Erratum to: Characterizing plasma albumin concentration changes in TB/HIV patients on anti retroviral and anti –tuberculosis therapy
- Kuteesa R Bisaso^{1}Email author,
- Joel S Owen^{2},
- Francis W Ojara^{1},
- Proscovia M Namuwenge^{3},
- Apollo Mugisha^{4},
- Lawrence Mbuagbaw^{5},
- Livingstone S Luboobi^{6} and
- Jackson K Mukonzo^{1, 3, 7}
DOI: 10.1186/s40203-014-0005-7
© Bisaso et al.; licensee Springer. 2015
Received: 9 December 2014
Accepted: 10 December 2014
Published: 11 February 2015
Erratum
- 1.
We would like to retract the relation between ABCB1c.3435C > T gene mutation and baseline albumin secretion rate. This is because, even though the mutation in the gene was identified as a significant covariate with our data, we are still unable to biologically explain the relationship.
- 2.
The final model equation (equation 7), referred to here as the “Simplified Solution” is not the direct solution of the differential equations preceding it. We would therefore like replace it with the unsolved differential equation below and show a comparison of the results of the two equations.
The equation was fit to the data in NONMEM version 7.2, using a differential equations solver specified by the ADVAN6 and TOL = 3 subroutines. The First Order Conditional Estimation with interaction (FOCEI) estimation method was used.
The Interaction term was not used in the previous analysis because it has been reported not to be useful when there are small number of observations per individual and therefore does not provide different results (Peter 2011).
The two models, i.e. the previously defined simplified solution and the unsolved differential equation above were compared with respect to fit, difference and precision of parameter estimates, goodness of fit, prediction bias and precision as well as length of runtimes given the same initial parameter estimates.
NONMEM estimated relative standard errors, percentage difference in parameter estimates, numerical predictive checks and other model comparison criteria for model1 and model2
The unsolved differential equation model | The previous simplified solution | % parameter difference | |
---|---|---|---|
Relative standard errors | |||
Q_{0} | 2.6 | 2.5 | 0.28 |
Q_{SS} | 18.5 | 17.3 | -0.16 |
R | 48.2 | 46.0 | 17.78 |
Q_{0}_TB = 1(proportional increase in Q_{0} with TB) | 13.9 | 14.1 | 1.27 |
IIV_Q_{0} | 18.0 | 17.8 | 0.73 |
Residual error | 5.4 | 5.4 | -0.31 |
Other model criteria | |||
OFV | 57.151 | 58.457 | NA |
Condition Number | 25.38 | 21.39 | NA |
runtime (seconds) | 5.48 | 1.79 | NA |
Measures of model prediction | |||
Bias (%PE) | -0.66478 | -0.66329 | NA |
Precision( 1-RMSE) | 0.72481 | 0.72464 | NA |
The total run time (parameter estimation plus covariance) for the unsolved differential equations model above was more than three times that of the previously defined model and this ratio was higher during more intensive procedures like bootstrapping and stepwise covariate analysis.
Conclusion
We would like to change model equation to the unsolved differential equation model. The model provided here and the previously defined model differ mostly in one parameter, R (rate of change of albumin secretion) and the computation times, but the other outputs including parameters, predictions and goodness of fit plots were similar.
Notes
Authors’ Affiliations
References
- Bisaso KR, Owen JS, Ojara FW, Namuwenge PM, Mugisha A, Mbuagbaw L, et al. Characterizing plasma albumin concentration changes in TB/HIV patients on anti retroviral and anti -tuberculosis therapy. In Silico Pharmacol. 2014; 2(1):3. doi:10.1186/s40203-014-0003-93.View ArticlePubMed CentralPubMedGoogle Scholar
- Peter LB. Nonlinear Mixed Effects Models: Theory. In: Peter LB, editor. Pharmacokinetic-Pharmacodynamic Modeling and Simulation. 2nd ed. New York: Springer; 2011: p. 256.Google Scholar
Copyright
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.