Table 6 Positive predictive value of a positive gFOBT result (values given as percentages and the denominator (n) from which they are derived)
 First round % (n) Second round % (n) Third round % (n) Cancer Total 12.0 (3464) 7.0 (3123) 7.5 (2044) Males 13.0 (2144) 7.1 (1911) 7.7 (1226) Females 10.2 (1320) 7.0 (1212) 7.1 (818) Non-responders in all previous rounds – 9.4 (350) 12.6 (175) Responders in any previous round – 6.6 (2125) 7.1 (1218) Adenoma Total 36.5 (3464) 30.3 (3123) 29.1 (2044) Males 41.6 (2144) 35.0 (1911) 33.9 (1226) Females 28.2 (1320) 22.8 (1212) 22.0 (818) Non-responders in all previous rounds – 38.0 (350) 34.9 (175) Responders in any previous round – 28.9 (2125) 28.7 (1218) High-risk adenoma Total 4.3 (3464) 3.1 (3123) 3.1 (2044) Males 5.9 (2144) 4.3 (1911) 4.1 (1226) Non-responders in all previous rounds – 4.6 (350) 5.1 (175) Responders in any previous round – 2.7 (2125) 3.0 (1218) Total neoplasia Total 48.4 (3464) 37.4 (3123) 36.6 (2044) Males 54.6 (2144) 42.1 (1911) 41.6 (1226) Females 38.4 (1320) 29.8 (1212) 29.1 (818) Cancer+high-risk adenoma Total 16.4 (3464) 10.1 (3123) 10.6 (2044) Males 18.9 (2144) 11.4 (1911) 11.8 (1226) Females 12.0 (1320) 8.3 (1212) 8.8 (818) Non-responders in all previous rounds – 47.4 (350) 47.4 (175) Responders in any previous round – 35.5 (2125) 35.8 (1218)
• There was a statistically significant decline in the PPV for cancer between the first and second round (p<0.01, χ2 test), but not between the second and third rounds.

• The difference between males and females in all rounds and in all variables was statistically significant at the p<0.01 level, with the exceptions of a positive predictive value for cancer in the second and third rounds (χ2 test).

• gFOBT, guaiac faecal occult blood testing.