False-negative test results — tests that indicate you are not infected, when you are — seem to be uncomfortably common. Increasingly, and disturbingly, I hear a growing number of anecdotal stories from my fellow doctors of patients testing negative for coronavirus and then testing positive — or people who are almost certainly infected who are testing negative.

Unfortunately, we have very little public data on the false-negative rate for these tests in clinical practice. Research coming out of China indicates that the false-negative rate may be around 30 percent. Some of my colleagues, experts in laboratory medicine, express concerns the false-negative rate in this country could be even higher.

There are many reasons a test would be falsely negative under real-life conditions. Perhaps the sampling is inadequate. A common technique requires the collection of nasal secretions far back in the nose — and then rotating the swab several times. That is not an easy procedure to perform or for patients to tolerate. Other possible causes of false negative results are related to laboratory techniques and the substances used in the tests.

So, where does that leave us? Even with more testing, we are likely to be underestimating the spread of the virus. For now, we should assume that anyone could be carrying the virus. If you have had likely exposures and symptoms suggest Covid-19 infection, you probably have it — even if your test is negative. We should all continue to practice the behaviors — rigorous hand washing, not touching the face, social distancing — that impede its spread. And we need better information about the performance of these tests — including any new tests that are introduced — in the real world.

Even as better tests emerge, we should always put the test result in the context of the other information we have. It’s a lesson that endures throughout medicine: Look at the big picture, not a single piece of data. Triangulate on the truth, using all the sources of information you have, no matter how good a single test. And don’t be shy about questioning a conclusion that doesn’t fully fit the facts.

Harlan Krumholz, M.D., is professor of medicine at Yale and director of the Yale New Haven Hospital Center for Outcomes Research and Evaluation.