Results
Table 1 summarises the number of participants in the study and their outcomes. Those undergoing colonoscopy had a mean age of 62.8 years and 56.4% were male subjects. Table 2 shows the number in each clinical outcome group at increasing f-Hb. Table 3 further classifies those with a neoplastic lesion according to features of the most serious adenoma or cancer detected along with the median (and 95% CI) f-Hb and p values.
f-Hb in those with cancer was significantly higher than in all other groups (p<0.02), apart from the HRA group (p=0.07). In addition, f-Hb was greater in HRA compared with LRA and diverticular disease and those with no pathology detected (p<0.005). There was no statistically significant difference between the LRA group and those without neoplasia.
Of the 39 participants with cancer, 29 had f-Hb>1000 ng Hb/ml and 10 had f-Hb that could be measured within the analytical working range of 0–1000 ng Hb/ml. These included four participants with a confirmed polyp cancer (Dukes' stage A), two non-polyp Dukes' A cancers, three Dukes' B and one Dukes' stage C1 rectal cancer with f-Hb of 442 ng/ml. In all, 36 of the cancers had staging available and 12 (six polyp; 27.3%), 11 (33.3%), 12 (36.4%) and 1 (3.0%) cancers were Dukes' A, B, C1 and C2, respectively. The differences in median f-Hb between different stages were not statistically significant.
f-Hb was significantly higher in those with a large compared with a small adenoma (p<0.0001). Those with adenoma with HGD had higher f-Hb than with LGD (p<0.009). Although f-Hb in those who had an adenoma with a villous component was higher than in non-villous adenoma, this was not statistically significant (p=0.07) nor was the difference between those with their most serious adenoma found proximally and distally (p=0.08). No significant difference in f-Hb was found between those with multiple adenomas (defined as ≥3) and those with only one or two adenomas found (p=0.64).
The significant difference in f-Hb seen between HGD and LGD adenomas was not evident when holding size constant, with no difference between small LGD and HGD adenomas (p=0.88), or between large LGD and HGD adenomas (p=0.09). A multiple linear regression model using size, degree of dysplasia, presence or absence of villous component, site and number of adenomas as categorical explanatory variables showed adenoma size was the only characteristic to be significantly related to f-Hb (p<0.0001; all other variables p>0.1).
Table 4 shows the range and median size of lesions in those with hyperplastic polyp (HPP), adenoma or cancer detected and p values for comparisons with significant differences in bold. Significantly larger lesions were found between any adenoma and HPP; HRA and LRA; HGD and LGD adenomas; villous and non-villous adenomas; and more advanced cancers and polyp cancers. In addition, all cancers were significantly larger than HRA (p<0.0001) and indeed any adenoma (p<0.0001). Adenomas in the distal colon were larger than in the proximal region, in contrast to cancers, which were larger proximally.