Development, validation and initial application of a patient-reported outcome measure to assess treatment burden for people living with multimorbidity in low-income settings in South Africa (SIMMBA)
Myrna van Pinxteren, Charlotte Slome, Peter Delobelle, Lovemore Mapahla, Naomi S. LevittBackground
Treatment burden is a key determinant of outcomes for people living with multimorbidity (PLWMM). However, contextually appropriate measures are lacking in low-income settings. We developed and conducted initial validation of the SIMMBA patient-reported outcome measure (PROM) to assess multidimensional treatment burden in South Africa.
Methods
Following COSMIN guidelines, items were generated through literature review, expert consultation, and cognitive interviews, and translated into local languages, Afrikaans and IsiXhosa. A cross-sectional study was conducted among 332 adults with multimorbidity attending public primary care clinics in Cape Town. Psychometric evaluation included exploratory factor analysis (EFA), internal consistency (McDonald’s omega and Cronbach’s alpha), test–retest (n=99) reliability (Spearman correlation and intraclass correlation coefficients [ICC]), and differential item functioning (DIF) by gender.
Results
Internal consistency was acceptable to good across all domains (ω=0.54–0.83; α=0.643–0.803), except medication burden (ω≈0.21). Most domains showed no evidence of DIF, with two items flagged. Test–retest reliability was predominantly poor to fair (ICC range 0.33–0.55), indicating limited temporal stability. EFA supported a 64% of variance, with generally strong item loadings, although some cross-loadings and low communalities were observed. Participants reported highest burden in the financial domain and lowest in social support.
Conclusions
The SIMMBA PROM demonstrates promising preliminary validity in capturing context-specific treatment burden among PLWMM in low-income South African settings. However, further structural refinement, convergent validation, and improved reliability testing are required prior to implementation.