General diagnostic procedures of infectious diseases

1. Big picture

The diagnosis of infectious diseases is not “order every test.” It is a clinical–microbiological reasoning process:

Patient pattern → likely syndrome → likely source → correct specimen → correct test → interpretation → treatment decision.

The examiner wants you to understand that infectious disease diagnosis has two parallel tracks:

1. Clinical diagnosis

   • History, exposure, risk factors, symptoms, physical signs, severity.

2. Etiological diagnosis

   • Identify the pathogen and, if bacterial/fungal, its antimicrobial susceptibility.

A central rule: collect appropriate microbiological samples before antibiotics whenever possible, but never delay life-saving antibiotics in sepsis, meningitis, septic shock, or severe invasive infection. Modern guidance emphasizes choosing tests according to syndrome, specimen quality, transport conditions, and clinical usefulness. ([Infectious Diseases Society of America][1])

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