A new protocol for quantifying CD34(+) cells in peripheral blood of patients with cardiovascular disease.

Increasing evidence points to a role for circulating CD34-positive (CD34(+)) cells in vascular maintenance and neovascularization. Although there are established methods for evaluating absolute numbers of CD34(+) cells in bone marrow or mobilized peripheral blood, there is no convenient and highly reproducible method for quantifying low numbers of CD34(+) cells in blood samples, such as those from the peripheral blood of patients with cardiovascular disease. With current commonly used methods, the mean percentage of CD34(+) cells in leukocyte fractions from such patients was only 0.02%, and the cumulative intra-assay coefficient of variation was approximately 30%. With use of the protocol described herein, actual counts of CD34(+) cells increased approximately 5-fold and cumulative intra-assay coefficients of variation were reduced to approximately 7%. The new method is useful to precisely measure low numbers of CD34(+) cells in samples, and it has potential as a screening tool to evaluate cardiovascular risk in large patient populations.