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Table 2 Example calculation for determining number of patients classified as TP/TN/FP/FN per 1,000 based on pre-test probability of 20% (based on population with 20% prevalence of CMA in target population)

From: Application of GRADE: Making evidence-based recommendations about diagnostic tests in clinical practice guidelines

   Reference standard  
   Disease present Disease absent  
New Test Positive TP = sensitivity × 200 FP = (1 - specificity) × 800  
  Negative FN = (1 - sensitivity) × 200 TN = specificity × 800  
Prevalence: 20% 200 800 1000