ABSTRACT
This review discusses the various technical problems likely to be encountered in digoxin assay using 125I methods. Many of these difficulties are not limited to digoxin, but are potential dangers when measuring a wide variety of substances by radio-ligand techniques. Emphasis is placed on ways to avoid or solve these problems. Beside error induced through technical aspects, which include radio-ligand reagents, dispensing equipment, and well counters, other potential sources of interference which are considered are the effects of medications, serum proteins, and previously administered radioactivity.
Subject(s)
Digoxin/blood , Radioimmunoassay/methods , Antibody Specificity , Antigen-Antibody Complex , Blood Proteins/analysis , Digoxin/administration & dosage , Dose-Response Relationship, Drug , Humans , Iodine Radioisotopes , Protein Binding , Quality Control , Radioimmunoassay/instrumentation , Radioligand Assay/methodsABSTRACT
A cold area within a benign autonomous thyroid nodule comprises the "owl eye" sign. A case of thyroid carcinoma is presented whose scan appearance simulates that of a benign autonomous nodule with the "owl eye" sign.
Subject(s)
Carcinoma, Papillary/diagnosis , Goiter, Nodular/diagnosis , Radionuclide Imaging , Thyroid Neoplasms/diagnosis , Aged , Diagnosis, Differential , Female , Humans , Iodine RadioisotopesABSTRACT
Pitfalls in Iodine-125 digoxin methods are reviewed. Problems may arise from instrumentation, reagents, methodology, medications and variation in patient specimens. The laboratory has an obligation to avoid these errors and ways are available to accomplish this.
Subject(s)
Digoxin/analysis , Iodine Radioisotopes/analysis , Antibodies , Antigens , Blood Proteins/analysis , Centrifugation , Disease/metabolism , Humans , Metabolism/drug effects , Methods , Quality Control , Radioimmunoassay/instrumentation , Temperature , Time FactorsABSTRACT
Spironolactone and prednisone reportedly cause measurable values for apparent digoxin, even when none is present. Effects of these medications were evaluated with 125I-labeled digoxin kits from five different manufacturers. Values obtained for apparent digoxin were either negligible or not sufficiently great to be clinically significant, regardless of kit methodology or manufacturer.
