dPCR results are in copies per microliter. How do I calculate host cell DNA impurities in femtogram per microliter or picogram per microliter?

Host cell DNA contamination in products such as vaccines, drugs and other biopharmaceuticals imposes great health risks. Therefore, its safe limits are tightly regulated by agencies such as the FDA and WHO. Clear guidelines for the upper limits of residual DNA are established based on the nature of drug administration, infectivity and oncogenicity of the contaminating cell DNA. For instance, parenteral administration of non-tumorigenic cell DNA should be limited to 10 ng/dose and a maximum length of 200 bp, whereas less than 100 µg/dose of residual DNA is recommended by WHO for orally administered vaccines.   Detection of such contaminations requires highly sensitive and accurate measurements of the extremely low amounts of specific host cell DNA present in the products.  Digital PCR is the preferred method for residual DNA (resDNA) quantification. This is due to its unmatched sensitivity and accuracy, especially at trace levels of contamination compared to other detection methods such as qPCR. QIAcuity Residual DNA Quantification Kits provide the accurate and precise detection of Escherichia coli (E. coli), Chinese Hamster Ovary (CHO) and Human Embryonic Kidney 293 (HEK293) host cell DNA. The QIAcuity HEK293 resDNA Sizing Kit allows quantification and fragment size determination to meet guidelines for residual DNA size (<200 bp). This kit also allows for multiplexing with oncogene targets like E1A (Geneglobe ID DMA00938), E1B (GeneGlobe ID DMA01000) or SV40 (GeneGlobe ID DMA00936) for added safety testing flexibility.  The QIAcuity resDNA Quant Standard Kits are dPCR-verified absolute quantification standards that can be used in combination with resDNA Quant and Sizing Kits for validation of quantitation accuracy or bridging studies.