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How Cancer is Diagnosed

There are many different ways cancer can be diagnosed or detected. Below is a list of the different categories of test/exams -- click on a category to read a little about it, then you can click on the types of tests below that to read details.

Diagnostic Imaging

Imaging is the process of producing valuable pictures of body structures and organs. It is used to detect tumors and other abnormalities, to determine the extent of disease, and to evaluate the effectiveness of treatment. Imaging may also be used when performing biopsies and other surgical procedures. There are three types of imaging used for diagnosing cancer: transmission imaging, reflection imaging, and emission imaging. Each uses a different process.

Transmission Imaging

Transmission Imaging

X-rays, computed tomography scans (CT scans), and fluoroscopy are radiological examinations whose images are produced by transmission. In transmission imaging, a beam of high-energy photons is produced and passed through the body structure being examined. The beam passes very quickly through less dense types of tissue such as watery secretions, blood, and fat, leaving a darkened area on the x-ray film. Muscle and connective tissues (ligaments, tendons, and cartilage) appear gray. Bones will appear white.

X-ray

X-Rays

X-rays are the most common type of imaging. The images produced by X-rays are due to the different absorption rates of radiation from tissues. Calcium in bones absorbs X-rays the most, so bones look white on an X-ray film, also known as a radiograph. Muscle and other soft tissues absorb less radiation, and have more gray tones on the radiograph. Air absorbs the least, so lungs look black on a radiograph. The most familiar use of X-rays is checking for broken bones, but X-rays can also be used to check for cancer. For instance, chest radiographs are sometimes used to see if cancer has spread to the lungs or other areas in the chest.

Source: National Cancer Institute

Computed Tomography Scan (CT or CAT scan)

Computed Tomography Scan (CT or CAT scan)

A computed tomography scan (also called a CT scan or a CAT scan) also uses X-rays to create images of the body. However a radiograph and a CT scan show different types of information. Although an experienced radiologist can get a sense for the approximate three-dimensional location of a tumor from a radiograph, in general, a plain radiograph is two-dimensional.

An arm or chest radiograph looks all the way through a body without being able to tell how deep anything is. A CT scan is three-dimensional. By imaging and looking at several three-dimensional slices of a body (like slices of bread) a doctor could not only tell if a tumor is present, but how deep it is in the body.

A CT scan can be three dimensional because the information about how much of the X-rays are passing through a body is collected not just on a flat piece of film, but on a computer. The data from a CT scan can then be computer-enhanced to be more sensitive than a plain radiograph. With both plain radiographs and CT scans the patient can be given a contrast agent in a drink and/or by injection to more clearly show the boundaries between organs or between organs and tumors.

Source: National Cancer Institute

4D CT Scanning

4D CT Scanning

CTRC has the ability to perform 4D CT scans along with the standard CT scans. Typically, CT scans show patient anatomy at a point of time. The scan will show the physician where the internal tissues and organs were at the time the scan was performed, but they do not show how the organs move inside the patient when the patient breathes. For organs that tend to move, this is very important information the physicians did not have access to until 4D scans. A 4D CT scan is a CT scan that is taken over a longer time period, and it allows the physician to see exactly how the organs and tissues move inside the patient while the patient breathes. This is critical when a radiation oncologist is deciding how to treat a patient, and it allows the radiation oncologist the ability to track the tumor while the patient breathes to make sure that the tumor is receiving the correct amount of radiation even if it moves.

Source: National Cancer Institute

Bone Scan

Bone Scan

Bone scans are pictures or x-rays taken of the bone after a radioactive material has been injected that is absorbed by bone tissue. These scans are used to detect tumors and bone abnormalities.

Lymphangiogram (LAG)

Lymphangiogram (LAG)

Lymphangiogram is an imaging study that can detect cancer cells or abnormalities in the lymphatic system and structures. It involves a dye being injected into the lymph system

Mammogram

Mammogram

A mammogram is an x-ray examination of the breast. It is used to detect and diagnose breast disease in women who either have breast problems such as a lump, pain, or nipple discharge, as well as for women who have no breast complaints. Mammography cannot prove that an abnormal area is cancerous, but if it raises a significant suspicion of cancer, a biopsy may be performed. Tissue may be removed by needle or open surgical biopsy and examined under a microscope to determine if it is cancer. Mammography has been used for about 30 years, and in the past 15 years technical advancements have greatly improved both the technique and results. Today, dedicated equipment, used only for breast x-rays, produces studies that are high in quality but low in radiation dose. Radiation risks are considered to be negligible.

