. 2018 Oct 4;9(4):e0027. doi: 10.5041/RMMJ.10351

Table 1.

Evaluation of the Detection of a Disease in a Specific Study, Using Disease-oriented Sampling. Lower-case Letters Describe the Study Population. The vertical line (|) denotes “given.”

	Gold Standard

		S_POS	S_NEG

Clinical Test	T_POS	a = True Positive	b = False Positive

	T_NEG	c = False Negative	d = True Negative

	Total	a + c	b + d
$s e n s i t i v i t y = P (T_{P O S} ∣ S_{P O S}) = \frac{a}{a + c}$
$s p e c i f i c i t y = P (T_{N E G} ∣ S_{N E G}) = \frac{d}{b + d}$
$overall detection accuracy = \frac{a + d}{a + b + c + d}$

where:

a, number of persons with S_POS and T_POS
b, number of persons with S_NEG and T_POS
c, number of persons with S_POS and T_NEG
d, number of persons with S_NEG and T_NEG