Table 1

MSI test result parameters for diagnosis of HNPCC in individuals unselected by age of onset or family history1-a

MSI detected in:One carcinomaOne adenomaTwo carcinomasTwo adenomas
Positive predictive value6%32%29%95%
Negative predictive valueb >99%>99%98%>99%
  • 1-a based on 15% of colorectal cancers and 3% of adenomas having MSI, 1% of colorectal tumours being due to HNPCC, and 95% of HNPCC tumours having MSI, see text for details.8 ,12 ,21-26 b based on not finding MSI in a single tumour, or in both of two tumours.