Digital Mammography

Digital Mammography

Digital mammography is a new method of diagnosing breast cancer that allows the images to be improved digitally as opposed to conventional mammography. Conventional mammography uses x-rays to look for tumors or suspicious areas in the breasts. Digital mammography also uses x-rays, but the data is collected by a computer instead of on a piece of film. This means that the image can be computer-enhanced, or areas can be magnified. Eventually, a computer could, in certain situations, screen digital mammograms, theoretically detecting suspicious areas that humans might miss.

Source: National Cancer Institute

Reflection Imaging (Ultrasound)

Reflection Imaging (Ultrasound)

Ultrasound uses sound waves that are at a higher frequency than sound that is heard by the human ear. A transducer gives off the sound waves. The sound waves are then reflected back to the transducer by organs and tissues in the body. The reflected sound waves are then used to draw a picture on a computer screen showing what is inside the body. Ultrasound can be used to look for certain types of tumors, and can also be used to guide doctors during biopsies or treating tumors with radiation therapy.

Source: National Cancer Institute

Emission Imaging

Emission Imaging

Emission imaging occurs when tiny nuclear particles or magnetic energy are detected by a scanner and analyzed by computer to produce an image of the body structure or organ being examined. Nuclear medicine uses emission of nuclear particles from nuclear substances introduced into the body specifically for the examination.

Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) uses radio frequency waves in the presence of a strong magnetic field produced by an MRI machine to cause cells to emit a radio frequency. Different tissues (including tumors) emit different signal intensities based on their chemical structure. Using these signals, a picture of what is inside the body can be created and shown on a computer screen. Much like CT scans, MRI can produce three-dimensional images of sections of the body, but MRI is sometimes more sensitive than CT scans. MRI is also an established technique for imaging many other organs and tissues including the heart, the brain, bone marrow, cartilage, and the abdomen.

Source: National Cancer Institute

Positron Emission Tomography (PET)

Positron Emission Tomography (PET)

PET is a specialized radiology procedure used to examine various body tissues to identify certain conditions. PET may also be used to follow the progress of the treatment of certain conditions. PET is a type of nuclear medicine procedure. This means that a tiny amount of a radioactive substance, called a radionuclide (radiopharmaceutical or radioactive tracer), is used during the procedure to assist in the examination of the tissue under study. Specifically, PET studies evaluate the metabolism of a particular organ or tissue, so that information about the physiology (functionality) and anatomy (structure) of the organ or tissue is evaluated, as well as its biochemical properties. Thus, PET may detect biochemical changes in an organ or tissue that can identify the onset of a disease process before anatomical changes related to the disease can be seen with other imaging processes such as computed tomography (CT) or magnetic resonance imaging (MRI).

Source: National Cancer Institute

Laboratory Tests

Clinical chemistry uses chemical processes to measure levels of chemical components in body fluids and tissues. The most common specimens used in clinical chemistry are blood and urine. Many different tests exist to detect and measure almost any type of chemical component in blood or urine. Components may include blood glucose, electrolytes, enzymes, hormones, lipids (fats), other metabolic substances, and proteins. The following are some of the more common laboratory tests:

Blood Tests

Blood Tests

A variety of blood tests are used to check the levels of substances in the blood that indicate how healthy the body is and whether infection is present. For example, blood tests revealing elevated levels of waste products, such as creatinine or blood urea nitrogen (BUN), indicate that the kidneys are not working efficiently to filter those substances out. Other tests check the presence of electrolytes - chemical compounds such as sodium and potassium that are critical to the body's healthy functioning. Coagulation studies determine how quickly the blood clots.

A complete blood count (CBC) measures the size, number, and maturity of the different blood cells in a specific volume of blood. This is one of the most common tests performed. Red blood cells are important for carrying oxygen and fighting anemia and fatigue; the hemoglobin portion of the CBC measures the oxygen carrying capacity of the red blood cells while the hematocrit measures the percentage of red blood cells in the blood. White blood cells fight infection. Increased numbers of white blood cells, therefore, may indicate the presence of an infection. Platelets prevent the body from bleeding and bruising easily.

