One of the most commonly done blood tests, the CBC test is basically the calculation of the cellular elements of blood. The test evaluates the three main types of blood cells, the red blood cells, white blood cells, and the platelets. A blood sample collected from the patient is sent to the laboratory for a detailed analysis. 

Electrocardiogram (ECG or EKG) is a non-invasive test which can diagnose adverse effects on the heart by blood clots to the lung. Electrocardiogram is done to reflect the underlying heart conditions by measuring the electrical activities of the heart. Leads are positioned in standardized locations of your body and information about heart conditions can be obtained by looking up patterns on the EKG.

MRI produces detailed anatomic images of your body’s internal organs by using radio waves and a powerful magnetic field. As there is no exposure to radiation at all, MRI is most suitable for pregnant women and for people whose kidneys may have been affected by contrast dyes used in CT scan and in pulmonary angiogram.

Ultrasonography is a non-invasive test which uses high frequency sound waves to look for blood clots. The test makes use of a wand-like device called the transducer to direct sound waves to the veins being tested. The waves are reflected back to the device and are translated into a moving image on a computer monitor. 

D-dimer is a clot-dissolving substance found in blood and it being present in higher levels might indicate an increased likelihood of blood clots. However, elevated levels of D-dimer in blood might be due to other factors such as a recent surgery. 

Pulmonary angiogram employs the use of a small, flexible tube called catheter which is inserted into the large vein, threaded through the right atrium and ventricle and then advanced into the pulmonary arteries. With the help of the the catheter, a certain dye is injected. Next, X-rays are taken while the dye travels through the arteries and into the lungs. Pulmonary angiogram can also be performed to ascertain the pressure in the right side of the heart. Abnormal readings usually indicate blood clots. You should keep in mind that pulmonary angiogram involves potentially serious risks and it requires a highly skilled personnel to execute the test. The test is usually done when no other diagnostic tests can provide a suitable result. 

Spiral or helical CT scan can diagnose blood clots faster and with a greater precision than the regular CT scans. For a suspected case of blood clots, a contrast material is injected intravenously followed by an immediate spiral CT scan. A conventional CT scan forms 2D images of the internal anatomy by combining X-ray images taken from different angles. In a spiral CT scan, the scanner is made to rotate around your body in a spiral manner to create 3D images. 

Lung scan, also called a ventilation-perfusion (V/Q) scan is done to study the airflow (ventilation) and the blood flow (perfusion) in the lungs. The test uses small amounts of radioactive substances. You’ll be required to inhale a small amount of a certain radioactive substance while a specialized camera designed to detect radioactive materials will record the air movement inside your lungs. Again a certain amount of radioactive substance is injected into a vein in your arm. Images taken after the injection reveals whether you have a normal or a diminished blood flow to your lungs. However, in the case of smokers, lung test is not a reliable diagnostic test for blood clots. 

Chest X-ray is a non invasive test which can be used to obtain images of the heart and lungs. Although a chest X-ray cannot effectively diagnose blood clots, this test is mostly used for ruling out the possibility of their occurrence.