Urinalysis

Specimen

Morning urine put in clean container

Reference Range

Absence

What is being tested?

A urinalysis is a group of physical, chemical, and microscopic tests. The tests detect and/or measure several substances in the urine, such as byproducts of normal and abnormal metabolism, cells, cellular fragments, and bacteria.

Urine is produced by the kidneys, two fist-sized organs located on either side of the spine at the bottom of the ribcage. The kidneys filter wastes out of the blood, help regulate the amount of water in the body, and conserve proteins, electrolytes, and other compounds that the body can reuse. Anything that is not needed is eliminated in the urine, traveling from the kidneys through ureters to the bladder and then through the urethra and out of the body. Urine is generally yellow and relatively clear, but each time a person urinates, the color, quantity, concentration, and content of the urine will be slightly different because of varying constituents.

Many disorders may be detected in their early stages by identifying substances that are not normally present in the urine and/or by measuring abnormal levels of certain substances. Some examples include glucose, protein, bilirubin, red blood cells, white blood cells, crystals, and bacteria. They may be present because:
There is an elevated level of the substance in the blood and the body responds by trying to eliminate the excess in the urine.
Kidney disease is present.
There is a urinary tract infection present, as in the case of bacteria and white blood cells.

A complete urinalysis consists of three distinct testing phases:
Visual examination, which evaluates the urine's color and clarity
Chemical examination, which tests chemically for about 9 substances that provide valuable information about health and disease and determines the concentration of the urine
Microscopic examination, which identifies and counts the type of cells, casts, crystals, and other components such as bacteria and mucus that can be present in urine

See below for details on each of these examinations.

A microscopic examination is typically performed when there is an abnormal finding on the visual or chemical examination, or if a healthcare practitioner specifically orders it.

Abnormal findings on a urinalysis may prompt repeat testing to see if the results are still abnormal and/or may be followed by additional urine and blood tests to help establish a diagnosis.

How is the sample collected for testing?

One to two ounces of urine is collected in a clean container. A sufficient sample is required for accurate results.

Urine for a urinalysis can be collected at any time. In some cases, a first morning sample may be requested because it is more concentrated and more likely to detect abnormalities.

Sometimes, you may be asked to collect a "clean-catch" urine sample. For this, it is important to clean the genital area before collecting the urine. Bacteria and cells from the surrounding skin can contaminate the sample and interfere with the interpretation of test results. With women, menstrual blood and vaginal secretions can also be a source of contamination. Women should spread the labia of the vagina and clean from front to back; men should wipe the tip of the penis. Start to urinate, let some urine fall into the toilet, then collect one to two ounces of urine in the container provided, then void the rest into the toilet.

A urine sample will only be useful for a urinalysis if taken to the healthcare provider's office or laboratory for processing within a short period of time. If it will be longer than an hour between collection and transport time, then the urine should be refrigerated or a preservative may be added.

Source: Online Lab Test

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Acid-Fast Bacillus (AFB) Testing

Specimen

Sputum put in clean container

Reference Range

Absence

What is being tested?

Most samples that are submitted for acid-fast bacilli (AFB) testing are collected because the health practitioner suspects that a person has tuberculosis (TB), a lung infection caused by Mycobacterium tuberculosis. Mycobacteria are called acid-fast bacilli because they are a group of rod-shaped bacteria (bacilli) that can be seen under the microscope following a staining procedure where the bacteria retain the color of the stain after an acid wash (acid-fast). AFB laboratory tests detect the bacteria in a person's sample and help identify an infection caused by AFB.

There are a several types of AFB that may be detected with this testing; however, the most common and medically important ones are members of the genus Mycobacterium. Mycobacterium tuberculosis is one of the most prevalent and infectious species of mycobacteria.

Since TB is transmitted through the air when an infected person sneezes, coughs, speaks, or sings, it is a public health risk. It can spread in confined populations, such as in the home and schools, correctional facilities, and nursing homes. Those who are very young, elderly, or have preexisting diseases and conditions, such as AIDS, that compromise their immune systems tend to be especially vulnerable. AFB testing can help track and minimize the spread of TB in these populations and help determine the effectiveness of treatment.

