In this section of the NCLEX-RN examination, you will be expected to demonstrate your knowledge and skills of laboratory values in order to:

  • Identify laboratory values for ABGs (pH, PO2, PCO2, SaO2, HCO3), BUN, cholesterol (total) glucose, hematocrit, hemoglobin, glycosylated hemoglobin (HgbA1C), platelets, potassium, sodium, WBC, creatinine, PT, PTT & APTT, INR
  • Compare client laboratory values to normal laboratory values
  • Educate client about the purpose and procedure of prescribed laboratory tests
  • Obtain blood specimens peripherally or through central line
  • Obtain specimens other than blood for diagnostic testing (e.g., wound, stool, urine)
  • Monitor client laboratory values (e.g., glucose testing results for the client with diabetes)
  • Notify primary health care provider about laboratory test results

Identifying Laboratory Values

Arterial Blood Gases

  • Partial pressure of oxygen (PaO2): 75 - 100 mmHg
  • Partial pressure of carbon dioxide (PaCO2): 38 - 42 mmHg
  • Arterial blood pH: 7.38 - 7.42
  • Oxygen saturation (SaO2): 94 - 100%
  • Bicarbonate - (HCO3): 22 - 28 mEq/L

The oxygen value is lower with an altitude of > 3,000 feet.

Electrolytes

  • Ammonia: 15-50 µmol/L
  • Ceruloplasmin: 15-60 mg/dL
  • Chloride: 95-105 mmol/L
  • Copper: 70-150 µg/dL
  • Creatinine: 0.8-1.3 mg/dL
  • Blood urea nitrogen: 8-21 mg/dL
  • Ferritin: 12-300 ng/mL (men), 12-150 ng/mL (women)
  • Glucose: 65-110 mg/dL
  • Inorganic phosphorous: 1-1.5 mmol/L
  • Ionized calcium: 1.03-1.23 mmol/L
  • Magnesium: 1.5-2 mEq/L
  • Phosphate: 0.8-1.5 mmol/L
  • Potassium: 3.5-5 mmol/L
  • Pyruvate: 300-900 µg/dL
  • Sodium: 135-145 mmol/L
  • Total calcium: 2-2.6 mmol/L
  • Total iron-binding capacity: 45-85 µmol/L
  • Total serum iron: 65-180 µg/dL (men), 30-170 µg/dL (women)
  • Transferrin: 200-350 mg/dL
  • Urea: 1.2-3 mmol/L
  • Uric acid: 0.18-0.48 mmol/L
  • Zinc: 70-100 µmol/L

Hematology

  • Hemoglobin: 13-17 g/dL (men), 12-15 g/dL (women)
  • Hematocrit 40%-52% (men), 36%-47%
  • Glycosylated hemoglobin 4%-6%
  • Mean corpuscular volume (MCV): 80-100 fL
  • Red blood cell distribution width (RDW): 11.5%-14.5%
  • Mean corpuscular hemoglobin (MCH): 0.4-0.5 fmol/cell
  • Mean corpuscular hemoglobin concentration (MCHC): 30-35 g/dL
  • Reticulocytes 0.5%-1.5%
  • White blood cells (WBC) 4-10 x 10^9/L
  • Neutrophils: 2-8 x 10^9/L
  • Bands: < 1 x 10^9/L
  • Lymphocytes: 1-4 x 10^9/L
  • Monocytes: 0.2-0.8 x 10^9/L
  • Eosinophils: < 0.5 x 10^9/L
  • Platelets: 150-400 x 10^9/L
  • Prothrombin time: 11-14 sec
  • International normalized ratio (INR): 0.9-1.2
  • Activated partial thromboplastin time (aPTT): 20-40 sec
  • Fibrinogen: 1.8-4 g/L
  • Bleeding time: 2-9 min

Lipids

  • Triglycerides: 50-150 mg/dL
  • Total cholesterol: 3-5.5 mmol/L
  • High-density lipoprotein (HDL): 40-80 mg/dL
  • Low-density lipoprotein (LDL): 85-125 mg/dL

Acid Base Values

  • pH: 7.35-7.45
  • Base excess: (-3)-(+3)
  • H+: 36-44 nmol/L
  • Partial pressure of oxygen (pO2): 75-100 mm Hg
  • Oxygen saturation: 96%-100%
  • Partial pressure of carbon dioxide (pCO2): 35-45 mm Hg
  • Bicarbonate (HCO3): 18-22 mmol/L

Gastrointestinal Tests

  • Albumin: 35-50 g/L
  • Alkaline phosphatase: 50-100 U/L
  • Alanine aminotransferase (ALT): 5-30 U/L
  • Amylase: 30-125 U/L
  • Aspartate aminotransferase (AST): 5-30 U/L
  • Direct bilirubin: 0-6 µmol/L
  • Gamma glutamyl transferase: 6-50 U/L
  • Lipase: 10-150 U/L
  • Total bilirubin: 2-20 µmol/L
  • Total protein: 60-80 g/L

Cardiac Enzymes

  • Creatine kinase: 25-200 U/L
  • Creatine kinase MB (CKMB): 0-4 ng/mL
  • Troponin: 0-0.4 ng/mL

