President Barack Obama signed the Patient Protection and Affordable Care Act into law on March 23, 2010.

Although a major target of Mitt Romney in the recent campaign, it was reaffirmed on Nov. 6, when voters re-elected the president.

As with Social Security and Medicare, there will be ongoing resistance from the political right. As with any legislation, it is far from perfect. The Affordable Care Act, however, captures and will set a direction for American health care for the immediate future.

In a preceding piece, I discussed benefits of this law that accrue to all of us. This column will address deeper changes that are occurring in medicine and the support these changes receive from the ACA.

Medicine is changing from a cottage industry to an organized system of care. The model of individual providers practicing independently is being replaced by more standardization of care for common and routine conditions. This change is and will continue to be disruptive.

Interestingly, Maine played a significant role in this process. In the early 1970s, a physician, Jack Wennberg, studied discharge data in Vermont and discovered vast differences in the rate of surgical procedures, differences based on where people lived.

Most of this variation turned out to be based on physician discretion rather than other variables, such as frequency of diseases or informed patient choice.

Wennberg’s work was first published in the Journal of the Maine Medical Association.

The ability of computerized databases to study these variations continues to drive best practices.

Medicare was designed around a model of acute care episodes, which simply does not reflect the way we practice medicine today.

Preventive care and chronic care now dominate the world of medicine. Models driven by the experience of large organizations such as the Mayo Clinic, Kaiser Health Care, Geisinger Clinic and Intermountain Health show that different models and organization of care can improve outcomes for populations of patients.

The ACA has built in an aim to bring more accountability into the formula for value for all purchasers of health care.

We will see broader implementation of Accountable Care Organizations, organizations of enough size to be able to take responsibility for the health care of populations of people.

New means of measurement through increasing use of computerized data and electronic medical records will provide the tools to measure effectiveness and to hold organizations accountable. This change will pose a significant challenge for rural states such as Maine.

At the ground level, where we all interact with the health care system, the major change being advanced by the ACA is the Patient Centered Medical Home. At the practice level, the patient will receive a higher integration of service, with coordination of subspecialists and care management, so that multiple needs of those with chronic medical conditions can be met.

Accountability will be measured through EMR and other administrative databases. We will learn more about what does and does not work. We will learn the limits of our knowledge in the actual practice of medicine and thus advance. This too will be a challenge to available resources in rural states.

This process is already disruptive.

The guidelines for accountable care represent unique challenges for geriatricians. Many of the guidelines for measurement have never been tested in older patients with multiple illnesses.

For example, what is the right level of blood sugar control for a frail elder individual? This requires more research and understanding but is clearly not the same as for a younger person with Type I diabetes. This system will force us to learn in ways we have not been asked to in the past.

Another challenge we will face, especially in primary care, will be the need to maintain the relationship between a patient and his/her primary care provider, while working in an environment that is more team-oriented.

The management of chronic medical illness will benefit from this relationship, a recognized value of the PCMH concept.

Affirmation of the ACA by the recent election will accelerate change. That change, although disruptive, will, if managed well, lead to a more coordinated and efficient system of care from which we will all benefit.

Roger A. Renfrew, M.D., of Skowhegan, is an internist and geriatrician. He has been practicing medicine in Skowhegan since 1979.