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  • Writer's pictureDr. Samir Desai

MMI Interview Practice Questions: What Discovery Has Had the Greatest Impact on Medicine?

Updated: May 17, 2022

Scientist looking into microscope
The history of medicine is full of impactful discoveries, so it can be challenging to respond to this question

Why is this MMI interview question, focused on the history of medicine, asked?

Medical school interviewers have an appreciation for the history of medicine. They like to see that future physicians have given some thought to the history of the profession and how it has developed.

Many medical school leaders believe that historical perspectives are an important part of the medical school curriculum. In a survey of US medical schools, almost 40% of the schools had formal lectures or seminars about the history of medicine.

History teaches us about disease and how our approach to disease and treatment has changed over time. This requires an understanding of social, economic, and political forces. History provides us with this context.

If you search the internet, you'll find rankings of the most important discoveries or inventions in medicine. These rankings differ considerably as to what is considered the most important discovery.

What does that mean for you as an applicant when answering this MMI interview question?

That means that there really is no right answer. There are so many discoveries that have had tremendous impact, and it's impossible for people to agree on the most impactful. Therefore, the best way to answer this question is by choosing one discovery and then doing your research.

Use the information that you learn to develop a powerful answer: one that reveals the depth of your knowledge as well as something about you.

In my experience, the most common answers given by applicants have to do with the discovery of penicillin or the use of vaccines. There's nothing wrong with discussing penicillin or vaccines, but it can be hard to stand out when just about every applicant is using one of these two discoveries in their answer.

Fortunately, there are plenty of other important discoveries—and just a little background reading will uncover the fascinating stories behind these other discoveries.

Also, remember that a response that includes something about you or your experiences (in addition to the discovery) will make for a more powerful response.

The History of Oral Rehydration Solutions

Before I delve into my own response to this question, let me tell you a story to provide some context. Back in the 1970s, around the time that India and Pakistan were firmly entrenched in a war, monsoon season hit. With its heavy rains and ensuing floods, it led to a calamitous situation for thousands and thousands of refugees. These refugees were deprived of necessities and poured into medical camps seeking assistance.

The Government of India, the state government of West Bengal, and a number of non-governmental organizations sought to provide assistance. These overwhelmed organizations were taxed even further when a cholera epidemic broke out. Although IV saline solutions were available, they weren't enough to provide for the enormous population. There was also a lack of trained volunteers to administer them. Within a few days, 30% of patients died, many being children.

This disaster deeply affected Dilip Mahalanabis, a member of the staff of the Johns Hopkins Center for Medical Research and Training in Calcutta. Mahalanabis was part of a team that had developed a new oral rehydration solution to replace the water and electrolytes that are lost through vomiting and diarrhea.

He was not the first to discover oral rehydration therapy, but the therapy up until that point had only been used in tertiary referral centers. Dilip felt that this therapy could make a difference during the cholera epidemic.

He and his team worked feverishly--measuring the ingredients, placing them in plastic bags, writing out instructions, sealing the bags with a hot iron and then sending them urgently to the camps.

The packets were received at the camps, and healthy parents, family members and staff had their patients drink large volumes of this solution.

The Results Of Oral Rehydration Solutions Were Simply Amazing

Over eight weeks, there was a steep drop in mortality--from almost 30% to less than 1%.

If the story ended right there, it would certainly be remarkable. But let me tell you what happened next.

Dilip wrote a paper about the dramatic results. Unfortunately, his findings were met with skepticism. Leading experts in the field rejected it.

This miraculous medical development might have ended there, if not for a cholera expert from the World Health Organization named Damon Baruah. He agreed to see things for himself.

And when he went, he was absolutely stunned by what he saw.

The World Health Organization Adopts The Use Of Oral Rehydration Solutions

What he saw was the successful treatment of cholera with just oral rehydration solution. He realized that oral rehydration treatment could completely change the way in which diarrhea was treated all over the world. In his mind, he imagined millions of children's lives being saved.

He returned to the World Health Organization and shared what he had seen. This led to the creation of the World Health Organization's Diarrheal Disease Control Program. Studies were also done that showed no clinically important differences in effectiveness between oral and IV fluid replacement in children with diarrhea.

The impact of this discovery was enormous. In the 1980s, close to 5 million children under the age of 5 years died each year from diarrhea. Twenty years later, that figure had dropped to 1.8 million.

In poor countries, children can expect to have three episodes of diarrhea every year, which means they face a potentially life-threatening infection as often as every 4 months. With oral rehydration therapy, their risk falls tremendously.

In the last 25 years, more than 50 million lives of children have been saved with oral rehydration therapy.

Although there have been tremendous strides in the treatment of diarrhea, it still remains the second most common cause of death among poor children. With this cheap and easily prepared solution, the world has the power to prevent even more deaths due to diarrhea.

My Response to the MMI Interview Question on the Most Important Discovery in Medicine

"So many discoveries in medicine have had a tremendous impact. And although it's hard for me to single out one as the most impactful, I would like to share one discovery which has saved the lives of over 50 million children suffering from vomiting and diarrhea. That is called oral rehydration solution.

I learned so much about it during my international health trip to Kenya. I went to Kenya with a team of healthcare professionals. We worked side by side with some Kenyan doctors in rural parts of the country. We had a wonderful opportunity to care for patients who have limited access to health care.

One of the Kenyan doctors had told me about oral rehydration therapy, and how much of a difference it had made in his country. Amazingly as a child, he too benefited from the solution. That made me think about how this solution has transformed lives and families, and allowed children to become adults.

It's amazing to think what some of these adults have done for our world, whether it's by becoming a nurse, a doctor, or researcher, and so on. When you look at it that way, the impact is tremendous, not only in terms of the lives saved, but the contributions these survivors have made to the world. I know that diarrhea is still a major cause of death in children. And I hope that with my interest in global health, that I can be a part of the solution."

Analysis of This MMI Interview Response

In analyzing this answer, it is clear that the interviewee has a strong knowledge about diarrheal illness in children and the use of oral rehydration therapy. The answer states the impact of the discovery in terms of lives saved. He weaves in his own story and demonstrates that he has an interest in global health. He ends by indicating that he hopes to make a difference in this area down the road.

This answer does a great job of answering a challenging question while also revealing something specific about the applicant.


Dr. Rajani Katta is the creator of Medical School Interviewing 101, the course that teaches students how to ace their interviews. She is also the author of the Multiple Mini Interview: Winning Strategies from Admissions Faculty, the Casper Test Prep Guide, and The Medical School Interview. Dr. Katta is a practicing dermatologist and served as a Professor of Dermatology at the Baylor College of Medicine for over 17 years.

Dr. Samir Desai is the author of The Clinician's Guide to Laboratory Medicine, The Medical School Interview, and Multiple Mini Interview: Winning Strategies from Admissions Faculty. He is an Internist, on faculty at the Baylor College of Medicine, and has served on the medical school admissions and residency selection committees at the Baylor College of Medicine and Northwestern University Feinberg School of Medicine.

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