Quantitative Extra Long PCR to Detect DNA Lesions in Patients Exposed to Low Doses of Diagnostic Radiation

Abstract

Background: Radiation causes oxidative lesions and strand breaks in DNA of exposed cells. Extended length<br />PCR is a reliable method for assessing DNA damage. Longer DNA strands with DNA damage are difficult to amplify<br />compared to smaller DNA strands by PCR. The present study was aimed to evaluate DNA damage caused by ionising<br />radiation exposure in therapeutic and diagnostic medicine. Materials and Methods: The study group comprised 50<br />cases with low dose single exposure (LDS), low dose multiple exposure (LDM) and low dose angiography (LDA)<br />which were compared with 25 high dose controls (HDC) and 25 controls with no exposure (NEC). Blood samples were<br />collected within 1 hour of radiation exposure. DNA was isolated using a kit based protocol, 50 ng aliquots of DNA<br />were used to amplify a long 13kbp DNA fragment of the β-actin gene by conventional PCR and band intensity was<br />then quantified. Relative amplification was calculated and damage was expressed in terms of lesions per kilobase (kbp)<br />by assuming a Poisson distribution. Result: Relative amplification was found to be 1.0, 0.87, 0.86, 0.72 and 0.69 with<br />NEC, LDS, LDM, LDA and HDC groups, respectively. Cases undergoing angiography as well as high dose controls<br />had high values, compared to NEC. The lesions/kbp calculated for LDS was 0.13, for LDM 0.15, for LDA 0.32 and<br />for HDC 0.37 suggesting a linear increase in quantity with increasing radiation dose. Conclusion: DNA damage, even<br />at low doses of radiation can be assessed by quantitative extra long PCR.