Книга_3777_Библиотеки_им_академика_М_И_Перельмана

CHAPTER 9 Urine Tests

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Figure 9-2 One-time urine collection container.

First Morning Specimen

The patient will void before going to sleep for the evening and discard the specimen. When getting up, the patient will collect the urine specimen, which is identi ed as  rst morning specimen. The  rst specimen is more concentrated and may contain small amounts of abnormal elements. First morning specimens are preferred for screening for bacteria because they provide incubation time necessary for multiplying bacteria.

Midstream Specimen

The patient will begin to urinate in the toilet. When approximately half of the voiding is completed, without interrupting the process of urination, the patient will collect a portion of urine in the container, and then pass the last portion of urine  ow into the toilet.

Clean-Catch Specimen

The external genitalia are washed by the patient using a mild antiseptic solution. A midstream specimen is then collected in a clean container.

Figure 9-3 Twenty-four-hour collection container.

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PART 2 Blood and Urine Collection

Give the patient the following instructions for cleansing the genital area:

Men

1. If you are not circumcised, draw back the foreskin before

cleansing.

2. Clean the tip of the penis using a sterile cleansing towelette,

beginning at the tip and moving toward the base. Repeat the cleansing process using a second towelette.

Women

1. Squat over the toilet and use the  ngers of one hand to separate

and hold open the folds of the skin in the genital area.

2. Clean the urinary opening and surrounding area with a sterile

cleansing towelette, moving from front to back. Repeat.

Timed-Collection Urine Specimen

1. Obtain a large-mouth plastic container from the laboratory.

2. Have the patient void completely and discard the specimen.

3. Note the time, and collect all urine voided thereafter until the

end of the collection time. Have the patient void completely at the end of the collection time and save the  nal specimen, adding it to the previously voided specimen.

4. Keep the urine collection on ice or refrigerated until the collec-

tion time is completed.

If any urine during the collection time is lost accidentally due to spillage, leakage, or loss with a bowel movement, the collection must be terminated and begun again at the start of the process.

During the time of collection, individual specimens should not be removed for routine urinalysis, glucose tolerance urines, etc. The entire amount of all the voided specimens must be pooled together and submitted to the laboratory.

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CHAPTER 9 Urine Tests

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Urine Culture Collection

A urine specimen is collected by the patient using the clean-catch midstream collection procedure. The urine container must be a sterile container. The specimen must be cultured within one hour of collection.

SUMMARY

If urinalysis is to provide accurate test results, it is mandatory that attention be given to proper specimen handling and preservation. Examination of a fresh specimen is very important. Because urine is unstable, changes begin to occur in a voided specimen, which may cause misleading results. As urine decomposes, glucose decreases, bilirubin decreases, and other chemical reactions occur. If a urine specimen cannot be examined within two hours, the specimen should be refrigerated.

REVIEW ACTIVITIES

1. The urinary system is composed of

.

2. Urine components include

.

3. The major three functions of the urinary system are:

a. b. c.

DISCUSSION QUESTIONS

1. Describe the different factors that can produce erroneous test

results in urine testing.

2. Discuss the functions of the urinary system.

3. Describe the urine collection procedure for:

a. Random specimen b. Fasting c. Midstream specimen d. Clean-catch specimen e. Timed-collection specimen

specimen

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“The role of the laboratory

in diagnosis and treatment

continues to gain

importance as newer tests

and analytic methods allow

diagnoses that were not

possible before. Clinicians

increasingly depend on

laboratory test data.”

Common Laboratory Tests

After studying this unit, it is the responsibility of the learner to be able to:

1. Discuss the most common laboratory tests and explain why they might

be ordered.

2. Name the appropriate collection tubes for the most common laboratory

tests.

3. Discuss abnormal test results for the most common laboratory tests.

—Jacques Wallach, M.D.

