Trust as an Omnichannel-to-Advocacy Transmission Mechanism in Mandatory Health care Services: Empirical Evidence from Indonesia.

Background: In Indonesia, omnichannel integration in healthcare is intensifying, yet the psychological mechanisms that convert omnichannel integration into patient advocacy remain insufficiently understood, particularly in mandatory healthcare settings characterised by credence-service properties, high perceived risk, and constrained choice. This study uses the Stimulus-Organism-Response (S-O-R) framework to examine brand trust as a mediating mechanism linking omnichannel integration to brand advocacy. Methods: Data were collected from 230 patients across three health care facilities in Jakarta and Tangerang through questionnaires validated via forward translation, back translation, face validity, content validity, and pre-testing. Partial least squares structural equation modelling (PLS-SEM) with 5,000 bootstrap subsamples, supplemented by cross-loading evaluation, heterotrait-monotrait (HTMT) inference, model comparison, and demographic control variables, was used for analysis. Results: Omnichannel integration was positively associated with brand trust (β = 0.715; p < 0.001) and brand advocacy (β = 0.671; p < 0.001). However, the direct effect of omnichannel integration on brand advocacy was not significant (β = 0.019; p = 0.793). The indirect effect of brand trust was significant (β = 0.480; 95% confidence interval [0.372, 0.586]), indicating a full mediation pattern (variance accounted for = 96.2%). After controlling for age, gender, and education, core relationships remained stable, and the model explained 46.8% of the variance in brand advocacy. Conclusions: These findings suggest that omnichannel integration is primarily associated with patient advocacy in mandatory health care services through trust. However, because this study does not directly compare service contexts, any inference regarding differences from conventional retail should be interpreted cautiously.