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Editor,—We read with interest the paper by Kronborg and colleagues (Gut2000:46:795–800)—a large multicentre study measuring faecal calprotectin levels in high risk populations for colorectal neoplasia.
The authors did not discuss their results in comparison with those of Roseth and colleagues1 or Kristinsson and colleagues2 who did the ground breaking work in this area and where calprotectin levels were shown to be far higher in patients with colonic polyps and cancer compared with normal controls (table 1).
Median values for the control subjects were higher and median values for the colorectal cancer (CRC) and polyp groups were much lower compared with the Norwegian group (who had much greater numbers in the CRC group), combining to markedly reduce the sensitivity of this test.
Furthermore, in the discussion, the authors claim that their results showing no fall in calprotectin levels in patients after polypectomy are similar to those of Kristinsson and colleagues2 before and after resection for colon cancer. This is a gross misrepresentation of their findings which clearly show that 24/26 patients who underwent colonic resection had a significant fall in faecal calprotectin levels. The other two patients had bypass operations.
Editor,—The values in our 488 controls (median 7 mg/l, range 5–7) did not differ from those in the 125 controls in the paper by Kristinsson1-1 (median 5.2 mg/l and not 2.5 as quoted by Brydon et al).
The lower median values in our 23 cancer patients compared with those in the two other studies1-1 1-2 is probably due to the less advanced cancers found in our study (six Duke's A, five Duke's B), which mostly included patients in the surveillance programmes. Unfortunately, nothing is told about the size and multitude of the polyps in the study by Roseth and colleagues1-2 but in our study the majority of patients had small adenomas and no more than 1–2, which may explain the slightly lower median values.
Brydon et al seem to have misunderstood our discussion of calprotectin levels after polypectomy. We mentioned that the levels after colonic resection for cancer in the study by Kristinsson and colleagues1-1 (median 10.3 mg/l, range 1–200) were similar or even higher than those after polypectomy in our study (median 7.07 mg/l, range 5.26–8.67), lending support to the possibility of a general intestinal mucosal defect.
The calprotectin test still has a sensitivity for colorectal neoplasia which is higher than that of ordinary guaiac tests, but the rather low specificity limits its usefulness to high risk groups.
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