Short survey may serve as valid measure of LOPD physical function

20-question PROMIS PF20a largely agreed with other survey scores

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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An easy survey of 20 questions agrees well with other tools used in clinical practice to measure physical function in people with late-onset Pompe disease (LOPD), according to a study that suggests it may aid in measuring and tracking symptoms over time.

Having a reliable way to measure physical function could help doctors understand how the disease affects everyday activities like walking or moving around, and how well a patient is responding to treatment.

The study, “Validation of the Patient-Reported Outcomes Measurement Information System (PROMIS®) physical function questionnaire in late-onset Pompe disease using PROPEL phase 3 data,” was published in the Journal of Patient-Reported Outcomes.

Pompe disease occurs because an enzyme is missing that breaks down glycogen into glucose, a simple sugar. Without it, glycogen builds up in cells, causing symptoms like muscle weakness and trouble breathing. The late-onset form arises during childhood or later.

Enzyme replacement therapy (ERT) may slow the disease’s progression by replacing the needed enzyme. To measure its benefit, LOPD patients are surveyed before and during treatment about their symptoms, but no standard survey is used.

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Short survey holds PROMIS

Here, researchers used a survey called Patient-Reported Outcome Measurement Information System Physical Function Short Form 20a (PROMIS PF20a) to measure physical function with LOPD. Part of the research team is from Amicus Therapeutics, which funded the study.

“This questionnaire is used for various diseases and tests someone’s ability to perform daily physical activities such as getting dressed,” the researchers wrote. In the study, they compared it with other clinical tools used to measure a variety of functions.

The researchers drew on data from 123 adults with LOPD who were able to walk (mean age, 47) and took part in PROPEL (NCT03729362), a Phase 3 clinical study that compared Amicus’ Pombiliti + Opfolda (cipaglucosidase alfa/miglustat) against Lumizyme (alglucosidase alfa). Both are approved for Pompe disease.

Data from all the patients were analyzed together without comparing the two treatment groups. At the study’s start, or baseline, the mean PROMIS PF20a score was 67 and increased after 52 weeks to 69. The PROMIS PF20a score ranges from 20 to 100, with a higher score indicating better physical functioning.

After 52 weeks, patients walked farther in six minutes (6MWD; 372 vs. 356 meters, which is equal to about 407 vs. 389 yards) and scored higher on the manual muscle test (MMT) of the lower extremities, a measure of muscle strength where a higher score indicates better muscle function (29 vs. 28).

The predicted forced vital capacity (FVC), a measure of lung function, did drop slightly from 70% to 69%. The Rasch-Built Pompe-Specific Activity (R-PAct), which looks at how the disease impacts daily activities and social participation, improved, however, indicating fewer limitations.

In general, the score provided by the PROMIS PF20a survey had moderate to strong agreement with other scores. The strongest agreement was with R-PAct scores. There was moderate agreement with the predicted FVC and the Gait, Stairs, Gowers’ Maneuver, Chair (GSGC) score, a measure of physical functioning, the 6MWD, and the MMT of the lower extremities.

For patients, the minimum difference in the PROMIS PF20a score considered relevant, that is, indicative of improvement or worsening of the disease, fell between 2.4 and 4.2 points.

Using a cutoff of 2.4 points, 46 (38%) patients had a change in their PROMIS PF20a score after 52 weeks over baseline equal to or larger than the minimum relevant difference for improvement. In contrast, 24% had a reduction of 3.4 points or more, indicating disease worsening.

“The results from this study show that PROMIS PF20a may be used to measure symptoms and follow symptoms over time in patients with LOPD,” the researchers wrote. “Its use should be considered in future clinical studies of patients with LOPD and potentially in clinical practice.”