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Why it can be hard to diagnosis pneumonia

Question: My grandmother was in a hospital intensive care unit where she was being treated for complications from heart failure.  During the first part of her hospital stay, she seemed to be getting worse. One doctor thought she had developed pneumonia and prescribed antibiotics. A few days later, another doctor concluded she didn’t have pneumonia and stopped the antibiotics.  I found this unnerving, and it made me wonder whether the doctors knew what they were doing.  If they can’t diagnose something as common as pneumonia, how are they going to do identify the really hard stuff?

Answer:  I am sorry to hear that this experience has shaken your confidence in your grandmother’s care plan.

I raised your question with several critical-care physicians at Sunnybrook Health Sciences Centre, and they all said it’s often difficult to tell if a patient has pneumonia.

“Most families think it’s just a lung infection and shouldn’t be hard to diagnose,” say Dr. Dominique Piquette. But the evidence isn’t always clear-cut, she adds.

For instance, even an X-ray of the lungs may not be of much help because many patients come into the ICU with pre-existing lung problems.  “The X-ray at baseline is not always normal,” explains Dr. Piquette, “so we are trying to decide if there is a change in the chest X-ray – and it becomes a rather subjective call.”

Blood tests can be of limited value, too.  “We look at the white blood cell count (a part of the immune system response) which is sometimes a marker for infection, but sometimes it’s not –for complex reasons.”

The job of diagnosing pneumonia is made more difficult by the fact that ICU patients often have multiple health problems. Any one symptom may be caused by a variety of underlying conditions.

The doctors must often rely on indirect evidence and a range of symptoms such as fever, cough and secretions. “We look at many things. But not one of those things, by itself, allows us to make the diagnosis of lung infection,” says Dr. Piquette.

Furthermore, certain life-supporting therapies used in the ICU can inadvertently increase the chances of a patient developing pneumonia, says Dr. Shelly Dev, another Sunnybrook critical-care physician.

Patients who must rely on ventilators – in which tubes are inserted into the airways to help them breathe – are especially vulnerable.

“The risk of getting a hospital-acquired infection is high because you’re connected to this machine,” says Dr. Dev. “You can’t clear all the germs from your body as easily as when you are up and walking around,” she adds.  “And the longer you are on a ventilator, the greater the risk that you are going to develop an infection.”

Doctors are constantly weighing the possibility that an ICU patient could develop pneumonia. “If someone has a fever and the oxygen requirements are going up on the ventilator, you think, ‘Ah! Maybe it’s pneumonia’,” says Dr. Dev.

Although the doctors may be uncertain of the diagnosis, it’s often prudent to begin a course of antibiotics. “You want to treat it like it is pneumonia, because you don’t want to miss a real case,” said Dr. Andre Amaral, another Sunnybrook critical-care physician.

A delay in the start of treatment could allow the bacteria to get the upper hand.  “The infection can make some patients extremely sick and lead to a further deterioration in their condition.”

So if the physicians think it is pneumonia, there is a tendency for them to treat it aggressively.

After a few days of continued observation, it may become apparent that the patient didn’t have pneumonia after all and the antibiotic treatment is then withdrawn.

That’s probably what happened in your grandmother’s situation.

“Many of the diagnoses we make in the ICU are tentative,” says Dr. Amaral, and are refined as more evidence becomes available. In a lot of these cases, he notes, it makes sense to treat now and re-assess later.



About the author


Paul Taylor

Paul Taylor, Sunnybrook's Patient Navigation Advisor, provides advice and answers questions from patients and their families, relying heavily on medical and health experts. Follow me on Twitter @epaultaylor