Table 1. Results of a hypothetical test validity study.

a		Gold-standard test
		Positive	Negative	Total
T1	Positive	TP: 85 π Se1	FP: 40 (1 – π)(1 – Sp1)	125
	Negative	FN: 15 π (1 – Se1)	TN: 360 (1 – π) Sp1	375
	Total	100	400	500
b		T1
		Positive	Negative	Total
T2	Positive	107 pr Se2,1	104 (1 – pr)(1 – Sp2,1)	211
	Negative	43 pr (1 – Se2,1)	346 (1 – pr) Sp2,1	389
	Total	150	450	600
c		Gold-standard test
		Positive	Negative	Total
T2	Positive	76 π Se2	64 (1 – π)(1 – Sp2)	140
	Negative	4 π (1 – Se2)	256 (1 – π) Sp2	260
	Total	80	320	400
a) a well-established test, T1, against the gold-standard test; b) a new test, T2, against T1; note that here, the true prevalence, π, is replaced by the apparent prevalence, pr (7) as T1 is not a gold standard; and c) another hypothetical study if T2 would have been tested against the gold standard. TP – True positive. FP – False positive. FN – False negative. TN – True negative. π – True prevalence. pr – Apparent prevalence. Sp – specificity. Se – sensitivity.