[Author: Lynda Williams, senior medwireNews reporter]
medwireNews: The first validated, age-specific, patient-reported measure has been developed to help monitor physical changes in people with fibrodysplasia ossificans progressiva (FOP).
“The FOP–PFQ [Physical Function Questionnaire] was demonstrated to be a reliable, valid measure that may be responsive to change in individuals with FOP, although some results were inconclusive for the pediatric versions,” say Robert Pignolo (Mayo Clinic, Rochester, Minnesota, USA) and co-authors.
As reported in Bone, the team created the 28-item self-reported questionnaire for adult patients and three pediatric versions, namely a 26-item self-reported questionnaire for children aged 8–14 years and two proxy questionnaires for the parents of those aged 2–4 years and 5–14 years, comprising 24 and 26 items, respectively.
Specifically, the FOP–PFQ asks respondents to assess total, upper extremity, and mobility scores using a 5-point scale, where 1 denotes inability to complete a task, such as “button shirt or pants,” and 5 indicates no difficulty in completing the task. The proxy versions also allowed respondents to describe a task as “not applicable.”
Baseline FOP–PFQ data was gathered for 389 individuals who participated in a natural history study, a patient registry, or a phase 2 clinical trial and its open-label extensions, but the study was limited by the availability of responses for just three patients in the youngest age group.
The FOP–PFQ scores were collated with information from other physical and clinical measures of disease status, including range of motion on the Cumulative Analogue Joint Involvement Scale and activities of daily living; the adult and pediatric forms of the PROMIS Global Health Scale; and whole-body computed tomography assessments of heterotopic ossification (HO) burden.
This allowed the researchers to test the FOP–PFQ for reliability, validity of the measurements against pre-existing assessments, and sensitivity to changes in patients with a known alteration in clinical status.
Initial analysis suggested that the best option was a two-factor solution assessing only upper extremity and mobility functions.
Using this approach, the FOP–PFQ showed “high internal consistency” for assessments at baseline and month 12 for the adult and most of the pediatric assessments, and patients without flare-ups had stable scores when tested repeatedly over 1–3 weeks.
In addition, FOP–PFQ scores for adults and children correlated with other measures of physical function and HO volume, and there were “moderate to large” correlations between the adult FOP–PFQ score and the PROMIS Physical Health score, as well as for the pediatric versions for those aged 8–14 and 5–14 years.
Patients with the most severe disease progression had the poorest FOP–PFQ scores, “suggesting the instrument performs effectively as a measure of severity and potentially disease progression over time,” write Pignolo et al.
Although there was only a moderate correlation between age and adult FOP–PFQ scores and “minimal” correlation with the pediatric versions, the authors remark that this “may be expected given the high variability in the rate of ossification” and the slow rate of disease progression.
The team suggests that in adult patients, a score change of 6–15 points for total and upper extremity measures and an 8–18-point change in mobility might be “considered minimally clinically meaningful,” with estimates also made for the pediatric scales.
“Additional work is needed to define a minimal clinically meaningful change for the FOP-PFQ,” the researchers conclude.
“However, the tool has potential for use in future drug development trials and clinical practice to help healthcare providers and individuals with FOP to better understand the impact of the disease on physical function.”
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