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Cytotechnology

, Volume 8, Issue 3, pp 231–236 | Cite as

Accuracy of the endpoint assay for virus titration

  • Lars K. Nielsen
  • Gordon K. Smyth
  • Paul F. Greenfield
Original Research Papers

Abstract

The statistics of estimators used with the endpoint assay for virus titration were investigated. For a standard assay with 10 wells/dilution, the graphical estimator traditionally used was found to produce estimates with significant positive bias and a relatively low accuracy. Furthermore, the graphical estimator was found to be inconsistent. A superior estimator based on the maximum likelihood principle was developed. The results are discussed in relation to the choice between the endpoint titration assay and the plaque assay, and an alternative two-stage assay is presented.

Keywords

Maximum Likelihood Estimator Plaque Assay Relative Bias Graphical Estimator Endpoint Titration 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

α

concentration of infective virus particles (PFU/ml)

v

volume of sample in well (ml)

λ=α.v

virus particles in well (PFU)

m

no. of dilutions

d≡(d1,d2,...,dm)

vector of dilutions

n≡(n1,n2,...,nm)

vector of no. of wells scored for each dilution

x≡(x1,x2,...,xm)

vector of observed no. of positive wells for dilutions

X≡(X1,X2,...,Xm)

stochastical vector representing the observation vector

E

exponential series {...,10−2,10−1,100,101,102,...}

λ=μɛ

μ=mantissa of λɛ [1,10]; ɛ=exponent of lambda ɛ E

δ=ɛd

relative dilution vector

t(X;d,n,λ)

estimator of λ

λ=t(x;d,n,λ)

estimate of λ

β

relative bias

γ

variance-coefficient

χ12(1−α)

(1-α)-percentile in χ2-distribution with 1 degree of freedom

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References

  1. Knudson DL and Tinsley TW (1974) Replication of a nuclear polyhedrosis virus in a continuous cell culture ofspodoptera frugiperda: purification, assay of infectivity, and growth characteristics of the virus. J. Virol. 14: 934–944.Google Scholar
  2. Rao CR (1973) Linear statistical inference and its applications, 2nd Ed. John Wiley & Sons, New York.Google Scholar
  3. Reed LJ and Muench H (1938) A simple method of estimating fifty percent endpoints. Am. J. Hygiene 27: 493–497.Google Scholar
  4. Summers MD and Smith GE (1987) A Manual of Methods for Baculovirus Vectors and Insect Cell Culture Procedures. Texas Agricultural Experiment Station Bulletin No. 1555.Google Scholar

Copyright information

© Kluwer Academic Publishers 1992

Authors and Affiliations

  • Lars K. Nielsen
    • 1
  • Gordon K. Smyth
    • 2
  • Paul F. Greenfield
    • 1
  1. 1.Department of Chemical EngineeringThe University of QueenslandAustralia
  2. 2.Department of MathematicsThe University of QueenslandAustralia

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