The following studies were ordered: Studies Results Lyme disease test, Elevated IgM antibody titers against Borrelia burgdorferi (normal: low) Erythrocyte sedimentation rate (ESR), 30 mm/hour (normal: ≤15 mm/hour) Aspartate aminotransferase (AST), 32 units/L (normal: 8-20 units/L) Hemoglobin (Hgb), 12 g/dL (normal: 14-18 g/dL) Hematocrit (Hct), 36% (normal: 42%-52%) Rheumatoid factor (RF), Negative (normal: negative) Antinuclear antibodies (ANA), Negative (normal: negative) Diagnostic Analysis Based on the patient’s history of camping in the woods and an insect bite and rash on the thigh, Lyme disease was suspected. Early in the course of this disease, testing for specific immunoglobulin (Ig) M antibodies against B. burgdorferi is the most helpful in diagnosing Lyme disease. An elevated ESR, increased AST levels, and mild anemia are frequently seen early in this disease. RF and ANA abnormalities are usually absent. Critical Thinking Questions 1. What is the cardinal sign of Lyme disease? (always on the boards)