Test Description
Natriuretic peptides are structurally similar peptides produced by cells throughout the body. Two of these, A-type natriuretic peptide (also known as atrial natriuretic peptide, or ANP)and B-type natriuretic peptide (also known as brain natriuretic peptide, or BNP) are produced by the myocardial cells. ANP is made exclusively by atrial myocytes, while BNP is produced by both atrial and ventricular myocytes.
ANP and BNP maintain homeostasis by promoting diuresis and natriuresis. BNP is released from the ventricles, especially the left ventricle, during pressure or volume overload. It causes dilation of arteries and veins and also decreases levels of vaso- constricting and sodium-retaining neurohormones. It is now known that ventricular overload results in release of both BNP and N-terminal proBNP (NT-proBNP).
Although ANP was the first natriuretic peptide, it is the BNP that is widely used clinically. This is due in part to its longer half-life (20 minutes for BNP versus 3 minutes for ANP). Also, BNP levels are not affected by exertion or exercise, whereas ANP levels can be affected by routine activity. NT-proBNP has a half-life of 120 minutes, making it somewhat less useful for monitoring acute changes.
However, it is used in diagnosing heart failure and studies are suggesting it as a strong predictor of mortality.
The use of BNP in helping to diagnose heart failure is well-documented. Levels of BNP are elevated in individuals with symptomatic heart failure in a noncompensated state. However, patients who have left ventricular dysfunction that is compensated due to medical therapy may have normal BNP levels. BNP testing is especially useful in helping health-care providers distinguish between dyspnea due to heart failure and dyspnea due to other causes.
Normal Values
BNP: <100 pg/mL (<100 ng/L SI units) NT-proBNP: <400 pg/mL (<400 ng/L SI units) Possible Meanings of Abnormal Values
Increased Decreased
Acute lung injury Therapeutic response to antihypertensive Acute myocardial infarction therapy
Chronic renal failure Therapeutic response to diuretic therapy Cirrhosis
Congestive heart failure Coronary angioplasty Hypertension Hypervolemic states Left ventricular hypertrophy Nesiritide infusion Pulmonary hypertension
Contributing Factors to Abnormal Values
• BNP levels are increased with age, female gender.
• Obesity may cause falsely decreasedBNP levels.
• Patients in renal failure or on dialysis may have elevated BNP levels whether or not heart failure is present.
• Patients with right-sided heart failure (due to cor pulmonale, pulmonary emboli, pulmonary hypertension) have elevated levels (300–400 pg/mL).
• Nesiritide infusion causes BNP levels of 3000 pg/mL.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• No fasting is required before the test.
Procedure
• A 7-mL blood sample is drawn in a white-top EDTA (nonglass) collection tube.
• Plasma must be separated from cells by centrifuge within 2 hours and frozen.
• Gloves are worn throughout the procedure.
Posttest
• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued bleeding.
• Label the specimen and transport it to the laboratory.
• Report abnormal findings to the primary care provider.
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RClinical Alerts
• Patients in chronic heart failure have elevated BNP levels, but may be stable.
• Patients with newly elevated BNP require further evaluation, including echocardiogram.
Normal Values Reactive
Possible Meanings of Abnormal Values Nonreactive fetus
Contributing Factors to Abnormal Values
• Fetal immaturity, especially fetuses <28 weeks gestation, can cause a nonreactive NST.
• Fetal sleep.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test and the procedure to be done. Note that there is no discomfort associated with the NST.
• No fasting is required prior to the test. Instruct the patient to eat prior to the test to ensure a high maternal serum glucose level, which enhances fetal activity.
Procedure
• The patient is instructed to void.
• The patient is assisted into a Sims’ position.
• An external fetal monitor is applied to the patient’s abdomen, which will provide a graph of FHR and uterine contractions.
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• Although BNP and NT-proBNP are secreted in a 1:1 ratio, the NT-proBNP level may be much higher in the same patient because of its longer half-life.
Nonstress Test (NST, Fetal Activity Study)
Test Description
The nonstress test (NST) is a noninvasive technique used to evaluate the status of the fetus. Common reasons for an NST include: the patient having diabetes or hypertension, the fetus being small or not growing properly, and pregnancies extending past the due date.
