Source / episode info

• **Episode:**195
• **Title:**Divine Intervention Episode 195 – USMLE Step 2CK Rapid Review Series 27.
• **Published:**2019-12-24
• Source:Episode page

One-liner

This episode provides a rapid review covering antibiotic prophylaxis guidelines (SSI vs. Endocarditis), the pathophysiology and treatment of three types of urinary incontinence, the differential diagnosis and lab workup of microcytic anemias (IDA, ACD, Lead Poisoning), Behcet's disease, and fundamental biostatistics concepts like study power and diagnostic test accuracy.

High-yield summary

• Endocarditis Prophylaxis: Required for patients with prosthetic heart valves, history of endocarditis, or uncorrected congenital heart defects < 6 months; IV Cefazolin is preferred for SSI prophylaxis (30–60 min pre-incision).
• Incontinence Triad: Stressing incontinence involves increased abdominal pressure (e.g., coughing); Urgency incontinence results from bladder muscle hypertonia; Overflowing incontinence stems from detrusor hypotonia or quiescence, often presenting with high post-void residual (PVR) volume.
• Anemia Differentiation: Iron Deficiency Anemia shows low serum iron/ferritin and high TIBC/RDW. ACD shows high ferritin and low TIBC. Lead poisoning mimics iron overload (high serum iron/ferritin).
• Behcet's Disease: Characterized by recurrent, painful oral and genital ulcers; strongly associated with HLA-B51 and common in Mediterranean descent; diagnosis supported by a positive pathergy test.
• Biostatistics: To increase study power, one must either increase the population size (N) or increase the effect size. When increasing sensitivity of a diagnostic test, the Negative Predictive Value (NPV) increases, but the Positive Predictive Value (PPV) decreases.

Learning objectives

• Differentiate the indications and appropriate antibiotics for surgical site infection prophylaxis versus endocarditis prophylaxis.
• Classify and manage the three types of urinary incontinence based on underlying pathophysiology.
• Interpret serum iron panel values (serum iron, TIBC, ferritin) to distinguish between Iron Deficiency Anemia, ACD, and Lead Poisoning.
• Recognize the classic clinical presentation, associated HLA type, and diagnostic test for Behcet's disease.
• Apply biostatistical principles regarding study power and diagnostic test accuracy (Sensitivity/Specificity vs. NPV/PPV).

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