SAMPLE SUITABILITY FOR THE DETECTION OF MINOR WHITE CELL-POPULATIONS (MICROCHIMERISM) BY POLYMERASE-CHAIN-REACTION

BACKGROUND: There is increasing use of highly sensitive testing with p olymerase chain reaction (PCR) to study white cell microchimerism afte r transfusion and transplantation. This study investigated possible ar tifactual sources of allogeneic sample contamination before PGR testin g. STUDY DESIGN AND METHODS: Quantitative Y-chromosome PCR was used to study microchimerism among transfused patients with sickle cell disea se (SCD) and thalassemia by using residual specimens from the clinical laboratory. High levels of circulating male white cells among transfu sed patients with SCD but not thalassemia led to concern over the arti factual origin of male cells. To investigate, paired specimens were co llected from 26 female SCD patients: one specimen underwent processing only for PCR, while the other underwent testing in the clinical labor atory before PCR as a process control. All laboratory instruments were also assessed for their ability to impart male allogeneic cells to al iquots of female blood. RESULTS: Thirty-three (31%) of 107 SCD samples , but 0 of 20 thalassemia samples, gave a high-level PCR signal. One o f 26 paired samples that was not exposed to clinical laboratory equipm ent had low-level PCR positivity while 10 of the 26 became strongly po sitive after testing on a blood cell analyzer and a reticulocyte analy zer. Sixteen of 32 female samples became positive after reticulocyte a nalysis, while none became positive after blood cell analysis. Samples from thalassemia patients tested PCR-negative because reticulocyte co unts had not been performed. CONCLUSION: Allogeneic cell contamination is common with clinical laboratory equipment. These samples may not b e suitable for microchimerism studies. In addition to method controls, process controls should be employed where appropriate.