Diagnostic test performance parameters: Definitions of sensitivity, specificity, accuracy, and positive and negative predictive values

	Disease present	Disease absent
Test positive	A	B
Test negative	C	D
Sensitivity = A ÷ (A + C)
Specificity = D ÷ (B + D)
Accuracy = (A + D) ÷ (A + B + C + D)
Positive predictive value = A ÷ (A + B)
Negative predictive value = D ÷ (C + D)

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