Snowball in a Blizzard: A Physician's Notes on Uncertainty in Medicine

by Steven Hatch

There's a running joke among finding a tumor in a mammogram is akin to finding a snowball in a blizzard. A bit of medical gallows humor, this simile illustrates the difficulties of finding signals (the snowball) against a background of noise (the blizzard). Doctors are faced with similar difficulties every day when sifting through piles of data from blood tests to X-rays to endless lists of patient symptoms. Diagnoses are often just educated guesses, and prognoses less certain still. There is a significant amount of uncertainty in the daily practice of medicine, resulting in confusion and potentially deadly complications. Dr. Steven Hatch argues that instead of ignoring this uncertainty, we should embrace it. By digging deeply into a number of rancorous controversies, from breast cancer screening to blood pressure management, Hatch shows us how medicine can fail-sometimes spectacularly-when patients and doctors alike place too much faith in modern medical technology. The key to good health might lie in the ability to recognize the hype created by so many medical reports, sense when to push a physician for more testing, or resist a physician's enthusiasm when unnecessary tests or treatments are being offered. Both humbling and empowering, Snowball in a Blizzard lays bare the inescapable murkiness that permeates the theory and practice of modern medicine. Essential reading for physicians and patients alike, this book shows how, by recognizing rather than denying that uncertainty, we can all make better health decisions.

Genres: Nonfiction, Medicine, Science, Medical, Health, Health Care

314 pages, Kindle Edition

First published February 23, 2016

Reviews

[Sebastian · Rating 2 out of 5]

A cursory view of the diagnostics and interventions that are touted by the media or the medical establishment as certain in their benefits and risks, but in fact have significant complexity in assessing their suitability for a given individual.

Deep dives look at mammography, guidelines for hypertension (JNC8), Lyme disease diagnosis and treatment, and a couple other big ones.

The overall message is one that I agree with deeply: that patients need to become better informed about how much medicine does not know, how frequently the media misrepresents research, and ultimately should be encouraged and enabled to assert a greater degree of personal discretion in medical decision-making; there are very few truths ("this will definitely work") and so one should be encouraged to decide their own level of risk tolerance.

I did not love the book not because of the content or theme but mainly because (A) it was a bit too high-level, but more importantly (B) because the style annoyed me. Just tell the story, Steven, I am not reading this to hear about you and your relationship with your publisher.

I also felt that the Lyme chapter betrayed the message of the book a bit. What should have been a chapter on "here's another piece of evidence around why you should not trust what people tell you" became a chest-thumping diatribe against nonphysicians with opinions about healthcare and a strong endorsement to trust whatever the man in the white coat says.

[Michelle Welch · Rating 4 out of 5]

This was my favorite and most eye-opening bit: The recommendations for screening mammograms come from research that showed 70 deaths from breast cancer in a group who received them, versus 100 deaths in a group who didn't. A 30% reduction in deaths! Of course we're going to tell all women over 40 to get mammograms! But what people don't know is that each group in the study had 30,000 women, and when you do the math, the number of lives saved is less than 1%. A well-argued and very readable warning about keeping your eyes open when you look at medical claims.

[John · Rating 5 out of 5]

This is an excellent book which all doctors and lay people should read. There is far more uncertainty in medicine than most people realize including many doctors. Every medical test or treatment has its positives and negatives. All too frequently the positives are overestimated and the negatives are underestimated. A good example of this are mammograms which are heavily promoted by the medical community. Seems like a good idea on the surface. Detecting cancer early is good, right? Finding cancer may help some (if it is early enough and not aggressive enough) but to do so results in many false positives. This means getting diagnosed with "cancer" which is never destined to shorten your life. Having such a false positive diagnosis means cancer treatment including surgery, chemotherapy, and radiation therapy which have very definite negative effects on health. This is a far more likely occurrence than is realized by most and negates any small positive effect the test may bring.

This is but one topic covered in this outstanding book.

I also recommend Overdiagnosed: Making People Sick in the Pursuit of Health and Should I Be Tested for Cancer?: Maybe Not and Here’s Why which are equally excellent.

