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DEAR DR. ROACH: I was recently admitted to the hospital with pneumonia in both lungs. Given the recent outbreak of Legionella where I live, I was concerned whether I might have had this instead. They did do some tests in the hospital to try to find out. -- R.C.

ANSWER: I looked at the labs that you sent me, and several of them are consistent with Legionella. You had a very high C-reactive protein level, a relatively low procalcitonin level, pneumonia in both lungs, low blood sodium, and a relatively low heart rate. All of these suggest Legionella rather than pneumococcal pneumonia (the most common type). However, your doctors did two urine tests for Legionella, and they were both negative.

The urine test for Legionella isn't perfect. It detects 70% to 80% of only one of the several serogroups of Legionella (serogroup 1 -- the most common type and the one that's implicated in the current outbreak in New York). It doesn't detect the other serogroups at all.

Physicians often need to reconcile conflicting clinical information, and sometimes there are formal mathematical models to help. In your case, you meet at least three of the four criteria for Legionella. In one study, people with three or more criteria points had a 98% to 100% likelihood of having Legionella. Busy clinicians who are taking care of sick patients usually don't have the time to read research papers and calculate point scores to help determine the likelihood of a Legionella infection versus pneumococcal pneumonia.

However, clinicians need to know that they shouldn't exclusively rely on one test result against the results of many other tests. When there is uncertainty, clinicians should choose a treatment that will be effective against both possibilities. Many patients have a hard time understanding that our lab tests aren't perfect.

Now that you're out of the hospital and (presumably) mostly recovered, it still may be prudent to complete a course of an effective treatment for Legionella, such as azithromycin. I advise consultation with an expert in pulmonology or infectious diseases.

DEAR DR. ROACH: Last week, I had some blood work done. Some tests for my liver didn't come back well. My thinking is that it's because I no longer have a gallbladder. My alkaline phosphatase level was 151 U/L. (Normal in my lab is up to 104 U/L.) My AST level was 31 U/L (normal being up to 35 U/L), and my total bilirubin level was 1.5 mg/dL (normal being up to 1.2 mg/dL). Is my thinking correct? -- T.

ANSWER: Immediately after surgery, liver enzymes such as alkaline phosphatase and AST (aspartate aminotransferase) transiently increase. However, when a person is 10 or more years out from surgery, there's still an increased risk of an elevated alkaline phosphatase level (but not AST or bilirubin).

Your alkaline phosphatase level is mildly elevated, and your AST is normal. Your bilirubin level, however, is also mildly elevated. I can't tell you definitively whether this is worrisome, but I don't think that the gallbladder surgery explains everything. Some people have a benign condition called Gilbert's syndrome with elevated bilirubin levels of no clinical significance.

What's important is why these tests were obtained. It's not recommended to get them just for screening. If your doctor ordered them because they were worried about a medical issue, then the next step might be an ultrasound to look for a liver problem that blocks bile flow, such as a retained gallstone or primary biliary cholangitis.

If there was no particular reason for you to get these tests, then my suspicion of there being something wrong is small. There are simple reasons as to why the lab tests might be abnormal. (A fatty meal right before testing is one, but your normal levels simply being higher than others is another.)

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.

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