I. Marschner

Verbesserung und Qualitätskontrolle der radioimmunologischen Thyreotropin-Bestimmung

Durch Messung der Reaktionskinetiken von J-TSH mit Anti-H-TSH bei verschiedenen Temperaturen wurde die Inkubation bei Raumtemperatur als optimal erkannt. Die Präzipitationsreaktion mit Anti-y-Globulin erfolgt bei den meisten der geprüften Chargen bei Raumtemperatur komplett innerhalb weniger Stunden. Die Anwendung von niedrig markiertem J-TSH (20—70 mCi/mg) führt wegen der gut erhaltenen Immunoreaktivität des Tracers zu empfindlichen Eichkurven, und im Vergleich zu Wiederfindekurven in Humanserum richtigen TSH-Werten. Durch Wiederfindekurven in Serum erreichen wir einen Interassay-Variationskoeffizienten von etwa 10 Prozent und verbessern dadurch die relative Richtigkeit der gefundenen TSH-Werte.

Iodine deficiency, hypothyroidism, and endemic goitre in Southern Tanzania* A survey showing the positive effects of iodised oil injections by TSH determination in dried blood spots

The Ukinga and Uwanji regions, located in the southern highlands of Tanzania, were studied for the degree of iodine deficiency and the incidence of goitre and hypothyroidism, respectively. A urinary iodine excretion as low as 17.6 +/- 9.3 micrograms/g creatinine was observed in Wangama village. The mean goitre prevalence in 27 villages in Uwanji ranged between 65 and 96% (n = 3031 schoolchildren). Of 681 pregnant women from Ukinga 79.6% had goitre. The prevalence of cretinism as estimated on clinical criteria was 3% in Magoye (Uwanji). A normal serum TSH (below 2.1 mU/l) was observed in only 12 out of 66 school children before iodine prophylaxis, whereas the T4/TBG ratio was decreased in 36 of 63 cases. Blood spot TSH levels in newborn infants (n = 219) from mothers without iodine supplementation were above 12 mU/l in 45%. In contrast, only 20.3% of the newborn (n = 118) had elevated blood spot TSH (p less than 0.002) when the mothers had received an iodised oil injection during pregnancy. Most of the newborn (n = 18; 75%) of the latter group with elevated TSH (n = 24) came from mothers who had received the iodine injection only 1-25 days before delivery. Maternal iodine prophylaxis in late pregnancy does not increase the rate of neonatal hypothyroidism. Conclusions: It has been confirmed that severe iodine deficiency resulting in endemic goitre, cretinism, and hypothyroidism is prevalent in the regions studied. Dried blood spot TSH determinations may serve as an index for the efficiency of iodine prophylaxis programmes. Such a programme was carried out with relatively little expenditure and effort on a large scale basis.

Comparison of four different algorithms for the calculation of radioimmunoassay standard curves.

Standard curves from 150 determinations of 10 different hormone radioimmunoassays have been evaluated using the following four procedures: logit transformation as performed by Rodbard, Healys 4-component-logit, spline approximation and a linear interpolation program. The results, calculated by computer, have been compared with manual analysis as the refernce method. The influece of various correction factors has been studied by artificial insertion of outliers. Approximately two thirds of all investigated curves could be calculated with almost equal success using all 4 methods. In calculating the remaining third of the standard curves, each method showed characteristic errors which depended upon the reliability of the assay data and the kind of outliers. The results suggest that the smoothing by spine function is the most flexible method in approximating a radioimmunoassay standard curve. In comparison with the other methods it is less influenced by random errors and fits the characteristic and symmetry of the ideal curve most exactly. The 4-component logit which has been extended by data screening is an improvement of the original logit transformation. Certain reservations exist, however, in elimination of outliers because of the dispersion of the data points, and also because of the arbitrarily set thresholds.

