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Feasibility of Synthetic Materials as Primary Standards. John Saldanha Medical and Scientific Affairs, Roche Molecular Systems, Pleasanton, CA, USA SoGAT XVIII, FDA, NIH Campus, Bethesda, MD, USA 24-25 May, 2005. YES!. BUT NOT YET. Biological vs Synthetic Standards.

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feasibility of synthetic materials as primary standards
Feasibility of Synthetic Materials as Primary Standards

John Saldanha

Medical and Scientific Affairs, Roche Molecular Systems, Pleasanton, CA, USA

SoGAT XVIII, FDA, NIH Campus, Bethesda, MD, USA

24-25 May, 2005

slide2

YES!

BUT NOT YET

biological vs synthetic standards
Biological vs Synthetic Standards

ParameterBiologicalSynthetic

Actual agent determined/quantitated

by assays √ X

Matrix similar to matrix of specimen √ X

Contains all sequences recognised by

probes in all different assays √ X

Different assays yield similar results √ ?

Long term stability √ √

biological vs synthetic standards1
Biological vs Synthetic Standards

ParameterBiologicalSynthetic

Homogenous material with little

inherent variability X √

Well-characterised material X √

Abundant source material X √

Consistency between replacement

lots X √

Ease of calibration of subsequent

replacement standards X √

historical results for the first who hcv international standard
Historical Results for the First WHO HCV International Standard

ndu/ml ge/ml

1st IS Study (1997) 5.01(25)5.82(8)

WR Calibration (1999) 5.26(18)5.70(3)

Genotypes Study (2000) 4.92(22)5.78(1)

ndu : NAT detectable units from qualitative assays

ge : Genome equivalents from qualitative assays

major concerns
Major Concerns
  • Establishment of replacement International Standards
  • WHO collaborative study to establish standard includes all laboratories → bias, inconsistent quantitation
  • Stringent requirements by regulatory authorities regarding assay performance necessitates accurate calibration of replacement standard with regard to previous standards
discussion points
Discussion Points
  • Commutability with previous IS essential to prevent ‘drift’ in IU
  • Variation in assay results ~ log10 0.5-0.6
  • Limited study using proficient laboratories to establish replacement standards
  • Feasibility of using synthetic materials as calibrators
  • Establishment of SI standard which will include reference material, reference method and reference laboratory
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