An enzyme-immunoassay for estriol

Area of Science:

• Biochemistry
• Immunology
• Analytical Chemistry

Background:

• Serum estriol measurement is crucial for monitoring pregnancy.
• Existing methods like radioimmunoassay may have limitations.
• Development of a stable and sensitive enzyme-immunoassay (EIA) is needed.

Purpose of the Study:

• To develop a practical and reliable enzyme-immunoassay (EIA) for serum estriol determination.
• To utilize alkaline-phosphatase as a marker enzyme for enhanced sensitivity and stability.
• To validate the EIA method against established radioimmunoassay techniques.

Main Methods:

• Conjugation of alkaline-phosphatase with estriol-6-(O-carboxymethyl) oxime.
• Purification of the estriol-alkaline-phosphatase complex using Sephadex G-200 gel filtration.
• Separation of bound and free estriol via the double antibody method.

Main Results:

• A stable estriol-alkaline-phosphatase conjugate was developed, stable for at least 3 months at 4°C.
• The EIA demonstrated a linear response in the estriol concentration range of 0.2-100 ng/ml.
• High correlation coefficients (r=0.90 for total, r=0.98 for free estriol) were observed when compared to radioimmunoassay.
• Negligible cross-reactivity and no interference from endogenous alkaline-phosphatase were noted.

Conclusions:

• The developed enzyme-immunoassay provides a practical, sensitive, and stable method for serum estriol measurement.
• This EIA method is suitable for routine clinical use during pregnancy monitoring.
• The assay shows excellent correlation with radioimmunoassay, offering a viable alternative.