Urine Tests

Urine Tests

Urinalysis breaks down the components of urine to check for the presence of drugs, blood, protein, and other substances. Blood in the urine (hematuria) may be the result of a benign (noncancerous) condition, but it can also indicate an infection or other problem. High levels of protein in the urine (proteinuria) may indicate a kidney or cardiovascular problem.

Tumor Markers

Tumor Markers

Tumor markers are substances either released by cancer cells into the blood or urine or substances created by the body in response to cancer cells. Tumor markers are used to evaluate how well a patient has responded to treatment and to check for tumor recurrence. Research is currently being conducted on the role of tumor markers in detection, diagnosis, and treatment of cancers.


According to the National Cancer Institute (NCI), tumor markers are useful in identifying potential problems, but they must be used with other tests for the following reasons:

  • People with benign conditions may also have elevated levels of these substances in their blood.
  • Not every person with a tumor has tumor markers.
  • Some tumor markers are not specific to any one type of tumor.

The following is a brief description of some of the more useful tumor markers:

  • Prostate-Specific Antigen (PSA)
    Prostate-specific antigen is always present in low concentrations in the blood of adult males. An elevated PSA level in the blood may indicate prostate cancer, but other conditions such as benign prostatic hyperplasia (BPH) and prostatitis can also raise PSA levels. PSA levels are used to evaluate how a patient has responded to treatment and to check for tumor recurrence.
  • Prostatic Acid Phosphatase (PAP)
    PAP originates in the prostate and is normally present in small amounts in the blood. In addition to prostate cancer, elevated levels of PAP may indicate testicular cancer, leukemia, and non-Hodgkin's lymphoma, as well as some noncancerous conditions.
  • CA 125
    Ovarian cancer is the most common cause of elevated CA 125, but cancers of the uterus, cervix, pancreas, liver, colon, breast, lung, and digestive tract can also raise CA 125 levels. Several noncancerous conditions can also elevate CA 125. CA 125 is mainly used to monitor the treatment of ovarian cancer.
  • Carcinoembryonic Antigen (CEA)
    CEA is normally found in small amounts in the blood. Colorectal cancer is the most common cancer that raises this tumor marker. Several other cancers can also raise levels of carcinoembryonic antigen.
  • Alpha-Fetoprotein (AFP)
    Alpha-fetoprotein is normally elevated in pregnant women since it is produced by the fetus. However, AFP is not usually found in the blood of adults. In men, and in women who are not pregnant, an elevated level of AFP may indicate liver cancer or cancer of the ovary or testicle. Noncancerous conditions may also cause elevated AFP levels.
  • Human Chorionic Gonadotropin (HCG)
    HCG is another substance that appears normally in pregnancy and is produced by the placenta. If pregnancy is ruled out, HCG may indicate cancer in the testis, ovary, liver, stomach, pancreas, and lung. Marijuana use can also raise HCG levels.
  • CA 19-9
    This marker is associated with cancers in the colon, stomach, and bile duct. Elevated levels of CA 19-9 may indicate advanced cancer in the pancreas, but it is also associated with noncancerous conditions, including gallstones, pancreatitis, cirrhosis of the liver, and cholecystitis.
  • CA 15-3
    This marker is most useful in evaluating the effect of treatment for women with advanced breast cancer. Elevated levels of CA 15-3 are also associated with cancers of the ovary, lung, and prostate, as well as noncancerous conditions such as benign breast or ovarian disease, endometriosis, pelvic inflammatory disease, and hepatitis. Pregnancy and lactation also can raise CA 15-3 levels.
  • CA 27-29
    This marker, like CA 15-3, is used to follow the course of treatment in women with advanced breast cancer. Cancers of the colon, stomach, kidney, lung, ovary, pancreas, uterus, and liver may also raise CA 27-29 levels. Noncancerous conditions associated with this substance are first trimester pregnancy, endometriosis, ovarian cysts, benign breast disease, kidney disease, and liver disease.
  • Lactate Dehydrogenase (LDH)
    LDH is a protein that normally appears throughout the body in small amounts. Many cancers can raise LDH levels, so it is not useful in identifying a specific kind of cancer. Measuring LDH levels can be helpful in monitoring treatment for cancer. Noncancerous conditions that can raise LDH levels include heart failure, hypothyroidism, anemia, and lung or liver disease.
  • Neuron-Specific Enolase (NSE)
    NSE is associated with several cancers, but it is used most often to monitor treatment in patients with neuroblastoma or small cell lung cancer.

