This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'All is true regarding case fatality rate except ? \nSelect and explain. \nA. Represents killing power of disease, B. Closely related to viruleance, C. Very useful for chronic diseases, D. May vary in different epidemic for same disease', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Very useful for chronic disease CFR is typically used in acute infectious disease e.g. food poisoning, cholera, measles. o Its usefulness in chronic disease is limited, because the period from onset to death is long and variable. CFR is closely related to virulence of agent. o Limitation of CFR is that time period is not specified. o The case fatality rate for the same disease may vary in different epidemics because of changes in host, agent and environment factors. o Case fatality rate is the complement of survival rate. CFR =1 - survival rate CRF will be more if survival rate is less more patients are dying due to disease (i.CFR) or in other words less patients are surviving survival rate).", 'role': 'assistant'}]