[Judy · Rating 3 out of 5]

I'm not sure what the intended audience is for this book. The author's point is simple: don't believe all the health news you read or hear. A long read later, the reader has been introduced to the elements required to conclude that any particular drug or medical treatment is both safe and effective. It seems to me, though, that anyone who can wade through this material is already savvy enough to understand that medical treatments come with both risks and benefits, and medical decisions need to be made based on the relative values of both. The author occasionally tries to make the text more reader-friendly with light-hearted remarks, but they tend to come across as patronizing or snarky. And in the true spirit of statisticians, he never considers the value of a human life. He points out, for example, that a particular screening tool statistically will only save three lives per 100,000 people, and never acknowledges the value of those three lives to the ones living them.

[CatReader · Rating 4 out of 5]

Dr. Steven Hatch's Snowball in Blizzard is a medical manifesto akin to Dr. Gilbert Welch and colleagues' Overdiagnosed: Making People Sick in the Pursuit of Health, Dr. Paul Offit's Overkill: When Modern Medicine Goes Too Far, and Dr. Jerome Groopman's How Doctors Think. Hatch focuses on areas of uncertainty in medicine and how these uncertainties are rarely perceived as such by laypeople, the mass media, and sometimes other healthcare providers as well.

This book is largely told in a series of vignettes, the most compelling of which I think come from Dr. Hatch's own practice as an infectious disease doctor (Lyme disease, pandemics -- this book was published pre-COVID-19) and as a family member of a patient in dire straits whose care was mired in medical uncertainty. He keeps coming back to the analogy of the spectrum of certainty analogy, where treatments/interventions range from high benefit with strong evidence to high harm with strong evidence, and discusses many common misconceptions of treatments/interventions that might be best classified as around the middle of the spectrum (no strong evidence of either benefit or harm, with insufficient evidence to make a better determination) or slightly tilted to the harm end that the general public continues to think are of unmitigated benefit, like mammography for younger women with no other known risk factors for breast cancer.

As a fellow doctor, Dr. Hatch is preaching to the choir, and though I think he makes a valiant effort to reach laypeople, I'm not sure how well the information might be received (judging by some other GR reviews I saw), as this book is very densely-written and is jargon-y at times.

My statistics:
Book 167 for 2024
Book 1770 cumulatively

[Kai JD · Rating 5 out of 5]

Strongly recommend to anyone looking to make a good-faith effort in understanding medical (or broadly scientific) literature. Easily accessible to the lay-person, with concise descriptions of medical controversies. The nerd in me would have loved to read more about, say, the pathophysiology of Lyme disease that requires two specific tests to make the diagnosis, but that's beside Dr Hatch's point.

Don't let the reactive right-wing commentators looking to dunk on medicine and scientific research in your life read this book. Too many quotes to take out of context.

Also Hatch's reference to the coronavirus phylogeny was way too spot-on in 2025.

[Nancy · Rating 5 out of 5]

Quacks and religious healers are know for diagnosing cancers that don't actually exist so they can "cure" them. (Forty-five year ago I worked with a woman who was diagnosed with cancer and cured of it by Jim Jones, the minister who got his followers to drink the poison Kool-Aid.) MDs do this too. Not intentionally, but because they err on the side of calling abnormal cells cancer when in reality some will never develop into life threatening cancers. Hatch demonstrates that increases in some cancers and and their cure rates are both related to this fact.

Steven Hatch writes about medical statistics in a manner easily accessible to lay people. If you've ever wondered about the conflicting studies about mammograms, statins, PSA testing or other medical issues that pop up so frequently in the news, this book will help you make sense of it. How big does a study need to be to truly show a treatment works? Were the people enrolled in the study enough like me to tell how the treatment will affect me? Is that benefit enough to be worth potential side effects?

Well worth reading.

[Sasha · Rating 5 out of 5]

"Exercise more. Eat less. Don't smoke. Everything else is commentary."
...I can't personally corroborate the statistics used herein but assuming they are true this is a great book. Doctors and patients should read it.

[Michael H · Rating 2 out of 5]

Interesting book, although it should be subtitled, "why cancer screening and preventive care are bad". The author (Dr. Hatch) apparently doesn't approve of any cancer screening test or most preventive therapies. I agree that over-screening (and associated overtreatment) are extremely important issues and need to be addressed. However, Dr. Hatch presents multiple stories highlighting the lack of evidence for a range of tests/therapies without discussing the lack of evidence for harms. For example, he correctly highlights the lack of evidence for statin therapy in certain patient populations but provides only vague comments about how this therapy may be harmful - as indicated in the book's title, the benefit/harm ratio is clearly uncertain. That doesn't mean that it should be immediately excluded from medical care as Dr. Hatch seems to suggest.