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atherosclerosis a disease in which arteries are

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severely narrowed by lipid deposits on the inner walls

bile a yellow or greenish liquid secreted by the

liver that aids in digestion

bilirubin a reddish-yellow pigment in urine,

blood, or bile

cirrhosis in ammation of an organ, particularly

the liver

colitis in ammation of the colon

enzymes protein substances produced by living

cells; they are essential to life, as they act as catalysts in metabolism

occult hidden

urobilinogen compound formed in the intestine

from the breakdown of bilirubin

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P

PART 2 Blood and Urine Collection

hlebotomists are not responsible for ordering tests or interpreting

laboratory test results. However, a general knowledge of labora-

tory tests and what constitutes a normal result is helpful.

Laboratory tests are delegated for testing to speci c departments. Such delegation may differ among health care facilities. For instance, a urinalysis may be performed in the hematology department in one laboratory and the chemistry department in another. Specimen collection requirements can also vary among laboratories. This chapter will review collection requirements and normal test values for 50 of the most common laboratory tests, as well as some of the reasons a physician may order the tests. Normal-value ranges may vary slightly, depending on the testing methods used in individual laboratories. Collection tube requirements also may vary.

50 COMMON TESTS

ABO

Collection tube: red top The ABO (blood typing) test is used to determine the blood type

(A, B, or O) of all blood donors and all potential blood recipients. Patients who need blood must receive blood products that are compatible with their own blood group. Surgical patients are typed prior to surgery.

Acid Phosphatase (ACP)

Collection tube: red top Normal values:

Men: 0.5–11.7 units/L

Women: 0.3–9.2 units/L Acid phosphatase is an enzyme that is widely distributed in tissue.

A signi cant concentration of acid phosphatase is found in the prostate gland in men. The test is used to diagnose metastatic cancer of the prostate and to follow the effectiveness of treatment. Acid phosphatase is also present in high concentrations in seminal  uid, and this test may be ordered in an investigation of rape. Moderately elevated levels may also

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CHAPTER 10 Common Laboratory Tests

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occur with any cancer that has metastasized to the bone, hepatitis, acute renal failure, and sickle cell crisis.

Activated Partial Thromboplastin Time (APTT)

Collection tube: blue top Normal values: 30–45 sec

The APTT is a screening test for coagulation disorders. It is important

for monitoring heparin therapy.

Alanine Aminotransferase (ALT)

Collection tube: red top Normal values: 2–45 units/L

This test (formerly called SGPT) evaluates enzyme levels, primarily to

diagnose liver disease.

Alcohol (Ethyl, Legal, or Medical)

Collection tube: red top Normal values: none detected

Testing is done to detect the presence of alcohol, to indicate overdose

or alcohol-impaired driving.

Aldolase

Collection tube: red top Normal values: 1.5–12.0 units/L

Aldolase is a glycolytic enzyme that catalyzes the breakdown of glucose.

It is used in diagnostic situations where acute hepatitis, muscular atrophy, myocardial infarction, or malignancy is suspected.

Alkaline Phosphatase (ALP)

Collection tube: red top Normal values:

Adult: 20–70 units/L

Child: 20–150 units/L ALP is an enzyme originating mainly in the bone, the liver, and the

placenta. It is used as a tumor marker and an index of liver and bone disease.

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PART 2 Blood and Urine Collection

Ammonia

Collection tube: 10 mL green top. Pack in ice Normal values: ⬍50 mcg/dL

Ammonia is a nonprotein nitrogen compound that helps maintain

acid-base balance. Normally, the body uses the nitrogen fraction of ammonia to rebuild amino acids. It then converts the ammonia to urea in the liver for excretion by the kidneys. In liver diseases, ammonia can bypass the liver and accumulate in the blood. A test for ammonia levels is ordered to monitor the progression of severe hepatic disease and the effectiveness of therapy.

Amylase

Collection tube: red top Normal values: 50–150 units/L

Amylase is an enzyme that is produced by the pancreas, salivary

glands, liver, and fallopian tubes. It changes starch to sugar. If there is an in ammation of the pancreas or salivary glands, there is an increased level of this enzyme. Increased levels may also occur in mumps, alcohol poisoning, ruptured tubal pregnancy, and cholecystitis (in ammation of the gallbladder).

