Study Design: A household survey was conducted in East-Azerbaijan Province of Iran in 2015. This study is part of a larger project designed to assess the baseline and time trend of health variables affected by a PHC reform in Iran. Methodological details were published previously as the research [3] and intervention protocols [27].
Study Setting: Iran PHC system is one of the successful systems in the world with outstanding achievements. Some of PHC performance indicators are as following: Infant mortality rate (IMR) per 1000 live births=9.48, access to PHC in rural areas=99%, Maternal mortality rate (MMR) per 100 000 live births=19 and vaccine uptake rate was 99% in most of vaccine programs [28, 29]. PHC services are delivered through health houses in rural and health centers in urban areas. Medical University in each province is the responsible governing body for health system. Due to active follow-up by health centers, nearly all of the households are in contact with PHC system and familiar with and using its common free services. In urban areas, it is free to bypass PHC and contact hospital services but in rural, individuals should be referred through referral system[28, 29].
East Azerbaijan Province with a total population around 3900000 people (based on 2016 census) is located in northwest of Iran. Tabriz as the capital city is the most developed, populated (1773033 people) and oldest city in the province. Beside the city health centers, Medical Universities and provincial authorities are placed in capital cities, such as Tabriz, in Iran. Moreover, private and other sectors providing health services are mostly established in capital cities. In contrast, in other cities than capital of a province, majority of health services are provided by government [29, 30].
Sampling: Sampling was done using two-stage cluster with probability proportional to size (PPS) approach. One county was selected randomly as representative of each of five geographical parts (Central, Northeast, Northwest, Southeast and Southwest) of the province.
Regarding, Tabriz metropolitan as the province capital, Oskou in central part, Varzeghan and Marand city from northeast and northwest, respectively and Bonab from southwest and Mianeh in southeast of the province were selected.
120 clusters comprising 20 households were allocated as Tabriz city sample and the National Demographic Health Survey study (2011) was used as sampling framework. Similarly, 120 clusters were allocated to the other cities based on PPS. In cities other than Tabriz, the national population census was used as sampling framework.
Questionnaires: PHC trust questionnaire was used for data collection [26]. The questionnaire validity (Kappa coefficient = 0.94) and reliability (Cronbach-Alpha=0.98, ICC=0.94; CI: 0.87- 0.97) was approved. The questionnaire included 2 sections: first, demographic data such as age, gender, education, insurance, marital status and household dimension, and the second, comprising 30 items on trust in PHC. Moreover, Ultra-short version of socio-economic status assessment questionnaire (SES-Iran) which was validated in previous studies was used for data collection [31, 32].
Data collection and analysis: According to the main study data collection plan [3], households number 6-10 (600 households) in each cluster, were asked to response the PHC trust questionnaire. Each household was approached for data 3 times. Head of the households or housewife were interviewed by a trained questioner. An educated and informant member with age higher than 15, was interviewed, in case of the households head or housewife inability. At least 6 months of residency was used as inclusion criteria for the households. Descriptive statistics including frequency, mean and standard deviation and inferential statistics based on data normality were used for data analyzing through STATA 15.