Table 1.

Screening phases of the Caerphilly study: Phases 1 to 4

Screening Phase	Years	N	Comment
Phase 1	1979–83	2512/2818	Response rate 89%
Phase 2	1984–88	2398	477 added, 561 lost
Phase 3	1989–93	2154
Phase 4	1993–97	1701	344 died, 353 moved