Tumor Biopsy

What are the different types of tumor biopsies?
A biopsy is a procedure performed to remove tissue or cells from the body for examination under a microscope. Some biopsies can be performed in a physician's office, while others need to be done in a hospital setting. In addition, some biopsies require use of an anesthetic to numb the area, while others do not require any sedation.

Biopsies are usually performed to determine whether a tumor is malignant (cancerous) or to determine the cause of an unexplained infection or inflammation. The following are the most common types of biopsies:

Sentinel Node Mapping

Sentinel Node Mapping

When patients are being diagnosed with breast cancer it has been standard practice to surgically remove all of the lymph nodes under the arm to determine if the cancer has spread beyond the breast and what treatment is appropriate. Removing all the lymph nodes can result in long-term complications and discomfort for the patient from lymphedema (a condition where excess lymph fluid collects in tissues and causes swelling). Trials are underway now, however, to test an alternative, less damaging procedure in which imaging plays an important role.

In this alternative procedure, called sentinel node mapping, only the sentinel node (the first lymph node to which breast cancer is likely to spread) is removed rather than all the lymph nodes. In order to identify the sentinel node, the doctors inject either a blue dye or a relatively non-toxic radioactive substance and see which lymph node it reaches first. This lymph node is the sentinel node, and is surgically removed.

Endoscopic Biopsy

Endoscopic Biopsy

This type of biopsy is performed through a fiberoptic endoscope (a long, thin tube that has a close-focusing telescope on the end for viewing) through a natural body orifice (i.e., rectum) or a small incision (i.e., arthroscopy). The endoscope is used to view the organ in question for abnormal or suspicious areas, in order to obtain a small amount of tissue for study. Endoscopic procedures are named for the organ or body area to be visualized and/or treated. The physician can insert the endoscope into the gastrointestinal tract (alimentary tract endoscopy), bladder (cystoscopy), abdominal cavity (laparoscopy), joint cavity (arthroscopy), mid-portion of the chest (mediastinoscopy), or trachea and bronchial system (laryngoscopy and bronchoscopy).

Bone Marrow Biopsy

Bone Marrow Biopsy

Bone Marrow Biopsy

This type of biopsy is performed either from the sternum (breastbone) or the iliac crest hipbone (the bone area on either side of the pelvis on the lower back area). The skin is cleansed and a local anesthetic is given to numb the area. A long, rigid needle is inserted into the marrow, and cells are aspirated for study; this step is occasionally uncomfortable. A core biopsy (removing a small bone 'chip' from the marrow) may follow the aspiration.

Excisional or Incisional Biopsy

Excisional or Incisional Biopsy

This type of biopsy is often used when a wider or deeper portion of the skin is needed. Using a scalpel (surgical knife), a full thickness of skin is removed for further examination, and the wound is sutured (sewed shut with surgical thread). When the entire tumor is removed, it is called excisional biopsy technique. If only a portion of the tumor is removed, it is called incisional biopsy technique. Excisional biopsy is often the method usually preferred when melanoma (a type of skin cancer) is suspected.

Fine Needle Aspiration (FNA) Biopsy

Fine Needle Aspiration (FNA) Biopsy

This type of biopsy involves using a thin needle to remove very small pieces from a tumor. Local anesthetic is sometimes used to numb the area, but the test rarely causes much discomfort and leaves no scar. FNA is not used for diagnosis of a suspicious mole, but may be used to biopsy large lymph nodes near a melanoma to see if the melanoma has metastasized (spread). A computed tomography scan (CT or CAT scan) - an x-ray procedure that produces cross-sectional images of the body - may be used to guide a needle into a tumor in an internal organ such as the lung or liver.

Punch Biopsy

Punch Biopsy

Anatomy of the skin
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Punch biopsies involve taking a deeper sample of skin with a biopsy instrument that removes a short cylinder, or "apple core," of tissue. After a local anesthetic is administered, the instrument is rotated on the surface of the skin until it cuts through all the layers, including the dermis, epidermis, and the most superficial parts of the subcutis (fat).

Shave Biopsy

Shave Biopsy

This type of biopsy involves removing the top layers of skin by shaving it off. Shave biopsies are also performed with a local anesthetic.

Skin Biopsy

Skin Biopsy

Skin biopsies involve removing a sample of skin for examination under the microscope to determine if melanoma is present. The biopsy is performed under local anesthesia. The patient usually just feels a small needle stick and a little burning for about a minute, with a little pressure, but no pain.

