Why do I have persistent fever?

Q: I am a 38 years old man having fever for the last month. It comes at night, with a temperature of 99-100 degree F. The doctor suspected some infection in the body and confirmed it through blood test. Thereafter, he carried out x-ray and CT-scan and found that there is some infiltration in the left lower lobe of the lungs so he started the treatment for tuberculosis (TB). However, I do not have the symptoms of TB, like cough (dry/wet), no pain, etc. except some mild fever. There is no weight loss either. Please advise.

A:Fever of unknown origin (FUO-as the name implies) is a condition where arriving at a specific diagnosis might be quite difficult.

There may be infectious as well as non-infectious causes of FUO. In the Indian context tuberculosis (TB) is an important cause of FUO.

In many cases of TB specific microbiological diagnosis either by a microscopic examination of a clinical sample (e.g. sputum) or bacteriological culture might not be positive. This is due to a variety of reasons such as inadequacy of the clinical sample, low sensitivity of the available diagnostic method, or inability to get a representative sample because of the specific area of the body involved.

Many experienced physician including chest physicians specializing in TB arrive at provisional diagnosis of TB based on a process of exclusion of other possible causes, which might have a similar clinical presentation.

Any clinical diagnosis is reached based on a combination of various factors, namely, history including past medical history, epidemiological context, symptoms, signs, laboratory findings, imaging findings (from X-ray or CT scan, etc), and response or lack of response to previous medications. It is common that all the classical signs and symptoms of a disease might not be present in a given case, and an experienced physician is able to reach a diagnosis based on his/her knowledge, experience and analytical abilities. This is what physicians are trained to do.

However well intentioned and rational the advice of lay relatives might be, it can never be a substitute for clinical judgement which is based on years of training, hard work and extensive knowledge of the anatomy, physiology and pathology of the disease.

If you have concerns about the diagnosis and its management it is always preferable to speak the physician first, who might be able to explain to you the rationale behind his/her clinical decision. If you still have doubts then you may seek the opinion of a second consultant or specialist (in your case a chest or a respiratory physician). And do not forget to tell the second specialist if need arises the whole history including previous prescriptions from any other doctor, lab test and X-ray/CT scan results, current or past medications. This will help to prevent duplication, save time and money and help the second physician to take an informed decision.