Unsupervised item response theory models for assessing sample heterogeneity in patient-reported outcomes measures.

PURPOSE: Unsupervised item-response theory (IRT) models such as polytomous IRT based on recursive partitioning (IRTrees) and mixture IRT (MixIRT) models can be used to assess differential item functioning (DIF) in patient-reported outcome measures (PROMs) when the covariates associated with DIF are unknown a priori. This study examines the consistency of results for IRTrees and MixIRT models. METHODS: Data were from 4478 individuals in the Alberta Provincial Project on Outcome Assessment in Coronary Heart Disease registry who received cardiac angiography in Alberta, Canada, and completed the Hospital Anxiety and Depression Scale (HADS) depression subscale items. The partial credit model (PCM) based on recursive partitioning (PCTree) and mixture PCM (MixPCM) were used to identify covariates associated with differential response patterns to HADS depression subscale items. Model covariates included demographic and clinical characteristics. RESULTS: The median (interquartile range) age was 64.5(15.7) years, and 3522(78.5%) patients were male. The PCTree identified 4 terminal nodes (subgroups) defined by smoking status, age, and body mass index. A 3-class PCM fits the data well. The MixPCM latent classes were defined by age, disease indication, smoking status, comorbid diabetes, congestive heart failure, and chronic obstructive pulmonary disease. CONCLUSION: PCTree and MixPCM were not consistent in detecting covariates associated with differential interpretations of PROM items. Future research will use computer simulations to assess these models' Type I error and statistical power for identifying covariates associated with DIF.

Changes in Health-Related Quality of Life During Multiple Myeloma Treatment: A Qualitative Interview Study.

PURPOSE: To explore whether patients with multiple myeloma changed their construct of health-related quality of life during treatment. PARTICIPANTS & SETTING: 14 participants were selected from 10 hematology-oncology departments in Denmark. METHODOLOGIC APPROACH: This interview study used a prospective, longitudinal, exploratory design. Semistructured interviews were conducted while participants were undergoing active treatment for multiple myeloma and six months after the baseline interview. Interviews were analyzed using systematic text condensation. FINDINGS: The overall theme at baseline was insecurity, and the overall theme at six months was coping. The following subthemes were also identified based on participants' description of their health-related quality of life: concerns about having a meaningful life, dealing with everyday limitations, and maintaining social networks; adjusting expectations to abilities; expanding social networks; and exploring a meaningful life. IMPLICATIONS FOR NURSING: Patients' ability to use coping strategies should be considered when screening for rehabilitation needs. During systematic in-depth symptom screening, unmet rehabilitation needs (e.g., physical functioning, fatigue, pain) may become apparent.