Postmortem digoxin-like immunoreactive substances (DLIS) in patients not treated with digoxin

Area of Science:

• Forensic Toxicology
• Clinical Chemistry
• Pharmacology

Background:

• Endogenous digoxin-like immunoreactive substances (DLIS) can interfere with digoxin immunoassays.
• The postmortem increase in measured digoxin levels might be influenced by DLIS, but their presence and behavior postmortem are not well understood, especially in non-digoxin-treated patients.

Purpose of the Study:

• To investigate the presence and concentration of DLIS in postmortem blood samples from patients not treated with digoxin.
• To determine if DLIS concentrations increase after death.
• To assess the impact of sampling site on postmortem DLIS concentrations.

Main Methods:

• Blood samples were collected antemortem from ICU patients and postmortem (femoral artery and cardiac chambers) at least 12 hours after death.
• DLIS were measured using the TDx assay (Abbott), quantifying them as digoxin equivalents.
• Statistical analysis considered age, ICU stay, and postmortem sampling time.

Main Results:

• DLIS concentrations of at least 0.2 ng/ml were detected in 44% of patients antemortem and 40% postmortem (femoral).
• No significant difference was observed in DLIS levels between antemortem and postmortem samples (femoral and cardiac).
• Age, ICU stay, and postmortem interval did not influence postmortem DLIS levels; all measured levels were below the toxic range.

Conclusions:

• DLIS are present after death and their concentrations do not appear to increase postmortem.
• Caution is advised when interpreting postmortem digoxin levels within the therapeutic range, as they may represent endogenous DLIS rather than drug misuse.
• These findings are crucial for accurate forensic and clinical interpretation of postmortem toxicology in non-digoxin-treated individuals.