Defining the minimally clinically important difference of the SF-36 physical function subscale for paediatric CFS/ME:...

Area of Science:

• Pediatric Rheumatology
• Clinical Measurement
• Rehabilitation Medicine

Background:

• Establishing the minimally clinically important difference (MCID) is vital for clinical trial design and ensuring meaningful outcomes.
• Previous research has defined the MCID for the SF-36 physical function sub-scale (SF-36-PFS) in adults, but not in pediatric populations.
• This study addresses the gap by defining the MCID of the SF-36-PFS in children and adolescents with Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (CFS/ME).

Purpose of the Study:

• To determine the minimally clinically important difference (MCID) of the SF-36 physical function sub-scale (SF-36-PFS) in pediatric patients diagnosed with CFS/ME.
• To utilize a triangulation approach combining distribution, anchor, and qualitative methods for robust MCID estimation.
• To provide a clinically meaningful benchmark for future research and clinical practice involving pediatric CFS/ME.

Main Methods:

• Quantitative analysis of routinely collected data from a specialist pediatric CFS/ME service.
• Anchor-based method using Clinical Global Impression (CGI) at 6-month follow-up.
• Distribution-based method using the standard deviation of baseline SF-36-PFS scores.
• Qualitative methods involving semi-structured interviews with young patients (12-17 years) and their parents, alongside SF-36-PFS completion.
• Thematic analysis of qualitative data to understand patient-perceived meaningful change.

Main Results:

• Quantitative data from 198 children (mean age 14 years) showed a mean SF-36-PFS difference of 9.0 for 'a little better' on CGI.
• Half the standard deviation of baseline SF-36-PFS scores was 11.0.
• Qualitative findings from 21 children and parents indicated a median minimal improvement of 10 on the SF-36-PFS.
• Participants highlighted that small functional improvements significantly impact social and family life.
• Triangulation of all methods yielded a consensus MCID of 10 for the SF-36-PFS in pediatric CFS/ME.

Conclusions:

• Converging evidence from distribution, anchor, and qualitative methods supports an MCID of 10 for the SF-36-PFS in pediatric CFS/ME.
• This established MCID value of 10 should be adopted in future clinical trials and research involving this population.
• The findings emphasize the importance of considering patient-reported outcomes and perceived changes in physical function for meaningful clinical interpretation in pediatric CFS/ME.