This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infectious disease, Subject name: Pediatrics
Patient was given chioroquine and doxycycline for 7 days. Patients fever decreases in 4 days, but, peripheral smear showed occasional gametocytes of plasmodium falciparum. This type of drug resistance is 
Select and explain. 
A. R type, B. R2 type, C. R3 type, D. R4 type
B: R2 type
Answer: B: R2 type 
Explanation: R2 is high grade resistance i.e. reduction of parasitemia by more than 75% at 48 hours of completing treatment but failure to clear the organism within 7 days. Types of Drug Resistance : In defining criteria for resistance to the aminoquinoline antimalarial drugs. WHO has described three grades of resistance following treatment (Low grade) R1 : Recrudescence of infection between 7 and 28 days of completing treatment following initial resolution of symptoms and parasite clearance. (High grade) R2 : Reduction of parasitaemia by > 75% at 48 hours but failure to clear parasites within 7 days. R3 : Parasitaemia does not fall by >75% within 48 hours. Reference: Ghai essential pediatrics 9 th edition Page 256