Endoscopic Examination

What are the different types of endoscopic examinations?
An endoscope is a small, flexible tube with a light and a lens on the end used to look into the esophagus, stomach, duodenum, colon, or rectum. It can also be used to take tissue from the body for testing or to take color photographs of the inside of the body. Cystoscopes, colonoscopes, and sigmoidoscopes are types of endoscopes and are described below:

Colonoscopy

Colonoscopy

Illustration demonstrating a colonoscopy
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Colonoscopy is a procedure that allows the physician to view the entire length of the large intestine, and can often help identify abnormal growths, inflamed tissue, ulcers, and bleeding. It involves inserting a colonoscope, a long, flexible, lighted tube, in through the rectum up into the colon. The colonoscope allows the physician to see the lining of the colon, remove tissue for further examination, and possibly treat some problems that are discovered.

Virtual colonoscopy

Conventional colonoscopy uses a colonoscope—a thin, lighted tube used to view the inside of the colon— to screen for polyps or tumors in the colon, part of the gastrointestinal tract. A possible alternative now in clinical trials is the virtual colonoscopy, where a spiral CT scan is taken of the gastrointestinal area, then a computer puts together an image of the person's colon for examination by a radiologist.

Virtual colonoscopy sounds like a far more appealing option than conventional colonoscopy, however a person undergoing the virtual technique still must take laxatives and endure the insertion of a probe to push air into the colon. Additionally, clinical trials so far have not yet proven whether virtual colonoscopy is as good at finding tumors as the conventional technique, or if the extra expense and analysis time associated with virtual colonoscopy is justified. It is possible that virtual colonoscopy will be beneficial for some groups of people in appropriate situations.

Endoscopic Retrograde Cholangiopancreatography (ERCP)

Endoscopic Retrograde Cholangiopancreatography (ERCP)

ERCP is a procedure that allows the physician to diagnose and treat problems in the liver, gallbladder, bile ducts, and pancreas. The procedure combines x-ray and the use of an endoscope - a long, flexible, lighted tube. The scope is guided through the person's mouth and throat, then through the esophagus, stomach, and duodenum. The physician can examine the inside of these organs and detect any abnormalities. A tube is then passed through the scope and a dye is injected, which will allow the internal organs to appear on an x-ray.

Esophagogastroduodenoscopy

Esophagogastroduodenoscopy (Also called EGD or upper endoscopy.)

Illustration of an esophagogastroduodenoscopy procedure
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An EGD (upper endoscopy) is a procedure that allows the physician to examine the inside of the esophagus, stomach, and duodenum. A thin, flexible, lighted tube, called an endoscope, is guided into the mouth and throat, then into the esophagus, stomach, and duodenum. The endoscope allows the physician to view the inside of this area of the body, as well as to insert instruments through a scope for the removal of a sample of tissue for biopsy (if necessary).

Sigmoidoscopy

Sigmoidoscopy

A sigmoidoscopy is a diagnostic procedure that allows the physician to examine the inside of a portion of the large intestine, and is helpful in identifying the causes of diarrhea, abdominal pain, constipation, abnormal growths, and bleeding. A short, flexible, lighted tube, called a sigmoidoscope, is inserted into the intestine through the rectum. The scope blows air into the intestine to inflate it and make viewing the inside easier.

Cystoscopy

Cystoscopy (Also called cystourethroscopy.)

An examination in which a scope, a flexible tube and viewing device, is inserted through the urethra to examine the bladder and urinary tract for structural abnormalities or obstructions, such as tumors or stones. Samples of the bladder tissue may be removed through the cystoscope for examination under a microscope in the laboratory.

Genetic Testing

Genetic illustration demonstrating disease families
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The following are the main types of genetic testing, Tests for cancer susceptibility genes are usually done by DNA studies.

Chromosome Studies

Chromosome Studies

Chromosomes are the long stretches of DNA that contain our genes. "Cytogenetics" is a word used to describe the study of chromosomes. The chromosomes need to be stained in order to see them with a microscope. When stained, the chromosomes look like strings with light and dark "bands." A picture (an actual photograph from one cell) of all 46 chromosomes, in their pairs, is called a "karyotype." A normal female karyotype is written 46, XX, and a normal male karyotype is written 46, XY. The standard analysis of the chromosomal material evaluates both the number and structure of the chromosomes, with an accuracy of over 99.9 percent. Chromosome analyses are usually performed using a blood sample (white blood cells), prenatal specimen, skin biopsy, or other tissue sample. Chromosomes are analyzed by specially trained healthcare personnel that have advanced degrees in cytogenetic technology and genetics. Chromosome studies may be performed when a child is born with multiple birth defects. Chromosome studies may also be performed when people have certain types of leukemias and lymphomas, to look for specific chromosome rearrangements (changes in the order of the chromosome material) associated with these types of cancers.

