Responsiveness and minimum important change of the Pharmacotherapeutic Symptom Evaluation-20-Australian version: a...

Monitoring patient-reported symptoms over time may support early detection of medicine-related harms. The Pharmacotherapeutic Symptom Evaluation-20-Australian version (PHASE-20-Australian version) is an 11-point rating scale designed for longitudinal monitoring of medicine-related symptoms; however, its responsiveness and minimum important change (MIC) have not been established.

To evaluate the responsiveness and MIC of the PHASE-20-Australian version for monitoring changes in medicine-related symptoms over time.

A prospective cohort study was conducted among Australian adults (≥ 18 years) taking medications. Participants completed the PHASE-20-Australian version at baseline and follow-up and reported perceived symptom changes using the Global Rating Scale (GRS) at follow-up. Responsiveness was assessed by correlating score changes with the GRS and calculating the area under the receiver operating characteristic (ROC) curve (AUC). MIC was estimated using ROC anchor-based and 0.5 standard deviation (SD) distribution-based methods and then compared with the Smallest Detectable Change (SDC).

Among 102 participants, 52% were aged ≥ 60 years and 65.7% were female. Strong correlations were observed for overall score changes (rho = 0.815) with the GRS as well as for 84.2% of individual symptoms (rho = 0.701-0.897). The tool demonstrated good to strong discriminative ability (AUC = 0.739-0.975 for improvement; 0.764-0.977 for deterioration), with sensitivity and specificity ≥ 0.75 for 16 symptoms. The MIC values ranged from 0.5 to 1.5 using the ROC method and 0.9-1.8 using the 0.5 SD approach. The estimated MIC values exceeded the SDC for 84.2% of symptoms. Limited responsiveness (rho < 0.7, AUC < 0.7) and MIC values below the SDC were noted for forgetful, swollen legs/ankles and frequent urination/incontinent of urine.

The PHASE-20-Australian version is responsive for most symptoms, with a clinically meaningful change of approximately 2.0 points on a 0-10 scale. The estimated MIC is applicable at the individual level, although caution is needed for symptoms with an MIC below the SDC.