Validation of the Standardized Outcomes in Nephrology-Life Participation (SONG-LP) Instrument in People with CKD

BACKGROUND: Life participation has been identified as a critically important core outcome by people with CKD not yet requiring kidney replacement therapy. In this study we aimed to validate the Standardised Outcomes in Nephrology Life Participation (SONG-LP) instrument. METHODS: A psychometric evaluation of the SONG-LP was conducted in adults with CKD not yet requiring kidney replacement therapy. The instrument includes four equally-weighted domains of life participation including leisure, family, work and social activities, scored on a five-point Likert scale that specifies frequency over a one month recall period from never (0) to always (4) with a range of 0 to 4 possible (calculated as a mean of the 4 responses). Internal consistency, test-retest reliability, convergent validity, hypothesis testing, and acceptability were assessed. RESULTS: In total, 179 participants from 16 countries participated. The SONG-LP instrument demonstrated strong internal consistency (Cronbach's a = 0.92, 95% confidence interval [CI]: 0.89- 0.94; baseline; McDonald's ω = 0.93, CI: 0.91-0.95; baseline ) and strong test-retest reliability over one week (n=165, intraclass correlation coefficient of 0.81; 95% CI: 0.76-0.86) with mean scores 2.97 ± 0.91 and 3.07 ± 0.92 at baseline and at week one, respectively. There was strong positive correlation with the PROMIS Ability to Participate in Social Roles and Activities Short Form 8a that assesses a similar construct (0.81; 95% CI: 0.72-0.86), and moderate correlation with measures that assess related concepts including EQ5D (0.72; 95% CI: 0.63-0.79), and PROMIS Cognitive Functional Abilities Subset Short Form 4a (0.61; 95% CI: 0.50-0.70). CONCLUSIONS: The SONG-LP instrument is a valid, reliable and internally consistent instrument to assess life participation in people with CKD not yet requiring kidney replacement therapy. It can potentially facilitate routine and consistent assessment of life participation in trials and routine clinical care in people with CKD.