Interferência de anticorpos em testes de funçäo tireoidiana: relato de caso / Antibodies interference in thyroid function tests: repost of case

Na avaliaçäo da funçäo tireoideana utiliza-se como método diagnóstico as medidas de TSH, T4 e T3 totais e livres. Entretanto, em alguns casos acorre a ligaçäo näo específica com reagentes dos ensaios que väo, desta forma, interferir com as medidas destes hormônios. Estas interferências iräo resultar em concentraçöes séricas anormais de hormônios tireoideanos, näo consistentes com a avaliaçäo clínica e demais exames laboratoriais destes pacientes. Auto-anticorpos anti-hormônio tireoideano säo a classe de fatores que mais frequentemente interferem com vários ensaios. Relatamos o caso de uma paciente de 62 anos, com queixas de ansiedade e palpitaçöes e exame físico normal. na avaliaçäo laboratorial detectamos níveis séricos persistentemente elevados de T3 total, com níveis séricos normais de TSH e T4 total. A presença de anticorpos anti-T3 foi confirmada por radioimunoprecipitaçäo. Resultados que parecem ser inconscientes ou imcompatíveis com os demais exames laboratoriais, na presença ou näo de sintomas em geral inespecíficos, devem levantar a suspeita da presença de fatores interferentes no ensaio. Desta forma, evita-se o diagnóstico errôneo de disfunçäo tireoideana e, consequentemente, um tratamento desnecessário e até mesmo deletério.

Capacidad de predecir una recaída de lupus eritematoso generalizado, mediante anticuerpos anti-DNA de hebra doble, por la técnica de Farr / Predictive capacity of double stranded anti DNA antibodies for relapses in patients with inactive systemic lupus erythematosus using Farr technique

Background: Patients with inactive systemic lupus erythematosus (SLE) and elevated high affinity double-stranded anti-DNA antibodies (anti-dsDNA), measured using Farr technique, would have a risk of relapse that fluctuates between 40 to 80 percent according to different series. Aim: To study the association between anti-dsDNA levels measured using Farr technique and disease activity and their predictive capacity for relapses. Material and methods: Anti-dsDNA antibodies were measured according to Farr method in 60 healthy subjects, 69 patients with other connective tissue diseases and in 120 patients with SLE. Farr positive were considered those individuals with anti-dsDNA levels over 10.4 IU/ml. Disease activity, assessed using MEX-SLEDAI score was related with anti-dsDNA levels in 101 patients. Forty seven patients with inactive disease were followed for 17ñ14 months. Results: Anti-dsDNA levels were 3ñ2.5 IU/ml (range 1-26) in subjects without LED, and 127ñ500 IU/ml (range 1-5280) in patients with LED. Sixty subjects had an active SLE and 43 (72 percent) were Farr positive; in 41 the disease was inactive and 13 (32 percent) were Farr positive (p <0.001), OR 5.45. Twelve of the 47 followed patients had a relapse and 10 (83 percent) were Farr positive. Of those that did not have a relapse, 13 (37 percent) were Farr positive (p< 0.02, RR 5.22). Six of 15 patients that were followed for more than on year (40 percent), were Farr positive. Conclusions: Elevated anti-dsDNA antibodies measured using Farr technique in patients with inactive generalised lupus erythematosus, predicted the risk of relapse. However less than half of patients with inactive disease and elevated Farr relapsed in a period of one year. The need to treat patients with inactive SLE and positive Farr should therefore be considered debatable