United Kingdom. The general health policy in the UK is established by the Parliament, and service delivery is through the National Health Service (NHS). The system is financed from general taxes, and a small proportion of payroll tax. The NHS also receives copayments and payments from private patients. Coverage is universal. For primary care, the population must enroll in local institutions of their choice, but the offer is limited to the care of general practitioners (GPs). To reduce disparities in access, the NHS ensures resources for local areas, as well as monitoring the results for at-risk groups [19]. At the community level, general practice is addressed at local regions, where they focus on prevention and education for health, facilitating access and adequate treatments to avoid over medicalization and specialized research [20].

The access problems have been solved through a universal health model focused on primary care [20], but there are still problems with the large waiting lists to access the Health Center or "walking centers" "with the GP and the attention of general practitioners and the NHS Direct, which is a telephone consultation service [21].  The NHS of England is intervening to reduce inequalities in access to general practice services through the Operational Planning and Contracting Guide 2017-2019, and the practical resources guide - Improving access for all: reduction of inequalities in access to general practice services [22], which aims to promote access by community groups that are experiencing barriers to accessing services and help address those barriers, to as improvements in access to general practice services are implemented.

France: France and Germany represent forms of SHI, where the coverage is universal and mandatory too. According to Mossialos et al (2016) [18], in France, health policy and provision is the responsibility of the Ministry of Social Affairs, Health and Women's Rights, through compulsory health insurance and the Administration of Health and Social Affairs that have the Regional Agencies of health. The SHI is financed through payroll taxes of employees and employers by 64%, 7.5% made by employees and 13.10% made by employers, and the national income tax with a specific allowance of 36%. There is also private voluntary insurance that covers the difference between the SHI reimbursement rates through vouchers. To mitigate inequalities, all employees benefit from insurance, sponsored at 50% by the employer, for dental and vision care. The Regional Health Agencies (RHA) were created in 2009 to allow better decentralized access conditions [23].

For financial reasons, some citizens and residents currently do not find the necessary treatment, for dental or vision care. Others cannot find an independent health care provider that charges the rates reimbursed by national health insurance, especially if there are no local doctors. To solve this problem, the French model within public health insurance for all citizens, as well as for long-term residents, provides a "Vital Card", which covers the total cost of essential care for the most serious conditions (such as cancer and diabetes) and a part of the cost of other care [24].

The Carte Vitale is the health insurance card since 1998 to allow a direct health care of the SHI. Since 2008, a second generation of smart cards is being introduced, which has additional functions of an electronic health insurance card to carry electronic documents of the treatment process. Medical visits and treatments are reimbursed for social security at a rate of 70%. The remaining 30% is the responsibility of the patient. The SHI covers 100% in case of maternity, work accident and occupational disease [25].

Germany: Germany has the SHI and Private substitute Health Insurance (PHI). The states provide services through university hospitals, and the municipalities focus on primary health care and public health activities. Health spending is financed by taxes on benefits provided by SHI through sickness funds that are financed by compulsory contributions collected at 14.6% of salary. About 86% of people receive primary coverage through SHI and 11% through PHI.

There are special programs for soldiers and policemen. The provision of primary prevention services is mandatory for sickness funds. To reduce disparities, sickness funds cover the health of socially disadvantaged people (Mossialos et al. 2016) [18].

Although the costs per person in health in Germany are one third higher than the OECD average, the role of PHI is important for the need for more outpatient care centers associated with the hospital with the objective of a better balance in utilization, strengthening organizational capacity in the ambulatory care sector, with better access to low-cost care.  The German SHI emphasizes equity, universal coverage and free choice, but the difference is the large number of providers and technological equipment that guarantee easy access. The SHI has implemented easy access using highly sophisticated technological equipment. Therefore, formal waiting lists and prioritization are virtually absent. Projects such as an electronic card, computerized systems for entering medical orders, remote monitoring systems and other tools can improve information and access [26].

United States: In the United States, the health system consists of several forms of insurance, including private insurance, Medicare, Medicaid and CHIP. According to a report from the US Census Bureau in 2014, public programs covered approximately 36.5% of residents: Medicare covered 16%, and Medicaid 19.5 %. In addition, 55.4% received insurance provided by the employer and 14.6% directly purchased. About 10.4% remain uninsured. Patients in U.S have relatively rapid access to specialized medical care, but paradoxically, delayed access to primary care compared with people in other developed countries.

