Genotyping patients with recent blood transfusions

Many studies have used polymerase chain reaction amplification (PCR) to genotype for common polymorphisms in intensive-care units (ICUs) where blood transfusions are common. Evidence that donor leukocytes in transfused blood can be detected by PCR of the recipient blood suggests that this minor population of donor white cells (microchimerism) can interfere with genotyping of allelic polymorphisms in critically ill transfused patients. To investigate this possibility, we assayed DNA extracted from the blood and buccal cells of ICU patients for 2 common polymorphisms in the TNF-beta gene and the surfactant protein-B (SP-B) gene.

Study subjects were ICU patients from the Massachusetts General Hospital (Boston, MA) enrolled into a study on the molecular epidemiology of acute respiratory distress syndrome between January 1999 and October 2000. Blood and buccal cells were collected and DNA was extracted from 145 patients. Genotyping was performed by enzyme digestion and pyrosequencing.

The Kappa statistics comparing the genotype results from blood and buccal cells were 0.98 (95% confidence interval [CI] = 0.94-1.01) for TNFB and 0.95 (CI = 0.87-1.02) for SP-B. When the analysis was restricted only to the 107 patients who were transfused, the Kappa statistic remained high at 0.97 (CI = 0.93-1.01) for TNFB and 0.93 (CI = 0.84-1.03) for SP-B.

We conclude that microchimerism from allogeneic blood transfusion is unlikely to have major effects on the genotype results of common polymorphisms in large molecular epidemiology studies conducted in the critical care setting if DNA is collected within a day after transfusions.