Pilot Study of the Sensitivity and Specificity of the DNA Integrity Assay for Stool-based Detection of Colorectal Cancer in Malaysian Patients

Background: To assess the diagnostic potential of tumor-associated high molecular weight DNA in stoolsamples of 32 colorectal cancer (CRC) patients compared to 32 healthy Malaysian volunteers by means ofpolymerase chain reaction (PCR).
Methods: Stool DNA was isolated and tumor-associated high molecularweight DNA (1.476 kb fragment including exons 6-9 of the p53 gene) was amplified using PCR and visualizedon ethidium bromide-stained agarose gels.
Results: Out of 32 CRC patients, 18 were positive for the presenceof high molecular weight DNA as compared to none of the healthy individuals, resulting in an overall sensitivityof 56.3% with 100% specificity. Out of 32 patients, 23 had tumor on the left side and 9 on the right side, 16 and2 being respectively positive. This showed that high molecular weight DNA was significantly (p = 0.022) moredetectable in patients with left side tumor (69.6% vs 22.2%). Out of 32 patients, 22 had tumors larger than 1.0cm, 18 of these (81.8%) being positive for long DNA as compared to not a single patient with tumor size smallerthan 1.0 cm (p <0.001).
Conclusion: We detected CRC-related high molecular weight p53 DNA in stool samplesof CRC patients with an overall sensitivity of 56.3% with 100% specificity, with a strong tumor size dependence.