Summary
The direct acid/molybdate method for measuring phosphate levels is unreliable in multiple myeloma patients due to turbidity, leading to inaccurate pseudohyperphosphataemia results. This method should be avoided in patients with serum paraproteins.
Area of Science:
- Clinical Chemistry
- Hematology
Background:
- Pseudohyperphosphataemia can interfere with accurate phosphate level measurement.
- Multiple myeloma patients often exhibit paraproteinaemia, a condition that may affect laboratory test results.
Purpose of the Study:
- To compare the accuracy of four different methods for measuring phosphate concentrations.
- To investigate the incidence of pseudohyperphosphataemia in patients with multiple myeloma and paraproteinaemia.
- To identify the most reliable method for phosphate measurement in this patient group.
Main Methods:
- Phosphate concentrations were measured in 41 multiple myeloma patients with paraproteinaemia.
- Four distinct analytical methods were employed for comparison.
- Turbidity in reaction mixtures was assessed as a potential source of error.
Main Results:
- The direct acid/molybdate method yielded the highest number of anomalous phosphate readings.
- Erroneously high phosphate concentrations were linked to turbidity in the reaction mixture.
- No correlation was observed between paraprotein type and the occurrence of turbidity.
Conclusions:
- The direct acid/molybdate method is unreliable for phosphate measurement in patients with serum paraproteins.
- This method should not be used for determining phosphate levels in multiple myeloma patients with paraproteinaemia.
- Accurate phosphate measurement in this cohort requires alternative, validated methods.