Lab Values
Overview of Laboratory Values and Their Interpretations
Purpose of Lab Values
Screening Tests:
Should be sensitive, meaning very few false negatives.
A negative result can provide confidence that the person does not have the condition of interest.
May also use a test with a good negative predictive value and/or a very small negative likelihood ratio.
Diagnostic Tests:
Should be specific, meaning very few false positives.
A positive result can provide confidence that the person has the condition of interest.
May also use a test with a good positive predictive value and/or a very large positive likelihood ratio.
Key Definitions
Sensitivity:
Defined as the True Positive Rate, which is the proportion of people with the condition who test positive.
With a high true positive rate, false negatives decrease.
Specificity:
Defined as the True Negative Rate, which is the proportion of people without the condition who test negative.
A high true negative rate leads to decreased false positives.
Lab Values as Puzzle Pieces
Some lab values:
Have high sensitivity and specificity for a diagnosis.
Provide only one piece of information for a single diagnosis.
Are crucial for mobility and need to be reviewed prior to physical therapy (PT) sessions.
Are not pertinent to mobility or PT.
Lab Draw Considerations
Consider the Date and Time of the lab draw.
Comparison to Past Medical History is essential (e.g., HbA1c for diabetes diagnosis).
Reference Range:
Standard range of normative values for each given lab value can be modified based on the lab’s procedure for processing blood.
Important Suffixes
-penia:
Indicates a deficiency or lack, often used in hematology (e.g., leukopenia).
-themia:
Refers to the condition of blood (e.g., polycythemia).
-poiesis:
Refers to the formation or production of blood cells (e.g., erythropoiesis).
Clinical Approach
Recommendations (DO)
Look at the direction of trends in lab values.
Weigh the anticipated benefits of physical therapy against potential risks.
Collaborate with an interdisciplinary team.
Use a symptoms-based approach for patient care.
Recommendations (DO NOT)
Do not hold for one isolated lab value without assessing the whole context of the patient’s condition.
Patient Demographics
Gender, Age, and Race:
Must be taken into account when interpreting lab values.
Units of Measurement
Mass:
g (gram), ng (nanogram), mg (milligram), µg (microgram)
Volume:
L (liter), mL (milliliter), dL (deciliter)
Count:
U (unit), IU (international unit), mU (milliunit), µU (microunit)
Concentration:
mmol (millimole), mEq (milliequivalent)
Cell Count:
mm³ (cubic millimeter), µm (micron)
Complete Blood Count (CBC)
Leukocytosis: Trending up if > 10.0K cells/mm³
Leukopenia/Neutropenia: Trending down if < 5.0K cells/mm³.
If < 1.0K cells/mm³: modify interventions, monitor for signs of infection.
White Blood Cells (WBC): A routine test to identify the presence of infection, inflammation, and allergens.
Normal range: 5.0-10.0K cells/mm³
Thrombocyte Count
Thrombocytosis: Trending up if > 1,000K cells/uL, indicating the patient is prone to thrombosis; monitor closely.
Thrombocytopenia: Trending down if < 20-50K/uL; adjustments to therapy needed.
Platelets (Plts): Routine test to assess clotting capacity.
Normal range: 150-400K cells/uL.
Hemoglobin Levels
Polycythemia: Trending up, indicating excess red blood cells.
Anemia: Trending down when hemoglobin is < 8g/dL; transfusions may be required.
Hemoglobin Normal Ranges:
Adult males: 14-18 g/dL
Adult females: 12-16 g/dL
Impact of Hemoglobin on PT Outcomes
Study by Peterson et al. (2015) shows adverse events in PT sessions:
Hemoglobin > 8 g/dL: 3236 total sessions reviewed, with 448 adverse events (13.8%).
Hemoglobin < 8 g/dL: 78 sessions reviewed, 5 adverse events (6.4%).
Basic Metabolic Panel (BMP)
A group of tests assessing:
Electrolytes
Blood glucose
Renal function
Acid-Base balance
Sodium (Na+):
Normal range: 136-145 mEq/L.
Trending up indicates hypernatremia; trending down indicates hyponatremia.
Potassium Levels
Hyperkalemia: Trends up > 6.5 mEq/L (modify or hold).
Hypokalemia: Trends down < 2.5 mEq/L (modify or hold).
Potassium Normal Range:
3.5-5.0 mEq/L.
Calcium Levels
Hypercalcemia: Trending up > 13 (modify or hold).
Hypocalcemia: Trending down < 6 (modify or hold).
Calcium Normal Range:
9-10.5 mg/dL.
