Contamination Information and Courses from MediaLab, Inc.

Examples of sources of pigment other than oxyhemoglobin and bilirubin that can cause xanthochromia include: methemoglobinincreased CSF protein (> 150 mg/dL)contamination by skin antiseptic (iodine or merthiolate)

The reagent strips must be handled and stored properly in order to ensure that results are accurate. The following precautions should be observed: Store strips according to the manufacturer's recommendation. DO NOT expose strips to moisture, direct sunlight or volatile fumes. Remove only enough strips for immediate use and immediately recap the bottle. Avoid contamination of test strips. Do not touch the test areas with fingers or do not lay the test strips directly on the workbench. DO NOT use discolored strips. Compare the color of the unused strip to the negative area on the color chart provided by the company. The color should be similar. Check the expiration date. Re-label the container with a revised expiration date if the manufacturer states a shortened usage period once the container has been opened. Reagent strips must be tested periodically (frequency defined by the laboratory) for clinical reactivity with normal and abnormal urine controls. Urine controls are available commercially or may be prepared and preserved in-house.

A false positive result for blood on the reagent strip can occur when oxidizing contaminants, such as hypochlorite (bleach), remain in collection bottles after cleaning. Contamination of the urine with provodine-iodine, a strong oxidizing agent, used in surgical procedures can result in a false positive reaction. Microbial peroxide found in association with urinary tract infections may also cause false-positive results. Capoten® (Captopril) can cause decreased reactivity. The muscle tissue form of hemoglobin, myoglobin is a well-known cause of false-positive reactions on the blood portion of the reagent strip. When tissue hemoglobin is present, the urine specimen has a clear red appearance. Patients suffering from muscle-wasting disorders or muscular destruction due to trauma, prolonged coma, or convulsions or individuals engaging in extensive exertion may have myoglobin in their urine. Specific tests for myoglobin, such as immunodiffusion techniques or protein electrophoresis, are needed to confirm the presence of this substance in a urine specimen. Levels of ascorbic acid normally found in urine do not interfere with this test.

Some global specimen collection and handling issues to consider include: Specimens that contain nucleated cells will be of interest in DNA methodologies while specimens lacking nucleated cells are more useful in RNA methodologies. rRNA is more stable than mRNA, which is labile and sensitive to contamination. DNA is relatively stable and can be obtained from nonviable sources. Serum or plasma obtained by standard routine venipuncture procedures can be used as long as proper site selection and decontamination occur. Standard anticoagulants such as Ethylenediaminetetraacetic Acid (EDTA) and Acid Citrate Dextrose (ACD) can be used; however avoid the use of heparin as an anticoagulant as it interferes with some polymerase chain reaction (PCR) methodologies. When using fluorescence, fasting serum or whole blood specimens should be used to decrease the interference by lipids.

Stay inside or get inside quickly. Find a “Shelter-in-place”. To “shelter in” is a way to make the building you are in safe as possible to protect yourself until help arrives. You should not try to “shelter in” in a vehicle unless you have no other choice. The best room to use is one with as few windows and doors as possible. Be sure to close all windows and doors, and turn off the furnace, air conditioners, and exhaust systems. As best as possible, seal all openings in windows and doors. Monitor your radio for instructions from authorities. If you believe you’ve been exposed and you can’t get to a hospital, shed all your clothes as quickly as possible. Don’t take the clothes inside because you may spread contamination. Go straight to the shower and thoroughly wash all body parts with a coarse soap. It is important not to ingest radiation by eating contaminated food or even chewing on contaminated fingernails. Also, certain types of radioactivity can be flushed from the body by drinking large amounts of water. After an attack don’t travel through heavily contaminated areas. If you can get out of the general area through an uncontaminated route, do so—otherwise, stay indoors until assistance arrives.               

Small blood spills on work surfaces may be cleaned by first laying paper towels on the spill to blot and avoid splattering, and then applying disinfectant.Larger spills will require other methods.Use an approved cleaning method.Use appropriate personal protective equipment.Be aware of the potential for splatter and contamination.

This phlebotomist violated hospital procedures in several ways that could adversely impact patient care: Cleaning the site only with alcohol, not iodine, could result in a false-positive contaminated blood culture. This might result in the patient receiving unnecessary intravenous antibiotics, and could prolong the patients hospital stay unnecessarily. Drawing both cultures at the same time lessens the chance of recovering a bloodstream organism.Drawing both cultures from the same site might result in both of them being contaminated, making it very difficult for the physician to distinguish contamination from a “real” bloodstream infection.Relevant topics:Blood cultures: introduction, Avoid skin contamination, Blood culture site preparation 1, Blood culture site preparation 2

Contaminated blood cultures may have very serious consequences in terms of patient care.Always draw blood cultures prior to drawing other blood tubes to minimize the risk of contamination. Do not draw blood cultures from a central line, unless cultures are being drawn to determine whether or not the line is contaminated.

If you need to feel for a vein again, you must first prep your gloved finger tip with iodine to prevent contamination.

To ensure the safety of those performing patient testing, controls do not contain HIV or the hepatitis B virus. Manufacturers place the same batch of control material into small vials. This allows only a small portion of the control to be handled while the remainder is stored until needed. Storage information for controls is printed on the label. These instructions should be followed carefully in order to prevent contamination or false results.

Contamination of the staining solutions rarely occurs, but should be suspected when smears repeatedly contain the same organisms, and these organisms do not grow or are inconsistent with the clinical picture. Yeast and gram negative rods can occur as stain contaminants.

Red blood cells (RBCs) may also be found in the urine sediment. The presence of RBCs in the sediment is associated with damage to the glomerular membrane or vascular injury within the genitourinary tract (the possibility of menstrual contamination must be considered).

Avoid transport of an active TB patient if possible. If transport is necessary the active TB patient must wear a surgical mask when leaving the room and transport staff should consider using a respirator.An active TB patient must bypass the common waiting area.Schedule an active TB patient for the last of day procedure to maximize time for airborne contamination removal.