Part 1

Sample processing

Sample processing

Involving centrifugation and aliquoting.

Centrifuge

Spins blood tubes at a high relative centrifugal force to separate serum or plasma from the blood cells.

Plasma

Is obtained by centrifugation of anticoagulated blood, and serum is similarly obtained from clotted blood.

2

• To prevent contamination of plasma and serum by cellular constituents, it is recommended that samples be separated within _____ hrs?

• Required specimen conditions such as chilling, protection from light, and keeping the specimen warm must continue to be maintained throughout processing and until the specimen is tested.

hemolysis

Tests that are seriously affected by__________ include potassium, plasma-free hemoglobin, troponin I and T, AST, and LDH.

microclots

Tests negatively affected by _________ include CBCs and related tests such as hemoglobin and hematocrit, platelet counts, and red and white blood cell counts.

separate

Nonadditive, clot activator, and gel-containing tubes used for serum tests must clot for the serum to ___________ from the cells. They must not be centrifuged until clotting is complete.

30 - 60

Complete clotting normally takes ___________ minutes at room temperature (22° to 25°C).

Complete clotting

• ________________can be determined by tilting or inverting the tube gently to see if a solid clot has formed

• According to CLSI, the practice of rimming the tube with an applicator stick to release the clot from the walls of the tube or the stopper before centrifuging the tube, is a potential source of hemolysis and contamination, and is not recommended..

centrifuged

By 2 hours after blood collection significant changes in some analytes, such as decreased glucose, increased potassium, and increased lactate dehydrogenase, are seen in blood that has not been ____________.

cause hemolysis

Loosening clots from the side of the tube (rimming) before centrifugation is not recommended because it may ______ ______.

Blood Tubes

must remain closed before, during, and after centrifugation to avoid contamination with dust or glove powder, accidental spills, formation of aerosols, and evaporation of the specimen.

Blood Samples

should be stored in an upright position while clotting.

gravity, radius

The relative centrifugal force (RCF) of a centrifuge is expressed as ________ and is determined by the _________ of the rotor head and the speed of rotation (revolutions per minute [rpm]).

850-1000, 10

Most laboratory samples are centrifuged at____________ g for ____ minutes

rotor

The part of the centrifuge that holds the tubes and spins is called the __________.

once

Specimens should not be centrifuged more than?

Relative Centrifugal Force

• Force acting on sample being centrifuged. Function of rpm and radius.

• RCF =

Revolutions per minute

Speed of centrifugation, determined by tachometer.

Radius

Distance in cm from center of rotation to bottom of tube when rotating.

Horizontal – Head Centrifuge

• Tubes are in horizontal position when rotating and vertical in rest.

• Recommended for serum separator tubes.

• Produces a tightly packed, flat, sediment surface.

Angle – Head Centrifuge

• Tubes are at fixed angle (25°- 40°) when rotating. Capable of higher speeds

• Produces a slanted sediment surface that is not tightly packed.

• Used when rapid centrifugation of solutions containing small particles is needed; an example is the microhematocrit centrifuge

Ultra-Centrifuge

• High speed, capable of 100, 000rpm

• Used to separate lipoproteins

• Refrigerated to reduce heat from friction

Sample Aliquoting

• Separation of serum and plasma from the cellular elements.

• Require careful attention to detail so that specimens are placed in properly labeled tubes.

aliquot

is a is a portion of the sample that is placed in a separate tube.

Disposable pipettes

should be used to transfer the specimen from one tube to another

8, 2 8

• Based on the tests requested, separated serum or plasma may remain at room temperature for ______ hours.

• If testing has not been completed in 8 hours, the specimen should be refrigerated (__°C to __°C).

Pre-examination Consideration

• Samples collected for electrolytes must not be stored at 2ºC to 8°C before centrifugation and testing.

• Specimens can only be thawed once. Repeated freezing and thawing of the specimen can destroy substances for testing.

Samples for local transport

• should be placed in securely closed, leak-proof primary containers (tubes and screw-top containers).

• The primary containers are enclosed in a secondary leak-proof container with sufficient absorbent material present to separate the samples and absorb the contents of the primary containers in case of leakage or breakage.

• Containers should be labeled as biohazardous.

• Samples can be kept cool by transporting them in Styrofoam containers using plastic refrigerant packs.

