Gram stain

Urethral discharge – Gram stain; Feces – Gram stain; Stool – Gram stain; Joint fluid – Gram stain; Pericardial fluid – Gram stain; Gram stain of urethral discharge; Gram stain of the cervix; Pleural fluid – Gram stain; Sputum – Gram stain; Skin lesion – Gram stain; Gram stain of skin lesion; Gram stain of tissue biopsy

A Gram stain is a test used to identify bacteria. It is one of the most common ways to quickly diagnose bacterial infection in the body.

How the Test is Performed

How the test is performed depends on what tissue or fluid from your body is being tested. The test may be quite simple, or you may need to prepare ahead of time.

• You may need to provide a sputum, urine, or stool sample.
• Your health care provider may use a needle to take fluid from your body to test. This could be from a joint, from the sac around your heart, or from the space around your lungs.
• Your provider may need to take a tissue sample, such as from your cervix or skin.

The sample is sent to a laboratory.

• A small amount is spread in a very thin layer on a glass slide. This is called a smear.
• A series of stains are added to the sample.
• A lab team member examines the stained smear under the microscope, looking for bacteria.
• The color, size, and shape of the cells help identify the specific type of bacteria.

How to Prepare for the Test

Your provider will tell you what to do to prepare for the test. For some types of tests, you will not need to do anything.

How the Test will Feel

How the test will feel depends on the method used to take a sample. You may not feel anything, or you may feel pressure and mild pain, such as during a biopsy. You may be given some form of pain medicine so you have little or no pain.

Why the Test is Performed

You may have this test to diagnose an infection caused by bacteria. It can also identify the type of bacteria causing the infection.

This test can help find the cause of various health problems, including:

• Intestinal infection or illness
• Sexually transmitted diseases (STDs)
• Unexplained swelling or joint pain
• Signs of a heart infection or fluid buildup in the thin sac that surrounds the heart (pericardium)
• Signs of infection of the space around the lungs (pleural space)
• Cough that will not go away, or if you are coughing up material with a foul odor or odd color
• Infected skin sore

A normal result means that no bacteria or only “friendly” bacteria were found. Some types of bacteria normally live in certain areas of the body, such as the intestines. Bacteria normally don’t live in other areas, such as the brain or spinal fluid.

Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Abnormal results may indicate an infection. You will need further tests, such as a culture, to find out more about the infection.

Risks

Your risks depend on the method used to remove tissue or fluid from your body. You may have no risk at all. Other risks are rare, but may include:

• Infection
• Bleeding
• Heart or lung puncture
• Collapsed lung
• Breathing problems
• Scarring

Stool Gram stain

Gram stain of stool; Feces Gram stain

A stool Gram stain is a laboratory test that uses different stains to detect and identify bacteria in a stool sample.

The Gram stain method is sometimes used to quickly diagnose bacterial infections.

How the Test is Performed

You will need to collect a stool sample.

There are many ways to collect the sample.

• You can catch the stool on plastic wrap that is loosely placed over the toilet bowl and held in place by the toilet seat. Then you put the sample in a clean container.
• A test kit is available that supplies a special toilet tissue that you use to collect the sample. After collecting the sample, you put it in a container.
• Do not take stool samples from the water in the toilet bowl. Doing this can cause an inaccurate test result.

Do not mix urine, water, or toilet tissue with the sample.

For children wearing diapers:

• Line the diaper with plastic wrap.
• Position the plastic wrap so that it will prevent urine and stool from mixing. This will provide a better sample.

Your health care provider will give you instructions on when and how to return the sample.

The sample is sent to a laboratory. A small amount is spread in a very thin layer on a glass slide. This is called a smear. A series of special stains are added to the sample. The lab team member looks at the stained smear under the microscope to check for bacteria. The color, size, and shape of the cells help identify the specific bacteria.

How the Test will Feel

A lab smear is painless and does not directly involve the patient.

There is no discomfort when a stool sample is collected at home because it only involves normal bowel functions.

Why the Test is Performed

Your health care provider may order this test to help diagnose an intestinal infection or illness, sometimes involving diarrhea.

Normal Results

A normal result means only normal or “friendly” bacteria were seen on the stained slide. Everyone has friendly bacteria in their intestines.

Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.

What Abnormal Results Mean

An abnormal result means that an intestinal infection may be present. Stool cultures and other tests can also help diagnose the cause of the infection.

Risks

There are no risks.

Stool guaiac test

FOBT; Guaiac smear test; Fecal occult blood test – guaiac smear; Stool occult blood test – guaiac smear

The stool guaiac test looks for hidden (occult) blood in a stool sample. It can find blood even if you cannot see it yourself. It is the most common type of fecal occult blood test (FOBT).

Guaiac is a substance from a plant that is used to coat the FOBT test cards.

How the Test is Performed

Usually, you collect a small sample of stool at home. Sometimes, a doctor may collect a small amount of stool from you during a rectal examination.

If the test is done at home, you use a test kit. Follow the kit instructions exactly. This ensures accurate results. In brief:

• You collect a stool sample from 3 different bowel movements.
• For each bowel movement, you smear a small amount of the stool on a card provided in the kit.
• You mail the card to a laboratory for testing.

DO NOT take stool samples from the toilet bowl water. This can cause errors.

For infants and young children wearing diapers, you can line the diaper with plastic wrap. Place the plastic wrap so that it keeps the stool away from any urine. Mixing of urine and stool can spoil the sample.

How to Prepare for the Test

Some foods can affect test results. Follow instructions about not eating certain foods before the test. These may include:

• Red meat
• Cantaloupe
• Uncooked broccoli
• Turnip
• Radish
• Horseradish

Some medicines may interfere with the test. These include vitamin C, aspirin, and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen. Ask your health care provider if you need to stop taking these before the test. Never stop or change your medicine without first talking to your provider.

How the Test will Feel

The at-home test involves a normal bowel movement. There is no discomfort.

You may have some discomfort if the stool is collected during a rectal exam.

Why the Test is Performed

This test detects blood in the digestive tract. It may be done if:

• You are being screened or tested for colon cancer
• You have abdominal pain, changes in bowel movements, or weight loss
• You have anemia (low blood count)
• You say you have blood in the stool or black, tarry stools

Normal Results

A negative test result means that there is no blood in the stool.

What Abnormal Results Mean

Abnormal results may be due to problems that cause bleeding in the stomach or intestinal tract, including:

• Colon cancer or other gastrointestinal (GI) tumors
• Colon polyps
• Bleeding veins in the esophagus or stomach ( esophageal varices and portal hypertensive gastropathy)
• Inflammation of the esophagus ( esophagitis )
• Inflammation of the stomach ( gastritis ) from GI infections
• Hemorrhoids
• Crohn disease or ulcerative colitis
• Peptic ulcer

Other causes of positive test may include:

• Nosebleed
• Coughing up blood and then swallowing it

If the stool guaiac results come back positive for blood in the stool, your doctor will likely order other tests, usually including a colonoscopy .

The stool guaiac test does not diagnose cancer. Screening tests such as colonoscopy can help detect cancer. The stool guaiac test and other screenings can catch colon cancer early, when it is easier to treat.

Risks

There can be false-positive and false-negative results.

Errors are reduced when you follow instructions during collection and avoid certain foods and medicines.