Omnichannel retailing, service quality, brand trust, and customer brand engagement as drivers of brand advocacy in Indonesian health care services: A cross-sectional PLS-SEM study

Background Indonesian health care providers must now integrate physical and digital channels, yet how patients advocate for a health care brand remains poorly understood. Omnichannel retailing, service quality, brand trust, customer brand engagement, and brand advocacy have been examined in isolation, and their integration within a single stimulus–organism–response (S-O-R) framework is rarely discussed. This study investigates whether channel integration has displaced service quality as the driver of patient trust and advocacy, or whether the two operate through distinct mechanisms. Methods A total of 324 patients were surveyed at a primary clinic, a private hospital, and a regional public hospital in Greater Jakarta. A 49-item, five-point Likert-type questionnaire, adapted from validated English-language scales through back-translation, expert content validation, face validation, and a pretest (n = 50), was digitally administered after the service encounter. Partial least squares structural equation modelling was applied using a disjoint two-stage approach for the higher-order constructs and 5,000 bootstrap subsamples. Results All six hypotheses were supported. Service quality raised trust (β = 0.430) almost twice as strongly as omnichannel retailing (β = 0.259): competence outweighs cross-channel convenience. Trust raised customer brand engagement (β = 0.442), the strongest path through which every mediated effect passed. The three paths into advocacy — engagement (β = 0.239), trust (β = 0.209), and omnichannel retailing (β = 0.206) were of comparable size, so advocacy has no dominant driver. All seven indirect paths were significant; omnichannel retailing reached advocacy mainly directly (71.8% of its total effect) and service quality only through mediation. Conclusions The two antecedents operate through distinct mechanisms — functional versus relational stimuli — refining S-O-R for high-risk services and positioning brand trust as the gateway to engagement and advocacy. Managers should prioritise service quality and treat digital integration as a complement, not a substitute.