Unlike the contraction stress test, the NST does not include stimulation with oxytocin. The fetal activity monitored in this test may be spontaneous or induced by uterine contraction or external manipulation. Normally, the fetal heart rate (FHR) should accelerate in response to fetal movement. The fetus is reported as being
“reactive” when two or more FHR accelerations are detected within a 20-minute period. Each of the accelerations must be at least 15 beats per minute and last for at least 15 seconds. The NST is highly reliable for determining fetal viability. Only with a “nonreactive” result, is a contraction stress test (CST) indicated.
• The patient is instructed to push a button on the fetal monitor whenever she feels fetal movement. This is then indicated on the graph, allowing correlation to be made with the FHR at that time.
• If there is no fetal movement for 20 minutes, the fetus is externally stimulated by rubbing or compressing the patient’s abdomen or by producing a loud noise near the abdomen.
• If there is no fetal movement for 40 minutes, the test is considered nonreactive.
Posttest
• Report abnormal findings to the primary care provider.
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RClinical Alerts
• If the test finds the fetus to be nonreactive (no change in the fetal heart rate when the fetus moves), the patient is scheduled for a CST.
• Explain to the patient that a nonreactive NST does not always mean there is a problem with the fetus. Conducting the test during the fetus’ sleep cycle may cause it to be nonreactive.
5 ′ -Nucleotidase (5′-N)
Test Description
Testing for 5′-nucleotidase (5′-N) is used in conjunction with alkaline phosphatase (ALP) to differentiate between hepatobiliary diseases and bone diseases. 5′-N is an enzyme found in the plasma membranes of liver cells and cells of the bile duct. Its limited location makes this test relatively specific in nature. When both 5′-N and ALP are elevated, the presence of liver metastases is probable.
Normal Values
1–11 U/L (0.02–0.18 àkat/L SI units) Possible Meanings of Abnormal Values
Increased Biliary obstruction Cholestasis Cirrhosis Hepatitis Late pregnancy Liver disease Liver metastases
Contributing Factors to Abnormal Values
• Drugs which may increase 5′-N levels: anabolic steroids, antibiotics, aspirin, codeine, hepatotoxic drugs, imipramine, indomethacin, meperidine, morphine, phe- nothiazines, phenytoin, thiazide diuretics.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• No fasting is required before the test.
Procedure
• A 7-mL blood sample is drawn in a red-top collection tube.
• Gloves are worn throughout the procedure.
Posttest
• Apply pressure 3 to 5 minutes at venipuncture site. Apply dressing, periodically assess- ing for continued bleeding.
• Teach the patient to monitor the site. If the site begins to bleed, the patient should apply direct pressure and, if unable to control the bleeding, return to the laboratory or notify the primary care provider.
• Label the specimen and transport it to the laboratory.
• Report abnormal findings to the primary care provider.
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RClinical Alerts
• With liver dysfunction, the patient may have prolonged clotting time.
Osmolality, Blood (Serum Osmolality)
Test Description
The osmolality of the blood measures the number of osmotically active particles in the serum. The test is useful in assessing fluid and electrolyte imbalances and in determining fluid requirements. It provides valuable information regarding a patient’s hydration status, the concentration of the urine, and the status of ADH (antidiuretic hormone) secretion, and is used in toxicology workups. Serum osmo- lality is primarily ordered to investigate hyponatremia. Hyponatremia may be due to sodium loss through the urine or due to increased fluid in the bloodstream.
Normal Values
280–296 mOsm/kg of H2O (280–296 mmol/kg SI units)
Possible Meanings of Abnormal Values
Increased Decreased
Acidosis Addison’s disease
Advanced liver disease Congestive heart failure
Alcohol overdose Edema
Azotemia Hepatic cirrhosis
Burns Hepatic failure with ascites
Convulsions Lung cancer
Dehydration Overhydration
Diabetes insipidus Postoperative
Diabetes mellitus Syndrome of inappropriate
Edema ADH secretion (SIADH)
Ethylene glycol overdose High protein diet Hyperaldosteronism Hyperbilirubinemia Hypercalcemia Hyperglycemia Hypernatremia Hypokalemia Ketoacidosis Methanol overdose Shock
Trauma Uremia
Contributing Factors to Abnormal Values
• Test results may be altered due to hemolysis of the blood sample.
