Enzyme-linked immune sorbent assay (ELISA) is a type of test that is used to detect antibodies or infectious agents in a blood sample.

When it's done:

The test is often performed to see if the person is exposed to viruses or other substances that may cause infection. ELISA is most commonly used to diagnose chronic infections with human immunodeficiency virus (HIV).

This test is done for many reasons:

• In the high-risk group (commercial sex workers, injection drug users and their sexual partners, etc.), to prevent spread of HIV infection
• To screen people with long-standing or recurring infections
• To screen for current or past infections
• Pregnant women, as a preventive measure from passing the HIV virus to the baby
• To screen blood, blood products and organ donors to prevent the spread of HIV infection

When to Avoid:

The ELISA test should NOT be performed in the following conditions:

• If the patient is taking medicines that may interfere with the test
• If the patient is suffering from bleeding disorders
• If the patient had trouble giving blood in the past
• In case of allergic reactions, consult the doctor before the test is performed

The complete blood count (CBC) is the most commonly performed laboratory investigation test to evaluate a person's overall health and also to detect a wide range of disorders such as anaemia, infection or any other blood abnormalities.

When it's done:

A CBC is performed as a routine health examination or if a person shows any signs or symptoms related to abnormalities of blood cells. This test is performed to assess the presence of infection or any other general diseases that may impact the blood count. It is used to monitor the conditions in patients who have been diagnosed with a blood-related disorder and also to determine the effectiveness of the treatment in patients receiving treatment for blood disorders.

When to Avoid:

There is no specific condition when this test should be avoided.

Ultrasound is a type of scanning technique that uses high-frequency sound waves to produce images of structures inside the body. It is also known as sonography or medical sonography.

When it's done :

Ultrasound is recommended depending on the symptoms and for:

• The assessment of a breast lump
• The assessment of the foetus inside the uterus during pregnancy
• The evaluation of the thyroid gland
• The diagnosis of cancer
• The diagnosis of infections
• The diagnosis of a gallbladder disease
• Assessing abnormalities of muscles and tendons

When to Avoid:

There is no specific condition when this scan should be avoided.

Magnetic resonance imaging (MRI) is a diagnostic test that uses magnetic and radio waves to produce images of the structures in the body. It can be used to produce 3D images from different angles.

When it's done :

MRI is performed to diagnose brain and spinal cord abnormalities, breast diseases, heart and blood vessels disorders, bone and joint disorders and internal organs disorders.

MRI can help diagnose various conditions such as:

• Disorders of the eye and internal ear
• Multiple sclerosis
• Stroke
• Tumours
• Spinal cord injuries
• Ballooning of the blood vessels (aneurysms)
• Joint disorders such as arthritis and bone infections
• Breast cancer

When to Avoid:

Consult your doctor if you are pregnant, because the effect of magnetic waves on the baby is not well understood, or if you suffer from any kidney or liver diseases, as they may limit the use of injected contrast agents during the test.

Consult the doctor if you have any metal or electronic devices in your body that may interfere with the test such as:

• Artificial heart valves
• Cardiac pacemaker
• Any implants
• Metallic prosthesis