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 carcinoembryonic 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 individuals with no cancer history. After erythrocyte removal, samples were subjected 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 samples were negative when collected via needle venesection and positive when collected via pre-aspirated cannula, compared with positive by needle venesection and negative by pre-aspirated cannula for both 29 (P = 0.016) and 35 (P = 0.0111) RT-PCR cycles. Venesection technique (P = 0.01) and number of cycles (P = 0.003) were significant predictors of a positive result. Positive results in healthy subjects were reduced to less than 3% when an aspirated cannula was used for venesection and >29 PCR cycles were avoided.