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Antinuclear Antibody (ANA)

Collection tube: red top Normal values: negative

An ANA test is used to diagnose autoimmune diseases, such as lupus

erythematosus (SLE), scleroderma, and rheumatoid arthritis.

Arterial Blood Gases

Specimen type: Arterial blood obtained by special collection.

The purpose of the test is to assess the adequacy of oxygenation, assess

the adequacy of ventilation, and assess the acid-base status by measuring the respiratory and nonrespiratory components. Arterial blood gases are used to monitor critically ill patients, to establish baseline values in the perioperative period, to follow up postoperative patients in the detection and treatment of electrolyte imbalances, and in conjunction with pulmonary function testing.

CHAPTER 10 Common Laboratory Tests

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Aspartate Aminotransferase (AST)

Collection tube: red top Normal values

Men: 27–47 units/L

Women: 5–55 units/L AST is an enzyme (formerly called SGOT) that is released into

the circulation following the injury or death of cells in tissues of high metabolic activity. Following a severe injury, the enzyme level will rise in 12 hours and remain elevated for about 5 days. In the case of myocardial infarction, the enzyme may be increased to 4 to 10 times its normal value. Liver disease also elevates the level, to 10 to 100 times the normal level.

Bilirubin

Collection tube: red top Normal values:

Total: 0.2–1.0 mg/dL

Conjugated: 0.0–0.2 mg/dL

Indirect unconjugated: 0.2–0.8 mg/dL

Newborn: 1.5–12.0 mg/dL

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Bilirubin is a by-product of hemolysis. The reddish-yellow pigment is

removed from the body by the liver through the excretion of

bile, a  uid

that aids in digestion. A rise in serum levels can occur if there is excessive destruction of red blood cells or if the liver is unable to excrete the normal amounts of bilirubin. A normal level of total bilirubin rules out impairment of the excretory function of the liver or excessive hemolysis of red cells. Excessive amounts of bilirubin give the yellow hue to the skin that is a sign of jaundice. In newborns, critical levels of bilirubin call for aggressive treatment to prevent mental retardation.

Bleeding Time (Duke and Ivy Methods)

Collection tube: special procedure Normal values: 3–10 min

Bleeding time measures the interaction of platelets with the blood

vessel wall and the formation of a clot. It is used to detect vascular abnormalities and platelet abnormalities or de ciencies.

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PART 2 Blood and Urine Collection

Blood Culture

Collection tube: broth culture bottles Normal values: no growth

Blood cultures are used to detect septicemia.

Blood Urea Nitrogen (BUN)

Collection tube: green or red top Normal values:

Adult: 7–18 mg/dL

Child: 5–18 mg/dL Urea is formed in the liver. It is carried to the kidneys by the blood,

to be excreted in the urine. A BUN test measures the nitrogen portion of urea. The most common cause of elevated BUN levels is inadequate excretion of urea due to kidney or urinary obstruction. Inadequate excretion may occur with shock, dehydration, gastrointestinal hemorrhage, infection diabetes, some malignancies, acute myocardial infarction, chronic gout, and excessive protein intake.

Calcium

Collection tube: red top Normal values:

Total: 8.8–10.0 mg/dL

Ionized: 4.4–5.4 mg/dL A calcium test measures the concentration of total calcium in the

blood. It is used to evaluate parathyroid function, calcium metabolism, and malignancies.

Cholesterol

Collection tube: red top Normal values: 140–220 mg/dL

Cholesterol testing is primarily used to detect disorders of blood lipids

and to evaluate the risk potential for atherosclerosis, a disease in which arteries are narrowed by lipid deposits on the inner walls.

Chromosome Analysis

Specimen types: Leukocytes from peripheral blood collected in sodium heparin tube, bone marrow biopsies, fibroblasts from skin or surgical

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