Idiographic Patient Reported Outcome Measures (I-PROMs): A Narrative Systematic Review on Patient-Centred Measurement in Psychotherapy

Objectives: In psychotherapy, self-report measures with standardized item-sets are widely used to evaluate therapy progress and outcome. However, relying solely on standardized (nomothetic) measures may overlook person-specific (idiographic) problems. Idiographic patient-reported outcome measures (I-PROMs) allow patients to formulate their items, capturing therapy-relevant aspects that standardized measures might miss. To provide guidance on implementing I-PROMs and improving item quality, we conducted a pre-registered narrative systematic review (PROSPERO:CRD42022361535).Methods: We searched "Web of Science," "PsycINFO," "PubMed," and "EMBASE," along with reference screenings, to identify studies using I-PROMs in therapy settings, including a psychometric evaluation, published before March 18th 2025.Results: Our search yielded 32 empirical articles (51 studies) examining 13 I-PROMs and 6,706 participants. Four I-PROMs assessed therapy-relevant aims (three assessed goals, measuring goal-attainment; one assessed values, measuring value-directed behaviour), four problems (measuring problem-duration, -severity or -change), three both goals and problems (measuring motivational variables), and two assessed helpful aspects of therapy (measuring helpfulness/hindrance). Items were generated via self-administration (four I-PROMs), interviews (six I-PROMs), or both (three I-PROMs). We identified two strategies to enhance item quality: improving item-wording (e.g., instructions, examples, (re)formulation guidelines) and ensuring relevance to therapy (e.g., predefined focus-areas, prioritization-procedures). I-PROMs were applied across therapy settings, talking-therapy schools, nationalities, genders, and disorders, but differences in applicability across these remained unclear.Discussion: Our synthesis helps therapists and researchers evaluate I-PROMs' strengths and limitations, enabling informed choices for selection and implementation, and offers guidance to improve item quality – thereby, facilitating comprehensive measurement and promoting a broader adoption of I-PROMs moving forward.