Radioassay for serum and red cell folate

Area of Science:

• Biochemistry
• Clinical Chemistry
• Analytical Chemistry

Background:

• Accurate folate measurement is crucial for diagnosing and managing folate-deficiency anemias and related health conditions.
• Existing folate assays, such as microbiologic methods, can be affected by various medications, leading to inaccurate results.
• The need for a simple, reliable, and less interference-prone assay for serum and red cell folate remains.

Purpose of the Study:

• To develop and describe a novel, simple, and reliable radioassay for determining serum and red cell folate levels.
• To utilize readily available materials like milk as a binder in the folate assay.
• To overcome limitations of existing folate assays, particularly interference from medications.

Main Methods:

• A radioassay employing 125I-tyramide of pteroylglutamic acid (PGA) as the radiolabeled tracer.
• Utilization of plain, untreated liquid or powdered milk as a folate binder, eliminating the need for endogenous serum folate binder.
• Assay performed at pH 9.3 to allow the use of stable PGA standards instead of unstable methyltetrahydrofolic acid (MeTHFA).

Main Results:

• The milk-based radioassay demonstrated comparable results to the standard Lactobacillus casei microbiologic method.
• The assay successfully avoided false low results caused by antibiotics, tranquilizers, and chemotherapeutic agents.
• The method simplifies radioactivity counting using a gamma-emitting isotope.

Conclusions:

• The described radioassay provides a simple, reliable, and robust method for measuring serum and red cell folate.
• Milk serves as an effective and accessible binder, simplifying the assay procedure.
• This assay offers an advantage over existing methods by minimizing interference from common medications.