Serum immunoreactive trypsin (IRT) concentrations were measured blind in sera from 33 patients with cystic fibrosis and in 32 age-matched controls. Thirty-two patients had abnormal trypsin concentrations. In 30 of these patients the level of IRT was very low whereas in the other two (the youngest of the group) it was extremely high. All 30 patients with low IRT concentrations had clinical or bi...

The inspiratory drive to hypoglossal (XII) motoneurons originates in the caudal medullary intermediate reticular (IRt) region. This drive is mainly glutamatergic, but little is known about the neurochemical features of IRt XII premotor neurons. Prompted by the evidence that XII motoneuronal activity is controlled by both muscarinic (M) and nicotinic cholinergic inputs and that the IRt region co...

BACKGROUND Since its beginnings, newborn screening for cystic fibrosis (CF) using an assay for immunoreactive trypsinogen (IRT) has been plagued by a high rate of false-positive results (screen positive, diagnosis negative), despite attempts to reduce this rate by use of altered cutoffs and second-tier DNA testing. IRT exists as 2 isoforms: IRT1 and IRT2, with IRT2 being more closely aligned wi...

CONTEXT Item response theory (IRT) measurement models are discussed in the context of their potential usefulness in various medical education settings such as assessment of achievement and evaluation of clinical performance. PURPOSE The purpose of this article is to compare and contrast IRT measurement with the more familiar classical measurement theory (CMT) and to explore the benefits of IR...

The authors discuss the applicability of nonparametric item response theory (IRT) models to the construction and psychometric analysis of personality and psychopathology scales, and they contrast these models with parametric IRT models. They describe the fit of nonparametric IRT to the Depression content scale of the Minnesota Multiphasic Personality Inventory--2 (J. N. Butcher, W. G. Dahlstrom...

The progress test is used to provide useful summative and formative judgments about medical students' knowledge without distorting learning. The test samples the complete knowledge domain expected of new graduates on completion of their course, regardless of the year level of the student. Item Response Theory (IRT) have been proposed for evaluating examinations in medical education. Although IR...

We compare test construction using CTT and IRT in several sample sizes (from N=20 to N=5000) and degrees of representativeness (represented by selecting the top 20%, 40%, 60%, 80% or 100% of a population) using a Monte-Carlo simulation design. Little support was found for our hypothesis that IRT would outperform CTT in building informative tests, especially in large or unrepresentative samples....

Immunoreactive trypsin (IRT) content in blood spots from 17 cystic fibrosis (CF) children born between 1975-80 were assayed with reagents from two commercial radioimmunoassay kits. The manufacturers' procedures were modified to allow assay of blood spot IRT. Half of the CF samples had a significantly raised IRT content compared to normal blood spots. Of the blood spots from five children whose ...

This study investigates the impact of item parameter drift (IPD) on parameter and ability estimation when the underlying measurement model fits a mixture distribution, thereby violating the item invariance property of unidimensional item response theory (IRT) models. An empirical study was conducted to demonstrate the occurrence of both IPD and an underlying mixture distribution using real-worl...

Anaemia is common in advanced cancer, may develop for several reasons, and is not always symptomatic. Our observations of the seemingly indiscriminate prescription of iron-replacement therapy (IRT) for anaemic palliative care patients, and our practice of discontinuing IRT in patients with normal red-cell indices, prompted a study to determine (1) the prevalence of anaemia in our patients, (2) ...