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T L Groth

Publications and source records attributed to T L Groth.

5 recordsLinked to original sources
PubMed1991

Conversion of diurnal plasma hormone concentration profiles into secretion rates.

Various methods for the calculation of hormone secretion rates from plasma hormone concentration time-series are described. Problems related to the description of the basic processes of hormone kinetics, including secretory pulsatility, distribution, and elimination are discussed, as well as methods for the experimental validation of models. Computer modeling and simulation techniques are shown to be very useful in this respect. It is suggested that more sophisticated biophysical models are developed to describe hormone dynamics more accurately, for example, with regard to kinetically different molecular forms of the same hormone, and to the interaction of hormones with hormone-binding proteins. Such models would provide the basis for more accurate estimation of hormone secretion rates.

Circadian Rhythm↗
PubMed1983

Optimal screening for patients with hyperparathyroidism with use of serum calcium observations. A decision-theoretical analysis.

The conventional upper 95 percentile references limit of serum calcium does not necessarily constitute an optimal decision limit in screening for patients with hyperparathyroidism. The design of optimal screening procedures has to consider (a) the prevalence of disease; (b) the relative importance of making correct classifications of patients; and (c) the influence of analytical imprecision and inaccuracy. Based on serum calcium determinations from three reference sample groups (healthy individuals, patients with hyperparathyroidism, and patients with hypercalcaemia due to malignant disease) optimal decision limits were calculated for different screening situations. Optimum was defined in terms of estimated 'costs' due to misclassification. Different values for disease prevalence were used, as well as different weighting factors reflecting the importance related to correct classification of healthy and pathological patients. For a disease prevalence of 5% the optimal decision limit varies between 2.59 and 2.65 mmol/l for a weighting ratio false positives to false negatives of between 1:5 to 5:1. For a prevalence of 0.1% the corresponding range was 2.67-2.72 mmol/l. Compared to classification on the basis of the conventional upper reference limit, the application of optimal decision limits means significantly lower costs due to misclassification. Analytical bias then has to be kept stable within +/- 0.01 mmol/l. Inter-laboratory analytical variation also has to be reduced to the same level in order to make it possible to transfer reference values, decision limits and single patient values to other laboratories.

Adolescent↗