 Likewise, they report greater access problems related to cost that is the double in comparison with Australia, Canada and the UK [27].

Barriers to health services in the United States system include high cost of care, inadequate or no insurance coverage, lack of availability of services, and lack of culturally competent care. There is inequality of access to care because it varies according to race, ethnicity, socioeconomic status, age, sex, disability status, sexual orientation, gender identity and residential location [28]. Disparities exist with all levels of access to care, including medical and dental insurance, which have a continuous source of care and access to primary care. Disparities also exist by geography, as millions of Americans living in rural areas lack access to primary care services due to labor shortages. Future efforts should focus on the deployment of a primary care workforce that is better geographically distributed and trained to provide culturally competent care to diverse populations [29].

To improve this situation, the Affordable Care Act (ACA) has had the potential to assign incentives and create opportunities for providers to be rewarded for the delivery of patient-centered primary care. By introducing local care models, the growth in the cost of care has slowed. Primary care physicians, nursing professionals and medical assistants who provide 60% of their services in primary care codes for office visits, visits to nursing centers and home visits receive a bonus. In addition, providers in areas of resource scarcity for surgical procedures may receive an additional increase. The model called Patient-Centered Medical Home (PCMH) or Medical Homes has several provisions that seek to strengthen the system by allowing the patient access to a regular source of primary care, stable and continuous relationships with the personal physician who runs a care team, promoting preventive services and facilitating better management of chronic conditions [30].

The specific solutions that are proposed both in healthcare systems in the US as in Colombia, include: Increasing access to the entire care process (from preventive clinical services to long-term palliative care). Both health systems, the United States and Colombia, should make the provision of primary care more frequent. According to the US Office of Disease Prevention and Health Promotion [31], it is intended that PCMH and team attention reduce access barriers, in addition to monitoring the increasing use of telehealth as a method of medical care.

Singapore: In Singapore, the Ministry of Health regulates the country's health system. Provides services through health and hospital networks, day care centers and nursing homes. It offers universal coverage, financed by general taxes by schemes of multiple levels and private individual savings that are used for subsidies for patients and certain institutions that provide care. The system is known as the "3M": Medisave is a mandatory health savings program where workers and employers contribute a percentage of their salaries to a personal account. MediShield is an insurance for catastrophic events of low cost and major diseases. About 10% of health expenses come from private prepaid plans that complement the MediShield. Medifund is the subsidy fund for the destitute. Patients choose the primary care physician, and it is not necessary to register [18].

The government provides access to a basic level of care and subsidizes most of the cost so that none is left without fundamental medical care, but paradoxically the system is designed so that patients contribute to the cost of care, because patients spend their own money in care beyond the basic level. To reduce inequalities, in 2007, the Ministerial Committee on Aging was established to coordinate the problems of aging in a health care system that provides older people access to care for their particular needs at an affordable price. In 2009, the Agency for Integrated Care (AIC) was established to work in the care units at the local level and to improve the level of care and carry out the integration of the primary, intermediate and long-term care sectors. All parties involved in the various levels of care with a patient must work together in a more coordinated manner. In 2012, greater subsidies were offered for intermediate and long-term care, a greater and better care infrastructure, more doctors and nurses who were added to the system with competitive remuneration [32].

The healthcare systems in both Singapore and Colombia share that universal access to medical care needs two regimes: mandatory and subsidized. While in Singapore the Medifund ensures that no Singaporean is denied access to the health system due to the inability to pay, Colombia subsidizes only half of the eligible population. This means 50% of the entire population is under SR or the SR covered. The SR and Medifund subsidies are assigned to those who really cannot afford medical care. Another major difference is that in Singapore, at least 65% of the beds of public hospitals receive large subsidies, to facilitate universal access and promote quality. In Colombia, there is no supply-side subsidy, only demand subsidy.

To avoid lack of access to healthcare in Singapore, primary care is strengthened through an extensive network of private medical clinics, which provide 80% of primary health care services, as well as 18 government polyclinics, which they provide the remaining 20%. The public sector represents 80% of public tertiary care hospitals [33,34].

Table 2 compares the problems and solutions in potential access to health care, of each country with the situation currently in Colombia.

Table 1: Population-level indicators of potential and realized access in Colombia and select OECD countries.