Endogenous substance in newborn infants causing false positive digoxin measurements

Area of Science:

• Neonatal Medicine
• Clinical Chemistry
• Pharmacology

Background:

• Digoxin is a critical medication for treating heart conditions in infants.
• Accurate measurement of digoxin levels is essential for safe and effective treatment.
• Existing immunoassays may be affected by endogenous substances.

Purpose of the Study:

• To investigate the presence of digoxin-like substances in neonatal and infant samples.
• To determine the source and impact of these substances on digoxin measurements.
• To assess the reliability of digoxin radioimmunoassays in this patient population.

Main Methods:

• Immunoassays were used to detect digoxin-like immunoequivalent substances.
• Plasma and amniotic fluid samples from neonates and infants were analyzed.
• Time-course and recovery studies were conducted in individual infants.

Main Results:

• A digoxin-like immunoequivalent substance was detected in the plasma of neonates and infants, and in amniotic fluid.
• Endogenous production of this substance is suggested by time-course studies.
• The presence of this substance caused falsely elevated digoxin values in radioimmunoassays.

Conclusions:

• Digoxin radioimmunoassay measurements in neonatal and infant serum or plasma may be unreliable.
• The clinical utility of current digoxin assays in this population is questionable.
• Further research is needed to develop more accurate diagnostic methods for digoxin levels in infants.