Inka Wahl

A 4-item measure of depression and anxiety: Validation and standardization of the Patient Health Questionnaire-4 (PHQ-4) in the general population

BACKGROUND The 4-item Patient Health Questionnaire-4 (PHQ-4) is an ultra-brief self-report questionnaire that consists of a 2-item depression scale (PHQ-2) and a 2-item anxiety scale (GAD-2). Given that PHQ-4, PHQ-2, and GAD-2 have not been validated in the general population, this study aimed to investigate their reliability and validity in a large general population sample and to generate normative data. METHODS A nationally representative face-to-face household survey was conducted in Germany in 2006. The survey questionnaire consisted of the PHQ-4, other self-report instruments, and demographic characteristics. RESULTS Of the 5030 participants (response rate=72.9%), 53.6% were female and mean (SD) age was 48.4 (18.0) years. The sociodemographic characteristics of the study sample closely match those of the total populations in Germany as well as those in the United States. Confirmatory factor analyses showed very good fit indices for a two-factor solution (RMSEA .027; 90% CI .023-.032). All models tested were structurally invariant between different age and gender groups. Construct validity of the PHQ-4, PHQ-2, and GAD-2 was supported by intercorrelations with other self-report scales and with demographic risk factors for depression and anxiety. PHQ-2 and GAD-2 scores of 3 corresponded to percentile ranks of 93.4% and 95.2%, respectively, whereas PHQ-2 and GAD-2 scores of 5 corresponded to percentile ranks of 99.0% and 99.2%, respectively. LIMITATION A criterion standard diagnostic interview for depression and anxiety was not included. CONCLUSIONS Results from this study support the reliability and validity of the PHQ-4, PHQ-2, and GAD-2 as ultra-brief measures of depression and anxiety in the general population. The normative data provided in this study can be used to compare a subjects scale score with those determined from a general population reference group.

Health-related quality of life, depression, and anxiety in patients with autoimmune hepatitis

BACKGROUND & AIMS Improving health related quality of life (HrQoL) in patients with chronic diseases such as autoimmune hepatitis (AIH) should be a major treatment goal. However, little is known on the HrQoL in patients with AIH, and the topic is not given attention in current practice guidelines. We therefore conducted a single center study evaluating HrQoL in 103 consecutive outpatients with AIH. METHODS Patient-reported HrQoL data were analysed in relation to clinical disease parameters and compared to representative data of the German population as well as control patients. RESULTS Based on patient-reported data, a major depressive syndrome (10.8%) was found to be five times more frequent in AIH patients compared to the general population (p<0.001). The rate of severe symptoms of anxiety was also found to be significantly increased compared to the general population (p=0.006). In seven of the eleven patients who scored for a major depressive syndrome a psychiatric comorbidity had not been diagnosed before. Major factors associated with depression and anxiety were concerns with regard to the progression of the liver disease. CONCLUSIONS This study identified--for the first time--a high rate of previously unrecognized severe symptoms of depression and anxiety in patients with AIH. Of importance for daily clinical practice, the factors associated with these symptoms may in part be amenable to targeted counselling and adequate treatment of the disease, thereby offering the chance to improve the care and HrQoL of AIH-patients.

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 Stocking-Lord linking). By fitting a mixed-effects model and using Bland-Altman 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.

Impact of cross-calibration methods on the interpretation of a treatment comparison study using 2 depression scales

Background:Many questionnaires assessing depressive symptoms are available. Most of these questionnaires are constructed based on classical test theory, making comparisons of individual scores difficult. Item response theory (IRT) allows the comparison of scores from different instruments. In this study, the impact of IRT-based cross-calibration methods on the results of a treatment outcome study was evaluated using 2 instruments. Methods:Data collected during admission and discharge procedures from 1066 inpatients in 2 psychosomatic clinics using different depression measures were analyzed. To achieve comparability across the applied depression measures, we used an IRT-based conversion table to transform scores from one instrument’s scale to the other. Latent trait values were also estimated using different instruments in each clinic. We compared these methods to the traditional approach of using the same instrument in both clinics and examined their effects on the statistical analyses. Results:There was no substantial change in the interpretation of the study results when different instruments were used. However, F values, P values, and effect sizes in the analysis of variance changed significantly. This might be attributed to differences in the content or measurement properties of the instruments. Interestingly, no difference was observed between use of transformed sum scores and latent trait values. Conclusions:IRT cross-calibration methods are a convenient way to enhance the comparability of questionnaire data in applied clinical settings but seem not to be able to overcome differences in measurement properties of the instruments. As these differences can lead to biased results, there is a need for further research into more advanced techniques.

Language‐related differential item functioning between English and German PROMIS Depression items is negligible

To investigate differential item functioning (DIF) of PROMIS Depression items between US and German samples we compared data from the US PROMIS calibration sample (n = 780), a German general population survey (n = 2,500) and a German clinical sample (n = 621). DIF was assessed in an ordinal logistic regression framework, with 0.02 as criterion for R2‐change and 0.096 for Rajus non‐compensatory DIF. Item parameters were initially fixed to the PROMIS Depression metric; we used plausible values to account for uncertainty in depression estimates. Only four items showed DIF. Accounting for DIF led to negligible effects for the full item bank as well as a post hoc simulated computer‐adaptive test (< 0.1 point on the PROMIS metric [mean = 50, standard deviation =10]), while the effect on the short forms was small (< 1 point). The mean depression severity (43.6) in the German general population sample was considerably lower compared to the US reference value of 50. Overall, we found little evidence for language DIF between US and German samples, which could be addressed by either replacing the DIF items by items not showing DIF or by scoring the short form in German samples with the corrected item parameters reported.

Computer Adaptive Tests in der Medizin

Measurement of Patient-reported Outcomes (PRO) still lacks behind clinical standards. Most established tools are also either too burdensome or too imprecise to be used in clinical practice. Item Response Theory (IRT) methods and Computer Adaptive Tests (CAT) promise to overcome these shortcomings. Simulation studies have shown that individually tailored CATs can provide more precise and less burdensome measurements over a larger measurement range than static tools. Several studies with real CAT application have supported the psychometric superiority of CATs, but results from longitudinal studies are still scarce. IRT item banks also allow scoring different established tools measuring the same construct on one common metric, which could greatly facilitate the harmonization of PRO-assessments.