Collaborative national multicenter for the identification of conversion factors from copies/mL to international units/mL for the normalization of HCMV DNA load

Diagn Microbiol Infect Dis. 2019 Oct;95(2):152-158. doi: 10.1016/j.diagmicrobio.2019.05.012. Epub 2019 May 25.


The present multicentric (n = 11 laboratories) study aimed to identify conversion factors from copies/mL to international units (IU)/mL for the normalization of HCMV DNA load using the first WHO International Standard for HCMV nucleic acid amplification techniques and to enhance interlaboratory agreement of HCMV DNA quantification methods. Study protocols for whole blood and plasma (extraction and amplification) were performed to calculate conversion factors from HCMV DNA copy number to IU. The greatest variability was observed in samples with lower HCMV concentrations (3.0 Log10) in both biological matrices. Overall, 73.1% (206/282) of whole blood and 82.2% (324/394) of plasma samples analyzed fell within an acceptable variation range (±0.5 Log10 difference). An average of 0.64 (range 0.21-1.17) was the conversion factor calculated for the HCMV whole blood panel and 0.82 (range 0.39-2.2) for the HCMV plasma panel.

Keywords: HCMV; International standard; Multicenter study.

Publication types

  • Multicenter Study

MeSH terms

  • Cytomegalovirus / genetics
  • Cytomegalovirus / isolation & purification*
  • Cytomegalovirus Infections / blood
  • Cytomegalovirus Infections / diagnosis*
  • Cytomegalovirus Infections / virology
  • DNA, Viral / blood*
  • DNA, Viral / genetics
  • Humans
  • Nucleic Acid Amplification Techniques / standards
  • Reference Standards
  • Reproducibility of Results
  • Viral Load / methods*
  • Viral Load / standards*
  • World Health Organization


  • DNA, Viral