• Drugs which may alter test results: mineralocorticoids, osmotic diuretics.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• No fasting is required before the test.
Procedure
• A 7-mL blood sample is drawn in a red-top collection tube.
• Gloves are worn throughout the procedure.
Posttest
• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued bleeding.
• Label the specimen and transport it to the laboratory.
• Report abnormal findings to the primary care provider.
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RClinical Alerts
• Elevated serum osmolality levels result in worsening clinical condition:
• >385 mOsm/kg H20→stupor in hyperglycemia
• >400 mOsm/kg H
20→grand mal seizures
• >420 mOsm/kg H
20→death
Normal Values
Random specimen: 50–1200 mOsm/kg H20 (50–1200 mmol/kg SI units) After 12–14 hour fast: >850 mOsm/kg H20 (>850 mmol/kg SI units) Possible Meanings of Abnormal Values
Increased Decreased
Addison’s disease Acute renal failure
Azotemia Aldosteronism
Congestive heart failure Diabetes insipidus
Dehydration Edema
Diabetes mellitus Fever
Diarrhea Glomerulonephritis
Edema High protein diet
Glycosuria Hypercalcemia
Hepatic cirrhosis Hypokalemia
High protein diet Hyponatremia
Hyperglycemia Multiple myeloma
Hypernatremia Overhydration
Ketoacidosis Sickle cell anemia
Postoperative Urinary tract obstruction
Prerenal azotemia Water intoxication
Sodium overload
Syndrome of inappropriate ADH secretion (SIADH) Uremia
Contributing Factors to Abnormal Values
• Abnormal results may occur with intake of antibiotics, antidepressants, antipsychotics, bromocriptine, chemotherapy, dextran, diuretics, glucose, mannitol, and radiographic contrast agents.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test and the need for a urine specimen.
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Osmolality, Urine (Urine Osmolality)
Test Description
The urine osmolality measures the number of osmotically active particles in the urine, or the concentration of the urine. This, in turn, reflects the ability of the kid- neys to concentrate urine. The test is useful in assessing fluid and electrolyte imbal- ances and in determining fluid requirements. It is especially useful in the evaluation of hyponatremia and hypernatremia, and to distinguish prerenal azotemia from ischemic acute tubular necrosis. Following an overnight fast, the urine osmolality should be at least three times the osmolality of the blood.
• No fasting is required for random testing.
• Overnight fasting is required prior to the test, if ordered as a fasting urine specimen.
Procedure
• 10-mL of urine is collected in a plastic specimen container.
• Gloves are worn throughout the procedure.
Posttest
• Label the specimen and transport it to the laboratory immediately.
• Report abnormal findings to the primary care provider.
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Osteocalcin (Bone G1a Protein)
Test Description
Osteocalcin (bone G1a protein) is a protein synthesized in bone by osteoblasts.
After production, some of it is incorporated into the bone matrix and some enters the circulation. The bone matrix then mineralizes to create new bone. Research has found that the circulating level of osteocalcin reflects the rate of bone formation.
Thus, measurement of osteocalcin is useful for identifying individuals at risk for developing osteoporosis, for monitoring bone metabolism during and after menopause, and for monitoring response to antiresorptive therapy. The effect of antiresorptive therapy on osteocalcin levels can be assessed much sooner (in 3 to 6 months) than can be seen on bone density testing (1 to 2 years).
Normal Values
Male: 8–37 ng/mL (1.37–6.33 nmol/L SI units) Female: 7–38 ng/mL (1.20–6.50 nmol/L SI units) Osteoporosis: 17–49 ng/mL(2.91–8.38 nmol/L SI units) Possible Meanings of Abnormal Values
Increased Decreased
Acromegaly Antiresorptive therapy
Fracture Hypoparathyroidism
Hyperparathyroidism Osteoporosis
Contributing Factors to Abnormal Values
• There is a diurnal variation in osteocalcin levels.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• No fasting is required before the test.