This argument against certain types of screening/preventive care and "the escalation of medicalization" is understandable. However, the author also appears to have limited regarding for how patients themselves feel. In a section titled "Soul", Dr. Hatch criticizes depression diagnosis based on a well validated questionnaire that collect information from patients about their symptoms - what are known as patient-reported outcomes. Beyond "Soul" being an inappropriate title for this section (mental health care professionals are not clergy, and psychiatry is a science, not a religion), one of the most important changes in medicine over the past couple of decades has been the understanding that patients know their condition best. It is critical for health care professionals to help individuals with serious medical issues, including mental health conditions, describe how their symptoms affect their daily activities, quality of life, and wellbeing. By casually dismissing a questionnaire that helps patients explain how their mental state is affecting their lives and is a useful tool for diagnosing depression, Dr. Hatch ignores this important lesson. He asks "how, indeed, do you measure depression?" You measure it by paying attention to what matters to patients. Does that involve uncertainty? Absolutely, but it is the right way to practice medicine.

[Bonny · Rating 4 out of 5]

Medicine is a science of uncertainty and an art of probability. —Sir William Osler

Snowball in a Blizzard was a wonderful, informative, at times overwhelming, and sometimes soporific book. I found so much valuable medical information contained within its chapters, but at times this could also be too much information if you happen to be a patient trying to make the best medical decision possible in the areas of breast cancer, cardiology, or Lyme disease. Some aspects of medicine have been thoroughly researched, but Dr. Hatch writes about questioning research study designs along with how the data has been analyzed and reported. Many decisions in medicine have to be made in the paucity of well-researched information, and too often a well-defined answer simply does not exist. Medical uncertainty is a new way of thinking about things for me, but I think ultimately it may be the most realistic. Those (physicians and patients) who don't recognize this uncertainty may run the risk of overtreatment, which can be just as dangerous as undertreatment. Maybe someday medicine will be more of a Goldilocks field, but until that happens we would all do well to recognize the uncertainty.

[Patty · Rating 4 out of 5]

This book gives good insight into the world of medical uncertainty and research. The author did a good job of explaining uncertainty through case studies and examples. It helped explain the difference between various studies and how results are portrayed. Some parts were slow reading but the author has enough dry wit to keep the subject matter interesting.

[Jean · Rating 5 out of 5]

What I appreciate most about this book is the author's ability to explain complex concepts regarding health issues and testing in a way that helps patients understand the nuance of diagnoses and treatments. This book is engaging and important for those who long for definitive answers in uncertain circumstances. The appendix is especially enlightening.

[Pamela · Rating 4 out of 5]

The information on uncertainty in diagnosis and prognosis in medicine was helpful. Questions about pluses and minuses of screening were effectively explored. Dr. Hatch also discussed misinformation about several disorders and preventive measures such as vaccination. The book was well written and friendly to the reader.

[Jennifer · Rating 5 out of 5]

Very informative.

[fnadoc · Rating 4 out of 5]

Good book but a little wordy with details

[Brenda · Rating 5 out of 5]

Valuable book with interesting information.

[Katrina · Rating 3 out of 5]

Interesting read although I find the constant reference to future chapters and recaps of previous chapters to be a bit much.

[MS · Rating 3 out of 5]

3.5 starzzz

[Molliestudiesmed · Rating 5 out of 5]

A fantastic look into the complexity of scientific data in medicine and the absolute value of diagnostic tests such as mammograms. Definitely worth a read or two, especially if you are/thinking of going into the medical profession.
Can take a little while to worth though, since it is a little dense but very worth it.

[Mayur Bhanarkar · Rating 5 out of 5]

One of the best books I have ever read in the field of medicine. A mandatory book for medical practitioners/ medical students/general public. The book talks about uncertainty in medicine and how even the researchers sometimes have a difference of opinion for their treatment and recommendations. How can a common man be so patient enough to listen to one Doctor always then. The book's title is justified by the story of radiologists about how they are trying to figure out the tumour( snowball) among the breast tissue(Blizzard). It is so difficult that it lead to over diagnosis who did not have breast cancer at all. How a research can go wrong and how each individual should be concerned and question to his physician for whatever suggestion he gets. The book redefines the role of a patient and a doctor where patient should be the masters of their care and doctors should be advisors.

