CRP and Increased total leukocyte count: The diagnosis of serum sickness is primarily based on patient history, including recent medications but also can be suspected by specific symptoms (Online Resource 4) and laboratory data, including leukocytosis, mild thrombocytopenia, elevated acute-phase proteins such as C-reactive protein (CRP) and Factor VIII, low C3 and C4 complement factors, decreased total hemolytic complement (CH50), and elevated circulating IC, as detected by C1q consumption.