Venesection needle coring increases positive results with RT-PCR for detection of circulating cells expressing CEA mRNA

We assessed whether circulating cell positivity using RT-PCR for carcinoemb ryonic antigen (CEA) cDNA was affected by venesection via a needle compared /with a pre-aspirated venous cannula, and by increased PCR cycles. Systemic blood was sampled by needle and pre-aspirated cannula in 101 healthy indiv iduals with no cancer history. After erythrocyte removal, samples were subj ected to RT-PCR using specific primers for CEA, with 29 or 35 RT-PCR cycles . There was a significant difference between the number of subjects whose s amples were negative when collected via needle venesection and positive whe n collected via pre-aspirated cannula, compared with positive by needle ven esection and negative by pre-aspirated cannula for both 29 (P=0.016) and 35 (P=0.011) RT-PCR cycles. Venesection technique (P=0.01) and number of cycl es (P=0.003) were significant predictors of a positive result. Positive res ults in healthy subjects were reduced to less than 3% when an aspirated can nula was used for venesection and > 29 PCR cycles were avoided.