[Leib Mitchell · Rating 5 out of 5]

Book Review
5/5 stars
Snowball in a Blizzard
Steven Hatch, MD
"Epistemic foundations of uncertainty in medicine with examples from current events."

Reviewed in the United States on July 1, 2016

This book is excellent.

And I will start with (what I believe to be) the best quote of the entire book (p. 84): "When health technologies are discussed in terms of righteousness, and aren't simply thought of as tools by which we might or might extend our lives, it becomes difficult to evaluate the technology for what it is. For screening mammograms are not, and never were a moral good: they are X-rays...."

In a way, this book to me reads like something that Nicholas Taleb would discuss (he of the The Black Swan ), but minus the babbling, expatiation and overweening ego.

There is a huge volume of topics covered in a readable way (and this is not an exhaustive list, nor a listing on the meat of each chapter):

1. Cost benefit/ Risk benefit;
2. False positive/ false negative;
3. Bayesian probability/ Uncertainty quantification;
4. Correlation vs. Causation;
5. Loss of information as a result of transmission (the easiest way to lose intact information is to talk about it), a la Thomas Sowell's Knowledge And Decisions ;
6. Types of studies (observational, cohort, double blind placebo controlled);
7. Discussion of the quantification of magnitude of some benefit;
8 Examples of overdiagnosis of cancers (i.e., higher number of diagnoses, but with a constant death rate).

There are even a few $5 words thrown in (armamentarium [p.128]/ frisson [p.129] /soporific [p. 242]) to build your vocabulary while reading this book.

There are even a few cute allusions (eg. "Guide to the Perplexed", p 212), the Brady Bunch (p. 244)

There is a good bibliography and appendix at the end of the book.

The bad (only one point):

The author keeps incessantly saying "more of this later" or "I'll explain this later." (pps 56, 93, 142, 163, 223-- and these are just the instances that I took the time to write down after it was starting to become a problem).

Verdict: Worth the time. Worth the money ($11.99 plus shipping, and this is from a person who does not usually pay more than $0.01 for a book). Strongly recommended to put a dent in the cloying ignorance of the public with respect to how to intelligently discuss medical matters

[Susan Oleksiw · Rating 5 out of 5]

I am one of those people who read the science news and wonder, What does that mean? If you do the same, this book is for you. With little science background and almost no statistics, I managed to read and enjoy and admire this author's effort to explain what our current medical science can and cannot do. I remember the thalidomide controversy, wondering how this drug could spread so widely in Europe and not the US (fortunately), and I was on the edges of the hormone replacement therapy. This book explains how these and other medical circumstances came to be.

The author covers a number of topics to illustrate specific aspects of medical science, in particular our inability to be certain, or to make predictions based on medical tests, and often our inability to recognize when we have veered into doing harm with a treatment. The title comes from a description of what it's like to try to find a tumor in a mammogram. It's like looking for a snowball in a blizzard. Figuring out other test results isn't always easier.

The book covers issues around blood pressure (how low is good enough), Lyme disease (are antibiotics the answer for ongoing illness), and other topical medical issues. Through it all, Hatch examines the studies, controversies, and levels of judgment that are possible.

Even if you come away from this book feeling totally inadequate in your understanding of science through statistics, etc., you will gain a greater confidence in questioning any diagnosis you receive, asking questions, and exploring options. You will also learn how important asking questions can be in helping your own doctor become better in the practice of medicine.

[Karen · Rating 5 out of 5]

Excellent book. Really explains medical findings in a balanced way to help understand where the headlines and guidelines come from. It is still mystifying to me why clinical trials of drugs require so many people to discern benefits because it seems as though the benefits of a drug should be more obvious. I am willing to bet diet and exercise benefits would not require 30000 people and 10 years to get statistical significance.

[Isaac Hazard · Rating 5 out of 5]

Great book! Dr. Hatch illustrates the importance of understanding the level of uncertainty that health care professionals (and patients) face daily. While the content relates specifically to medicine, the lessons can be extrapolated to our approach to the rest of the sciences and even to life in general. In today's world, both professional and lay person alike are bombarded with information. As humans we are predisposed to fit that information into a category of true/untrue. While this mode of thinking has many advantages (speed, simplicity) it also leads to placing too much confidence in some information and not in others which can in turn lead to bad choices.

