What Are The Most Common Diagnostic Tests Used By Doctors In Medicine?

This scenario will be familiar to most of you — you go to see your doctor with certain symptoms, hoping for a quick answer and an even faster cure, only to find that your family doctor wants to conduct a series of diagnostic tests before getting you started with any treatment.

Have you ever wondered what the importance of these tests is? Well, diagnostic tests are tests which aid a physician in the detection or diagnosis of a disease, or to confirm a diagnosis the doctor has already made in their head. The clinician may have a hunch that you are suffering from a particular disease on the basis of the presenting symptoms.

An early diagnosis is imperative for starting early treatment. And the sooner the treatment is started, the better are the chances of curing the disease. At other times, a diagnostic test is done to confirm that you are free from a certain disease.

Diagnostic tests come in three distinct three types:

• Non-invasive diagnostic tests: A sample is collected without performing any invasive procedure. Examples of non-invasive diagnostic tests are taking a throat swab for a culture, collecting urine for urinalysis, etc.

• Minimally invasive diagnostic tests: Examples of such a procedure are fine needle aspiration cytology, endoscopic biopsy, etc.

• Invasive diagnostic tests: Examples are excising of a lymph node or a tumor and then sending it for pathological examination.

It is believed that when a patient understands the nature of the diagnostic test he or she was advised to undergo and is fully aware of its importance, it has a psychological value. Normal test results can be reassuring for the patient. However, care should be taken not to advise unnecessary tests and to interpret the results of the tests carefully.

Some of the commonly advised diagnostic tests in the medical field are as follows.

Chest X-Ray

Chest X-rays are one of the oldest diagnostic tests used to diagnose a variety of lung and heart pathologies. They can give a clue about the presence of a foreign body in the airway, fractured ribs, pneumonia, pleural effusion, cardiomegaly and many other medical conditions. They are ordered based on your symptoms and serve to confirm or rule out certain diagnoses.

For taking a chest x-ray, a technician puts a radiographic plate against your chest and then takes pictures from your front or back and from the sides while you are asked to take a deep breath. Care is taken to expose you to minimum amount of ionizing radiation, which do not cause any harm. However, pregnant women should avoid this diagnostic test in order to avoid any harm to the growing fetus.

Dense structures like bones appear white on an x-ray film as they absorb they x-ray beams. As the x-ray beams do not reach the photographic plate, these parts appear white. However, hollow body parts like lungs allow the beams to pass through them and appear dark on the final image.

Most common diagnostic tests in medical practice

Urine analysis

Analysis of a patient's urine sample is done quite often to examine its physical properties like color, pH and density, as well as its microscopic examination to test for the presence of any pus or blood cells and infection causing bacteria in a lab. While almost nobody likes to offer a urine sample, the upside of this diagnostic test is clear. It offers a lot of information and is entirely painless.

There are times when the urine is examined to test for the presence of certain hormones and chemicals. In cases where bacteria are detected during routine urinalysis, the urine sample is cultured in order to identify the bacteria. Once, the micro-organism is identified, antibiotics are prescribed accordingly.

For urinalysis, the patient is asked to collect his or her urine sample in a sterile cup. A mid-stream sample is preferred as there is a lower chance of the sample being contaminated by bacteria present on the skin surface in this case.

Sugar in the urine can be a sign of diabetes, while ketones in the urine are usually a result of starvation or a complication of diabetes. The presence of blood in a patient's urine may signify the presence of stones in the urinary tract or a urinary tract infection. Similarly, pus cells in a person's urine also result from infection. Human Chorionic gonadotropin (HCG) in the urine may alert a physician about a pregnancy, while steroids in urine may suggest abuse in case of athletes.

Abdominal ultrasound

An ultrasound uses sound waves to click pictures of structures inside the human body. A jelly is applied on the skin of your abdomen to reduce friction. Then, an ultrasound transducer which generates ultrasound waves is placed on the abdominal wall. These waves are reflected from the different structures present in the abdominal cavity in the form of echoes which are captured by the transducer and transformed into images. These images can be visualized on a monitor.

The patient is usually asked to fast before the test. This is because the normal digestion of food produces gases which may interfere with the sound waves.

An ultrasound of the abdomen is usually performed to detect the presence of gallstones, any fluid in the abdominal cavity and the development of a fetus. It may also reveal pathologies like liver cirrhosis or necrosis, and cancers.

Pap smear

A Pap smear, named after Dr. George Papanicolaou, is a diagnostic test that is employed at regular intervals to collect and examine the cells found in the cervix and the vagina. This test can pick up any abnormal cells which may be a result of cervical cancer, one of the most common cancers seen in women.

Cervical cancer is often caused by infection with certain strains of the human papillomavirus (HPV). According to the National Cancer Institute (NCI), the American Cancer Society (ACS), and the American College of Obstetrics (ACOG), all women above the age of 21, irrespective of whether they are sexually active or not, should undergo a Pap smear at least once every three years. This process should continue till the woman is above 65 years of age, is sexually inactive and the last three Pap smear results are negative.

The test is done when the woman is not menstruating. She should avoid sexual intercourse, douches, tampons, vaginal creams for 24 hours before the test. While lab analysis takes a while, the test itself is quick and minimally invasive. It will be over before you know it, and Pap smears are nearly always conducted by female medical staff.

Prostate Specific Antigen (PSA) Test

The levels of “prostate specific antigen” produced by the prostate gland in men and present in the blood are measured with the help of this test. It is used to detect the presence of prostate cancers. Elevated PSA levels may alert the physician towards the possibility of the cancer, even when it is in its early stage and the patient would have little to no symptoms.

The patients are asked to avoid sexual intercourse 24 hours before the test. They should also stop taking any prostate specific medicines which may interfere with the result. To conduct this test, a blood sample is withdrawn and PSA levels are measured in the lab.

Lately, there have been many controversies around this test. Some physicians believe that it leads to unnecessary treatment of a cancer which would in all probability have remained confined to the prostate gland. However, other physicians believe that it is an important diagnostic test which can help in treating prostate cancer at an early stage, thus saving the life of the patient.

Lumbar puncture

Lumbar puncture is a procedure wherein a needle is inserted in the sub-arachnoid space in the lumbar region and spinal fluid is withdrawn. The test has both diagnostic and therapeutic value. The spinal fluid tapped by this procedure can be studied to detect various conditions like meningitis, encephalitis, bleeding in the sub-arachnoid space, myelitis, neuro-syphilis, GB syndrome, cancers of the brain and spinal cord and several demyelinating conditions like multiple sclerosis. These diseases are diagnosed after analyzing the color, clarity and pressure of the cerebrospinal fluid and the presence of sugar, red and white blood cells, proteins and micro-organisms in the fluid.

A lumbar puncture can be used as a therapeutic procedure to relieve increased fluid pressure. It is also used to give patients spinal anesthesia, to inject contrast dye for procedures like myelography, and for injecting chemotherapy drugs.

The patient may complain of a minor headache following the procedure and is advised to lie down for several hours following the procedure to avoid the headache.