In vitro effect of dipyrone on several peroxidase labelled immunoassays.

We studied the in vitro effect of dipyrone on the determination of free triiodothyronine (free T3), cortisol, progesterone, estradiol, carcinoembryonic antigen, human chorionic gonadotropin and alpha-fetoprotein measured with an immunoenzyme assay based on enhanced luminescence that uses peroxidase as label. We found significant interference from dipyrone (p < 0.01) in the determination of all the analytes mentioned: for progesterone and estradiol the interference was present at high doses of dipyrone; for free T3 and cortisol the minimum dipyrone concentration producing interference was 712 mumol/l and for carcinoembryonic antigen, human chorionic gonadotropin and alpha-fetoprotein 44 mumol/l. Dipyrone has an analytically and statistically significant interference effect on the determination of the mentioned analytes.

Evaluation of Ciba Corning ACS:180 automated immunoassay system.

We evaluated the technical performance of the Ciba Corning ACS:180 automated immunoassay system for the following analytes: thyroid-stimulating hormone, free thyroxine, luteinizing hormone, follicle-stimulating hormone, prolactin, human chorionic gonadotropin, carcino-embryonic antigen, and prostate-specific antigen. The characteristics evaluated were: precision, carryover, linearity, lower limit of detection, analytical interferences, and comparison with other methods. Satisfactory results were obtained in the within-run and between-run precision studies. Neither sample nor reagent carryover was found for any assay. The range of linearity was acceptable. For some of the assays evaluated, the lower limit of detection was better than that claimed by the manufacturer. Correlation between ACS:180 methods and compared methods was adequate. We conclude that the ACS:180 offers good reliability, practicability, and performance capabilities.

[Evaluation of a new strategy for detecting thyroid dysfunction]. / Evaluación de una nueva estrategia para la detección de disfunción tiroidea.

The results of a diagnostic strategy to evaluate thyroid function were assessed. This strategy consists of TSH measurement as the initial biochemical test, assuming that all individuals with normal TSH concentrations are euthyroid and do not require additional measurements of other hormones. The study was carried out in 576 patients whose serum samples had been referred to the laboratory during 4 consecutive weeks for the evaluation of thyroid function. In all cases TSH and free T4 (FT4) concentrations were measured by chemoluminescence, using one tube for each parameter and patient. Total T3 concentrations (T3) were only measured (RIA) in patients with subnormal TSH values, using duplicate samples. With TSH measurement as the initial test, 447 patients (78%) in whom further hormone assessment would not have been required were detected. This rate would have been 75% if FT4 measurement had been adopted as the screening test. In addition, 55 patients with subclinical thyroid dysfunction were identified with TSH measurement. They would have been missed if the screening had been based on FT4 only. T3 measurement only contributed to the identification of one patient with T3 thyrotoxicosis, and it did not provide additional useful information for the diagnostic classification of the remaining patients. The results of these assays show that TSH measurement is the biochemical test of choice as the first step of a strategy to detect thyroid dysfunction. Its use to this end makes the concomitant measurement of other hormonal parameters unnecessary, resulting in a considerable reduction of cost.

Technical and clinical performance of six sensitive immunoradiometric assays of thyrotropin in serum.

We evaluated the analytical and clinical performance of six commercial immunoradiometric assay kits for thyrotropin (TSH) in serum in 218 subjects, with and without thyroid dysfunction. Detection limits of the six kits were lower (from 0.07 to 0.25 milli-int. unit/L) than that of conventional TSH RIA (0.7 milli-int. unit/L). Precision was adequate over a wide range of concentrations, although interassay CVs at very low concentrations were good for only two kits (7.3% and 13.1%). Results by all the kits correlated to about the same degree with the TSH RIA (r = 0.92 to 0.98). All showed a positive correlation between both the basal and post-thyroliberin (TRH)-stimulation values for TSH (r = 0.78 to 0.88), and all showed similar euthyroid reference ranges for basal concentrations of TSH. With four of the six kits we could clearly distinguish most of the hyperthyroid patients from healthy euthyroids; however, basal and post-TRH TSH values were not sufficient to discriminate among groups of patients with different grades of thyroid hyperfunction.