Quality specifications in thyroid diseases.
BACKGROUND
Laboratory tests to support the diagnosis and management of thyroid diseases have undergone significant changes with the introduction of highly sensitive assays for thyroid stimulating hormone (TSH) and free T4 and T3 concentrations in plasma. Given the importance of these measurements, quality specifications are needed to ensure accurate results. Goals for precision and accuracy are available based on known intraindividual and interindividual biological variation.


METHODS
Results of external quality assurance (EQA) schemes are sufficient to document precision goals but survey materials are not commutable for use in determining bias or detect the presence of unusual antibodies on a case-by-case basis. Because TSH concentrations are inversely related to free T4, this physiologic relationship can be exploited for quality assurance purposes.


RESULTS
Significant discordance between this relationship can be caused by subclinical and potentially unrecognized disease, dysequilibrium caused by recent therapy, the presence of abnormal binding proteins or protein binding competitor drugs, and antibody interferences such as human antimouse antibody (HAMA) or rheumatoid factor.


CONCLUSIONS
A mechanism to automatically track discordances for subsequent follow and investigation can be an effective part of a quality assurance program for thyroid hormone measurements.
Wu
Alan H B
AH
Department of Pathology and Laboratory Medicine, Hartford Hospital, 80 Seymour St., Hartford, CT 06102, USA. awu@harthosp.org
D000910:Antibodies, Heterophile / Q000097:blood; D015415:Biomarkers / Q000097:blood; D006801:Humans; D011485:Protein Binding; D011786:Quality Control; D012217:Rheumatoid Factor / Q000097:blood; D013959:Thyroid Diseases / Q000097:blood / Q000145:classification / Q000175:diagnosis*; D013960:Thyroid Function Tests; D013972:Thyrotropin / Q000097:blood* / Q000276:immunology; D013974:Thyroxine / Q000097:blood* / Q000276:immunology; D014284:Triiodothyronine / Q000097:blood* / Q000276:immunology
D000910:Antibodies, Heterophile; D015415:Biomarkers; D014284:Triiodothyronine; D013972:Thyrotropin; D012217:Rheumatoid Factor; D013974:Thyroxine