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
Likelihood ratio for positive results is; 
Select and explain. 
A. Sensitivity / (1-specificity), B. Specificity / (1-Sensitivity), C. (1-Sensitivity) / Specificity, D. (1-specificity) / Sensitivity
A: Sensitivity / (1-specificity)
Answer: A: Sensitivity / (1-specificity) 
Explanation: Likelihood ratio for Positive :
       LR+= Sensitivity / (1-specificity)
Likelihood Ratio for Negative :
      LR- = (1-Sensitivity) / Specificity