Estimates of clonotypic contamination in stem cell components collected after melphalan and G-CSF mobilization in 15 patients are shown as a function of different factors. (A) Estimates of clonotypic contamination in 20 stem cell components (SCCs) are shown as a function of the type of PCR assay used. The results with light and heavy chain (V_L and V_H) patient-specific PCR were correlated (r² = 0.93, P < .01) and 35% (7 of 20) of the time were equal. Means were V_L = 2.7 × 10⁴ and V_H = 3.3 × 10⁴ clonotypic cells per kilogram per SCC. (B) Estimates of clonotypic contamination in 29 SCCs are shown as a function of CD34⁺ cells per kilogram in each SCC, calculated by flow cytometry. By simple linear regression, the line of best fit is y = (0.707)x – 0.669 with 95% confidence intervals as shown (r² = 0.42, F = 19.1, P < .01). There is a relatively constant ratio of CD34⁺ to clonotypic cells, as previously suggested by Moos and colleagues.¹⁸  (C) Clonotypic contamination is shown in relationship to the timing of mobilization. Medians for days 12 to 18 and 19 to 23 were 0.5 × 10⁴ and 0.35 × 10⁴ clonotypic cells per kilogram. Differences due to timing of mobilization were not significant (Mann-Wilcoxon, P = .68).