Procedure
• A 7-mL blood sample is drawn in a red-top collection tube at 7 AM.
• Gloves are worn throughout the procedure.
Posttest
• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued bleeding.
• Label the specimen and transport it to the laboratory.
• Report abnormal findings to the primary care provider.
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Oximetry (Ear Oximetry, Pulse Oximetry, Oxygen Saturation, SaO2)
Test Description
Oximetry is a noninvasive procedure used to monitor the oxygen saturation of arte- rial blood. Due to the simplicity and convenience of the procedure, oximetry is used in a variety of settings where monitoring of oxygenation status is needed. Examples of oximetry use include during surgical procedures, during mechanical ventilation, and during diagnostic testing such as stress testing.
Oximetry measures the percentage of oxygen being carried by the hemoglobin.
To perform this measurement, a light-emitting sensor is attached to a site such as a finger. The sensor emits beams of light through the skin tissue. A light-detecting sensor then records the amount of light absorbed by the oxygenated hemoglobin.
This absorption rate is converted to the percentage of oxygen saturation present in the blood, which is shown on the monitor.
THE EVIDENCE FOR PRACTICE
Screening for nocturnal hypoxia can be done easily and inexpensively with overnight pulse oximetry in the home. The oximeter is returned to the clinic, where the overnight oximetry and heart rate data are downloaded. If a significant portion of the night’s data indicates oxy- gen saturations below 88%, supplemental oxygen can be provided empirically at 1 to 2 L/min.
Home oximetry can be repeated at that level to verify correction of hypoxia. (ICSI, 2007)
Normal Values
≥95%
Possible Meanings of Abnormal Values
Increased Decreased
Adequate oxygen therapy Excessive blood loss Carbon monoxide poisoning Chronic obstructive lung disease Hypoventilation
Hypoxia
Inadequate available oxygen Pulmonary embolism Smoking
Contributing Factors to Abnormal Values
• False alarms may occur due to movement of the site to which the sensor is attached, equipment problems, or inadequate blood flow to the site.
• Inaccurate readings may occur if the patient is anemic or has received contrast media, or if there are bright lights in the room.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test, noting that no discomfort is associated with this procedure.
• Inform the patient of the presence of alarms. Explain that the alarm will sound should the sensor become displaced. Also inform the patient of steps which will be taken should the oxygen saturation be found to be low.
• No fasting is required prior to the test.
Procedure
• The site must have good circulation. Examples of possible sites include fingers, earlobes, and toes.
• Ensure that the skin is clean and dry. Rub the area to increase its blood flow.
• Apply the sensor to the chosen site.
Posttest
• Report abnormal findings to the primary care provider.
P RClinical Alerts
• Medicare currently provides coverage for home oxygen for beneficiaries with par- tial pressure measurements at or below 55 mm Hg or oxygen saturation at or below 88 percent. If certain other diseases/conditions are present, coverage is provided for patients with an oxygen partial pressure of 56 to 60 mm Hg or an oxygen sat- uration of 89%.
• Claims must be supported by valid qualifying test results, including oxime- try testing.
http://www.cms.hhs.gov/apps/media/press/release.asp?Counter=1815 http://www.cms.hhs.gov/transmittals/downloads/R166OTN.pdf
Papanicolaou Test (Exfoliative Cytologic Study, Pap Smear, Pap Test, Thin Prep)
Test Description
The Papanicolaou (Pap) smear can be performed on many body secretions, includ- ing gastric secretions, prostatic secretions, sputum, and urine. However, the term is most commonly associated with the test for detection of cervical cancer. A vagi- nal examination is performed and cells are obtained from the cervix. In the case of
THE EVIDENCE FOR PRACTICE
According to American Cancer Society and American College of Obstetricians and Gynecologists (ACOG) guidelines:
• All women should begin cervical cancer screening about 3 years after they begin having vaginal intercourse, but no later than when they are 21 years old. Screening should be done every year with the regular Pap test or every 2 years using the newer liquid-based Pap test.