Pneumatic Tube System

• This type of delivery system consists of a network of long tubes that connect special sending and receiving stations in certain laboratory areas (e.g., specimen processing) to stations located in various areas of the hospital, usually near a nurse’s station.

• The system works by propelling special canister-like carriers through the system tubes using compressed air or partial vacuum.

Body temperature

36.4° to 37.6°C (37°C average)

Room temperature

20° to 30°C (25°C average)

Refrigerated temperature

2° to 10°C

Frozen temperature

−20°C or lower

25

Although most specimens can be transported at room temperature, which for most labs is around _____°C (77°F), some specimens will precipitate or agglutinate if allowed to cool below body temperature.

Body Temperature Specimens

• These specimens need to be transported at or near the normal body temperature of 37°C.

• Temperature-sensitive specimens that can withstand slightly higher than 37°C can be wrapped in an activated heel warmer. Follow facility protocol.

Chilling

___________the specimen slows down blood cell metabolism. It also protects thermolabile (i.e., altered or destroyed by heat) analytes.

ice, water

Blood specimens that require chilling should be completely immersed in a slurry of crushed _____ and _____ or put in a special cooling rack and either tested immediately or refrigerated upon arrival in the laboratory

Specimens that must not be chilled

• Some specimens are negatively affected by chilling during transportation. For example, most coagulation specimens must not be chilled before processing because it can activate clotting factors and disrupt platelet function.

• Potassium specimens should not be chilled because cold inhibits glycolysis, which is what provides the energy to pump potassium into the cells

• Arterial blood gas (ABG) samples often also include testing for potassium. Although at one-time ABG samples required chilling, current recommendations are that ABG samples should not be placed on ice if analyzed within 30 minutes of collection. If a potassium test is ordered with other analytes that require chilling, it should be collected in a separate tube.

Light-Sensitive Specimens

• Some analytes are photosensitive (sensitive to light) and are broken down by light, resulting in falsely decreased values. The most common example is bilirubin, which can decrease by up to 50% after one hour of light exposure.

• An easy way to protect the blood in a collection tube from light is to wrap it in aluminum foil. Amber tubes, biohazard bags, or light-blocking transport containers can also be used.

UA physical examination

• involves macroscopic (i.e., visual) observation and notation of clarity (e.g., transparent, cloudy), color, odor, and measurements of volume and specific gravity (SG) or osmolality. SG and osmolality indicate urine concentration.

• The physical analysis can also help explain or confirm chemical and microscopic results.

• The SG reference range is 1.005 to 1.030.

• Urine is normally transparent.

• Causes of cloudy or turbid urine include bacteria or yeast, blood, precipitated crystals, and mucus.

refractometer

SG can be determined separately as part of the physical examination using an instrument called a?

urochrome

Urine gets its color from a pigment called _________ and normally ranges between light yellow (often referred to as “straw-colored”) and dark amber.

Darker Urine

• is generally more concentrated, as in the morning after not having anything to drink during the night. Urine that is dark during the day may indicate dehydration. Abnormal colors include bright yellow, brown, black, gray, red, and green.

• The color of urine can change when certain foods are eaten, for example, in some people, recent ingestion of beet root can result in red urine which could visually be mistaken for hemoglobin.

• Asparagus can impart a greenish color, and carrots can cause the urine to be dark yellow or orange.

Clear

Urine: No Visible particulates, Transparent

Hazy

Urine: Few particulates, print easily seen through urine

Cloudy

Urine: Many particulates, print blurred through urine

Turbid

Urine: Print CANNOT be seen through urine

Milky

Urine: May precipitate or be clotted

UA chemical examination

• is commonly performed using a plastic reagent strip, often called a dipstick, that contains absorbent pads impregnated with test reagents.

• Each test has its own pad.

• The strips are made by several manufacturers, but most can detect bacteria, bilirubin, blood (red blood cells and hemoglobin), glucose, ketones, leukocytes, nitrite, protein, and urobilinogen, and measure pH and specific gravity.

UA Microscopic examination

• identifies urine components such as cells, crystals, casts, and microorganisms by examining a sample of urine sediment under a microscope.

• To obtain the sediment, a measured portion of well-mixed urine is centrifuged in a special conical (tapered) plastic tube.

• After centrifugation, the supernatant (clear top portion of the specimen) is discarded.

• A drop of the remaining sediment in the bottom of the tube is placed either on a glass slide and covered with a small square of glass called a coverslip or placed in a special chamber

First morning sample

• is the specimen of choice for urinalysis because it is more concentrated.

