Diagnostic tests and procedures are used in clinical health-care settings to aid in the identification of a condition, disease, or prognosis with a high degree of accuracy. They are crucial to early detection and application of the proper treatment plan for each patient. Every provider is responsible for the analysis of each study and the individual action plan because of the interpretation. Every diagnostic has four phases. The first is to determine normal or acceptable ranges of the test. The second is to evaluate the accuracy of the test. The third is to determine clinical consequences of the results of the test. The fourth is to evaluate if more diagnostics are needed before determining an individual plan. Table A1 lists common laboratory tests and expected results. Table A2 displays commonly used diagnostic studies for providing competent and comprehensive patient care.
| Serum, Plasma, and Whole Blood | |
| Red blood cell (RBC) | 4.5–5.0 million cells/mm3 (female) 4.7–6.2 million cells/mm3 (male) |
| White blood cell (WBC) | 4,500–11,000 cells/mm3 |
| Platelets | 150,000–400,000/mm3 |
| Blood urea nitrogen (BUN) | 6–24 mg/dL |
| Serum creatinine | 0.6–1.2 mg/dL |
| Estimated glomerular filtration rate (eGFR) | > 60 mL/min/1.73m2 |
| Carbon dioxide | 23–29 mmol/L |
| Glucose | 65–110 mg/dL |
| Aldolase | 22–59 mU/L |
| Chloride | 95–105 mEq/L |
| Potassium | 3.5–5.2 mEq/L |
| Sodium | 135–145 mEq/L |
| Calcium | 8.3–10.2 md/dL |
| Phosphorus | 3.0–4.5 mg/dL |
| Magnesium | 1.3–2.1 mEq/L |
| Serum osmolality | 285–295 mOsm/kg H2O |
| Albumin | 3.5–5.5 g/dL |
| Total protein | 5.5–8.3 g/dL |
| Bilirubin | 0.1–1.2 mg/dL |
| Ammonia | 11–32 mcmol/L |
| Aspartate aminotransferase (AST) | 9–25 units/L (female) 10–40 units/L (male) |
| Alanine aminotransferase (ALT) | 7 – 20 units/L (female) 10 – 55 units/L (male) |
| Copper | 70–15 mcg/dL |
| Ferratin | 18–160 ng/mL (females) 18–270 ng/mL (males) |
| Folic acid | 3–13 ng/mL |
| Arterial Blood Gas (ABG) | |
| pH | 7.35–7.45 |
| Partial pressure of oxygen (PaO2) | 80–100% |
| Partial pressure of carbon dioxide (PaCO2) | 35–45 mmHg |
| Bicarbonate (HCO3) | 22–26 mEq/L |
| Hematology | |
| Fibrinogen | 200–400 mg/dL |
| Erythrocyte count | 3.6–5.0 × 1012/L (female) 4.2–5.4 × 1012/L (male) |
| ESR | 0–20 mm/h (females less than 50 yrs) 0–30 mm/h (females greater than 50 yrs) 0–15 mm/h (males less than 50 yrs) 0–20 mm/h (males greater than 50 yrs) |
| Hematocrit |
36–48% (female) 42–52% (male) |
| Hemoglobin | 12–16 g/dL (female) 13–17 g/dL (male) |
| International normalized ratio (INR) | 0.8–1.2 2–3 is normal for patients on warfarin |
| Prothrombin time (PT) | 11–13 seconds 1.5–2× longer if on anticoagulants |
| Partial thromboplastin time (PTT) | 60–70 seconds 1.5–2× longer if on anticoagulants |
| Activated partial thromboplastin time (aPTT) | 25–35 seconds 1.5–2× longer if on anticoagulants |
| Cardiac Markers | |
| Total creatine kinase (CK) | 500–2250 nkat/L (female) 917–2833 nkat/L (male) |
| Myoglobin | 5–70 ng/mL |
| Troponin | <0.4 ng/mL |
| Atrial natriuretic peptide (ANP) | 22–77 ng/L |
| Brain natriuretic peptide (BNP) | <100 ng/L |
| Lipid Panel | |
| High-density lipoprotein (HDL) | > 40 mmol/L |
| Low-density lipoprotein (LDL) | < 100 mmol/L |
| Triglycerides | < 120 mmol/L |
| Total cholesterol | < 170 mmol/L |
| Hemoglobin A1C | |
| Normal | < 5.7% |
| Prediabetes | 5.7–6.4% |
| Diabetes | > 6.5% |
| Proteins | |
| Protein total | 6–8 g/dL |
| Albumin | 3.5–5.2 g/dL |
| Globulin | 1.7–3.3 g/dL |
| Vitamins | |
| Vitamin A | 30–120 mcg/dL |
| Vitamin B1 | 1.6–4 mcg/dL |
| Vitamin B6 | 5–30 ng/mL |
| Vitamin B12 | 200–900 pg/mL |
| Vitamin E | 0.5–1.8 mg/dL |
| Zinc | 55–150 mcg/dL |
| Urine Chemistry | |
| Ketones | < 2.0 mg/dl |
| Amylase | 1–17 units excreted per hour |
| Calcium | 100–250 mg per 24/hour |
| pH | 4.5–8 |
| Osmolality | 50–1200 mOsm/kg |
| Glucose | Negative |
| Note: These values could change slightly based on parameters set by specific health-care facilities | |
| Diagnostic | Description |
|---|---|
| Angioplasty | Widens the arteries and increases cardiac blood flow |
| Biopsy | Removes a sample of tissue or cells from the body for microscopic examination to diagnose cancer or other diseases |
| Bronchoscopy | Examines the larger airways: trachea and bronchi |
| Chest X-ray | Evaluates the lungs, heart, or chest wall to diagnose pneumonia, heart failure, emphysema, lung cancer, and other medical conditions |
| Colonoscopy | Examines the colon, or large intestine |
| Computed tomography scan (CT) | Evaluates all major parts of the body, including the abdomen, back, chest, and head |
| Electrocardiography (EKG or ECG) | Records the heart’s electrical activity to detect abnormal rhythms, heart damage, or heart failure |
| Electroencephalogram (EEG) | Records the brain’s electrical activity |
| Endoscopy | Examines the inside of certain tube-like structures in the body with a fluoroscope; for example, upper GI series examines the esophagus, stomach, and duodenum |
| Fecal occult blood test | Examines stool samples for traces of blood; also called a stool guaiac or hemoccult test |
| Lumbar puncture | Uses a needle to remove a sample of fluid from the space surrounding the spinal cord to diagnose infections, such as meningitis, and some neurological conditions. |
| Magnetic resonance imaging (MRI) | Uses a magnetic field to produce pictures of structures inside the body |
| Ultrasonography | Uses high frequency sound waves to generate snapshots or moving pictures of structures inside the body, especially vital organs; also called sonography |
| Ventilation-perfusion scan (V-Q scan) | Nuclear scan that examines both airflow (ventilation) and blood flow (perfusion) in the lungs |
| X-ray | Uses waves of electromagnetic radiation to create images of organs and other structures inside the body |
References
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Committee on Diagnostic Error in Health Care; Board on Health Care Services; Institute of Medicine; The National Academies of Sciences, Engineering, and Medicine; Balogh, E.P., Miller, B.T., & Ball, J.R., eds. (2015, Dec 29). Improving Diagnosis in Health Care. National Academies Press (US), The Diagnostic Process. https://www.ncbi.nlm.nih.gov/books/NBK338593/
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