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) ...

BACKGROUND The Washington Radiation for In-Stent Restenosis Trial is a double-blinded randomized study evaluating the effects of intracoronary radiation therapy (IRT) in patients with in-stent restenosis (ISR). METHODS AND RESULTS One hundred thirty patients with ISR (100 native coronary and 30 vein grafts) underwent percutaneous transluminal coronary angioplasty, laser ablation, rotational a...

OBJECTIVE To investigate variation in immunoreactive trypsinogen (IRT) concentrations by race, sex, birth weight, and gestational age and their implications for the use of percentile-based cutoffs for cystic fibrosis (CF) newborn screening (NBS) programs. PATIENTS AND METHODS This cross-sectional population-based study of resident infants screened in Michigan investigates associations between...

1. Infrared thermography (IRT) for detecting body temperature is less accurate in women, elderly people, and those with fever. 2. The core temperature significantly but weakly correlates to the IRT temperatures obtained from frontal and lateral of the face, and the forehead. 3. Among the three areas, the forehead IRT temperature showed the largest discrepancy and poorest correlation with the co...

Embedding item response theory (IRT) models within a multilevel modeling framework has been shown by many authors to allow better estimation of the relationships between predictor variables and IRT latent traits (Adams, Wilson, & Wu, 1997). A multilevel IRT model recently proposed by Kamata (1998, 2001) yields the additional benefit of being able to accommodate data that are collected in hierar...

BACKGROUND Although item response theory (IRT) appears to be increasingly used within health care research in general, a comprehensive overview of the frequency and characteristics of IRT analyses within the rheumatic field is lacking. An overview of the use and application of IRT in rheumatology to date may give insight into future research directions and highlight new possibilities for the im...