This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostats, Subject name: Social & Preventive Medicine
You have clinically diagnosed a patient as having SLE and ordered 6 tests, out of which 4 have come positive and 2 have negative. To know the probability of SLE at this point, you need to know: 
Select and explain. 
A. Incidence of SLE and predictive value of each test, B. Incidence and prevalence of SLE, C. Relative risk of SLE in this patient, D. Prior probability of each test, sensitivity and specificity of each test
D: Prior probability of each test, sensitivity and specificity of each test
Answer: D: Prior probability of each test, sensitivity and specificity of each test 
Explanation: To know the probability of SLE at this point,We need to know Prior probability (Prevalence) of each test, sensitivity and specificity of each test Probability of having a Disease means PPV i.e. Positive Predictive Value and it depends upon (BAYES'THEORM) sensitivity specificity and disease Prevalence