• It may be used to confirm results obtained from random specimens

• Patients are provided with a container and instructed to collect the sample immediately after arising and to return it to the laboratory within 2 hours or refrigerate the sample.
  

Midstream clean-catch

• Are used for urine cultures.

• Patients are provided with sterile containers and antiseptic materials for cleansing the genitalia. Mild antiseptic towelettes are recommended.

• Are collected at the laboratory and delivered immediately to the microbiology section

• If a routine urinalysis is also requested, the culture should be performed first to prevent contamination of the sample.

carefully timed specimen

• is required for quantitative measurement of urine constituents.

• Patients are provided with large plastic containers that may contain a preservative.

• For accurate results, it is critical that the patient understand that all urine produced during the collection period be placed in the container.

• Patients who indicate they have not been able to collect a complete sample should obtain a new sample. To obtain an accurate timed sample, it is necessary for the patient to begin and end the collection period with an empty bladder.

• should obtain a new sample. To obtain an accurate timed sample, it is necessary for the patient to begin and end the collection period with an empty bladder.

Catheterized Urine Sample

• This sample is collected under sterile conditions by passing a sterile hollow tube through the urethra into the bladder

• This type of sample is collected on a patient unable to void, babies, or bedridden patients.

bacterial culture

The most commonly requested test on a catheterized sample is a?

Suprapubic Urine Sample

• is collected by external introduction of a needle through the abdomen into the bladder.

• The sample can be used for bacterial cultures and cytological examination.

• Catheterized and suprapubic samples are collected by personnel in the nursing units and delivered to the laboratory.

Suprapubic aspiration

is used when a sample must be completely free of extraneous contamination, particularly in infants or children.

Sample collection

• is the most vulnerable part of a drug-testing program. For urine samples to withstand legal scrutiny, it is necessary to prove that no tampering (e.g., adulteration, substitution, or dilution) took place.

• Acceptable identification of the person requires picture identification, the chain of custody (COC) must be carefully documented.

• Urine sample collection may be “witnessed” or “unwitnessed.

• If a witnessed sample collection is ordered, a same-gender collector will observe the collection of 30 to 45 mL of urine. Witnessed and unwitnessed collections should be immediately handed to the collector.

• The urine temperature must be taken within 4 minutes from the time of collection to confirm the sample has not been adulterated. The temperature should read within the range of 32.5°C to 37.7°C.

• A urine pH of greater than 9.0 suggests adulteration of the urine sample and requires that the sample be recollected if clinically necessary.

• A specific gravity of less than 1.005 could indicate dilution of the urine sample and would require recollection of the sample.

Random

Types of urine specimen and their purpose
-Routine screening

First morning

Types of urine specimen and their purpose
-Routine screening, Pregnancy Tests, Orthostatic protein

Fasting

Types of urine specimen and their purpose
-Diabetes screening/ monitoring

24-Hour (Or timed)

Types of urine specimen and their purpose
-Quantitative Chemical Tests

Catheterized

Types of urine specimen and their purpose
-Bacterial Culture

Midstream Clean-Catch

Types of urine specimen and their purpose
-Routine screening, Bacterial culture

Suprapubic

Types of urine specimen and their purpose
-Bladder urine for bacterial culture Cytology

Fecal Sample collection

• Random samples used for cultures, ova and parasites (O&P), microscopic examination for cells, fats and fibers, and detection of blood.

• Kits containing reagent-impregnated filter paper are provided to screen for the presence of occult (hidden) blood

Semen Sample collection

• are collected and tested to evaluate fertility and post vasectomy procedures.

• Patients presenting requisitions for semen analysis should be instructed to abstain from sexual activity for 3 days and not longer than 5 days before collecting the sample.

• Ideally, the sample should then be collected at the laboratory in a warm sterile container.

• Samples for fertility studies must not be collected in a condom because condoms frequently contain spermicidal agents.

• f the sample is collected at home, it must be kept warm and delivered to the laboratory within 1 hour

Collection of throat cultures

• They are performed primarily for the detection of a streptococcal infection, “strep throat.”

• is collected using a collection kit that contains a sterile swab in a transport medium collection tube.

• The purpose of the transport media in a culture swab kit is to keep the bacteria to be cultured alive during transport to the microbiology laboratory.

• Swabs for rapid streptococcal tests do not require transport media.