What are the steps to diagnose a patient?

Diagnostic Approach: A Systematic Framework for Patient Evaluation

The diagnostic process should follow a structured, stepwise approach beginning with a detailed history and targeted physical examination, followed by appropriate laboratory and imaging studies based on the clinical presentation.

Initial Evaluation

History Taking

• Obtain detailed information about:
  • Chief complaint and presenting symptoms (onset, duration, progression) 1
  • Predisposing factors and precipitating events 2
  • Position and activity when symptoms occurred 2
  • Associated symptoms (nausea, sweating, pain, visual changes) 2
  • Past medical history, focusing on relevant conditions 2, 1
  • Family history, especially for hereditary conditions 2
  • Medication history, including over-the-counter drugs 2

Physical Examination

• Perform a thorough examination focusing on:
  • Vital signs (blood pressure, pulse, respiratory rate, temperature) 1
  • Targeted examination of organ systems related to symptoms 1
  • Neurological assessment when appropriate 1
  • Cardiovascular examination (heart sounds, murmurs, jugular venous pressure) 2
  • Skin examination for relevant findings (rashes, lesions) 2

Laboratory and Imaging Studies

First-Line Investigations

• Basic laboratory tests based on clinical suspicion:
  • Complete blood count
  • Basic metabolic panel
  • Urinalysis when indicated 2
  • 12-lead ECG for suspected cardiovascular issues 2
  • Chest X-ray when respiratory or cardiac disease is suspected 2

Second-Line Investigations

• Specialized testing based on initial findings:
  • Microbiological cultures from suspected infection sites 2
  • Specific biomarkers relevant to suspected conditions 1
  • Echocardiography for suspected cardiac abnormalities 2
  • Advanced imaging (CT, MRI) for neurological or structural abnormalities 2, 1

Disease-Specific Diagnostic Approaches

Cardiovascular Disorders

• For suspected arrhythmias or structural heart disease:
  • ECG to document rhythm abnormalities 2
  • Echocardiography to assess cardiac structure and function 2
  • Exercise testing when appropriate 2

Neurological Disorders

• For suspected cognitive impairment:
  • Standardized cognitive assessment tools 2
  • Laboratory tests to rule out reversible causes 2
  • Brain imaging when indicated 2

Gastrointestinal Disorders

• For suspected inflammatory bowel disease:
  • Multiple biopsies from different sites during endoscopy 2
  • Immediate fixation of specimens in appropriate solution 2
  • Step-sectioning of biopsy specimens 2

Infectious Diseases

• For suspected sepsis:
  • Blood cultures before antimicrobial therapy when possible 2
  • Fluid or tissue sampling from suspected infection sites 2
  • Gram staining and culture with antibiotic susceptibility testing 2

Special Considerations

Diagnostic Confirmation

• Integrate all clinical, laboratory, and imaging findings to reach a diagnosis 1
• Consider the predictive value of each test in the context of pre-test probability 3
• Recognize when additional specialized testing is needed 1

Common Pitfalls to Avoid

• Premature closure (settling on a diagnosis too early)
• Failure to consider alternative diagnoses
• Over-reliance on laboratory tests without clinical correlation
• Delaying empiric treatment in life-threatening conditions 2

Decision-Making Algorithm

1. Assess clinical presentation and develop initial differential diagnosis
2. Select appropriate first-line investigations based on clinical suspicion
3. Evaluate results and refine differential diagnosis
4. Determine need for specialized testing or consultation
5. Integrate all findings to establish final diagnosis
6. Implement appropriate treatment plan

The diagnostic process is iterative and may require reassessment as new information becomes available. The goal is to establish an accurate diagnosis efficiently while avoiding unnecessary testing and delays in treatment.