Anticuerpos anti-tiroglobulina en el seguimiento de pacientes con cáncer diferenciado de tiroides: ¿marcadores de enfermedad residual o recidivante? / Anti thyroglobulin antibodies in the follow up of patients with differentiated thyroid cancer

Background: Anti thyroglobulin antibodies are present in 25 percent of patients treated for a differentiated thyroid cancer, invalidating thyroglobulin determination. Those patients subjected to total thyroidectomy and free of disease, should reduce the production of these antibodies, due to the lack of antigenic stimulus. Therefore, anti thyroglobulin antibodies could be useful to detect early relapses. Aim: To assess the relationship between anti thyroglobulin antibodies and the evolution of the disease in patients treated for thyroid cancer. Material and methods: Retrospective analysis of 26 patients treated for thyroid cancer with positive anti thyroglobulin antibodies, followed for three years. These were divided in those with or without lymphocytic thyroiditis (19 and 7 respectively). Results: At the first year of follow up, anti thyroglobulin antibody concentration was 401ñ94.9 UI/ml (xñsem) in patients with thyroiditis and 38.9ñ8.9 UI/ml in those without thyroiditis (p < 0.005). During the three years of follow up, no differences in anti thyroglobulin antibodies were observed between patients with or without tumor relapse. Conclusions: Concentration of anti thyroglobulin antibodies was higher in patients with thyroiditis and did not differentiate patients with tumor relapse

Medición de 17-OH progesterona sanguínea en recién nacidos chilenos: antecedentes para implementar un programa de detección neonatal de hiperplasia suprarrenal congénita / 17 OH progesterone measurement in blood of chilean newborns: as a background to start a congenital adrenal hyperplasia screening program

Background: The early diagnosis and therapy of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency can prevent adrenal crises and erroneous gender assignment in affected newborns. To achieve this goal neonatal mass-screening programs have been developed, measuring blood 17 alpha-hydroxyprogesterone (17OHP). In Chile there is no experience with this type of screening. Aim: To develop a method for measuring 17OHP in filter paper blood specimens. To obtain reference ranges and determine neonatal 17OHP threshold levels according to gestational age and birth weight. To analyze factors affecting the cost-efficiency ratio and suggest recommendations for the organization of a neonatal screening program for CAH in Chile. Material and methods: Nine hundred twenty two newborns were studied. 17OHP was measured using double antibody radioimmunoassay in filter paper blood samples obtained 48 h after birth. Reference ranges were determined according to gestational age and birth weight and a cutoff point of 25 ng/ml was established. Results: Seventeen newborns had 17OHP over the cutoff value. They were assessed by a pediatric endocrinologist and in none of them, CAH was confirmed. Therefore the false positive rate of the determination was 1.8 percent. Among these newborns with elevated 17OHP, 66 percent had a birth weight below 1.5 kg and 5.8 percent, a birth weight between 1.5 and 2.5 kg. The cost per reported result was US $ l. Timing of the recall was between the 3 and 10 days of life. No newborn missed the follow-up. Discussion: To increase the cost-efficiency ratio of an eventual neonatal screening program, newborns with birth weights below 1.5 kg should be excluded and cutoff points should be defined according to birth weight

Autoanticuerpos anti-tiroglobulina: detección y posible interferencia en la medición de tiroglobulina en suero / Thyroglobulin autoantibodies: detection and possible interference in serum thyroglobulin measurement

Background: Thyroglobulin measurement is useful for the follow up of patients subjected to total thyroidectomy for differentiated thyroid carcinoma. Thyroglobulin autoantibodies may interfere with its determination. Aim: To measure thyroglobulin autoantibodies and their interference with thyroglobulin determination. Material and methods: The presence of thyroglobulin autoantibodies was investigated in 801 serum samples sent to the laboratory for measurement of thyroglobulin levels. A serum was considered positive for these autoantibodies when radioactivity corresponding to 125I-thyroglobulin bound to thyroglobulin autoantibodies, precipitated with human gamma globulin, exceeded in 1.4 times that of a negative sera pool. In positive sera, thyroglobulin autoantibody concentration was measured and its interference with thyroglobulin radioimmunoassay was assessed through a recuperation test using exogenous thyroglobulin. Results: Thyroglobulin autoantibodies were detected in 149 sera (18.6 percent). Of these, 65 had a recuperation that fluctuated between 1 and 80 percent. Thyroglobulin autoantibody concentration was negatively correlated with recuperation percentages (r= -0.64; p <0.001) but not with thyroglobulin concentrations (r= 0.08). Thyroglobulin was higher in positive sera with a recuperation over 80 percent than in sera with a recuperation of less than 80 percent (12.7 ñ 1.7 and 5.9 ñ 0.6 ng/ml, respectively; p <0.001). Conclusions: Thyroglobulin autoantibodies interfere with thyroglobulin measurement by radioimmunoassay, sequestering variable amounts of thyroglobulin. The presence of these autoantibodies must be investigated prior to thyroglobulin determination