Serum digoxin‐like immunoreactive factor in children and its relation to sodium metabolism

Abstract

Serum digoxin‐like immunoreactive factor (DLIF), an endogenous substance that cross‐reacts with anti‐digoxin antibodies, was assessed (fluorescence polarization immunoassay) in children (n= 134) aged 5‐16 y, who had never been treated with cardiac glycosides. DLIF was found in 50% of serum samples at a mean concentration of 0.16 ± 0.06 ng/ml (range 0.03–0.35 ng/ml). Although the study population as a whole was apparently homogeneous with regard to serum sodium content, and none had clinical signs of sodium imbalance, children with DLIF showed significantly lower natraemia (p= 0:0002), higher urinary concentration (p= 0:001) and fractional excretion (p= 0:001) of sodium, and increased systolic blood pressure (p= 0:009) compared with children without DLIF. Inverse correlations were found between DLIF concentration and serum sodium (p < 0:01), urine sodium content (p < 0:001), 24‐h sodium excretion (p < 0:001), systolic (p < 0:001) and diastolic (p < 0:01) blood pressure. These findings suggest that sodium handling is different in children with and without DLIF, since this material seems to be released preferably in subjects who show a trend towards negative sodium balance. Such an association suggests that DLIF may be a physiologically relevant material involved in sodium homeostasis.