More and more we live in a society that deifies the role of the expert. When faced with a question outside of our own particular milieu, we place near 100% faith in the recommendations of one or more selected experts without appreciating the level to which that expert is or should be confident in that recommendation. In this book, Dr. Hatch helps us to identify when this type of mistake is likely to happen and provides us with a framework (the 'spectrum of uncertainty') to place this information in a more rational context. Let's hope we listen

[Joanna Elm · Rating 5 out of 5]

As soon as I started reading the chapter from which the title takes its name, I knew I had found a treasure of a book. That chapter deals with the accuracy of mammograms, and how difficult it is to detect cancerous cells when mammograms are used as screening tools on healthy women rather than diagnostic tools used on women who present with some symptoms.
As I say in my full review which I just posted on my website, "http://www.joannaelm.com" "I would like to know where Dr. Steven Hatch hangs out so that I could go there and kiss the ground he walks on."
The full review is intertwined with my personal experience of doctors and others who have attempted for 25 years to convince me to make the mammogram an annual medical ritual. So far I have resisted, and given what I have read in Dr. Hatch's book will continue to resist -- absent any symptoms.
For me, the book was a validation of a decision I made many years ago. For others, maybe younger women who come to it with questions about this recommended annual screening procedure, the book could well be an invaluable eye opener.

[Christina Dudley · Rating 4 out of 5]

Very good, very informative book that will make me rethink any health news I hear and am tempted to pass on. Hatch discusses the elephant in the room when it comes to studies and treatments and media hype--what does the data tell us? Do absolute benefits outweigh downsides? How many people have to be put through the treatment for those benefits to show up?

It made me glad I'd talked my doctor down to biannual mammograms, although reading this made me want to go even lower in frequency. It also made me want to talk to my mom about her high blood pressure medication.

The best medical advice, that can be trusted and which we all ignore? Exercise more, eat less, and don't smoke. Uh huh. Well, I managed not to smoke, but as for the other recommendations...no wonder I'd rather just hear about the latest superfood, even if the data and benefits are minimal!

[Marilyn McEntyre · Rating 5 out of 5]

This readable, thoughtful reflection on uncertainty in medicine is a valuable appeal to both practitioners and patients to recognize, accept, and include in their conversations the fact that medical treatment of all kinds involves uncertainty. The desire to reassure or be reassured often leads to overstatement of chances, probabilities, or promises of effectiveness, and sometimes to dangerous oversimplifications. I appreciate Hatch's determination to honor the complexity of what people in healing professions take on, and of the decisions patients have to make about how to be discerning about the kinds of treatment and advice they seek, what questions to ask, and when to stop. Useful statistics and other kinds of documentation are gracefully folded in to each chapter, and rather than becoming a species of medical jargon, serve helpfully to clarify and illustrate.

[Terry · Rating 5 out of 5]

"A Physician's Notes on Uncertainty ni Medicine" Great book, too much data for some, but you can pick out the chapters of interest. Hatch asks, if the detection rate of some cancer goes up (ie, we find more w/ improved tech, not that the cancer is occurring more freq.), but the death rate stays flat (ie, no improvement on curing/preventing death), then why do the test especially if it has its own costs (false positives, risk of infection, surgical error, etc.)

His own experience is quite telling - his father w/ a DNR and no tubation has a fall at home, EMTs take him to hospital where he's given a new treatment which includes tubation. Hatch the son and a doctor has difficulty w/ the medical mind set as he works to enforce his dad's wishes.

[Nancy · Rating 5 out of 5]

The author discusses information in medicine from the viewpoint of understanding both the degree of uncertainty in a study or diagnosis and the impact of the uncertainty. I found the book heavy going in places but it really helped me understand issues that affect health treatment, from mammograms to blood pressure medications. He often refers to a chart used to evaluate the balance between benefits and harm. He illustrates the differences in studies, including type of study and number of participants. It's a book to make the reader a more discerning consumer of medical care and medical news.

[Traci · Rating 5 out of 5]

This is what people need to understand. It is important to not trust your doctor completely and have enough knowledge of your health deficiencies so you can ask knowledgeable questions and understand that the care plan by your doctor actually makes sense based on the most recent information available. It is not logical to expect any doctor to have the latest information on all health problems. It just isn't possible.