Chloride Levels
Hyperchloremia: Trending up;
Hypochloremia: Trending down;
Chloride Normal Range:
98-106 mEq/L.
Renal Function Tests
Blood Urea Nitrogen (BUN):
Normal range: 10-20 mg/dL.
Trending up can indicate renal disease or dehydration.
Serum Creatinine:
Normal range: 0.6-1.2 mg/dL.
Glomerular Filtration Rate (GFR) Diagnostic Stages of Chronic Kidney Disease
GFR > 90 mL/min: Stage 1, normal or high.
GFR 60-89 mL/min: Stage 2, mild CKD.
GFR 45-59 mL/min: Stage 3A, moderate CKD.
GFR 30-44 mL/min: Stage 3B, moderate CKD.
GFR 15-29 mL/min: Stage 4, severe CKD.
GFR < 15 mL/min: Stage 5, end-stage CKD.
Causes of CKD
Chronic:
Idiopathic, long-standing hypertension, trauma.
Acute:
Rhabdomyolysis, acute kidney injury (AKI).
Endocrine Lab Values
Blood Glucose Monitoring
Hyperglycemia: >200 mg/dL.
Hypoglycemia: <70 mg/dL.
Seek medical help if <60 mg/dL.
Normal fasting range: 70-130 mg/dL.
Hemoglobin A1C Levels
Pre-diabetic: 5.7-6.4%.
Diabetic: >6.5%.
Normal: <5.7%.
Thyroid Hormones
Thyroxine (T4): 4-12 µg/dL.
Triiodothyronine (T3): 70-205 ng/dL.
Thyroid Stimulating Hormone (TSH): 0.4-4.5 U/mL.
Hypothyroidism vs Hyperthyroidism
Hypothyroidism:
Causes: Autoimmune diseases, Hashimoto’s thyroiditis, iatrogenic.
Hyperthyroidism:
Causes: Goiter, Graves' Disease, iatrogenic.
Arterial Blood Gas (ABG) Interpretations
Use a systems-based approach based on the cause of elevated anion gap levels, not just the value.
Address conditions such as metabolic acidosis and alkalosis through coordinated mobility and treatment plans.
Hepatic Panel
Liver Function Tests
Serum Bilirubin: Normal range: 0.3-1.0 mg/dL.
Ammonia (NH3):
Trending up indicates severe liver injury.
Normal range: 10-80 µg/dL.
Serum Proteins
Serum Albumin:
Normal range: 3.5-5 g/dL.
Trending down indicates nutritional compromise.
Serum Pre-Albumin:
Normal range: 15-36 mg/dL.
Lipid Panel Interpretations
High-Density Lipoprotein (HDL):
Normal: >45 mg/dL.
Low-Density Lipoprotein (LDL):
Normal: <110 mg/dL.
Total Cholesterol:
Desirable: <200 mg/dL.
Triglycerides:
Normal range: 40-160 mg/dL.
C-Reactive Protein (CRP)
Normal levels indicate low risk (<1 mg/L).
Bleeding Ratio and Viscosity
Prothrombin Time (PT)
Normal: 11-12.5 seconds.
Therapeutic range for anticoagulation: ~20 seconds.
Activated Partial Thromboplastin Time (aPTT)
Normal: 30-40 seconds; therapeutic level can rise to ~70 seconds.
International Normalized Ratio (INR)
Normal: 1; therapeutic levels typically range from 2-3.5.
Cardiovascular-Specific Labs
Cardiac Biomarkers
Cardiac Troponin I (cTnI):
Normal: <0.03 ng/mL; peaks 12-24 hours post-injury.
B-type Natriuretic Peptide (BNP):
Normal: <100 pg/mL; increases with heart failure severity.
Muscular Disorders
Creatine Kinase (CK) Levels
Elevated CK indicates muscle injury; monitoring required for various isoenzymes (CK-MB, CK-MM, CK-BB).
Various Punctures and Patient Management
Lumbar puncture: Patient may need to lay supine after procedure.
Arthrocentesis, Thoracentesis, Paracentesis: Patients may require monitoring and specific positioning post-procedure to avoid complications.
References
Academy of Acute Care Physical Therapy-APTA Task Force on Lab Values. Laboratory Values Interpretation resource. 2012, 2017.
Goodman C, Fuller K. Pathology Implications for the Physical Therapist. 4th ed. St. Louis: Elsevier Saunders; 2015.
Paz J, West M. Acute care Handbook for Physical Therapists. 3rd ed. St. Louis: Saunders Elsevier; 2009.