This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology Pa-2 (RNA Virus Pa-1,2 & Miscellaneous Viruses), Subject name: Microbiology
In dengue infection, number of petechial spot per square inch in cubital fossa should be: 
Select and explain. 
A. >5, B. >10, C. >15, D. >20
D: >20
Answer: D: >20 
Explanation: 1. Dengue hemorrhagic fever is diagnosed by positive Tourniquet test which indicates number petechial spot per square inch in cubital fossa is >20 per 2.5 cm (1cm) square area. 2. Tourniquet test: Done to detect thrombocytopenia. The standard method uses the blood pressure cuff. To identify dengue and chikungunya infection. Positive tourniquet test - Number of petechial spot per square inch in cubital fossa is 20. Any of the following may be present - petechiae, purpura, ecchymosis, epistaxis, gum bleeding hematemesis or melena. 3. Criteria for diagnosis of dengue hemorrhagic fever (DHF): Fever - acute, high and continuous for 2-7 days. Positive tourniquet test. Enlargement of liver.