[Interference of digoxin like immunoreactive substances with four recent reagents for digoxin determination]

The sensitivity of four new digoxin assay methods (on mini-Vidas bioMérieux, with Cedia reagent on Hitachi 911, with Syva Emit 2000 third generation reagent on Cobas-Mira and with Roche digoxin Online reagent on Cobas-Mira) to interference by digoxin like immunoreactive substances (DLIS) was studied in sera from 21 healthy controls, 18 pregnant women (9th month of pregnancy), 26 newborn infants and 42 patients with chronic renal failure undergoing hemodialysis. None of these individuals had been treated with digoxin or others cardiotonic drugs. For each method, results are different according to the population being studied, suggesting that the nature of DLIS is not the same. On the whole, interferences with DLIS seem to be more important in samples from newborn infants (for three methods out of four, the mean concentration of digoxin is significantly different from those observed in control samples). Digoxin assay on mini-Vidas and with Cedia reagent seems to be more sensitive to interference by DLIS, especially in samples from newborn infants and less in samples from pregnant women and patients with chronic renal failure. Online and Emit 2000 reagents seem to be poorly sensitive to interference by DLIS. However, for Emit 2000, the mean concentration of digoxin in samples from newborn infants is significantly different from the one observed in control samples. These results show that testing the sensitivity of new digoxine assay methods to interference by DLIS is very important because it can be a limitation to the use of a reagent independently of its analytical qualities.