Hormones

  • 17 hydroxyprogesterone (female, follicular): 0.2-1 mg/L
  • Adrenocorticotropic hormone (ACTH): 4.5-20 pmol/L
  • Estradiol: 1.5-5 ng/dL (male), 2-14 ng/dL (female, follicular), 2-16 ng/dL (female, luteal), < 3.5 ng/dL (postmenopausal)
  • Free T3: 0.2-0.5 ng/dL
  • Free T4: 10-20 pmol/L
  • Follicle-stimulating hormone (FSH): 1-10 IU/L (male), 1-10 IU/L (female, follicular/luteal), 5-25 IU/L (female, ovulation), 30-110 IU/L (postmenopause)
  • Growth hormone (fasting) : 0-5 ng/mL
  • Progesterone: 70-280 (ovulation), ng/dL
  • Prolactin: < 14 ng/mL
  • Testosterone (male): 10-25 nmol/L
  • Thyroxine-binding globulin: 12-30 mg/L
  • Thyroid-stimulating hormone (TSH): 0.5-5 mIU/L
  • Total T4: 4.9-11.7 mg/dL
  • Total T3: 0.7-1.5 ng/dL
  • Free T3: 0.6-1.6 ng/mL

Vitamins

  • Folate (serum) : 7-36 nmol/L
  • Vitamin A: 30-65 µg/dL
  • Vitamin B12: 130-700 ng/L
  • Vitamin C: 0.4-1.5 mg/dL
  • Vitamin D: 5-75 ng/mL

Tumor Markers

  • Alpha fetoprotein: 0-44 ng/mL
  • Beta human chorionic gonadotropin (HCG): < 5 IU/I
  • CA19.9: < 40 U/mL
  • Carcinoembryonic antigen (CEA): < 4 ug/L
  • Prostatic acid phosphatase (PAP): 0-3 U/dL
  • Prostate-specific antigen (PSA): < 4 ug/L

Miscellaneous

  • Alpha 1-antitrypsin: 20-50 µmol/L
  • Angiotensin-converting enzyme: 23-57 U/L
  • C-reactive protein: < 5 mg/L
  • D-dimer: < 500 ng/mL
  • Erythrocyte sedimentation rate (ESR): Less than age/2 mm/hour
  • Lactate dehydrogenase (LDH): 50-150 U/L
  • Lead: < 40 µg/dL
  • Rheumatoid factor: < 25 IU/ml

Comparing the Client's Laboratory Values to Normal Laboratory Values

The client's current laboratory values are compared to the normal laboratory values, as above, in order to determine the physiological status of the client and to compare the current values during treatment to the laboratory values taken prior to a treatment.

Educating the Client About the Purpose and Procedure of Prescribed Laboratory Tests

As previously discussed, clients must be educated about the purpose of the prescribed laboratory test, the procedure for the laboratory test and any preparation the laboratory tests that is indicated. For example, a client in the community may be instructed to remain NPO after midnight. More information about this client education was previously discussed in the section entitled "Applying a Knowledge of Related Nursing Procedures and Psychomotor Skills When Caring for Clients Undergoing Diagnostic Testing".

Obtaining Blood Specimens Peripherally and Through a Central Line

Peripheral Venous Blood Samples

Drawing a peripheral venous blood sample is done in this manner:

  • Gather and organize the correct laboratory tubes for the specimens that you will be collecting.
  • Choose a suitable site for the venipuncture.
  • Place the tourniquet on the client's arm about 3 to 4 inches above the selected site.
  • Palpate the vein.
  • Clean the site with an alcohol prep pad with a circular pattern from the site of the venipuncture to the area surrounding the site of the venipuncture.
  • Allow the area to air dry.
  • Ask the patient to make a fist.
  • Pull the skin taunt so that the desired and suitable vein is accessible.
  • Insert the sterile needle into the vein at a 15 to 30 degree angle.
  • Pop the tube onto the tubing.
  • Take the tourniquet off when the last tube is filled.
  • Take the needle out.
  • Place sterile gauze on the site using sufficient pressure to prevent bleeding for about 1 or 2 minutes.
  • Remove the gauze.
  • Place an adhesive bandage over the site.
  • Label the specimen with the data that is required according to your facility's policy and procedure for laboratory blood samples.

Central Line Blood Samples

Some central venous catheters have a couple or several lumens, one of may be used to withdraw a blood sample. The port that can be used to draw a blood sample is cleansed with alcohol. Then a small amount of blood is drawn out and discarded, after which the intended blood sample is drawn. After the sample is taken, the central line is then flushed with 20 mL of sterile saline.

Obtaining Specimens Other Than Blood for Diagnostic Testing

Other than blood, other specimens that are collected include urine, stool and wound specimens. Urine and stool specimens were discussed earlier in this NCLEX-RN review in the section entitled "Applying a Knowledge of Related Nursing Procedures and Psychomotor Skills When Caring for Clients Undergoing Diagnostic Testing"

Wound specimens are obtained in the following manner:

  • Gently irrigate the wound with sterile normal saline to remove any debris and extraneous matter.
  • Remove the swab from the Culturette tube.
  • Gently place the swab and rotate the swab on the wound's granulating tissue.
  • Place the swab into the Culturette tube.
  • Crack the Culturette tube so the culture medium soaks into the swab

Monitoring the Client's Laboratory Values

Client's laboratory values are monitored prior to, during and after therapeutic interventions and treatments. For example, diabetic clients should have their blood glucose levels are taken and monitored by the nurse and they are also monitored by the client in their home. This monitoring permits the nurse and the client the opportunity to evaluate how well the diabetes is being managed.

Notifying the Primary Health Care Provider About Laboratory Test Results

The primary health care provider is immediately informed about all abnormal laboratory test results.

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