Hydroxyurea interferes negatively with triglyceride measurement by a glycerol oxidase method

Area of Science:

• Clinical Chemistry
• Biochemistry
• Pharmacology

Background:

• Hydroxyurea is a medication used to treat myeloproliferative diseases.
• Accurate triglyceride measurement is crucial for patient management.
• Certain enzymatic assays may be susceptible to interference from therapeutic agents.

Purpose of the Study:

• To investigate the cause of extremely low triglyceride concentrations observed in patients on hydroxyurea therapy.
• To identify interference in triglyceride assay methods by hydroxyurea.

Main Methods:

• Comparison of triglyceride measurements using a "cascaded" enzymatic assay (Technicon RA-1000) and a glycerol kinase-based assay (Beckman Instruments).
• In vitro addition of hydroxyurea to serum samples to assess its effect on the "cascaded" assay.
• Analysis of the enzymatic steps involved in the "cascaded" assay for potential inhibition.

Main Results:

• The "cascaded" enzymatic triglyceride assay showed falsely low results in the presence of hydroxyurea.
• Hydroxyurea demonstrated stoichiometric inhibition of glycerol oxidase within the "cascaded" assay.
• A glycerol kinase-based triglyceride assay did not exhibit interference from hydroxyurea.

Conclusions:

• Hydroxyurea interferes with the glycerol oxidase step in a specific "cascaded" enzymatic triglyceride assay.
• This interference leads to underestimation of triglyceride levels in patients receiving hydroxyurea.
• Alternative triglyceride assays, such as those using glycerol kinase, should be considered for patients on hydroxyurea therapy.