Another group of mycobacteria referred to as nontuberculous mycobacteria (NTM) can also cause infections. However, only a few of the more than 60 species of mycobacteria that have been identified cause infections in humans. Some examples include Mycobacterium avium-intracellulare complex (MAC), which can cause a lung infection in people with weakened immune systems, and Mycobacterium marinum, which can cause skin infections. (See the article on Nontuberculous Mycobacteria for more details on different types). In addition to TB, AFB testing can help identify infections caused by these nontuberculous mycobacteria.

AFB laboratory tests include:

1. AFB smear — a microscopic examination of a person's specimen that is stained to detect acid-fast bacteria. This test can provide presumptive results within a few hours. It is a valuable tool in helping to make decisions about treatment while culture results are pending.
2. Molecular tests for TB (nucleic acid amplification test, NAAT) — detect the genetic components of mycobacteria and are often done when the AFB smear is positive or TB is highly suspected. Like AFB smears, they can provide a presumptive diagnosis, which can aid in the decision of whether to begin treatment before culture results are available. Results of NAAT are typically available several hours after a sample is collected.
3. AFB cultures to grow the bacteria are set up at the same time as the AFB smears. Though more sensitive than AFB smears, results of cultures may take days to several weeks.

Susceptibility testing on the acid-fast bacteria grown in the cultures that are positive will determine the organism's susceptibility or resistance to drugs most commonly used to treat the infection.

How is the sample collected for testing?

Since M. tuberculosis and M. avium most frequently infect the lungs (pulmonary disease), sputum is the most commonly tested sample. Sputum is phlegm, thick mucus that is coughed up from the lungs. Usually, three early morning samples are collected on consecutive days in individual sterile cups to increase the likelihood of detecting the bacteria.

If a person is unable to produce sputum, a health practitioner may collect respiratory samples using a procedure called a bronchoscopy. Bronchoscopy allows the health practitioner to look at and collect samples from the bronchi and bronchioles. Once a local anesthetic has been sprayed onto the patient's upper airway, the practitioner can insert a tube into the bronchi and smaller bronchioles and aspirate fluid samples for testing. Sometimes, the health practitioner will introduce a small amount of saline through the tubing and into the bronchi and then aspirate it to collect a bronchial washing.

Since young children cannot produce a sputum sample, gastric washings/aspirates may be collected. This involves introducing saline into the stomach through a tube, followed by fluid aspiration.

If the health practitioner suspects TB is present outside of the lungs (extrapulmonary), a condition fairly common in AIDS patients, he or she may test the body fluids and tissues most likely affected. For instance, one or more urine samples may be collected if the practitioner suspects TB has infected the kidneys. A needle may used to collect fluid from joints or from other body cavities, such as the pericardium or abdomen. Occasionally, the practitioner may collect a sample of cerebrospinal fluid (CSF) or perform a minor surgical procedure to obtain a tissue biopsy.

Source: Online Lab Test

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HIV Antibody and HIV Antigen (p24)

Specimen

Serum 1ml

Reference Range

Negative

What is being tested?

Human immunodeficiency virus (HIV) is the cause of AIDS (acquired immunodeficiency syndrome). HIV screening tests detect the HIV antigen(p24) and/or HIV antibodies produced in response to an HIV infection in the blood. Some tests detect HIV antibody in oral fluid.

When a person becomes infected with HIV, through exposure to the blood or body fluids of an infected individual or a contaminated needle, for example, the virus begins to replicate itself, producing a large number of copies. During the first few weeks of infection, the amount of virus (viral load) and the p24 antigen level in the blood can be quite high.

About 2-8 weeks after exposure to the virus, the immune system responds by producing antibodies directed against the virus that can be detected in the blood. As the initial infection resolves and the level of HIV antibody increases, both virus and p24 antigen levels decrease in the blood.

