A guide to some common symptoms, associated lab tests, when to perform these tests
1. Fever
- Common Tests:
- Complete Blood Count (CBC): Assesses overall health and detects infections.
- Blood Cultures: Identifies bacterial infections in the blood.
- Urine Analysis (UA): Checks for urinary tract infections.
- Chest X-ray: May be done if a respiratory infection is suspected.
- When to Perform: If fever persists for more than 3 days or is accompanied by other severe symptoms (e.g., difficulty breathing, confusion).
- Normal Values:
- WBC count: 4,000 – 11,000 cells/mcL.
- Changes:
- Elevated WBC: Suggests infection or inflammation.
- Positive Blood Cultures: Indicates bacterial infection.
- Urinalysis: Presence of leukocytes, nitrites, or bacteria suggests a UTI.
2. Fatigue
- Common Tests:
- Thyroid Function Tests (TFTs): TSH, T3, T4 to assess thyroid function.
- CBC: To rule out anemia.
- Fasting Blood Glucose: To screen for diabetes.
- Liver Function Tests (LFTs): To check liver health.
- When to Perform: If fatigue persists for more than 2 weeks or is accompanied by weight changes, depression, or other systemic symptoms.
- Normal Values:
- TSH: 0.4 – 4.0 mIU/L.
- Hemoglobin: 13.8 – 17.2 g/dL (men), 12.1 – 15.1 g/dL (women).
- Changes:
- High TSH/Low T3, T4: Indicates hypothyroidism.
- Low Hemoglobin: Suggests anemia.
- High Blood Glucose: Indicates diabetes.
3. Chest Pain
- Common Tests:
- Electrocardiogram (ECG): Assesses heart rhythm and ischemia.
- Troponin: A cardiac marker indicating heart muscle injury.
- Lipid Profile: Assesses cholesterol levels.
- Chest X-ray: May be done to rule out lung conditions.
- When to Perform: Immediately if chest pain is sudden, severe, or associated with shortness of breath, sweating, or radiating pain.
- Normal Values:
- Troponin: <0.04 ng/mL.
- Total Cholesterol: <200 mg/dL.
- Changes:
- Elevated Troponin: Suggests myocardial infarction (heart attack).
- Abnormal ECG: May indicate ischemia or arrhythmias.
4. Shortness of Breath
- Common Tests:
- Arterial Blood Gas (ABG): Assesses oxygen and carbon dioxide levels.
- CBC: To rule out anemia.
- Chest X-ray: To check for pneumonia, heart failure, or lung conditions.
- D-dimer: To rule out pulmonary embolism.
- When to Perform: Immediately if acute or worsening shortness of breath occurs.
- Normal Values:
- Oxygen Saturation: 95-100% (on room air).
- D-dimer: <0.5 µg/mL.
- Changes:
- Low Oxygen Saturation: Indicates hypoxemia.
- Elevated D-dimer: Suggests thromboembolic disease.
5. Jaundice
- Common Tests:
- Liver Function Tests (LFTs): Measures enzymes like ALT, AST, and bilirubin.
- CBC: To check for hemolysis.
- Ultrasound: To visualize liver and biliary structures.
- When to Perform: If jaundice is new, unexplained, or associated with other symptoms like dark urine or pale stools.
- Normal Values:
- Bilirubin: 0.1 – 1.2 mg/dL.
- ALT: 7 – 56 U/L.
- Changes:
- Elevated Bilirubin: Suggests liver dysfunction or hemolysis.
- High ALT/AST: Indicates liver injury.
6. Unexplained Weight Loss
- Common Tests:
- CBC: To rule out anemia or malignancy.
- TFTs: To assess thyroid function.
- Fasting Blood Glucose: To check for diabetes.
- Stool Occult Blood Test: To screen for gastrointestinal bleeding or malignancy.
- When to Perform: If weight loss exceeds 5% of body weight over 6-12 months without clear cause.
- Normal Values:
- TSH: 0.4 – 4.0 mIU/L.
- Changes:
- Low TSH: May indicate hyperthyroidism.
- Positive Stool Occult Blood: Suggests gastrointestinal bleeding.
7. Persistent Cough
- Common Tests:
- Chest X-ray: To rule out pneumonia, tuberculosis, or lung cancer.
- CBC: To detect infection or inflammation.
- Sputum Culture: To identify pathogens in the lungs.
- Allergy Tests: If asthma or allergies are suspected.
- When to Perform: If the cough lasts more than 3 weeks, is worsening, or is associated with hemoptysis or weight loss.
- Normal Values:
- Chest X-ray: Clear lung fields.
- Changes:
- Abnormal Chest X-ray: May indicate pneumonia, TB, or malignancy.
- Positive Sputum Culture: Identifies the causative pathogen.