An External Quality Control Survey (EQCS) for Serum Cortisol

The external quality control survey (EQCS) was based on those already published from this department (Marschner, I. et al. (1976) J. Clin. Chem. Clin. Biochem. 14, 345-351; Marschner, I. et al. (1974) Horm. Metab. Res. 6, 293-296; Horn, K. et al. (1976) J. Clin. Chem. Clin. Biochem. 14, 353-360). Each participant received 20 sera sent in dry-ice by express post or airmail, together with a detailed questionnaire requesting assay details and raw data from his own standard curve as well as from the 20 samples.

A second external quality control survey (EQCS) for serum triiodothyronine (T3) and thyroxine (T4) assays using the "Munich model".

Over 100 laboratories participated in an external quality-control survey (EQCS) for T3 and T4, using the Munich Model as conceived in this laboratory ((1-4): Marschner,!, et al. (1974), Horm. Met. Res. 6, 293-296; Horn,K. et al. (1976), this J. 14,353-360; Marschner J. et al. (1976), this J. 14,345-351; Wood, W. G. et al. (1980), this J. 18, 183-192) and carried out over the past 6 years. Twenty lyophilised serum samples, including independant hidden standard curves for T3 and T4, were dispatched by post together with a detailed questionnaire and full instructions on reconstitution of the samples. The returned data were processed as previously described ((4): Wood, W. G. et al. (1980), this J. 18,183-192) and each participant received a full analysis of his«own data and a set of histogrammes with which he could visually check his performance against other laboratories. An explanatory letter was sent, which explained the computer print-out, the coding of the kits and contained a constructive report of the participants performance and helpful advice as to how to improve the assay if this was necessary.

A modular analyzer system for double antibody radioimmunoassays

The increasing number of determinations performed by radioimmunoassays necessitates rationalization of the procedures. An analyzer system has been developed in order to fully mechanize double antibody radioimmunoassays, which is essentially composed out of four independently working modules. The samples, in microliter vials, are carried in sample chains of up to 650 links. The first pipetting step is performed by syringes with displacement pistons. Additional reagents are rapidly added by an electronically controlled Hamilton repeating dispenser, which makes shaking procedures for mixing unnecessary. The bound/free separation is achieved discontinuously by use of Nuclepore-filters, which are carried in 3 inches distance (76 mm) by a 35 mm dark leader film. After covering the radioactive filter positions with an adhesive plastic foil from both sides, the film spool is directly inserted into a specially constructed gamma-counter. The results of the evaluation of the efficiency and of the precision of each module are presented in this paper.

Methodische Untersuchungen und Vergleich von 7 kommerziellen Kits zur radioimmunologischen Thyrotropin- Bestimmung aus dem getrockneten Blutstropfen

Zusammenfassung: Zur Untersuchung Neugeborener auf konnatale Hypothyreose hat sich die Thyrotropin-Bestimmung aus dem getrockneten Blutstropfen auf Filterpapier durchgesetzt. Die vorliegende Arbeit untersucht methodische Probleme der Test-Optimierung anhand einer eigenen Methode in Gegenüberstellung zu Testkits. Geprüft wurde die Haltbarkeit der Proben sowie der Einfluß von Papierqualität, Plättchengröße, Entnahmezeitpunkt der Filterplättchen und Waschvorgang des Präzipitats auf das Analysenergebnis. Die zum Zeitpunkt der Untersuchung auf dem Markt befindlichen Kits unterscheiden sich erheblich hinsichtlich Testdauer, methodischem Aufwand, eingesetzter Plättchengröße (entspricht Probenvolumen) und Preis. Abgesehen von diesen formalen Unterschieden bestand keinerlei Übereinstimmung der erzielten Testergebnisse. Gravierende Unterschiede zeigten allein schon die beigegebenen Standardkonzentrationen, was bisher bei keiner Kittestung für andere Hormone in diesem Ausmaß gefunden wurde (Wiederfinderaten von 22 bis 185% zum Vergleichsstandard). Es wird die Erarbeitung gemeinsamer Richtlinien und Qualitätskriterien sowie die Etablierung einer externen Qualitätskontrolle vorgeschlagen.