An HIV infection may initially cause no symptoms or cause flu-like symptoms that resolve after a week or two. The only way to determine whether a person has been infected is through HIV testing.

If HIV is not detected early and treated, it may become a simmering infection that may cause few symptoms for a decade or more. If the infection is still not treated, eventually symptoms of AIDS emerge and begin to progressively worsen. Over time and without treatment, HIV destroys the immune system and leaves a person's body vulnerable to debilitating infections. (You can read more about this in the article on HIV Infection and AIDS.)

Detecting and diagnosing HIV early in the course of infection is important because:
It allows for early treatment that slows progression to AIDS.
An individual can learn of their status and modify behavior so as to prevent the spread of disease.
A pregnant woman can undergo treatment that would help prevent passing the disease to her child.

There are two types of HIV, 1 and 2. HIV-1 is the most common type found in the United States, while HIV-2 has a higher prevalence in parts of Africa.

A few different testing options are available for HIV screening:
Combination HIV antibody and HIV antigen test—the recommended screening test for HIV; it is available only as a blood test.
HIV antibody testing—all HIV antibody tests used in the U.S. detect HIV-1 and some tests have been developed that can also detect HIV-2. These tests are available as blood tests or tests of oral fluid.
p24 antigen testing—this is used alone without the antibody test only in rare cases when there is a question about interference with an HIV antibody test.

Regardless of the type of screening test used, a positive result requires follow up with supplemental testing to establish a diagnosis of HIV.

Source: Online Lab Test

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Albumin

Specimen

Serum 1ml

Reference Range

The normal range is 3.5 to 5.5 g/dL or 35-55 g/liter. This range may vary slightly in different laboratories.

What is being tested?

Albumin is a protein made by the liver. It makes up about 60% of the total protein in the blood and plays many roles. This test measures the level of albumin in the blood.

Albumin keeps fluid from leaking out of blood vessels; nourishes tissues; and transports hormones, vitamins, drugs, and substances like calcium throughout the body. Levels of albumin may decrease, to a greater or lesser degree, when conditions interfere with its production by the liver, increase protein breakdown, increase protein loss via the kidneys, and/or expand plasma volume (diluting the blood).

Two important causes of low blood albumin include:

1. Severe liver disease—since albumin is produced by the liver, its level can decrease with loss of liver function; however, this typically occurs only when the liver has been severely affected.
2. Kidney disease—one of the many functions of the kidneys is to conserve plasma proteins such as albumin so that they are not released along with waste products when urine is produced. Albumin is present in high concentrations in the blood, and when the kidneys are functioning properly, virtually no albumin is lost in the urine. However, if a person's kidneys become damaged or diseased, they begin to lose their ability to conserve albumin and other proteins. This is frequently seen in chronic diseases, such as diabetes and hypertension. In nephrotic syndrome, very high amounts of albumin are lost through the kidneys.

Source: Online Lab Test

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Partial Thromboplastin Time (PTT, aPTT)

Specimen

3.8% Sodium Cirtrate Plasma 3ml

Reference Range

Partial thromboplastin time (PTT) and activated partial thromboplastin time (aPTT) are used to test for the same functions; however, in aPTT, an activator is added that speeds up the clotting time and results in a narrower reference range. The aPTT is considered a more sensitive version of the PTT and is used to monitor the patient’s response to heparin therapy.

The reference range of the aPTT is 30-40 seconds.

What is being tested?

The partial thromboplastin time (PTT) is a screening test that helps evaluate a person's ability to appropriately form blood clots. It measures the number of seconds it takes for a clot to form in a person's sample of blood after substances (reagents) are added. The PTT assesses the amount and the function of certain proteins called coagulation factors that are an important part of blood clot formation.

When body tissue(s) or blood vessel walls are injured, bleeding occurs and a process called hemostasis begins. Small cell fragments called platelets adhere to and then clump (aggregate) at the injury site. At the same time, a process called the coagulation cascade begins and coagulation factors are activated. Through the cascading reactions, threads called fibrin form and crosslink into a net that adheres to the injury site and stabilizes it. Along with the platelets adhering, this forms a stable blood clot to seal off injuries to blood vessels, prevents additional blood loss, and gives the damaged areas time to heal.

