Differential Item Functioning (DIF) is investigated to ensure that each item displays a consistent pattern of responses irrespective of the characteristics of the respondents. Assessing DIF helps to understand the nature of instruments, to assess the quality of a measure and to interpret results. This study aimed to examine whether the items of the Quality of Life Enjoyment and Satisfaction Questionnaire-Short Form (Q-LES-Q-SF) and Short-Form 12 (SF-12) exhibit DIF. A total of 124 outpatients diagnosed with substance dependence participated in a cross-sectional, multicenter study. In addition to the Q-LES-Q-SF and SF-12 results, demographic data such as age, sex, type of substance dependence and education level were collected. Rasch analysis was conducted (using RUMM2020 software) to assess DIF of the Q-LES-Q-SF and SF-12 items. For SF-12, significant age-related uniform DIF was found in two of the 12 items, and sex-related DIF was found in one of the 12 items. All of the observed DIF effects in SF-12 were found among the mental health items. Three items showed DIF on the Q-LES-Q-SF; however, the impact of DIF item on the delta score calculation for the comparisons of self-reported health status between the groups was minimal in the SF-12 and small in the Q-LES-Q-SF. These results indicated that no major measurement bias affects the validity of the self-reported health status assessed using the Q-LES-Q-SF or SF-12. Thus, these questionnaires are largely robust measures of self-reported health status among substance users.

To determine whether patients' perception of early therapeutic alliance (TA) could predict time to achieve a target weight among adolescents undergoing treatment for anorexia nervosa. TA was assessed in a prospective cohort recruited from both inpatient and outpatient settings by self-administered and validated questionnaires. Kaplan-Meier survival curves were compared by log rank test, and Cox regression was used to test whether patients' perception of early TA predicted time to achieve a target weight. In total, 108 patients were included, and 79.6% achieved a target weight. Better patient perception of early TA increased the hazard ratio (HR) of achieving a target weight (HR = 2.7, 95% confidence interval: 1.7-4.4, p < .001) such as being in the inpatient setting by 6.7. Being very severely underweight at admission decreased the HR of achieving the target weight. Patients' perception of early TA is a good predictor of achieving a target weight. Because TA is a modifiable construct, it could be a target for intervention.

Background: Although research on health-related quality of life (HRQoL) has increased in the addiction field, few studies have focused on the determinants of HRQoL changes. This study aimed to describe dependent patients’ HRQoL changes at a 3-month follow-up and to assess whether satisfaction with care can predict those changes among outpatients starting care for alcohol or opioid dependence. Methods: HRQoL was measured with the SF-12 at baseline and 3 months later in a prospective cohort of dependent outpatients. Satisfaction was assessed with the EQS-C early after inclusion. Data on sociodemographics, clinical characteristics and patients’ levels of anxiety and depression were also collected. A multivariable analysis was performed to identify factors associated with HRQoL changes in both the physical and mental component summary scores (PCS and MCS, respectively). Results: Of the 172 patients included at baseline, a total of 136 patients assessed their satisfaction with care. The mean PCS and MCS scores were initially low, and HRQoL improvement was significant after 3 months for both the PCS and MCS. Never having been married (β = 5.5; p = 0.001) and a lower baseline PCS score (β = − 0.6; p < 0.0001) were associated with significant PCS improvement, whereas being legally compelled to undergo drug treatment (β = − 5.9; p = 0.02) was associated with less PCS change. Higher early satisfaction with care (β = 0.1; p = 0.02) and a lower baseline MCS score (β = − 0.7; p < 0.0001) were associated with significant MCS improvement. Conclusion: The study supported the hypothesis that greater satisfaction with care may predict HRQoL improvement among dependent outpatients. Further studies are needed to understand the factors that affect patients’ early satisfaction to identify areas of improvement and thus improve HRQoL.