Table 1.

The effectiveness of three mass-screening strategies in a test population of 100,000 persons (when FN/Pos^a = 0.4). The two-step strategy reduced the number of NAATs performed by approximately 95% compared to NAAT only, with an increase in false negatives by only 24 per 100,000 persons. Both NAAT only and two-step performed significantly better than free entry at limiting the number of false negatives.

	NAAT only			Two-stepb			Free entry
p	NAAT	Pos	FN	NAAT	Pos	FN	NAAT	Pos	FN
0·1%	100,000	100	40	549 [548–550]	76 [68–83]	64 [57–72]	0	0	140
0·2%	100,000	200	80	558 [556–559]	152 [136–166]	128 [114–144]	0	0	280
0·5%	100,000	500	200	583 [579–587]	380 [340–415]	320 [285–360]	0	0	700
1·0%	100,000	1000	400	626 [617–634]	760 [680–830]	640 [570–720]	0	0	1400

FN/Pos: ratio of false negatives to positives; p: proportion of NAAT positivity; NAAT: number of nucleic acid amplification test performed; Pos: number of positive results; FN: number of false positives.

^aFN/Pos is the ratio of infected persons who test negative to all test positives.

^bEstimated when the probability of CLEIA-positivity given NAAT-positivity is 76% in point estimates (90% credible interval between 68% and 83%).