Definition of diagnostic parameters Relationship between screening test result and presence of cancer

Screening test result	Cancer present
	Yes	No
Positive	True positive (a)	False positive (b)
Negative	False negative (c)	True negative (d)
The definitions used in the present guideline are as follows:
True positive (TP)	Those with a positive screening test and confirmed cancer
(a)
False positive (FP)	Those with a positive screening test and no confirmed cancer
(b)
True negative (TN)	Those with a negative screening test and no confirmed cancer
(d)
False negative (FN)	Those with a negative screening test and confirmed cancer
(c)
Positive predictive value (PPV)	Proportion of people with a positive screening test who have confirmed cancer
(a/[a+b])
Sensitivity	Proportion of people with cancer who have a positive screening test
(a/[a+c])
Specificity	Proportion of people who do not have cancer who have a negative screening test
(d/[b+d])