Using Patient Health Questionnaire-9 item parameters of a common metric resulted in similar depression scores compared to independent item response theory model reestimation

Objectives: To investigate the validity of a common depression metric in independent samples. Study Design and Setting: We applied a common metrics approach based on item-response theory for measuring depression to four German-speaking samples that completed the Patient Health Questionnaire (PHQ-9). We compared the PHQ item parameters reported for this common metric to reestimated item parameters that derived from fitting a generalized partial credit model solely to the PHQ-9 items. We calibrated the new model on the same scale as the common metric using two approaches (estimation with shifted prior and StockingeLord linking). By fitting a mixed-effects model and using BlandeAltman plots, we investigated the agreement between latent depression scores resulting from the different estimation models. Results: We found different item parameters across samples and estimation methods. Although differences in latent depression scores between different estimation methods were statistically significant, these were clinically irrelevant. Conclusion: Our findings provide evidence that it is possible to estimate latent depression scores by using the item parameters from a common metric instead of reestimating and linking a model. The use of common metric parameters is simple, for example, using a Web application (http://www.common-metrics.org) and offers a long-term perspective to improve the comparability of patient-reported outcome measures.

Impatient in experiments, but patient in simulations: a challenge to the heckman-type model

Intertemporal labour–leisure choice models typically assume agents have a very low degree of impatience. Yet there is a lot of empirical evidence indicating a high degree of impatience. Using a life-cycle model of consumption–saving and labour–leisure choice, we show that even if an agent displays a relatively moderate degree of impatience, his labour supply choice delivers highly counterfactual patterns. We resolve this counterfactual finding by augmenting the standard model with a time-dependent marginal utility of leisure assumption that is consistent with some recent evidences from leisure studies. We also introduce various extensions and discuss their relative importance and associated challenges.