a, Correlation between expected and IPDA-measured frequencies of intact proviruses per 106 cells. Genomic DNA from uninfected donor CD4+ T cells was spiked with JLat6.3 DNA cell equivalents and subjected to a serial fourfold dilution. This material was then analysed by the IPDA, and the IPDA-measured frequencies of intact proviruses per million cells were compared to the expected frequencies (998, 249.5, 62.4, 15.6 and 3.9 intact proviruses per 106 CD4+ T cells). This experiment was performed independently three times. The agreement between the expected and IPDA-measured frequencies of intact proviruses was determined using Pearson correlation. b, Reproducibility of the IPDA across independent assay runs. Reproducibility was assessed by determining the coefficient of variation (CV) across three independent assay measurements of genomic DNA from uninfected donor CD4+ T cells spiked with JLat6.3 cell equivalents and subject to serial fourfold dilution, as described in a.