• Beginning at age 30, women who have had 3 normal Pap test results in a row may get screened every 2 to 3 years. Women who have certain risk factors such as diethylstilbe- strol (DES) exposure before birth, HIV infection, or a weakened immune system due to
PAPANICOLAOU TEST 415
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a woman who has had a total hysterectomy (removal of the uterus and cervix), cells may be obtained from the vaginal wall. The cells are then classified according to a grading system such as the Bethesda System. The system was reviewed and updated by representatives of 45 professional societies at the 2001 conference, with the following components now included in Pap test results (Available at:
http://www.bethesda2001.cancer.gov/terminology.html).
The “Specimen Type” notes whether the specimen is of the conventional smear type or the newer liquid-based preparation. With liquid-based Pap tests, DNA testing can be performed to check for the presence of high-risk types of human papilloma virus (HPV) which have been associated with the development of cervical cancer.
The “Specimen Adequacy” is noted as being either satisfactory (with presence or absence of endocervical/transformation zone component noted) or unsatisfactory for evaluation. A reason is noted for an unsatisfactory specimen, such as an inade- quate number of cells or lubricant interfering with the evaluation. Even with a sat- isfactory specimen, there can be situations in which the quality of the specimen is somewhat compromised, such as partially obscuring blood or inflammation.
The “Interpretation/Result” section states “Negative for Intraepithelial Lesion or Malignancy” when there is no cellular evidence of neoplasia. If present, Trichomonas, fungal organisms (Candida), bacteria consistent with Actinomyces, cellular changes consistent with herpes simplex virus, or a shift in flora suggestive of bacterial vaginosis will be identified, as will reactive cellular changes (associated with inflam- mation, radiation, or presence of intrauterine device), glandular cells (after hys- terectomy), or atrophy (postmenopausal). If endometrial cells are seen in a woman age 40 and older, this is considered an abnormality and is noted in the report.
Epithelial cell abnormalities may include any of the following:
• Squamous cell
• ASC-US (atypical squamous cells of undetermined significance)
• LSIL (low grade squamous intraepithelial lesion)
• HSIL (high grade squamous intraepithelial lesion)
• Features suspicious for invasion
• Squamous cell carcinoma
• Glandular cell
• Atypical endocervical/endometrial/glandular cells
• Atypia, favoring neoplasia
• Endocervical adenocarcinoma in situ
• Adenocarcinoma (endocervical, endometrial, extrauterine)
organ transplant, chemotherapy, or chronic steroid use should continue to be screened annually.
• Women 70 years of age or older who have had 3 or more normal Pap tests in a row and no abnormal Pap test results in the last 10 years may choose to stop having cervical can- cer screening. Women with a history of cervical cancer, DES exposure before birth, HIV infection, or a weakened immune system should continue to have screening as long as they are in good health.
• Women who have had a total hysterectomy (removal of the uterus and cervix) may also choose to stop having cervical cancer screening, unless the surgery was done as a treat- ment for cervical cancer or precancer. Women who have had a hysterectomy without removal of the cervix should continue to follow the guidelines above.
• Women need to be educated that an annual pelvic exam is still needed, even when a Pap test is not done.
Normal Values
Satisfactory for evaluation
Negative for intraepithelial lesion or malignancy No organisms or other findings
Possible Meanings of Abnormal Values Atrophy
Bacterial vaginosis Cervical cancer Fungal infection Inflammation
Sexually transmitted infection (Trichomonas, herpes simplex virus)
Contributing Factors to Abnormal Values
• Pap test results may be altered by allowing the cells of the specimen to dry if using smear technique, using lubricating jelly on the vaginal speculum, douching, tub bathing, menstrual flow, and infections.
• Drugs that may alter test results include digitalis and tetracycline.
• Insufficient number of cells collected will not allow interpretation of the specimen.
Interventions/Implications Pretest
• Explain to the patient the purpose of the test and the need for a vaginal examination to be done. Note that minimal discomfort is felt during the insertion of the vaginal speculum.
• Instruct the patient to not use douches, tampons, vaginal medications, sprays, or powders for at least 24 hours before having a Pap test.
• Instruct the patient to void before the examination
• The health-care provider should allow discussion of concerns or fears, especially for women who have had problems with pelvic exams in the past, survivors of rape or sexual abuse, and for those who have never had a pelvic exam.
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