Search strategies and selection criteria
The literature search was conducted in PubMed, Embase, Cochrane Library databases, Clinicalkey, China National Knowledge Infrastructure (CNKI), China Scientific Journal Database (VIP), Wanfang Database and Chinese Biomedicine (SinoMed) covering the period from inception to June 2018. Following the Participants, Interventions, Comparisons, Outcomes and Study design (PICOS) principle, the key search terms included hypertension, high blood pressure, essential hypertension, auricular therapy, ear acupoint, acupressure, acupuncture, electroacupuncture, bloodletting, laser acupuncture, lasering, moxibustion and random.
Studies meeting the following criteria were included: (a) patients: adults (age>18 years old) with hypertension; (b) intervention: auricular therapy which includes acupressure, acupuncture, electroacupuncture, laser acupuncture, moxibustion, and bloodletting in the auricle; (c) comparison: sham auricular therapy, ADs or no intervention; (d) outcomes: blood pressure (BP) before and after treatment, magnitude of BP change between baseline and post-intervention and the efficacy rate; (e) study design: randomized controlled trial (RCT). The exclusion criteria were as follows: (a) patients with comorbidities and complications of hypertension; (b) trials comparing different methods of auricular therapy
Three researchers (CL, HQH, and QYH) independently screened all records according to the inclusion and exclusion criteria. Any inconsistencies were resolved by discussion among the three authors and were arbitrated by a fourth author (JL). Finally, we identified 44 qualified RCTs that were included in the current analysis.28–71 The complete process and the exclusion reasons are shown in Figure 1.
Figure 1.  Flow diagram of literature search and selection. HBP: high blood pressure; TCM: traditional Chinese medicine.