[The lanthanide fluorescence immunoassay of the total thyroxin in dried bloodstains on paper].

The lanthanide fluorescence immunoassay was elaborated for quantitative determination of the total thyroxin T4 in bloodstain dried in filter paper; the fields of its clinical application were defined. The method is based on the hardphase concurrent immunoassay with specific monoclonal antibodies to T4 marked by chelates of europium ions and with conjugate of the T3 heterologous hapten sorbed in plate holes with bovine serum albumin. Measurements of the fluorescence intensity were made by a fluorometer in the time resolution mode. The method ensures the T4 determination in a dry bloodstain with a diameter of 3.4 mm within the concentration range of 0 to 400 nmol/l and with the variation coefficient of below or equal to 15%; the results correlated with the findings of the T4 analysis by the DELFIA Neo T4 set, "Wallac Oy", Finland. The method efficiency was demonstrated for screening and verifying the congenital thyroid deficiency in newborns; it was also confirmed that the method can be used for monitoring the functional thyroid condition in adult patients.