Diagnosis

Your doctor may order lab work or imaging scans to help determine what's causing your symptoms.

Laboratory tests

Many infectious diseases have similar signs and symptoms. Samples of body fluids can sometimes reveal evidence of the particular microbe that's causing the illness. This helps the doctor tailor treatment.

• Blood tests. A technician obtains a sample of blood by inserting a needle into a vein, usually in the arm.
• Urine tests. This painless test requires you to urinate into a container. To avoid potential contamination of the sample, you may be instructed to cleanse your genital area with an antiseptic pad and to collect the urine midstream.
• Throat swabs. Samples from the throat, or other moist areas of the body, may be obtained with a sterile swab.
• Stool sample. You may be instructed to collect a stool sample so a lab can check the sample for parasites and other organisms.
• Spinal tap (lumbar puncture). This procedure obtains a sample of the cerebrospinal fluid through a needle carefully inserted between the bones of the lower spine. You'll usually be asked to lie on your side with your knees pulled up toward your chest.

Imaging scans

Imaging procedures — such as X-rays, computerized tomography and magnetic resonance imaging — can help pinpoint diagnoses and rule out other conditions that may be causing symptoms.

Biopsies

During a biopsy, a tiny sample of tissue is taken from an internal organ for testing. For example, a biopsy of lung tissue can be checked for a variety of fungi that can cause a type of pneumonia.