DNA Studies

DNA Studies

A gene is a short stretch of DNA on a chromosome. The stretch of DNA is a code, or recipe, for making a specific protein the body needs to function properly. To study genes, you have to analyze the DNA to determine whether the DNA "alphabet" has any "spelling errors" in it. There are two ways to analyze the DNA: by direct studies (looking at the actual gene itself), or by indirect studies (looking at areas of DNA, called markers, that are very close to the gene).

Direct DNA studies

Direct DNA studies

Direct DNA studies simply look directly at the gene in question for an error. Errors in the DNA may include a replication of the gene's DNA (duplication), a loss of a piece of the gene's DNA (deletion), an alteration in a single unit (called a base pair) of the gene's DNA (point mutation), or the repeated replication of a small sequence (for instance, 3 base pairs) of the gene's DNA (trinucleotide repeat). Different types of errors or "mutations" are found in different disorders. It is usually very important to find the mutation that is present in a family, by studying the family member with the disorder in question (in this case, cancer), before testing relatives without the cancer. When a particular mutation is found in a relative with cancer, other family members can choose to have testing for the mutation to determine if they have an increased risk to develop certain cancers and to pass the mutation on to the next generation. The DNA needed for direct DNA studies is usually obtained by taking a blood sample.

Indirect DNA studies

Indirect DNA studies

Sometimes, the gene that (when mutated) causes a condition has not yet been identified, but researchers know approximately where it lies on a particular chromosome. Or other times, the gene is identified, but direct gene studies are not possible because the gene is too large to analyze. In these cases, indirect DNA studies may be done. Indirect DNA studies involve using "markers" to find out whether a person has inherited the crucial region of the genetic code that is passing through the family with the disease. Markers are DNA sequences located close to or even within the gene of interest. Because the markers are so close, they are almost always inherited together with the disease. When markers are this close to a gene, they are said to be "linked." If someone in a family has the same set of linked markers as the relative with the disease, this person often also has the disease-causing gene mutation. Because indirect DNA studies involve using linked markers, these types of studies are also called "linkage studies." Indirect studies usually involve blood samples from several family members, including those with and without the disorder in question. This is to establish what pattern of markers appear to be associated with the disease. Once the disease-associated pattern of markers is identified, it is possible to offer testing to relatives to determine who inherited this pattern, and as such, is at increased risk of cancer.

The accuracy of linkage studies depends on how close the markers are to the faulty gene. In some cases, a reliable marker is not available and the test, therefore, cannot give any useful information to the healthy family members. In many cases, several family members are needed to establish the most accurate set of markers to determine who is at risk for the disease in the family. Linkage studies may take many weeks to complete because of the complexity of these studies.

Biochemical Genetic Studies

Biochemical Genetic Studies

Biochemical genetic testing involves the study of enzymes in the body that may be abnormal in some way. Enzymes are proteins that regulate chemical reactions in the body. The enzymes may be deficient or absent, unstable, or have altered activity that can lead to clinical manifestations in an adult or child (i.e., birth defects). There are hundreds of enzyme defects that can be studied in humans. Sometimes, rather than studying the gene mutation which is causing the enzyme to be defective in the first place, it is easier to study the enzyme itself (the gene product). The approach depends on the disorder. Biochemical genetic studies may be done from a blood sample, urine sample, spinal fluid, or other tissue sample, depending on the disorder.

Protein Truncation Studies

Protein Truncation Studies

Another way to look at gene products, rather than the gene itself, is through protein truncation studies. Testing involves looking at the protein a gene makes to see if it is shorter than normal. Sometimes a mutation in a gene causes it to make a protein that is truncated (shortened). With the protein truncation test, it is possible to "measure" the length of the protein the gene is making to see if it is the right size or shortened. Protein truncation studies can be performed on a blood sample. These types of studies are often performed for disorders in which the known mutations predominantly lead to shortened proteins.