Each component of this hemostatic process must function properly and be present in sufficient quantity for normal blood clot formation. If there is a deficiency in one or more of these factors, or if the factors function abnormally, then a stable clot may not form and bleeding continues.

With a PTT, a person's sample is compared to a normal reference interval for clotting time. When a person's PTT takes longer than normal to clot, the PTT is considered "prolonged." A prolonged PTT may be due to a condition that decreases or creates a dysfunction in one or more coagulation factors. Less often, it may be due to a condition in which the body produces certain antibodies directed against one or more coagulation factors, affecting their function.

Sometimes a PTT may be prolonged because the person tested produces an autoantibody called an antiphospholipid antibody that interferes with the test. This type of antibody affects the results of the test because it targets substances called phospholipids that are used in the PTT. Though antiphospholipid antibodies can prolong the PTT test result, in the body they are associated with excessive clotting. A person who produces these antibodies may be at an increased risk for a blood clot. A PTT maybe used as part of an evaluation of a person with signs and symptoms of excessive clotting or antiphospholipid syndrome. (See the article on Antiphospholipid Antibodies for additional details.)

When a PTT is used to investigate bleeding or clotting episodes, it is often ordered along with a prothrombin time (PT). A health practitioner will evaluate the results of both tests to help determine the cause of bleeding or clotting episode(s).

It is now understood that coagulation tests such as the PT and PTT are based on what happens artificially in the test setting (in vitro) and thus do not necessarily reflect what actually happens in the body (in vivo). Nevertheless, they can be used to evaluate certain components of the hemostasis system. The PTT and PT tests each evaluate coagulation factors that are part of different groups of chemical reaction pathways in the cascade, called the intrinsic, extrinsic, and common pathways. (For more on this, see the article on the Coagulation Cascade.)

Source: Online Lab Test

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ABO Blood Group and Rhesus

Specimen

EDTA Blood 2ml

Reference Range

The following table indicates the type of antibodies a person is expected to have based on their blood type.

What is being tested?

Blood types are based on the markers (specific carbohydrates or proteins) or antigens on the surface of red blood cells (RBCs). Two major antigens or surface identifiers on human RBCs are the A and B antigens. Another important surface antigen is called Rh. Blood typing detects the presence or absence of these antigens to determine a person's ABO blood group and Rh type.
People whose red blood cells have A antigens are in blood group A, those with B antigens are group B, those with both A and B antigens are in group AB, and those who do not have either of these markers are in blood group O.

If the Rh protein is present on the red blood cells, a person's blood type is Rh+ (positive); if it is absent, the person's blood is type Rh- (negative).
Our bodies naturally produce antibodies against the A and B antigens that we do not have on our red blood cells. For example, a person who is blood type A will have anti-B antibodies directed against the B antigens on red blood cells and someone who is type B will have anti-A antibodies directed against the A antigens. People with type AB blood have neither of these antibodies, while those with type O blood have both.

These antibodies are useful for determining a person's blood type and help determine the types of blood that he or she can safely receive (compatibility). If a person who is group A with antibodies directed against the B antigen, for example, were to be transfused with blood that is type B, his or her own antibodies would target and destroy the transfused red blood cells, causing severe, potentially fatal complications. Thus, it is critical to match a person's blood type with the blood that is to be transfused.

Unlike antibodies to A and B antigens, antibodies to Rh are not produced naturally. That is, Rh antibodies develop only after a person who does not have Rh factor on his or her red blood cells (Rh negative) is exposed to Rh positive red blood cells. This can happen during pregnancy or birth when an Rh-negative woman is pregnant with an Rh-positive baby, or sometimes when an Rh-negative person is transfused with Rh-positive blood. In either case, the first exposure to the Rh antigen may not result in a strong response against the Rh positive cells, but subsequent exposures may cause severe reactions.

Source: Online lab test

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